Prepared by: Team Spokesperson: Ashle Perry Date. Submitted: Reviewed: Revised: Approved: Team Member: Jeremy Robinson Date

Transcription

1 PACER Program Flight Readiness Review Document for the High Altitude Imaging and Atmospheric Data Collection Experiment by SABRE (Scientific Aerospace and Balloon Research Engineers) Prepared by: Team Spokesperson: Ashle Perry Date Team Member: Jeremy Robinson Date Team Member: Nedgby Marcelin Date Submitted: Reviewed: Revised: Approved: Team Member: Atin Sinha Date Institution Signoff (replace with name) Date Institution Signoff (replace with name) Date LA SPACE Signoff Date

2 Change Information Page Title: FRR Document for High Altitude Imaging and Atmospheric Data Collection Experiment Date: 07/23/2009 List of Affected Pages Page Number Issue Date 13 Add labels Add details to Add details to Add details to Pressure Sensor Schematic Add details to Temp Sensor Schematic Delete line from Control Electronics Add System Testing Results 27 Modify data format Modify software flow charts Modify flight software flow charts Modify incrementing in flow chart Modify adc flowcharts Modify sub routine flow charts Add set rtc subroutine Team SABRE ii

3 TBD Number Status of TBDs Section Description Date Created Date Resolved Team SABRE iii

4 TABLE OF CONTENTS Cover... i Change Information Page... ii Status of TBDs... iii Table of Contents... iv List of Figures... vi List of Tables... vii 1.0 Document Purpose Document Scope Change Control and Update Procedures Reference Documents Goals, Objectives, Requirements Mission Goal Objectives Science Background and Requirements Technical Background and Requirements Payload Design Principle of Operation System Design Electrical Design Software Design Thermal Design Mechanical Design Payload Development Plan Payload Construction Plan Hardware Fabrication and Testing Integration Plan Software Implementation and Verification Flight Certification Testing Mission Operations Pre-Launch Requirements and Operations Flight Requirements, Operations and Recovery Data Acquisition and Analysis Plan Project Management Organization and Responsibilities Configuration Management Plan Interface Control...46 Team SABRE iv

5 9.0 Master Schedule Work Breakdown Structure (WBS) Staffing Plan Timeline and Milestones Master Budget Expenditure Plan Material Acquisition Plan Risk Management and Contingency Glossary...58 Team SABRE v

6 LIST OF FIGURES 1. Temperature vs. Altitude in Standard Atmosphere Pressure vs. Altitude in Standard Atmosphere Summer Temperature Change at Ft. Worth during Payload Design Payload Design Picture Payload Insert Plate Insert Plate Picture High Level System Design Electrical System Design Temperature Sensor Process Temperature Sensor Pressure Sensor Process Pressure Sensor High Level Sensor Interfacing Pressure Sensor Schematic Temperature Sensor Schematic High Level Control Electronics Control System Schematic High Level Power Supply Power Subsystem Schematic Final Circuitry Picture of Batteries Derating of Main Battery Pack Derarting of Secondary Battery Pack Flowchart for Pre-flight Software Flowchart for In-flight Software Flowchart for Post-flight Software ADC Testing Subroutines Setting the RTC Thermodynamics Mechanical Design Payload Structure Picture of External Structure Picture of Internal Structure Variation of Pressure Data during Vacuum Testing Variation of Temperature Sensor A Data during Vacuum Testing Variation of Temperature Sensor B Data during Vacuum Testing Variation of Pressure Sensor Data during Thermal Testing Variation of Temperature Sensor A Data during Thermal Testing Variation of Temperature Sensor B Data during Thermal Testing Variation of Pressure Sensor Data during Shock Testing Variation of Temperature Sensor A Data during Shock Testing Variation of Temperature Sensor B Data during Shock Testing...47 Team SABRE vi

7 45. Pressure Sensor Calibration Plot Temperature Sensor A Calibration Plot Temperature Sensor B Calibration Plot Data Analysis Flowchart Timeline and Milestone for the Project Detailed Breakdown of Tasks between PDR to CDR Detailed Breakdown of Tasks between CDR to Science Presentation...59 LIST OF TABLES U.S. Standard Atmosphere Goals versus Measurement Traceability Matrix Power Budget Table Data Rates and Storage Requirements Comparison of Various Temperature Sensors Comparison of Various Pressure Sensors Thermal Calculations Thermal Chart Weight Budget Weight Table Vacuum Flight Profile Pressure Sensor Calibration Data Temperature Sensor A Calibration Data Temperature Sensor B Calibration Data Organization Chart Work Breakdown Structure Master Budget Expenditure Plan Risk and Contingency Assessment...78 Team SABRE vii

8 1.0 Document Purpose This document describes the preliminary design for the High Altitude Imaging and Atmospheric Data Collection experiment by Team SABRE for the PACER Program. It fulfills part of the PACER Project requirements for the Preliminary Design Review (PDR) to be held July 1, Document Scope This PDR document specifies the scientific purpose and requirements for the High Altitude Imaging and Atmospheric Data Collection experiment and provides a guideline for the development, operation and cost of this payload under the PACER Project. The document includes details of the payload design, fabrication, integration, testing, flight operation, and data analysis. In addition, project management, timelines, work breakdown, expenditures and risk management are discussed. Finally, the designs and plans presented here are preliminary and will be finalized at the time of the Critical Design Review (CDR). 1.2 Change Control and Update Procedures Changes to this PDR document shall only be made after approval by designated representatives from Team SABRE and a PACER Institution Representative. Document change requests should be sent to Team members and a PACER Institution Representative and put on file for the PACER Project. 2.0 References 1. Adiabatic Cooling and Heating of Gases. Retrieved: June 19, <physics-animations.com/physics/english/adia_txt.htm > 2. Digital Dutch Amsterdam. Retrieved: June 30, 2009 < 3. University of Tennessee-Knoxville. The Earth s Atmosphere. Retrieved: June 12, <csep10.phys.utk.edu/astr161/lect/earth/atmosphere.html> 4. Sparling, B., The Ozone Layer. Last updated: March 27, Retrieved: June 16, < 5. Buchdal, J., and Hare, S Troposphere. Retrieved: June 16, < 6. Ray, S., The Layers of Earth s Atmosphere. Retrieved: June 18, <airs-dev.jpl.nasa.gov/maps/satellite feed/atmosphere layers/> 7. Pidwirny, M., University of British Columbia Okanagan. Last updated: March 28, Retrieved: June 18, < 8. Genyuk.J., University Corporation for Atmospheric Research. Windows to the Universe. Last modified: July 16, Retrieved: June 19, < Team SABRE 1

9 9. National Weather Service - Southern Region Headquarters. Layers of the Atmosphere. Last Modified: April 17, Retrieved: June 19, < noaa.gov/jetstream/atmos/layers.htm> 10. Spencer, R. What is the troposphere? Retrieved: June 12, < 11. Dessler, A: The Chemistry and Physics of Stratospheric Ozone, Academic Press. 12. Parallax Inc. Basic Stamp microcomputer. Retrieved: July 2, < List/1/Default.aspx?SortField=ISBN,ISBN> 13. Microchip Technology Inc., KI 2 C Serial EEPROM. Retrieved: July 2, < 14. Maxim Integrated Products Dallas Semiconductor Corporation. DS 1302 Data Sheet. Retrieved: July 2, < 15. National Semiconductor. January ADC 0831/ADC 0832/ADC 0834 Data Sheet. Retrieved: July 2, < 16. Duracell Batteries. Ultra 245, Lithium/Manganese Dioxide. Retrieved: July 5, < 17. Omega Engineering, Inc Thermistor TH Retrieved: July 2, < 18. Measurement Specialities. Model 1230 UltraStable Pressure sensor. Retrieved: July 2, < pdf> 19. National Semiconductor. 1N457 High Conductance Low Leakage Diode. Retrieved: July 7, <eiec.usts.edu.cn/up/1n457.pdf> 20. West, J Prediction of barometric pressures at high altitudes with the use of model atmospheres, Journal of Applied Physiology 81: Team SABRE 2

10 3.0 Goals, Objectives, Requirements 3.1 Mission Goal The mission of this flight is to acquire data that can be compared to standard atmospheric model to verify the relationship between temperature, and pressure with altitude from the ground to the lower portion of the stratosphere. Additionally, the acquired data will be corelated with the experimentally observed values and possible causes identified if any variance is observed. 3.2 Objectives The objective of this mission is to send a payload from the ground to about 33 km into the atmosphere. The payload must have proper construction that allows it to survive and operate in this range. The payload has to be light and inexpensive. While the payload makes this flight, it will record temperature and pressure data as well as video images for visual experience such that it can be retrieved and analyzed post-flight. This data will then be compared to standard data sets (from both mathematical model and experimentally observed), and presented to peers and the PACER staff at the CSBF, Palestine, Texas Science Objectives Verify that temperature decreases with altitude in the troposphere and increases with altitude in the stratosphere as predicted in the standard atmospheric model Verify that the observed temperature falls within the recorded temperature variation in summer time in the region Verify that pressure decreases with increasing altitude as predicted in the standard atmospheric model Determine variation of the container surface temperature with the ambient temperature Determine the height of the tropopause and how far it extends Account for unexpected changes in temperature caused by albedo Technical Objectives Record the temperature, and pressure data during the flight Record video pictures during the flight Build a payload that can withstand the environmental conditions of the upper atmosphere (up to approximately 33 km), and will survive landing Stay within the project financial budget Provide power to the payload for at least 4 hours Complete PDR, CDR, and FRR on schedule Team SABRE 3

11 3.3 Science Background and Requirements The atmosphere plays an important role in the survival of the earth. It acts as an insulation to keep enough heat in contact with Earth to prevent freezing, and it acts as a barrier to shield the earth from overheating. The atmosphere has a unique structure that allows it to provide such an advantage to Earth. However the health of the atmosphere has been a major issue for all life on Earth. The ozone layer is depleting and the greenhouse effect is warming the earth more and more each year. Investigating the atmosphere provides insight so that we can understand its nature and know what to expect Science Background The Earth's atmosphere is composed of four major layers and three transition zones between those layers. The troposphere is the layer where weather is formed and most commercial airplane flights occur [3]. There are many mathematical models to describe the properties of atmosphere, one of which, 1976 US Atmosphere, is used to obtain information shown in Table 1 [2]. The atmosphere extends from the earth's surface to about 11 km (about 36,000ft) above the surface and is accountable for approximately 80% of the total mass of the atmosphere [10]. It is composed of 78% nitrogen, 21% oxygen, and a small amount of trace gases. The average temperature at the surface is about 15º C (288 K); however, the temperature decreases with height at a rate of approximately 6.4º C per km as demonstrated in Figure 1[6]. It is the temperature changes that are directly related to weather. The less dense warm air rise above the cooler air, and air convection forms which forms clouds. Pressure also decreases as height increases as shown in Figure 2[6]. At sea level, the pressure is about 1,013 millibars, but as the troposphere approaches the stratosphere, the pressure is only about 200 millibars. This explains the decrease in temperature because as a gas expands, there is less energy and work done by each molecule upon one another; therefore, the temperature drops [1]. The thin zone after the troposphere, called the tropopause identified by constant temperature, is a major portion of the atmosphere that will be studied. The height at which the tropopause starts, depends on the latitude and time of year. Generally, colder regions will have a lower tropopause [5]. The Figures 3 describes the variation of temperature during May and June of 2009 obtained from the recording of sounding balloons launched from Ft. Worth, TX and reported by the University of Wyoming. Examination of these data indicates that the beginning as well as the extent of the tropopause significantly varies from day to day even within a particular month and in a specific location. According to Figure 3 the temperature in the tropopause changed from approximately 76ºC to 60º C during the period the data was recorded. As the temperature decreases in the troposphere, it suddenly makes a turn and starts increasing. The point at which it no longer decreases is the start of the tropopause. The graphs will not show a distinct temperature change because the data isn't perfect, but it will provide a rough idea. Not only can the start of the tropopause be determined, but with sufficient data, the end of the tropopause can be determined as well. Team SABRE 4

12 Another term, isothermal layer is used to describe the tropopause and this will essentially be the characteristic that we will use to determine how far the tropopause extends. According to Figures 3, the tropopause lies between 13,000m to 20,000m. We will expect our data to prove that the tropopause indeed lies within this range. Figure 1. Demonstrating the characteristics of temperature as altitude increases (Source: PhysicalGeography.net [7]) The tropopause leads to the stratosphere, the second layer of the atmosphere. This layer extends from the tropopause to the stratopause which is about 11 to 50 km (about 36,000 ft to 164,000 ft) above Earth's surface % of the total mass of the atmosphere is found in the stratosphere [8]. The temperature in the stratosphere increases with increasing altitude. The reason for this phenomenon is the layer of ozone [4] that lies at the top portion of the stratosphere. 90% of the earth's ozone exists in this portion of the stratosphere. Ozone is made of three molecules of oxygen and is formed when O 2 is bombarded by ultraviolet radiation and is separated into two oxygen molecules. The separated oxygen molecule is then combined with other O 2 molecules in the atmosphere. O 2, N 2, and O can absorb radiation with wavelengths of 200nm or less, but the ozone is responsible for absorbing the majority of the ultraviolet rays including radiation greater than 200 nm. Radiation with such high energies is strong enough to disassociate DNA [11]. As shown in Figure 1, within the limits of the stratosphere, temperature reaches about 0º C (273 K), and also as shown in Figure 2, the pressure reaches close to vacuum. The stratopause is the transitional zone leading from the stratosphere to the mesosphere[9]. The mesosphere ranges from about 50 km to 80 km (about 164,000 ft to 263,000 ft). As meteors are entering the Earth's atmosphere, they are burned up and are observed as shooting stars in this layer. As shown in Figure 1 temperature decreases with increasing altitude in this layer. Temperature reaches about 90º C (183 K) at about 80 km which is the coldest average temperature of the atmosphere. Pressure in this layer goes down close to vacuum. Team SABRE 5

13 Figure 2. Demonstrating how pressure decreases with increasing altitude (Source: Physical Geography.net [7]) The mesopause is the zone that separates the mesosphere from the last layer of the atmosphere, the thermosphere (or ionosphere). This layer extends from 80 km (262,480 ft) all the way to outer space. Temperature increases with increasing altitude in this layer and can reach to about 1200º C (927 K). The balloon payload that we will construct will only reach to about 33 km (100,000ft), or from the troposphere to the lower portion of the stratosphere. The payload container will be subject to temperatures as low as about 75º C (198 K) and as high as about 35º C (308 K). The payload will also be subject to pressures as low as about 7 millibars and as high as about 1,013 millibars. Proper insulation will be necessary to keep the electronics protected from the lower portion of this temperature range. Although we have an idea of what to expect, experiments are not always perfect. The temperature profile will not always be what one expects. Albedo is one characteristic that can cause temperature to vary. The change in temperature depends on what the payload is passing through. Albedo refers to the amount of solar radiation that can be reflected by a Earth s surface [9]. Ground without vegetation such as dessert will reflect more radiation while dense forest and cloud cover will stop much of the sun s radiation to be reflected back to atmosphere. Team SABRE 6

14 Altitude Temperature Pressure Density Speed of sound [km] [Celsius] [mb] [kg/m3] [m/s] Table Standard Atmosphere ( Team SABRE 7

15 Altitude (m) Jun Jun Jun Jun May Temperature (C) Figure 3. Summer Temperature Changes at Ft. Worth during 2009 Team SABRE 8

16 Measurement Accuracy and Frequency The information provided in the Table 1 and Figures 1 through 3 demonstrate not only the ideal properties of the standard atmosphere as predicted by mathematical model but also what had been observed experimentally. This information also forms the basis of the accuracy and frequency of data collection procedure that should be adopted as requirement to successfully conduct our experiment to satisfy the mission goal. Temperature As per the standard atmospheric model, the ideal temperature as shown in Table 1 decreases by 6.5ºC per km from seal level to 11 km, remains constant from 11 to 20 km, there after increases by 1ºC per km for the remaining part of our projected flight. From the previous balloon flight by LaACES, an average ascent rate of about 1000 ft per minute was observed which translates to about 5 m per second. The balloon will take about 197 seconds to climb 1 km which ideally should change the temperature by 6.5º C at the troposphere which should decide the sampling rate because of faster change of temperature. So if we are interested to record 1ºC change in temperature, the sampling rate should be about once in 30 seconds. Similarly, as the positional accuracy measured by the GPS transmitter beacon located in the balloon is ±20 m, one can argue that it will take of the order of 8 seconds to climb the total 40 m. of height measurement uncertainty. So, the lower limit of sampling rate is decided to be once in 8 seconds. It is worthwhile to mention that a casual observation of the data in Figure 3 shows the variation of temperature for any given altitude in the tropopause is as much as 8ºC, which signifies sampling rate as high as once in 240 seconds can be justified also. But we should remember that the data in Figure 3 is not the result of any uncertainty of measurement but resulted from changes due to atmospheric conditions such as albedo or jetstream that has moved southward. Accuracy of the temperature sensor should be no less than 0.5ºC. Pressure Because of the nonlinear nature of the pressure profile, the pressure decrease is significantly higher at the lower altitude and this will determine the proper sampling rate for pressure. At the sea level, the pressure change is of the order of 115 mb per km which reduces to about 1mb per km at around 32 km altitude. As discussed above, our balloon will take about 197 seconds to climb 1 km. So, to ensure 1 mb change in pressure, one should sample about once in 2 seconds or less. But the uncertainty of measurement including the variation due to atmospheric condition is far off from 1 mb. Assuming uncertainty is of the order of 20 mb [20] the sampling rate should be of the order of once in 35 seconds. Accuracy of the pressure sensor should be determined by the total storage capacity of the ADC chip and the range of pressure data (7 to 1000 mb) to be recorded. Hence, looking at various criteria, we decided to adopt a synchronous sampling rate for both temperature and pressure reading one in every 15 seconds which not only will provide sufficient data to accurately portray the atmospheric properties but will be within the range of memory storage capability of the microchip. Team SABRE 9

17 3.3.2 Science Requirements Surface temperature on the payload container should be recorded for the entire flight Ambient temperature should be recorded for the entire flight Ambient pressure should be recorded for the entire flight Time should be recorded for the entire flight and synchronized with the rest of the data. Altitude should be recorded for the entire flight and synchronized with the rest of the data Video recording should be made during the entire flight to provide any visual clue for any discrepancy in expected result as well as total visual experience of the flight 3.4 Technical Background and Requirements Technical Background Our payload has two temperature sensors. The first sensor will be located on the exterior surface of the container. The second sensor will be located a few inches away from the surface. Between these two sensors, we expect to observe variances in temperature. Team SABRE s payload will include a pressure sensors that will measure ambient pressure. A real time clock will be used to time stamp the observed temperature and pressure data. At the end of the flight, the temperature and pressure data will be plotted vs. altitude and compared against experimentally observed data obtained from the sounding balloon launched from Ft. Worth, TX around the same time. Mechanical After examining different options on choosing insulators, we have concluded that Styrofoam brand polystyrene has the most efficient insulation properties. It is light and floats on water. By using this material we can keep our payload under the 500 g limit. Since Styrofoam is relatively inexpensive, and capable to withstand shock, the container made from it will help us stay within budget, and rugged enough to withstand the shock of the landing. In order to fabricate the container from Styrofoam, we will use the Gorilla Glue brand of polyurethane cement which foams up to join components without sacrificing the strength. Electrical The main computing platform for our payload is the BalloonSat board. The BalloonSat s main components include the BASIC stamp processor, EEPROM data storage chip, A/D converter, and Real-Time Clock. The BASIC stamp 2p 24-pin module serves as the brain of the electronics package that offers high execution speed of about 12,000 PBASIC instructions/sec, and ability to handle large program size up to approximately 4,000 PBASIC instructions [12]. The EEPROM data storage microchip is used to expand the available memory in the BASIC stamp processor [13]. The Real Time Clock (Trickle-Charge Timekeeping Chip) DS1302 microchip will time stamp the temperature and pressure data as they are collected [14]. The A/D converter chip will convert analog signal to digital value for display [15]. All the major components of the computing platform have an operating temperature range of 40C to +85C which exceeds the safe operational temperature requirement of our experiment. Power supply will be provided by a battery pack made from DuracellUltra 245 Lithium/Manganese Dioxide cells as they have one of the highest power to weight ratio [16]. The operating Team SABRE 10

18 temperature range of these cells is from 20ºC to +75ºC which still will be sufficient to meet the temperature variation expected in our experiment. Sensor The Model 1230 UltraStable PC Board Mountable Pressure Sensor [18] would be one of the suitable candidates for use in our payload. This pressure sensor has a 0-100mV output and a compensated temperature range of 20C to +85C. In addition, the Pressure sensor can be easily integrated into the BalloonSat board. We have also looked at different options for measuring temperature. Based on integration capabilities, operating temperatures, and measuring accuracy we have narrowed the options down to thermistors, thermocouple and diodes. A thermocouple consists of two dissimilar metals with different thermal characteristics, joined together at one end. Different temperatures produce varying voltage at the other end which can be interpreted in a calibrated temperature scale. A thermistor is a type of resistor whose resistance varies with temperature. One of the preferred thermistors is model TH [17] because it can be easily integrated into the BalloonSat board. In the end, we decided to use 1N457 High Conductance Low Leakage Diode to use as a temperature sensor because of its excellent reliability and linear response in the entire temperature range of our experiment Technical Requirements Equip the payload with sensors that will take measurements of surface temperature and ambient pressure and temperature once every 15 seconds during the ascent and descent phases of the balloon Provide a real time clock to time stamp the pressure and temperature data Include video camera in payload that will continuously record video images Maintain the interior temperature of the payload above -20ºC to protect the electronics package Write all information to a non-volatile memory microchip Use a sturdy, lightweight, inexpensive material to construct the payload such that it will survive the environmental conditions of the upper atmosphere and a rough landing Provide lightweight, inexpensive power supply for the duration of flight (4 hours) Construct and follow a detailed project management schedule to adhere to the time and cost schedule 4.0 Payload Design Our payload consists of one pressure sensor, two temperature sensors and a video camera. One of the temperature sensors will be used to measure temperature at the outside surface of the container and the other sensor will be placed sufficiently away from the container to measure the true ambient temperature. The video may have to be shot in blocks of 15 minutes and turned off for next 15 minutes if there are any operational limitations. This will ensure capturing the images of most of the flight including the descent and landing. The video camera being considered at present is capable of recording continuously for 4 hours which will adequately cover our entire flight duration if only recording is done in low resolution. Team SABRE 11

19 The payload, associated electronics instrumentations and power supply will be housed in a Styrofoam container whose exact dimension will be specified in the mechanical design section. The Balloon Sat configuration will be used to interface the payload and the required instrumentation. The available heat from the electronics package will be utilized as a thermal protection for efficient operation of the payload. Figure 4. Payload Design Figure 5. Picture of Payload Design Team SABRE 12

20 Figure 6. Insert Plate Figure 7. Picture of Insert Plate Team SABRE 13

21 4.1 Principle of Operation The temperature and pressure measurements will be done in accordance with the stated science objective of measuring the beginning and extent of tropopause as well as general variation of atmospheric properties with increasing height. As such sampling rate of temperature and pressure should be fast enough to capture their variation as the balloon climbs through the atmosphere. A sampling rate of once in every 15 seconds is proved to be sufficient as described in the section Measurement Accuracy and Frequency. The temperature sensor should have a resolution of at least 0.5º C and the pressure sensor should be able to measure with about 5 mb of accuracy. The model 1230 temperature compensated, piezoresistive silicon pressure sensor [18] is being considered as a candidate, which is primarily used in medical, process control industry and for airspeed and altitude measurements. This sensor has an operating temperature of 20º to + 85ºC. A high conductance low leakage diode, 1N457, built by National Semiconductor will be used as a temperature sensor because of its excellent reliability and linear response in the entire temperature range for our experiment. 4.2 System Design Figure 8. High Level System Design Team SABRE 14

22 4.2.1 Functional Groups Mechanical Support System The mechanical design subsystem provides protection of the payload and other components. It is a structure that is designed to enclose the components, and provides shock protection for the landing. Thermal Control System The thermal design subsystem provides an operating temperature for the payload components. It ensures that even while traveling through very low temperatures, the temperature inside the payload box will lie within the operating range. It also ensures that the box is not insulated to an extreme where the heat emitted from the components overheats the payload. The operating range of the payload will be determined when all components are specified. Power Supply The BalloonSat only requires 5V to operate. However, there must be more than 5V put into the BalloonSat. The voltage regulator will adjust the voltage to 5V. The power sensor requires 5V to operate, and the constant current source in the pressure sensor circuit requires 4V. The power supply will consist of a battery that will provide at least 12V and enough current. Data Archive The data archive subsystem allows measured data to be stored for later retrieval. The EEPROM stores temperature, pressure and time stamp the data in the form of hour minute and second. The camera has its own memory storage, called the SD card, for storing video images. Sensors The temperature sensor is responsible for measuring temperature. The signal will later go through signal conditioning, converted to digital, and stored to EEPROM. Before we decided on a sensor, these possibilities were considered: thermistors, RTDs, thermocouples, and diodes. Thermistors were considered, but there are disadvantages to using them. As temperature decreases, the output voltage doesn t vary enough to produce distinct ADC counts for particular temperatures, and a range of temperatures may have the same ADC count. In other words, thermistors are not very linear, especially in the low temperatures, so the low temperatures can not be measured to great accuracy even with precise calibration. After studying different datasheets, we have decided to use two 1N457 high conductance, low leakage diode will be used in this flight. The temperature sensor has to be as close to linear as possible to provide ADC counts that vary enough to represent a temperature within a certain range. The pressure sensor is responsible for measuring pressure of the atmosphere. This pressure signal will go through signal conditioning also before being converted to digital and sent to the EEPROM. Model 1230 UltraStable pressure sensor will be used. Team SABRE 15

23 Control The BalloonSat is the main device that controls components during flight. It consists of three major components: the basic stamp, analog to digital converter, and the EEPROM. The basic stamp is responsible for holding and executing the program. Without the basic stamp, the devices cannot be controlled using code. The ADC is responsible for converting analog signal to digital signal that can be stored to the EEPROM. Data Processing and Analysis The BASIC Stamp computer software will be used for this subsystem. The data collected by the BalloonSat will be extracted from the EEPROM and analyzed based on the signal conditioning. Each measurement will correspond to the counts produced by the ADC. The logic to convert ADC counts to actual temperature and pressure has already been developed and tested. The extracted temperature and pressure data will be plotted in a spreadsheet as a function of altitude and compared with the standard atmospheric table and experimentally observed values. Video images will help determine any unusual factor that may have affected the recorded data. Attempt will be made to locate the beginning and height of tropopause Group Interfaces In order for our payload to function properly each group in our payload must interface properly. The mechanical support system and the thermal control system interface with the payload box. The mechanical support system and the thermal control system are bidirectional; however both the thermal control system and the mechanical support system interface only unidirectional with the payload box in accordance with Figure 5. The power supply system interfaces unidirectional with the sensor system, control system, and data archive system. The control system and the data archive system are bidirectional with each other; however the sensor system and control system are unidirectional with one another. The secondary power supply is unidirectional with the camera; the camera is unidirectional with the data archive. Both the data archive and the data archive system are unidirectional with the data processing and analysis system. Team SABRE 16

24 4.2.3 Traceability Mission Goal and Objectives To acquire ambient temperature for comparison to standard atmospheric model to verify temperature vs. altitude relationship up to 33 km To acquire temperature data on the surface of the payload container To acquire ambient pressure for comparison to standard atmospheric model to verify pressure vs. altitude relationship up to 33 km To record time and synchronize with the remainder of data Record video images during the flight of the balloon. Provide lightweight and inexpensive power supply to power the electronics package All collected data has to be recorded and retrieved for post flight analysis Payload has to survive the condition of upper atmosphere Sturdy material to be used for payload construction such that they survive the landing on rough terrain or on water Payload has to be constructed from lightweight materials Payload should be relatively inexpensive Science and Technical Requirements To be able to record the temperature from -75ºC to 35ºC every 15 seconds with an accuracy 0.5ºC To be able to record the temperature from -75ºC to 35ºC every 15 seconds with an accuracy 0.5ºC To be able to record pressure from above 1000 mb to about 7 mb every 15 seconds with an accuracy of 5 mb To be able to record time from the real time clock at the time when temperature and pressure data is being recorded To be able to record video images continuously during the launch, descent and landing phases Provide supply voltage through a 12 V lithium ion battery pack to ensure regulated 5V supply at the Balloon SAT for a minimum of 4 hours Pressure and temperature data has to be recorded continuously during the flight on a nonvolatile memory to be extracted later. Maintain the temperature within the payload container to no less than -20ºC Design the container with sufficient shock absorbing ability Use components of least weight to restrict the overall weight to 500 gm Use least expensive parts keeping track of safety and reliability to restrict the total cost to $500 Design Elements Temperature Sensor Temperature Sensor Pressure Sensor Real Time Clock Video Recording Device Power Supply Data acquisition, archive and retrieval Thermal Insulation Mechanical Structure Weight Management Budget Test Procedure Test the circuit for operability of the sensor at simulated condition of low temperature and pressure of upper atmosphere Test the circuit for operability of the sensor at simulated condition of low temperature and pressure of upper atmosphere Test the circuit for operability of the sensor at simulated condition of low temperature and pressure of upper atmosphere Test the circuit for operability of the sensor at simulated condition of low temperature and pressure of upper atmosphere Program and test the video camera to record images at the simulated condition Test the a comparable battery pack for continuity of power supply and maintain the desired voltage at the simulated condition for 4 hour duration Test the prototype circuit to record the data at the simulated condition and retrieve afterwards Measure the temperature inside the container at the simulated condition of upper atmosphere Test the container by dropping from a height and measure the extent of damage Keep detailed record of weight for each individual component Maintain strict cost control in acquiring parts for the payload Table 2. Goal vs. Measurement Traceability Matrix Team SABRE 17

25 4.3 Electrical Design One power source will be used to power the BalloonSat and the sensors. A voltage regulator built into the BalloonSat board ensures that the voltage isn t too high for the board even if the input voltage is high. A direct connection will also be connected to the expansion board of the BalloonSat to power the sensors. A temperature and pressure sensor will be used in this system. When the input goes through the sensors, it will be sent through signal conditioning. The signal is the sent the analog to digital converter. Here, the analog signal will be converted to digital so that it can be read and recorded by EEPROM. Figure 6 shows the interfacing between the subsystems. 4.5V 4.5V Secondary Battery Pack Sensors Figure 9. Electrical System Design Two temperature sensors and a pressure sensor will be used during this flight. Both the temperature sensors will be located outside, one on the outside surface of the container and the other a few inches away. The pressure sensor will be located inside the container. Another important aspect of the sensors is the linearity and stability of the sensor. If a sensor response is linear, the calibration curve will be a straight line making it easier to develop and calculate the final data. Conversely, if the sensor behavior is non-linear, the calibration will require more data points to determine the true nature of the curve. However, linearity does not imply better precision of the measured data. Team SABRE 18

26 Temperature Sensor Figure 10. Temperature Sensor Process The temperature sensor will be subject to the physical temperature input. The signal then goes through signal conditioning where the voltage range is amplified and shifted to match that of the ADC. When the signal gets to the ADC, it is converted to digital so that it is understood by the BASIC stamp. Figure 7 shows this process at high level. These diodes are very linear in the temperature range that will be investigated. The nature of the sensors is quite simple. As temperature decreases, the resistance of the diode gets lower which means that if the current stays constant, the voltage will increase. Inversely, if the temperature increases, the resistance will get higher, which means the voltage will be smaller. Figure 11. Temperature Sensor Pressure Sensor Pressure Input Pressure Sensor Signal Conditioning Analog to Digital Converter Basic Stamp Figure 12. Pressure Sensor Process The pressure sensor will be subject to the physical temperature input. The signal then goes through signal conditioning where the voltage range is amplified and shifted to match that of the ADC. When the signal gets to the ADC, it is converted to digital so that it is understood by the BASIC stamp. Figure 10 shows this process at high level. We have decided to use the Model 1230 UltraStable [18] pressure sensor with a range of 0-15 psi. This range is adequate because at the surface, the pressure is slightly less than 15 psi, and at the highest altitude that the payload will reach, the pressure doesn t quite reach 0 psi. It has an operating temperature of 40C to 125C. Although the temperature in the atmosphere gets lower than that, with proper insulation, we can provide an adequate operating temperature within the payload. The actual nature of the pressure sensor is quite interesting. There is a metal tube that is able to measure ambient pressure. There is also a reference pressure of 0 psi next to the tube. There are four resistors that are connected and as pressure changes, it changes the resistance provided by the resistors. This causes a change in the two output voltages produced by the pressure sensor. Pressure is determined by the difference in these two voltages. Figure 13. Pressure Sensor Team SABRE 19

27 4.3.2 Sensor Interfacing The input will enter the sensors and go through signal conditioning. During signal conditioning, the input will be converted to a range of 0V-3V so that it can match the ADC voltage range. For example, a resistance temperature device will change the resistance according to the input. The voltage will change, and the ADC can then interpret that voltage change. After the ADC interprets the signal, it will produce a number corresponding to the input that will be recorded to the EEPROM located on the Basic Stamp. Interfacing the camera with the BalloonSat board depends on whether or not there is an option to operate the camera independently. In our case, the camera can operate without the BalloonSat board and requires no programming. Figure 9 describes this process as a high level schematic. Pressure Sensor Schematic Figure 14. High Level Sensor Interfacing The pressure sensor requires multiple components to work properly. Figure 12 shows these components, and how they are interfaced. The LM234 is a constant current source that provides a constant current of 1.5 ma to the circuit. The constant current source has the ability to act as a temperature sensor. An increase in internal temperature can mean a change in the current sent to the pressure sensor. Doing this ensures that only a change in voltage will be considered a change in pressure, and that an unintentional change in temperature will not be interpreted as a change in pressure. Simply adding two resistors and a diode to this circuit can fix this problem. The voltage decreases by about 2.2 mv every C for the diode, and voltage increases at about the same rate. This Team SABRE 20

28 allows this voltage change to cancel out; therefore, the change in temperature has no affect on the current going to the pressure sensor. The LM234 cannot do this without help from additional circuitry. The current is set by two resistors. The following formulas given in the datasheet were used to calculate the values of these two resistors V 0.134V A = R 1 = so R 1 = R A 1 After R 1 is calculated, plug it into this formula to find R 2. R 2 = 10R 1 R 2 = so R 2 = R 1 was calculated as 89.33Ω, and R 2 was calculated as Ω; however, the schematic has values other than the ones calculated. The reason for this is that standard value resistors were used, and this was as close to the values as we could get. The difference is negligible. The pressure input must undergo signal conditioning, and the circuit uses two integrated circuits containing three amplifiers to accomplish this. The reason for using the AD822 that contains two amplifiers is they are used as a buffer. The gain of these two amplifiers is one, so they have a function other than actually amplifying the signal. They help to isolate the signal so that as little current will be drawn away from the pressure sensor as possible and temperature will not have any unintended effects. After the signal reaches the AD822, it doesn t matter how much current is drawn, and the opamp has its own power being supplied. The AD820 that only contains one amplifier is the one that actually amplifies the signal. It has a gain of 30. During signal conditioning, the voltage range is amplified and shifted to match the voltage range of the ADC. The output voltage range of the pressure sensor is 0 mv-100 mv, and the input voltage range of the ADC is 0 V-3 V. This means that the 100 mv has to be amplified to 3 V (3000 mv). To do this, the gain has to be determined. Here is how gain was calculated. 3000mV = mV After the gain is calculated, the ratio of the resistors can be found. Here is how the ratio was calculated. R4 R R3 R3 Some other values of resistors can be used as long as the ratio is maintained. After signal conditioning, the voltage range of the sensor should be 0 V- 3 V the same as the ADC voltage range. We have already included values of the resistors. R4 and R6 are 300K V and R3 and R5 are 10K V. Notice the ratio is maintained at about 30:1. The difference from 29 to 30 is minor and can be ignored. Team SABRE 21

29 Temperature Sensor Schematic Figure 15. Pressure Sensor Schematic Like the pressure sensor, the temperature sensor also requires different components to work properly. Figure 11 shows these components and how they are interfaced. The LM234 is a constant current source, and it serves the same purpose as the one for the pressure sensor except 1 ma was used to calculate the value of the resistor used in the constant current source. This formula provided in the datasheet was used to calculate the value. VR R set = R set = I set I 1 bias 1mA ma 8 R set corresponds to R7 and R12 and those values were 68 Ω. The REF03 is a voltage reference that provides a stable 2.5V output to ensure that unintended variations in voltage will not be interpreted as a change in temperature. There are two 1N457 silicon diodes in the schematic diagram that will be used as the temperature sensors. The sensors only have a range of about 220 mv which means that the 220 mv has to be amplified to 3 V (3000 mv). A gain has to be determined just like with the pressure sensor. The gain was calculated to be 13.6, and the resistor ratio is A 643K Ω resistor and a 51K Ω resistor have been considered as actually values for the resistors. R 8 and R 9 will add up to give one value, preferably 643K Ω. R9 is a 620K Ω fixed resistor, and R 11 is a 10K Ω variable resistor which can be used to fine tune the resistance until it reaches 643K Ω. R 10 is the other important part of the ratio. It has the value of 51K Ω. R 11 doesn t play a large role in the gain because it such a small fraction of R 10. R 11 along with the REF03 plays a large role in setting the offset. Since the voltage reference provides 2.5V, and that would make the offset too large. Therefore, the 1K Ω variable resistor is added so that it can be set to a resistance that will decrease that voltage. The same process is used for the second temperature sensor, and the sensors will have the same values. The sum of R 13 and R14 will be 643K Ω, and R 15 will be 51K Ω. R 16, along with the voltage reference, will set the offset so that it will start at zero. Team SABRE 22

30 Figure 16. Temperature Sensor Schematic Control Electronics Figure 17. High Level Control Electronics Team SABRE 23

31 The basic stamp is responsible for controlling the entire BalloonSat board but specifically the ADC and the RTC. The basic stamp sends a command to the ADC telling it what channel to read and take measurements from. The basic stamp also communicates with the real time clock to get the time. The data then goes back to the basic stamp, and it records the data to the EEPROM. Control Electronics Schematic The BalloonSat contains major control electronics such as the basic stamp, the ADC, and the RTC. The numbered pins on the board represent the basic stamp which is the control center. Pins 4-7 are used to control the LEDs. The LEDs are basically used to indicate status. A program can be written that will light the LEDs when a particular action is taken. Pins 8 and 9 are connected to the EEPROM and allow data transfer. Pins are connected to the RTC. Pins are used for data transfer between the basic stamp and the ADC. Other pins on the basic stamp aren t being used. ADC channels 0-3 are used to interface sensors and other devices with the ADC. For our flight, channel 0 is used for the pressure sensor, channel 0 is used for temperature sensor A and channel 1 is used for temperature sensor B. A connection between the camera and the BalloonSat is not needed because the camera does not need to be controlled. On low resolution video, the camera is able to capture the entire flight. Figure 18. Control Systems Schematic Power Supply During prototyping and fabrication in the lab, a bench power supply providing 12V will be used. Figure 14 shows the battery sources that will be used during the flight. A battery pack will be constructed from two 6V Duracell Lithium battery cells. Lithium batteries are perfect to use because they are small, and have highest power to weight ratio. The battery pack will provide 12V power supply. 12V is exceeding the requirements for the BalloonSat, but the BalloonSat has a voltage regulator that de-rates the voltage to 5V. It was discussed that there will also be a direct connection from the battery pack to the prototyping area to provide voltage to the sensors, but the Team SABRE 24

32 space is very constricted. So there will be a direct connection from the 12V battery pack to the specified components in the sensor circuits. The camera will have its own battery source. Power Supply Schematic Figure 19. High Level Power Supply Figure 15 shows the schematic of the three power sources that will be used during flight. There will be a 3V battery pack directly connected to the camera because the rechargeable battery isn t capable of operating the camera for 4 hours. The 3V RTC BUB refers to the backup battery that will be attached to the BalloonSat board. This battery is responsible for keeping time even if the BalloonSat board is not powered. The 12V power supply refers to the Duracell battery pack constructed from two 6V battery cells that will power the BalloonSat board, the sensors, amplifiers and voltage reference. There will be fuse connected to protect the electronics from an overload. A voltage regulator is located on the BalloonSat board to lower the voltage to 5V because that is what the BalloonSat components can handle. Team SABRE 25

33 Figure 20. Power Subsystem Schematic Figure 21. Final Circuitry Team SABRE 26

34 4.3.5 Power Budget Component Voltage(V) Current (ma) Duration (H) Power (mw) Capacity (ma-hr) BalloonSat Camera Temperature Sensor Circuitry Pressure Sensor Circuitry Total Total Excluding Camera (Note: These are approximations- The power is questionable at this level) Table 3. Power Budget A 12V Duracell Ultra 245 battery pack made from two 6V batteries, 3V Energizer battery pack made from two 1.5V battery cells, and a 3V lithium button battery cell will be used during this flight. Figure 22. Picture of Batteries Power Supply Source ma-hr Required 2 6V Duracell Ultra 245 Battery V Energizer Battery cells 1500 Team SABRE 27

35 Derating of 6V Duracell Ultra 245 Battery Figure 23. Derating of Main Battery Pack Above are two graphs that show the service life (in hours) of one 6V Duracell Ultra 245 battery. The graph on the right shows the service life at different temperatures. At room temperature, the battery is able to last for about 90 hours at 5V, and at -20 C, it is able to last for about 30 hours at 5V. We use 5V because this information relates to one single battery which means that two of them together will yield 10V; this is enough voltage to power the BalloonSat and the sensor system. This information provides a derating factor of 1/3, and this factor can be used to determine approximately how long the battery is expected to last during the flight. Although this graph is measuring the service life of a battery providing 14 ma, and the BalloonSat and sensors require about 60 ma, the derating factor can be applied to the graph on the left. This graph measures discharge at room temperature. The blue line represents an estimation of the lifetime of the battery providing about 60 ma. The graph shows that at 5V, the battery has close to 15 service hours at room temperature. Applying the derating factor suggests that at about -20 C, the battery can last about 5 hours which is more than enough time. Derating of 1.5 V Energizer Battery Cell -21C Figure 24. Derating of Secondary Battery Pack Above is a chart that shows the discharge of a 1.5 Energizer Battery Cell. The total power that needs to be supplied to the camera is 2250 mw; however, the power that needs to be supplied by one Team SABRE 28

36 battery cell is about 750 mw. The capacity that needs to be supplied by one battery cell is about 2250 mw. At room temperature, a battery cell can supply 4000 mwh at a discharge of about 750mW. At 0 C, a battery cell can supply 3000 mwh at a discharge of about 750 mw. This information can be used to calculate a derating factor of ¼. This factor was applied and this discharge was estimated at 21 C and represented by the bold black line on the graph. According to the estimation, a cell can provide about 2150 mw. This is slightly below the needed 2250 mw, but take into account that the payload temperature will be approximately 17 C which means that it will lie between the 0 C and the 20 C curves. 4.4 Software Design Data Format & Storage Team SABRE data record consists of 8 bytes of data. Three of these bytes are reserved for ADC channels 0, 1, and 2, which is out pressure and temperature data. The time stamp makes up the remaining five bytes, month, date, hour, minute, and second. For each month, date, hour, minute, and second there are a set of nibbles that make up the bytes for the time stamp. As you can see in Table 4, two nibbles are required for each month, each date, each hour, each minute, and each second. The two nibbles consist of 10 s of data, and 1 s of data. For flight we are going to be collecting data once every 15 seconds, 4 times a minute, 240 times an hour, and approximately 960 times for the duration of our flight. In order for us to do this we need at least 7680 bytes of space on our data EEPROM. The data EEPROM has 8,192 bytes of storage space available, so our storage requirements fit within our space constraints. DATA RECORD 8 bytes = 1data record 1 data record every 15 seconds 4 data records per 1 minute 240 data records per 1 hour 960 data records per 4 hours 960 data records x 8 bytes = 7680 bytes Team SABRE 29

37 Description Data type size(bits) size(byte) 10's of months Nibble 's of months Nibble 's of dates Nibble 's of dates Nibble 's of hours Nibble 's of hours Nibble 's of minutes Nibble 's of minutes Table 4. Data Nibble Rates and Storage Requirements 's of seconds Nibble 's of seconds Nibble Temperature sensor A Byte 8 1 Temperature sensor B Byte 8 1 Pressure sensor Byte 8 1 TOTAL N/A 64 8 Table 4. Data Rates and Storage Requirements Team SABRE 30

38 4.4.2 Flight Software PRE- FLIGHT Figure 14 represents the pre-flight software for the SABRE experiment. The program will first initialize all variables, identify pin directions, and initialize the EEPROM pin address to 0. Defines Max address for storage checking decision later on in program. Next the program sets the error count to 0, and sets the EEPROM address to 0. By setting the EEPROM to 0 this lets the program know to start writing to the very first address on the EEPROM. The error count is for the decision that checks to make sure all addresses written to the EEPROM are $FF. Next the program prompts the user to input the hours, minutes, and seconds for the real time clock. The program then writes $FF to all addresses in the EEPROM. This is useful because it will enable the program to be able to find the first free address by searching for $FF in the event of a power failure. Next the program increments the address written to by 1 event size (8 byte) and then checks to determine if there is enough space to continue writing to the EEPROM. If yes the program loops and continues writing, if not the program then set the data EEPROM address to 0. Setting the EEPROM to 0 tells the program to read from the very first address on the EEPROM. The program then reads the data from the EEPROM and goes into a decision to check if the data being read is $FF. If the data being read is $FF the program then increments the read from address by 1 and checks if there is any more data to read. If the data being read is not $FF then the program adds 1 to the Error count, it displays the address of the error and it displays the word ERROR. The program then checks if there is any more data to read. If there is then the program loops back to read data from EEPROM. If there is no more data then the program displays the final Error count and sets the BASIC Stamp EEPROM address to 0. The program then ends. Figure 25. Flowchart of Pre-Flight Team SABRE 31

39 IN-FLIGHT This in- flight software is designed to be programmed before the flight. The program first defines variables, constants, and pin directions. Mux is the syntax for initializing the pin direction for the ADC. Next the program sets the data EEPROM address to 0; this designates the first data EEPROM address to be written to. The Real Time Clock will be set before running the In flight program therefore the hours, minutes, and seconds can be read and stored in variables. The program then sends the Mux address to ADC channel 0 (pressure sensor channel), which initializes the ADC to start reading data from the channel. ADC channel 0 then stores the data from the channel in pressure variable. The program then sends the Mux address to ADC channel 1 (Temperature sensor A channel), which initializes the ADC to start reading data from the channel. ADC channel 1 then stores the data from the channel in a temperature variable. The program does the same for channel 2 in the ADC; reads and stores in temperature variable. Next the program formats and writes the event to the EEPROM. As stated in the Principles of Operation section, sensors collect data every 15 seconds; therefore, it is necessary to add a 15 second delay in the program before continuing the loop. Next the write to address is incremented by the event size. The program then makes a decision; the program checks to see if there are 8 bytes of spaces available to write to. If there are at least 8 bytes available then the program loops back to read the time stamp. If there are not 8 bytes available the program is put in an endless loop. Figure 26. Flowchart for Inflight Software Team SABRE 32

40 POST-FLIGHT Figure 15 represents the post-flight software for the SABRE experiment. The program will first define variables, constants, and initialize pin directions. The I2C chip is the pin direction syntax for the EEPROM, so by writing this in my program I can direct data to or from the EEPROM. The program then sets the EEPROM address to 0; this lets the program know to start reading from the very first address on the board. Next the program reads and formats the event of data from the EEPROM. After formatting the data, it is then displayed to the serial debugging screen. An event is the space (in bytes) for a full set of data, and in this program, the even size is 8 bytes. The program then increments the address location by the event size and checks to see if there are any data events left (at least 8 bytes remaining). If there are at least 8 bytes (1 event) of data left on the EEPROM then the program loops back to the reading stage, if not then the program ends.44 Figure 27. Flowchart for Postflight Software Team SABRE 33

41 ADC testing software The ADC testing software is identical to the flight software. The only difference is that the ADC testing delay is not fixed while the flight pause is pre-determined and fixed. Figure 28. ADC Testing Team SABRE 34

42 Figure 29. Subroutines Team SABRE 35

43 Figure 30. Setting the RTC subroutine Team SABRE 36

44 4.5 Thermal Design During the course of the Balloon flight the payload is going to travel through the Troposphere, the Tropopause, and the Stratosphere. While traveling through these levels in the atmosphere our payload will encounter temperatures ranging from approximately -60 C to 20 C. The payload will also have to encounter pressures ranging from approximately 100,000 pascals to 1000 pascals. In addition our payload box will encounter small amounts of shortwave radiation, also called albedo. Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. The balloonsat s thermal operating range is from -40C to 70C. I found this by looking at the major components of the balloonsat and determining the narrowest thermal operating range. Coincidentally the Basic STAMP, the ADC converter, the EEPROM, and the Real Time Clock all have the same thermal operating range so it was easy to determine the narrowest thermal operating range. We have looked at numerous temperature sensors; Table 5 shows the prospective temperature sensors for our experiment and their thermal operating range. Temperature sensor Operating Temp. Storage Temp. Min C Max C Min C Max C Series Thermistor Series Thermistor NTC Semiconductor Thermistor KX222J2 Precision interchangeable thermistor Table 5. Comparison of Various Temperature Sensors We have also looked at numerous pressure sensors; Table 6. shows the different pressure sensors and their thermal operating ranges. Pressure sensor Compensated Temp. Operating Temp. Min C Max C Min C Max C Model 1230 UltraStable PX DV Omega n/a n/a 0 70 SM5651 Silicone Microstructures inc Table 6. Comparison of Various Pressure Sensors To ensure that our payload stays within its thermal operating range we have come up with a few possible solutions. The payload box itself is being constructed from material that is used to insulate the walls and roofs of family homes. The digital camcorder has an LCD display that gives off a substantial amount of heat which would keep the payload warm. In addition the current running through though the components in the payload produces heat that conducts throughout the payload box and helps keep the payload warm. Team SABRE 37

45 Insulation Power Surface Material Inner Outer Emissivity Conductivity Absorbtion Thickness area Temp (m) (W) (m) Temp C C (W/mK) Aluminum foil Aluminum foil Aluminum foil Aluminum foil Aluminum foil Table 7. Thermal Calculations The temperature at time constant is -2.6 C. In our calculations we were able to determine the initial temperature and the steady state. The initial temperature depends on what time we fly in the morning. We assume it to be 25 C in our calculations. Also the steady state temperature is -65 C passing through the isothermal layer (Tropopause). With both values we were able to find our time constant. Using our results we developed a thermal chart. Using the chart below we will be able to get a basic notion on the different temperature ranges during flight and at what altitude the balloon will encounter in similar conditions. Knowing that the balloon will travel 1,000ft/min, we can basically use the chart to see where the temperature drops to a steady state. Team SABRE 38

46 Table 8 Thermal Chart Time (Mins) Temp (C ) Figure 31. Thermal Dynamics Table 8. Thermal Chart Team SABRE 39

47 4.6 Mechanical Design A Hexagonal Styrofoam enclosure will be constructed for the main structure of the payload. The type of material used for the structure will be polystyrene foam (Styrofoam ).During flight the payload will have to withstand isothermal conditions, be able to remain the same while ascending to high altitudes and descending back to earth, and maybe strong winds. Also, the Styrofoam will be durable to protect inner parts. It also has to be a certain mass, so a weight budget is necessary and imperative. It will be designed to survive any possible encounters during flight. Figure 32. Mechanical Design Figure 33. Payload Structure Team SABRE 40

48 4.6.1 External Structure Our external payload design will look like a hexagon. The height will be approximately 19 cm. The plan is to insert two holes in the exterior of the structure, to place one of the two sensors that will accurately read the temperature variations of the atmosphere. On the other hand, there will be two other holes inserted vertically onto the lid of the container. The holes will be 17 cm across from each other. With those insertions on to the lid, strings will be attached to the Balloon strings. It will be easy access the interior of the payload with an inset lid, which will be very feasible for access. Furthermore, to make sure the lid is securely closed; it will also be taped down but not tightly compressed Internal Structure Figure 34. Picture of External Structure Once the lid is open you will have sight of the interior part of the payload. The interior is home to the data archive system, control system, and power supply. The BalloonSat will be placed against the wall of 3 centimeters thick foam which will be able to slide in and out of the payload diagonally. Right below the BalloonSat will be the batteries that will also be set into the same foam. The camera will be on the opposite side of the foam tilted 10º down looking out of a hole with a radius 2.62 cm. The way the camera will be angled will aid to get a better view orientation of atmospheric conditions. The Camera slot will be extruded in a way that we ll be able to place the camera within the slot and make it tilt 10º down. The purpose of the Styrofoam is to hold all components in place and keep the interior well insulated during flight and descending back to earth for a safe landing. With a safe landing, we can extract our data and start on our post-flight documentation. Figure 35. Picture of Internal Structure Weight Budget A hexagonal Styrofoam structure will be the design for the container of our payload. It will be made from polystyrene Styrofoam which appears to be light and manageable. The Styrofoam material weighs roughly.2 grams per square inch of 2 cm thick foam. The goal is to build a payload that will be able to fit within the weight constraints. The Maximum mass of the full payload will be between 400 g and at most 500 g. Team SABRE 41

49 5.0 Payload Development Plan Table 9 Table 9. Weight Budget Table 10 Weight Table Weight Budget Uncertainty (g) Components Weight (g) BalloonSat BalloonSat Battery pack Camera Battery Pack (Wires/cables/sensors/screws/boards) BalloonSat with extra sensor board Camera Box/insulation Total Table 10 Weight Table Uncertainty (g) Components Weight (g) BalloonSat BalloonSat Battery pack Camera Battery Pack (Wires/cables/sensors/screws/boards) BalloonSat with extra sensor board Camera Box/insulation Total There are significant steps that needs to take place in order to have a successful transition from the PDR to CDR. A complete payload needs to have a full system design. System design is the overall design process. This process includes: Electrical, Software, Mechanical and Thermal designs. Each one plays an essential role that aids in a complete payload. Each design takes a certain amount of time to complete. First, there has to be a determination of what sensors that are needed for our experiment. For example, we need one sensor to measure the exterior temperature and the other to measure pressure levels. Moreover, the sensors, sensor interface, controllers, data acquisition, storage, and most importantly the power supply is required for the electrical design. Furthermore, we need to prototype our circuits on a solderless breadboard to test if they work prior to integrating the circuits onto the BalloonSat. On the other hand, it is important that we know what types of sensors Team SABRE 42

50 required for the project, so that we read and get accurate results. This will give us an idea of how much power is necessary to complete our experiment. Second, the flight software needs to be prompt and ready for the team to utilize to clock for preflight. This will lead to the decision of how much memory we will need to get enough data for the actual flight. Third, is the prototyping of the structural components, this process is the Mechanical design. The basic notions for the mechanical design have to be put in plan in order to begin the construction of the payload. Fourth, the thermal design is another key component that will ensure that our interior is well insulated during flight. Last, is the shock test to check for durability and to see if we need to modify the structure to avoid any possibilities of damage during flight. All the possibilities will be further discussed in risk management in another section. 5.1 Electrical Design Development Completing the electrical design requires planning. Sensors have to be finalized, schematics have to be designed, and values of components have to be designated. In order to finalize sensors, we will use datasheets to investigate the different properties of the sensors including operating temperatures and linearity. The right sensor will be chosen considering the specifications of the sensors. We will use the high level system diagrams as a guide to create schematic diagrams. Formulas can be used to get the values of certain components; however, these may not be exact numbers. The precise values may not be known until prototyping is complete. An estimated power budget can be calculated, but only based on what is known. It cannot be exact until all of the major components and their values are specified. At this point, capacity and power formulas can be used for the power budget. 5.2 Software Design Development Converting PDR flowcharts to CDR-ready flowcharts requires the inclusion of sub-routines will provide programmers with more detail about software language when written in BASIC Stamp. In addition to sub-routines, initializations such as variables, constants, and pin directions are important to include because they give the programmer insight into their variable limit. Variable initialization would include anything from I2C Pin direction to MAX_address variable, which the program uses for event data checking on the EEPROM. The programmer must include the delays that correspond to data collection intervals because it is how the data record is produced. Debugging statements and programming comments must be included in the software design to ensure that the program functions properly. 5.3 Mechanical Design Development In order to get to our final mechanical design, we need to get set dimensions. With these set dimensions we should know where to start and know how to construct our payload. Once the Team SABRE 43

51 Styrofoam is sliced and divided into different shapes with their exact measurements. We will be able to have a starting point to construct our payload. We need six sides with a width of 9.5 cm and a height of 19 cm for each side. All six sides will be mitered to make it feasible to construct and glue the sides together. Before the sides are glued together the insertions for the two strings will be done in a way that the two strings will be 17 cm across when the final construction is complete. On the other hand, to construct a full payload a weight table will have to be done with the exact masses of each component. Knowing the exact weight of each component will aid in building a certified and flight ready payload. Prototyping is very essential to the final design. We had to construct a prototype to get an idea where we can place our components. Also, get a notion for the dimensions we should include to the final hexagonal structure. Within the payload there will be 3 cm thick foam placed in the middle splitting the hexagon in half. On one side of the foam, there will be two slots within the foam to plant the BalloonSat and battery pack. On the other side of the foam, there will be a camera placed in a slot that will be extruded into the foam, and the camera will be tilted 20 degrees down to get a better view through a hole with a diameter of 5.24 cm. On the other hand, there will be another hole inserted adjacent to the BalloonSat in a wall for one of our two temperature sensors can be drawn through. Last, we will make an inset lid for the top so we can get easy access to the interior of the payload. 6.0 Payload Construction Plan Using our set dimensions we ll build the external structure. Once the structure is built, it will be time to focus on the key components, meaning the component layout within the interior of the payload. The components will be placed into their separate slots into the middle foam insert. Wires will be soldered to the battery pack and BalloonSat. Before proceeding on to anything else, wires will need to be checked to see if there is a proper connection. All connections need to be carefully verified so that the battery pack can supply 12 volts to the BalloonSat. On the other hand, the sensors will be soldered to a separate circuit board which will be interfaced with the BalloonSat through the ADC channels. After, the components are set into the payload to check if they fit in their locations. We can take the camera out and begin testing. With the Balloonsat and the battery pack still inside we ll start to test. We ll be doing the thermal, shock, and low-pressure tests. The Payload has to undergo these test assure our components will withstand the possible and expected atmospheric conditions. As soon as we concur that we ve done all the testing that s significant for flight, it will be time to analyze for pre-flight data. With our pre-flight data analyzed we will be able to avoid possible risk and justify that our payload is ready for flight. 6.1 Hardware Fabrication and Testing The mechanical aspect of the project will be first. The payload will need to be in the process of construction. While the mechanical process is being worked on, both software and electrical person will need to collaborate to get the components prompt and ready for our payload. The prototyping of sensors from the solderless breadboards will be deprived from the electrical person. The software person has to be dependent for the time being. In order for the software person to start programming, the electrical person will have to have the sensors soldered onto a separate board which will be interfaced with the BalloonSat. Moreover, also determine or verify that there is good connection from the battery pack to the BalloonSat. Once all the soldering is done, the Team SABRE 44

52 software person will now be able to load programs onto the BalloonSat to verify that it works. Last, we will test our payload using the shock, thermal, and low-pressure testing procedures. 6.2 Integration Plan When assembling our subsystems into our working payload, there is a specific order that we need to pay close attention to. Our subsystems are: mechanical, electrical, power, control, and sensors. The integration process will start with mechanical and all the construction required. Our payload will need to physically be interfaced with the external environment. Once the mechanical subsystem is implemented, we can use its implementation to go to the next step. The second step is the insulation process which falls under the thermal subsystem. The thermal subsystem is essential because it will avert or prevent the components from getting too cold while going through the Tropopause. Both pressure and temperature sensors will be soldered to and integrated with the BalloonSat. The control subsystem is chiefly the EEPROM which is integrated onto the BalloonSat already. The power subsystem consists of the power supply which will provide 12 volts and be connected to the control unit (data archive). Also, the sensors will be integrated to the control subsystem. To test all subsystems to ensure everything is appropriately integrated during flight, we will test in environments similar to the different atmospheric levels. We ll have to test in low pressure and cold conditions. As an end result, this will also aid to the determination that the circuits and solder joints we re integrated suitably. 6.3 Flight Software Implementation and Verification In order for the flight software to be implemented the flight software has to be written in the BASIC Stamp programming software. A series of loops and sub routines are required to implement data recording every 15 seconds in the pay load. The data recording consists of 6 bytes of data, written to the EEPROM every 15 seconds. The data recording will be implemented with a loop in the program code. This loop will run until there are no more available addresses to write to. The program will be written the Balloonsat board that will be used for the flights to ensure version control. After writing the software in the BASIC Stamp we will perform syntax checks and variable checks to make sure our program will run properly. If our program meets BASIC Stamp syntax and variable requirements it will then be programmed to the Balloonsat board. After being programmed, shock and thermal test will be conducted on the payload. If the data recorded matches the format for ADC data then it can be concluded that the program is suitable for flight. 6.4 Flight Certification Testing During the course of the Balloon flight the payload is going to travel through the Troposphere, the Tropopause, and the Stratosphere. While traveling through these levels in the atmosphere our payload will encounter temperatures ranging from approximately -60 C to 20 C. The payload will also have to encounter pressures ranging from approximately 100,000 pascals to 1000 pascals. In addition our payload box will encounter small amounts of shortwave radiation, also called albedo. Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. Also during the descent of the balloon flight, the payload will hit the ground at approximately 8 m/s. I approximated this number by combining the formula for Potential energy and Kinetic energy. I used a testing scenario of dropping the payload box from 10 feet which is Team SABRE 45

53 the equivalent of the payload returning to the ground with a parachute. To ensure that the payload will function in these conditions we will run thermal and shock test. Shock tests will be conducted by dropping the payload from two story building while collecting data. If the data can survive the shock (can still be read accurately) then the payload passes inspection. Also Cold test will be conducted by putting the payload in dry ice. If the data collected is accurate and can be read then the payload passes that test as well System Testing Procedures Shock Test Checklist Connect the test battery pack to BalloonSat board. Connect BalloonSat board to computer using USB serial port. Run ADC testing program. Disconnect BallonSat board from computer. Turn camera on and begin recording. Place BalloonSat board into payload box. Assure that all components are secured in the payload in the designated places. Shake payload to check if the components move within the Payload. (Components should not move) Secure payload box top in place. Throw payload box from the top on the stairs located in front of the physics building. Recover payload box. Remove BallonSat board from payload box. Connect BalloonSat board to computer using USB serial port. Run post-flight program. Disconnect battery pack. Open Term 232 software. Reconnect battery pack. Save data as text file. Transfer data to Excel. Use calibrations to convert ADC counts to pressure and temperature data. Plot each value vs. time in Graphical Analysis software. Thermal Test Checklist Analyze actual flight profile. Determine approximate time frames the payload will experience a major temperature change. Determine the materials needed to represent different temperature changes that occur during flight. Team SABRE 46

54 Determine how to utilize these materials to simulate an actual flight. Move Dry ice container next to the fridge. Connect the test battery pack to BalloonSat board using the USB serial cord. Run ADC testing program. Disconnect BallonSat board from computer. Turn camera on and begin recording. Place BalloonSat board and camera into payload box. Ensure that all components are in their appropriate places and are secure. Secure payload box top in place. Enforce the proposed process for simulating the actual flight. Remove BalloonSat board from the payload box. Connect BalloonSat board to computer with USB serial cord. Run post-flight program. Disconnect battery pack. Close BASIC Stamp software. Open Term 232 software. Reconnect the testing battery pack. Save data as text file. Transfer data to Excel. Use calibrations to convert ADC counts to pressure and temperature data Plot each value vs. time in the Graphical Analysis software. Proposed Process for Simulating the Actual Flight (Thermal Testing) Let the BallonSat collect data at room temperature for 20 minutes. Place payload box into fridge for 20 minutes. Move payload box to freezer for 20 minutes. Move payload box to container with dry ice for 20 minutes. Move payload box to freezer for 25 minutes. Move payload box to to dry ice for 10 minutes. Move payload box to freezer for 10 minutes. Move payload box to refrigerator for 10 minutes. Remove payload box from refrigerator and allow data to be collected at room temperature for an additional 10 minutes. Pressure Test Checklist Analyze actual flight profile. Determine the increments of altitude that will be used. Determine the length of time that will be spent within each range. Create vacuum testing flight profile using this information. Connect the BalloonSat board to computer with USB serial cord. Team SABRE 47

55 Run ADC testing program. Disconnect BallonSat board from computer. Turn camera on and begin recording. Place BalloonSat board and camera into the payload box. Ensure all components are in their appropriate places and are secure. Secure payload box top in place. Ensure the glass cover of the vacuum is as tight on the vacuum platform as possible. Ensure the pressure gage is connected to the vacuum. Turn on the vacuum. Follow the Vacuum Flight Profile. Remove payload box form vacuum. Remove BalloonSat board from payload box. Connect BalloonSat board to computer with USB serial cord. Run post-flight program. Disconnect battery pack. Close the BASIC stamp software. Open Term 232. Reconnect battery pack. Save data as text file Transfer data to Excel. Use calibrations to convert ADC counts to pressure and temperature data. Plot each value vs. time in the Graphical Analysis software. Vacuum Testing Flight Profile Time (min) *Pressure (torr) Pressure (mb) Ascent Team SABRE 48

56 Descent * The vacuum gage being used measures pressure in torr; we are more familiar with mb. Table 11. Pressure Flight Profile System Test Results Vacuum Test The pressure sensor data is expected to vary when a pressure test is being performed; however, the other sensors should not be affected drastically by a change in pressure. Below is a plot that shows how the pressure data varied during testing that lasted for about 2 hours and 30 minutes. Team SABRE 49

57 Figure 26. Variation of Pressure Data During Vacuum Testing The following figures are the plots for temperature sensor A and B during the pressure testing. It is expected that the temperature sensor will not vary much. The fact that they barely change proves that they can function under low pressure. Temperature sensor A had a variation range of about 4 C, and temperature sensor B had a variation range of about 3 C.. Figure 27. Variation of Temperature Sensor A Data during Vacuum Test Team SABRE 50

58 Figure 28. Variation of Temperature Sensor B Data during Pressure Test Thermal Test It is ideal that temperature does not affect the pressure sensor because it will then affect the data recorded. The plot of Pressure vs. Time shows that the pressure data barely changed during the thermal testing that lasted for about 2 hours and 30 minutes. The temperature got as low as about - 50 C. The fact that the data stayed constant proves that the pressure sensor can function in this low temperature range. Another thing to keep in mind is that the sensor will not actually experience temperatures this low during flight. Team SABRE 51

59 Figure 29. Variation of Pressure Data during Thermal Testing Of course a change in temperature should affect the temperature sensor, and the following plots of the two temperature sensors show that they were measuring various temperatures during the thermal test. Figure 30. Variation of Temperature Sensor A Data during Thermal Testing Team SABRE 52

60 Figure 31. Variation of Temperature Sensor B Data during Thermal Testing Shock It is ideal for the sensors to measure properly even when the payload may be put under stress. The pressure data collected during the shock test indicates that the impact on the ground had practically no effect on the pressure sensor. Below is a plot of the data collected during testing which lasted for about five minutes. Figure 32. Variation of Pressure Data during Shock Test Team SABRE 53

61 Data collected during the shock test for the temperature sensors also suggests that it had little to no effect on the temperature sensors. The little variation in temperature is most likely due to leaving the cool building and going outside where the temperature is higher. Figure 33. Variation of Temperature Sensor A Data during Shock Test Figure 34. Variation in Temperature Senor B Data during Shock Test Team SABRE 54

62 7.0 Mission Operations The following sections will describe our plans during launch, flight, and subsequent data analysis. 7.1 Pre-Launch Requirements of Operations A series of system testing has to be done before the payload gets clearance to make a flight. Software has to be tested to ensure that it is writing properly. The software must successfully command certain components to read and write data to the EEPROM in all extreme conditions that will be experienced inside the payload box. The sensors must be calibrated so that a formula can be determined that will convert ADC counts to actual temperature and pressure values. When doing software testing and sensor calibration, a separate battery pack will be used. This battery will be discarded, and a new battery will be inserted just before launch. A checklist can also be made to ensure that all tasks are complete before launch Calibrations The sensors have to be calibrated. A 1N457 diode will be subject to different temperatures. Dry ice and an antifreeze solution will be used to provide the lowest possible temperature to take measurements. Room temperature will be used as another data point as well as water at different temperatures. These temperatures will be measured by a thermometer before submerging the diode in. These temperatures will be plotted against their corresponding ADC count, and a best fit line can be drawn through the data points. The equation of this best lit line will be the formula that will be used to calculate a temperature for a corresponding ADC count. The coldest temperature will have the highest ADC count, and the hottest temperature will have the lowest ADC count. This calibration can be used for both of the 1N457 diodes. The pressure sensor must be calibrated as well. A vacuum will be used to get an ADC count for the lowest pressure to get an ADC count for the lowest pressure which is close to 0 psi. We can also set the vacuum to various pressures to get additional pressure data. These pressures will be plotted against their corresponding ADC count, and a best fit line can be drawn through these data points. The equation for this line is the formula that will be used to convert ADC count to actual pressure values. The lowest pressure will have the lowest ADC count, and the highest pressure will have the highest ADC count Calibration Procedures Calibrating the Temperature Sensor Ensure that the BalloonSat board and sensor circuit boards are interfaced. Connect power supply. Connect BalloonSat board to computer with a USB to serial cord. Take temperature of the room. Record ADC count for that temperature. Place equal parts ice and water into a container. Determine which thermometer will be used by seeing which one measures a temperature closest to zero. Place sensors into water. Team SABRE 55

63 Record ADC count for 0ºC. Put the antifreeze solution in metal container. Place dry ice in testing container making sure not to fill it completely. Place metal container in the testing container with dry ice. Fill gaps with more dry ice. Place sensors into solution. Ensure that the thermometer is in the same area of the sensors. Take measurements as temperature falls. Take note of corresponding ADC count for each temperature. Put dry ice inside of container with the antifreeze to speed up the fall of the temperature. Continue taking measurements as temperature falls. Continue taking note of corresponding ADC count for each temperature. Make a plot of temperature vs. ADC count in graphical analysis. Draw a best fit curve and get equation This equation can be used to get an ADC count for a particular temperature. Calibrating the Pressure Sensor Ensure that the BalloonSat board and sensor circuit boards are interfaced. Connect power supply. Connect BalloonSat board to computer with a USB to serial cord. Determine what pressure gage will be used. Use a tube to connect the vacuum to the sensor. Set the lowest and highest ADC count that will represent the lowest and highest pressures. Bring the pressure as low as possible. Increase pressure in increments of 1 torr until you reach 10 torr. Take note of corresponding ADC count for each pressure. Increase pressure in increments of 10 torr until 760 torr is reached. Take note of corresponding ADC count for each pressure. Make a plot of pressure vs. ADC count using graphical analysis ensuring that torr is converted to millibar. Draw best fit curve and get equation. This equation can be used to get an ADC count for a particular pressure Calibration Results For the pressure sensor, we were able to get to a pressure as low as about 2 torr, which is about 3 millibars. We set the resistors so that the ADC count for this pressure is 5. By graphing these pressures against their corresponding ADC count, we were able to obtain an equation that will convert ADC counts to actual pressure values. The graph came out to be linear and this is the equation that represents the best fit: Pressure = (4.101 ADC count) Below is a chart of the actual data obtained and the corresponding graph. Team SABRE 56

64 ADC Counts Pressure in Torr Pressure in Millibars Table 11. Pressure Sensor Calibration Data Team SABRE 57

65 Figure 35. Pressure Sensor Calibration Plot Team SABRE 58

66 For the temperature sensor A, we were able to get to a temperature as low as about -54ºC and as high as about. By graphing these temperatures against their corresponding ADC count, we were able to obtain an equation that will convert ADC counts to actual temperature values. The graph came out to be linear and this is the equation that represents the best fit line: Temp = ( ADC count) Although we didn t experience the full temperature range that the payload will experience, we were able to interpolate the remaining data points. Below is a chart of the actual data obtained and the corresponding graph. ADC Counts Temperature in C ADC Counts Temperature in C Table 12. Temperature Sensor A Calibration Data Team SABRE 59

67 Figure 36. Temperature Sensor A Calibration Plot Team SABRE 60

68 For the temperature sensor B, we were able to get to a temperature as low as about -54ºC and as high as about. By graphing these temperatures against their corresponding ADC count, we were able to obtain an equation that will convert ADC counts to actual temperature values. The graph came out to be linear and this is the equation that represents the best fit line: Temp = ( ADC count) Although we didn t experience the full temperature range that the payload will experience, we were able to interpolate the remaining data points. Below is a chart of the actual data obtained and the corresponding graph. ADC Counts Temperature C ADC Counts Temperature C Table 13. Temperature Sensor B Calibration Data Team SABRE 61

69 Figure 37. Temperature Sensor B Calibration Plot Pre-Launch Checklist 24 Hours Before Launch Remove testing battery pack Connect power supply Run pre-flight program Test components for operational status Team SABRE 62

70 Place components inside payload box Use balloon tracking to get the most updated anticipated flight profile Day of Launch Insert flight battery pack Ensure all components and secure and in place Secure the top of payload Launch Balloon Recovery Recover payload box and remove components Save data from EEPROM Run post-flight program Data analysis 7.2 Flight Requirements, Operations and Recovery The software is expected to command specified components to read data and write to EEPROM for the entire flight which is about 3 or 4 hours. The EEPROM as well as the SD card for the camera must have enough memory to store information for the entire flight. The BalloonSat must be powered for the entire duration of the flight so that data can be read and stored to EEPROM; the camera must also be power for enough time to capture video of the entire flight. This means that the battery packs must last for at least 3 or 4 hours. The GPS tracking system must be used during flight so that position as well as altitude of the balloon can be known during flight. We will also use the GPS system as well as a device that will make beeping sounds to help locate the balloon after landing. 7.3 Data Acquisition and Analysis Plan Ground Software To download the data from our payload we will use the post flight data software. The post flight software must be loaded onto the BASIC Stamp using the BASIC Stamp editor. The post flight software reads from the data EEPROM after initializing the EEPROM address to zero, and then the data is displayed to the BASIC Stamp debugging serial screen. Term 232 will then be used to transfer data from the debugging screen to Microsoft Excel. Term 232 saves the flight data to an event formatted file. To view the data collected from the Digital Video Camera we will use Microsoft media player. During flight, the video data will be stored on a SD card. We will retrieve the SD card and insert the card into the laptop and import the data into Microsoft media player. With the video data we will then analyze the data with our temperature data and time stamp to see the effects of albedo. Team SABRE 63

71 Figure 38. Data Analysis Flowchart Ground Software Implementation and Verification In order for the Ground Software to be implemented BASIC Stamp programming software, Term 232 software, Microsoft media player software, Microsoft Notepad software, Graphical analysis software, and Microsoft Excel software will be used. The Post flight software will first be ran to retrieve all data events from the data EEPROM. Once all data is retrieved from the data EEPROM, the Term 232 will be used to transfer EEPROM data to notepad. After declaring the proper Com port in the Term 232 software, the BASIC Stamp debugging serial screen data is displayed in the Term 232 editor. The editor then opens and saves the data in Microsoft Notepad. Using calibrations taken during calibrating the ADC counts will be converted using the Microsoft Excel Software. The equations used for calibrations will be programmed into the excel cells; therefore, by inserting the ADC counts into the excel spreadsheet we can get converted temperature and pressure data. The data is then taken from excel and plotted in graphical analysis to analyze the pressure and temperature curves against altitude. After getting our flight profile from the temperature and pressure plots, the data will then be plotted in excel against various flight profiles. For analyzing the Digital video data the SD card will need to be removed from the camera and inserted into the laptop for analyzing. The video data will then be imported and opened using Microsoft media player. The video time stamp will then be taken from the data and the duration of the video will be used to generate the rest of the data time stamp. Video data will be compared to temperature data taken at various times. Our observations will then be noted and documented for presentation Data Analysis Plan The data collected from the flight will be need for data analysis, as well as the data from the PACER APRS. The data from the PACER APRS contains altitude with a time stamp. By recording the data events on the payload with a time stamp we are able to synchronize the payload with PACER APRS s, and produce altitudes for our data events. Once the APRS altitude is matched with our event timestamps, they will be used to plot our temperature and pressure data against it. The data collected from the payload will be converted from ADC counts into pressure and temperature data using the Calibration excel spread sheet. The Calibration excel spread sheet will consist of the equations developed from our calibrations to convert ADC counts to pressure and temperature data. After retrieving data from the file created using Term 232 the data will be inserted into the Calibration excel spreadsheet and converted into pressure and temperature. The Temperature and pressure data will then be plotted against the altitude data taken from the PACER APRS and a profile will be created. The profile will then be plotted and compared to various other flight profiles for variances in data. For analyzing the Digital video data the SD card will need to be removed from the camera and inserted into the laptop for Team SABRE 64

72 analyzing. The video data will then be imported and opened using Microsoft media player. The start time of the video will be synchronized with the PACER APRS and noted accordingly. After retrieving the video data from flight we will have a video duration time stamp. By adding the duration of the video with the video start time we will develop a full video time stamp, and this will allow us to properly analyze video data to flight data. Video data will be compared to temperature data taken at various times. This will help us determine what land masses and clouds are contributing to the albedo affecting our payload. Our data observations will then be noted and documented for presentation. 8.0 Project Management Before every major deadline, the team SABRE will meet as a group to discuss what tasks needs to be done and in what time frame it has to be completed. Dr. Sinha is the Project Manager with final authority on job delegation. The complete documentation has to be submitted to him for his approval before it gets submitted. All team members must give him the documents they are working on for integration into the final version of PDR, CDR and FRR at least 24 hours before the final deadline. Ms. Ashle Perry is the team leader who will ensure smooth flow of work and completion of tasks delegated to each member in a timely fashion. The team SABRE will meet every weekday at 9:00 in the morning in the conference room which will be presided by one of the staff member of the PACER team. This will ensure any that there will not be any possibility of misunderstanding among the team members. Team SABRE 65

73 8.1 Organization and Responsibilities Team Member Atin Sinha Lead Role Responsibilities Phone Number Address Project Manager Finalize all documents for accuracy of statements, figures, tables and consistency in formatting. (229) Ashle Perry Team Leader Electrical Ensure that all electrical aspects of the project are taken care of including the circuit design and fabrication. Being team leader means making sure that task are delegated and completed. (229) Nedgby Marcelin Mechanical Ensure that all details dealing with the payload box itself are worked out including dimensions and shape. (305) Jeremy Robinson Software Ensure that all of the details dealing with programming are covered including the programs that control the hardware. (404) Table 14. Organization Chart Team SABRE 66

74 8.2 Configuration Management Plan During this project whenever changes in mechanical, software or electronic design are need, they will be conveyed to the team members during the team meetings; The person in charge of documentation will being in charge of documenting these changes. In addition these changes will be labeled by group, date, and lead to ensure version control. 8.3 Interface Control All changes to the software system, electrical system or payload system will be addressed at the meetings and the document lead will be in charge of documenting the changes. In addition it is the project manager s responsibility to update the other team members on the different area interfaces. Team SABRE 67

75 9.0 Master Schedule 9.1 Work Breakdown Structure (WBS) WBS Elements Estimated Time 3 Electronics 3.1 Electronics Design Detailed Circuit Design & Description 2 days Sensor selection (Datasheet) 1 day Electrical Parts Selection 1 day Power Supply & Power Budget 1 day Electrical Schematic Drawing 2 days 3.2 Electronics Prototyping & Development Develop Prototype Circuit 4 days Final Values for Components 2 days Finalization of Power Supply 1 day Schematics of Sub-systems 2 days Implement Prototype Circuit Interface to Power Supply 1 day Control Interface 1 day Test Prototype Circuit 2 days 4 Software 4.1 Flight Software Design Flowchart 1 day Software Design 3 days Data Format & Storage 2 days 4.2 Flight Software Prototyping & Development Data Acquisition and Flow Control 2 days Develop Prototype Software 4 days Testing and Validation 2 days 5 Mechanical 5.1 Mechanical Design Mechanical Layout Drawing 2 days External Structure 1 day Internal Structure 2 days Weight Budget 1 day 5.2 Mechanical Prototyping & Development Thermal Design 1 day Component Layout 3 days Final Mechanical Drawing 3 days Weight Table 1 day Total Project Estimate till CDR Table 15. Work Breakdown Structure 43 days Team SABRE 68

76 9.2 Staffing Plan The lead persons responsible for the major tasks are detailed below: Atin Sinha Project Management Master Schedule, Timeline and Milestone Review and finalize document preparation Ashle' Perry Team Leadership Electrical Circuit Design & Drawing Circuit Prototyping & Testing Nedgby Marcelin Science Requirements Payload Development Plan Thermal Calculation Weight Management Mechanical Drawing and Fabrication Jeremy Robinson Software Design and Integration Software Prototyping, Testing, Validation Data Processing and Analysis Plan Development Team SABRE 69

77 9.3 Timeline and Milestones Figure 39. Timeline and Milestone for the Project High Altitude Imaging and Atmospheric Data Collection Team SABRE 70

78 Figure 40. Detailed Breakdown of Tasks between PDR to CDR Team SABRE 71

79 Figure 41. Detailed Breakdown of Tasks between CDR to Science Presentation Team SABRE 72