SPHERES CDIO CDR Presentation CDR. Critical Design Review. November 23, 1999

Transcription

1 CDR Critical Design Review November 23, 1999

2 Outline Objective & Motivation Systems Overview Description, Requirements, Design Margins Subsystem Descriptions Structures, Propulsion, Metrology, Power, Avionics, Communications, Software Systems Integration Process, Integrated Prototype Tests Program Plan Hardware Procurement, Schedule, KC Ops Summary

3 Objective Program Objective To develop a testbed for the validation of metrology, formation flying, and algorithmic control between multiple autonomous satellites with six degrees of freedom, in a microgravity environment SPHERES Concept

4 Motivation SPHERES will allow testing of enabling technologies, validation of design process Relative attitude control and station-keeping between satellites Re-targeting and image plane filling maneuvers Collision avoidance and fuel balancing algorithms Algorithmic design, initialization, and de-bugging of iterative development processes Array geometry estimators Terrestrial Planet Finder TechSat 21 ST-3

5 CDR Purpose Familiarize audience with SPHERES design Prove SPHERES design supports testing of enabling technologies Autonomy Metrology Formation control algorithms Show analysis and experimentation results to support proof

6 Systems Overview

7 System Description 3 independent free flying SPHERES Laptop control and data collection station

8 System Overview Propulsion CO 2 Compressed gas system Power and Avionics Batteries, C40 and Tattletale Processors Software & Communications RF Ethernet Hierarchy Token Ring Protocol Metrology Inertial Navigation System IR/Ultrasound GPS-like system Structures Polyhedral truss and shell assembly made of plastics, metals, and alloys

9 General Specifications Diameter 0.2 m Mass 3.4 kg Max acceleration Linear: 0.17 m/s 2 Angular: 3.5 rad/s 2 Battery Life min Power 6.2 W Baud Rate bps Metrology Resolution 2.0 cm Tank Life Ranges from 20 s - 30 min

10 Systems Requirements Top level requirements for SPHERES program Test enabling technologies Distinct satellites that interact to maintain commanded position, orientation, and direction Interchangeable control algorithms Data acquisition and analysis Demonstrate key formation flying maneuvers Demonstrate autonomy and status reporting Adaptability to future formation flying missions Maintain compatibility with testbed environments Safe operation on KC-135, Shuttle middeck, and ISS

11 Systems Requirements: Strawman Minimum acceptable mission operations performance Translation 1 m in 5 s, start to stop Rotation 360 o in 5 s, start to stop Tolerances Translational deadband of 0.5 cm Rotational deadband of 3 o Propulsion lifetime 20 sec (one KC-135 parabola) Power lifetime 30 minutes (one set of 20 parabolas) Detailed requirements in subsystem sections

12 Design Margins Prototype vs. Strawman Requirements Prototype Strawman Margin Requirements Thrust 0.52N 0.544N (given % kg mass) Propulsion Lifetime 20 s 20 s 0% (minimum) Power Lifetime (minimum) 60 min 30 min 100% Middeck locker constraints 3 Prototype SPHERES, 4 Metrology Transmitters NASA Requirements Margin for consumables Mass kg 24.5 kg (54 lbs) kg (49%) Volume m m 3 (2 ft 3 ) m 3 (40%)

13 Structures David Carpenter

14 Structures: Requirements SPHERES structure serves multiple roles Physically integrates all subsystems into a complete unit Provides rigidity and support for the SPHERES satellites Requirements Must fit within a standard mid-deck locker Must provide sufficient rigidity and strength Must provide mounting points for components Must allow easy access to internal components Should be easy to manufacture and simple to assemble

15 Structure: Design Hierarchy SPHERES global structure Primary structure Internal subassembly Provides rigidity and support for SPHERES Provides mounting points for internal components and the external subassembly External subassembly Provides mounting points for external components and some internal components Secondary structure Provides mounting means for internal components

16 Structure: Internal Design Internal subassembly The physical base upon which SPHERES builds Three-dimensional grid configuration 36-element aluminum internal frame 12-member truss 24 end connectors All elements fastened with standard #4-40 screws

17 Structure: Internal Components Aluminum bars All 12 bars are identical for ease of manufacturing and assembly Regularly-spaced threaded (#4-40) holes allow for the mounting of components End connectors Three unique connectors account for internal asymmetries to make SPHERES externally symmetrical

18 Structure: External Design External subassembly 26 Lexan panels attach to the end connectors of the aluminum frame Provides a machineable surface for custom mounting of external components Flight hardware will see four panels replaced by two access hatches for easy replacement of consumables during experiment

19 Structure: External Components Lexan panels Four unique panel types: equilateral triangle, rectangle, and two varieties of square Attach to end connectors via standard #4-40 screws Thickness of is greater than the minimum thickness of required for compliance with NASA safety specifications

20 Structure: Power Integration Battery cases 2 casings made of aluminum sheeting to hold battery packs in place Case screws into Lexan and holds battery packs up against the panels Placed near access doors for easy exchanges Battery packs slide in and are held in place by stopper on Lexan door panel

21 Structure: Prototyping A CAD-based iterative process allowed for flexibility Baseline structural components developed in Pro/ENGINEER during design phase Pro/E models modified to evolve with changing design during prototyping phase Prototype hardware manufactured at end of Summer 1999 to allow for system-level prototype integration during Fall 1999

22 Structure: Remaining Tasks Modifications for flight hardware Access door May require a slight modification to two end connectors Should not significantly affect overall design Characterize system inertia properties Can experimentally determine principal system inertias by hanging from two parallel vertical wires and measuring period of natural oscillations when displaced by an angle about the vertical, φ. 2 φ 2 t + 2mgr I l z 2 φ = 0 2 T mgr 2π l I z = 2 2

23 Propulsion Bradley Pitts

24 Propulsion Requirements Safety Non-toxic byproducts Non-touch hazard: -18C<T<50C Propellant Propellant supply sufficient to last at least 20 seconds Control System must provide for 6 DOF System must provide constant performance throughout flight duration Thrust An acceleration of at least 0.16m/s 2

25 Propulsion Design Liquid CO 2 system Solenoid valves provide actuation System as designed for the NAR: Tank Heater Regulator Relief Valve Valves Nozzles

26 Propulsion Prototype Design Bare minimum design Focused on making the system operable Did not worry about safety requirements Did not worry about excess tubing/wiring Heater/Cradle Tank Regulator 7-Way Manifold T-Connectors Valves Nozzles

27 Propulsion Components Propulsion System Major Components CO 2 Propellant Tank Fixed Pressure Regulator psi to 70 psi 7-Way Manifold 6 Micro-solenoid Thruster Pairs Solenoids Nozzles Spacers Other System Components Tubing 3-Way Manifolds Electrical Connectors Tank Cradle/Heat Sink

28 Prototype Components Solenoid Valves Nozzles Lexan Panel Thruster Connection Screw Connection Screw Electrical Connector T-connector Spacer Tubing Mounted CO 2 tank Tank Cradle 7-Way Manifold Regulator

29 Propulsion Models Valve Nozzle Flow Direction P 1 P 2 Valve Constriction (A V ) Nozzle Constriction (A N ) P ATM Thrust = M dot V exit + A e (P e -P a ) Four Regimes (Determined by ratio of P upstream /P downstream ): M N = 1, M V < 1 M N = 1, M V = 1 M N < 1, M V = 1 M N < 1, M V < 1 Subsonic Flow: Sonic Flow: M = 1 P = throat P downstream

30 SPHERES Propulsion Models ( ) P P M PA F a v n = γ γ γ γ γ γ γ ( ) ( ) = γ γ γ γ γ γ v v v n M M A A M v A n /A v F/(P 0 A n ) F Analytic Model: Choose P o, A v Cycle through all 0< M v <1

31 Propulsion Prototype Results Accomplishments 6 DOF Prototype Specs: Thrust = 0.26 N Lifetime: 20 sec t L 1800 sec (30 min) Actuated Firings through Avionics and Communication Systems Prototype Problems Pressure leaks Time needed to make system modifications Liquid CO 2 build up downstream of regulator No pressure safety features Excess wiring/tubing

32 Propulsion Requirements Check Geometry Ensures 6 DOF movement Nozzle Design and Testing Provides 0.26 N of thrust (< 0.272N) Assures minimum lifetime of 20 sec Analysis Demonstrates that CO 2 toxicity is not an issue Demonstrates that performance is constant throughout flight duration Testing Demonstrates an acceleration of 0.11 m/s 2 (0.157 m/s 2 w/out test stand < 0.16 m/s 2 ) Reveals minimum tank temperature of -25 o C (< -18 o C )

33 Propulsion Modifications Solutions Lee Co. MINSTAC tubing and connectors Integration of purge, cut-off, and relief valves Decreasing wiring/tubing tolerances Connect DSP to Heat Sink Heater/Cradle Tank Regulator Purge Valve Master Cut-off (3) Relief Valves DSP HEAT 3-Way Manifolds 5-Way Manifold #1 5-Way Manifold #2 Valves Nozzles

34 Metrology Shannon Cheng

35 Metrology Requirements Position accuracy to 5 mm Attitude accuracy to 2.5º Refresh Rate of 50 Hz

36 Metrology Design Two independent systems Infrared/Ultrasound (IR/US) GPS-like ranging system Inertial navigation system (INS) Independent systems mitigate risk Systems augment each other Inertial navigation system operable at 50Hz IR/US system to provide initial position, update INS INS provides position/attitude guess for IR/US calculations

37 Metrology Block Diagram IR Receivers x 8 Ultrasonic Receivers x 8 DIO Lines Metrology Tattletale Processor Main C40 Processor 3 Single-Axis Gyros 3-Axis Accelerometer A/D Converter

38 Metrology INS INS measures: Angular Velocity Acceleration Integrates to provide: Velocity Position Attitude INS is sampled by controller at 50 Hz For flight metrology: Kalman filter will be used in integrating IR/US position/attitude estimate with INS state estimate

39 Metrology INS Components Onboard Components 1 Crossbow 3-axis accelerometer Provides linear acceleration in 3 principal axes 3 CFX single-axis gyros Provide rotation rate around 3 principal axes Tattletale processor Component Vendor Unit Mass (g) Unit Volume (cm 3 ) Voltage Unit Power (W) Resolution Picture (not to scale) 3-Axis Accelerometer Single-Axis Gyro Crossbow to 30 V mg CFX to 24 V deg/s

40 Metrology INS Models Yaw Error (deg) Position Error (cm) Time (s) Yaw error due to Gyro RMS noise Time (s) Position error due to Gyro RMS noise and Accelerometer RMS noise

41 INS Prototype Test Results CFX gyros validated using rate table 16.62x setup used to evaluate gyro performance Accelerometer validated using manufacturer s software Crossbow software used to evaluated 3-axis accelerometer performance

42 Metrology IR/US System IR/Ultrasound ranging 4 IR/US transmitter boxes at known locations in KC-135 or shuttle middeck 8 IR/US receiver pairs on triangular panels of each satellite Receivers measure time difference between arrivals of pulses IR arrival instantaneous, range between emitters and receivers is difference times speed of sound Modified 3-D Newton s method uses ranges, calculates position and attitude

43 Metrology IR/US Components Onboard components 8 US receivers 8 IR receivers Tattletale processor (discussed by Avionics) Transmitter box components US transmitter IR transmitter IR receiver Tattletale processor Component Vendor Unit Mass (g) 40 khz Ultrasonic Transceivers IR Receiver (880 nm) IR Emitter (880 nm) MuRata Electronics Vishay Telefunken Photonic Detectors Unit Volume (cm 3 ) Voltage Required Unit Power (W) ~ ~0 ~0 ~0 5 ~0 Picture (not to scale)

44 IR/US Prototype Test Results 1-D system tests Required linear accuracy achievable Multiple components tested, best performing components selected Conditioning circuits optimized 2-D system tests Developed position and attitude code Validated Newton s Method equations Developed stand-alone synchronized transmitters Systems level tests Propulsion jet noise affects US receivers Propulsion electronic noise affects unshielded metrology components

45 IR/US Prototype Results Built stand-alone 2D testbed Finalized IR/US conditioning circuits Verified 2D Newton s method equations Prototyped transmitter box design

46 Comparison with Requirements Position accuracy 2 cm 5 mm current requirement Attitude accuracy ±5 2.5 current requirement INS meets 50 Hz sampling requirement

47 Design Modifications for Flight Inertial system Develop better integration method Use error estimation to improve accuracy of metrology system Quantify gyro drift using rate table IR/US system Finalize design for transmitter boxes Develop equations to calculate 3D position and attitude Develop transmitter box auto-positioning system (BAPS) Integrate IR/US metrology systems and Inertial Navigation System Electrically shield all metrology components and connectors

48 Power Julie Wertz

49 Power Requirements Lifetime should be > 30 minutes Provide necessary power to all subsystems Provide power at necessary voltages Current Voltage and Power requirements Subsystem Component Power (W) Voltage (V) Avionics DSP 3 5 Communications Transmitters and Receivers Metrology Circuitry (at most) 5 Metrology Tattletale 2 12 Propulsion Propulsion Metrology Gyros ~ Metrology Accelerometers ~ Total 6.2 Compatible with KC-135, Shuttle and ISS specifications

50 Power Design 12 AA Alkaline Batteries in 2 battery packs on opposite sides of the SPHERE Alkaline now used on Shuttle (GFE) Easy to connect System can handle steep discharge curve 2 COTS DC regulators provide 5V and 12V Custom circuitry provides regulated 3.3V and 22V Unregulated voltage (18-12V) provided to IMU package Power distributed through circuit boards

51 Power Block Diagram Power Source 12 x 1.5 V REGULATOR ASTEC AA10B-012L-050S 5V Regulating Circuitry 22V REGULATOR ASTEC AA05A-024L-120S 12V Metrology Transmitters/ Receivers Regulating Circuitry 3.3V DSP Propulsion Firing Circuitry Tattletale Processor Metrology Rate gyros/ Accelerometers Comm Propulsion Solenoids Transmitters/ Receivers

52 Power Components COTS Regulator Specs Total Mass 35 g 37 g Length 2.0 in 2.0 in Width 1.0 in 1.0 in Height 0.4 in 0.4 in Input Volt V 9-36 V Output Volt. 12 V 5 V Max Load Cur A 2 A Max Out. Power 10 W 5 W Cost $60 $60 Alkaline Specifications Total Mass (12 ) 0.4 kg Total Volume 105 cm 3 Lifetime 90 min Number of Batteries 12 Capacity 2.8 Ahr Voltage per battery 1.5V Total Cost $20

53 Power Components Custom 22V regulating circuit Maxim 668 Kit Output Voltage when set for 22V Efficiency with 22V output Voltage Out (V) Efficiency (%) Voltage In (V) Voltage In (V)

54 Power Model Modeled entire system in laboratory with resistor loads to get battery discharge curve Load = V 2 /P 12 V conservative threshold for end-of-life Voltmeter 5V 12V 1-2 x (3.3 Ω) resistors in series 2-4 x (270 Ω) resistors in parallel 3-2 x (270 Ω) resistors in parallel 7Ω 1 72Ω 2 125Ω 3

55 Power Prototype Test Results 90 minute lifetime from modeled system 18 Battery Discharge Curves Voltage (V) NiMH Alkaline Series Time (minutes) Power draw of prototype 9.3 W Takes into account inefficiencies Lifetime estimated between 60 and 90 minutes

56 Power Comparison with Requirements Lifetime of minutes allows 100%-200% margin above requirement (30 min) All subsystems provided with necessary power at necessary voltages Within mass and volume constraints

57 Power Changes for Flight LED for low-battery and power-on Power On/Off switch on outside of SPHERE Duracell Ultra AA Alkaline (as shown) AA NiMH batteries (rechargeable) used for prototyping tests to save on waste Changes to other subsystems will affect power

58 Avionics Fernando Perez

59 Avionics Requirements Processor must provide enough computational power Approximately 23 MIPS Processor must have at least 35 DIOs and 6 A/Ds Must provide for serial communications Minimize weight and volume Minimize power usage

60 Avionics Design Need 2 processors for required DIO and A/D inputs Metrology dedicated Tattletale DSP 6 major avionics boards UARTs - Propulsion Power - DSP Metrology - Tattletale Additional supporting boards 8 small metrology US/IR connector boards 2 communication boards Most boards sent out for layout and population DSP, Tattletale, and Communications boards are COTS Power board layout and population done in house Metrology Ultrasound/IR connector boards populated in house

61 Avionics Design Required power and signals distributed through interconnecting boards under metrology and propulsion Reduces noise interference on important signals Reduces number of wires No extra card cage needed

62 Avionics Signal Flow Diagram DSP 8 7 J 13 Port A J 4 Port B J 3 IR/ Ultra Out A 16 In A In B 16 Out B DMA Thrusters UART UART 3 SIO 3 SIO Comm. Comm. Tattletale 8 A/D Accel. Gyro 8 3 SIO1 3 UART 3 SIO2

63 Avionics Components Processor Specifications Tattletale TIM-DIO 40 DIOs A/Ds 8 0 MIPS 4 30 Tot. Mass (kg) Tot. Vol. (cm 3 ) Power (W) RAM (MB) Tot. Cost($) TIM-DIO 40 Tattletale Model 8

64 Avionics Prototyping and Results Prototyping Acquire circuit boards Sketch from subsystems Design circuit board connectors Schematic captured in OrCAD Boards sent out for manufacturing Board layout and population verified All boards integrated Total mass 540 g Results Entire system was provided the require voltages and signals

65 Avionics Comparison with Requirements Needed computational power provided All needed DIO and A/D lines provided Serial Communications provided All signals and power routed to the required locations Total power draw acceptable Power of DSP higher than expected (3 W) Power of Tattletale lower than expected (< 2 W)

66 Avionics Changes for Flight Decrease size of several circuit boards Send power board out for professional layout and population Reset buttons added to outside of SPHERE for DSP and Tattletale resets Improve connectors between avionics boards and subsystems

67 Communications Sarah Carlson

68 Requirements Acquire, Manipulate & Transfer Data RF sensors for Satellite to Satellite Communication (STS) & for Satellite to Ground (STG) communication Health status reporting Interface with metrology and onboard systems Develop Control System Structure Local Level: station keeping, individual satellite systems Global Level: inter-satellite communications, maneuver execution Safety RFM sensor cannot interfere with Shuttle systems (EMI Considerations) Must be safe for human interaction

69 Communications Design Communications Hardware RFM Virtual Wire Kit RFM Transceiver Models Model Bandwidth Frequency DR1004-DK 22,500bps 916.5MHz DR1012-DK 22,500bps MHz

70 Communications Design STS Communication Hz Command New position or maneuver Telemetry Position Data Broadcast current position of each satellite to all the others Token Ring Control which satellite transmits and which listens STG Communication Hz Transmission Options: Command History Calculated Metrology Data Raw Metrology Data Health Status GTS (from the Laptop) Send Commands to Array Reprogram Satellites Collects data for post-flight analysis

71 Communications Protocol Token Ring Architecture Type Telemetry, Command, Token Source Original sender of the message Received? Was the message received by the intended recipient? GO/NOGO Can the message be processed? NOGO Received? Type Source

72 Communications Protocol Software Telemetry Protocol Sent out to all satellites Shotgun approach: No verification of reception needed Only intended recipients process information Command Protocol Sent out to all satellites Acknowledgement and accuracy verification GO/NOGO message sent Message then placed in recipient queue to be processed Token Ring Ensures only one source can speak at a time Virtual token passed between sources when outgoing queues emptied

73 Testing and Verification Setup: Hardware Laptop & Transceiver Units Software Main testing in C/C++ Stage 1: Transmission of Data Packet via Serial Cable Program sends packet from Comm1 to Comm2 (using only the laptop) Stage 2: Transmit Data packet via RF from PC to laptop Data sent through PC to DSP and then sent to laptop Stage 3: Integration of Communications Board with SPHERE Will allow laptop to transmit to the fully integrated & functioning SPHERE Stage 4: Refinement of time out controls & interrupt handlers Final stage of fall implementation process

74 Prototype Test Results Verified bandwidth The final useable rate is 18,000 bps (vs 19,200ps claimed) EMI / Multiple transmitter Interference tests Initial EMI testing procedure begun Verified command execution We can send: thruster number & thrust duration We can send: desired direction & duration Functionality of time-outs Retransmits command after 0.10 seconds (10Hz) Ensures no stalling when sending signals - if notification of command reception is not received, will send again

75 Comparison with Requirements Functional systems Data transmission rates meet requirements ( and then give the numbers here) Communications board / UARTs fully integrated Commands can be uploaded to the SPHERE STG works effectively Timeout operation functional Not yet implemented STS Communication: Protocol still being tested Health status reporting not up & running yet

76 Design Modifications for Flight No hardware modifications necessary Further develop durability of software Timeout processing procedure strengthened Ensuring data / command verification Constant STG communication and the recording of that data Refinement of code to increase efficiency and reduce run time Software integration techniques Algorithmic programs incorporated into test-bed design

77 Software

78 Software System Requirements Develop control system structure global level: communication, array maneuvers local level: station-keeping, error correction Control data flow between subsystems input IR/ultrasound data from Tattletale [50 Hz] output commands to thrusters [50 Hz] input and output RF data [10 Hz] output data to ground [1 Hz] IR/ Ultra. Accel. Gyro 10 Hz 50 Hz Tattletale 50 Hz DSP 50 Hz 10 Hz Thrusters Comm. (in) Comm. (out)

79 Software System Flowchart Goals test architecture of software system interface with metrology and communication

80 Outline of Processes Standard Interrupt Handler (SIH) Pull state data from UART State estimator coded by metrology team input: raw data converts raw data to position and velocity output: current state Control Algorithm inputs: current and reference positions calculates necessary thruster commands output: vector of thrust durations Save calculations in onboard RAM

81 Outline of Processes Propulsion Interrupt Handler (PIH) Activate specified thrusters input: global variable containing thrust durations decrement remaining thrust durations outputs: new thrust duration vector activate thruster valves Justification: high resolution control highest priority interrupt handler clocked at 1kHz written to maximize efficiency

82 Outline of Processes Background Processes (BG) STS communication inputs: commands, telemetry of other satellites convert data to or from packets (comm. team code) outputs: telemetry, possibly commands GTS/STG communication inputs: commands from laptop convert data to or from packets (comm. team code) outputs: stored telemetry data Monitor own health status inputs: tank and battery levels check actual levels against values indicating low levels outputs: activate LEDs if tank or battery is low

83 Software Timing Diagram

84 Software Verification Goal for CDR: verify integration with communication, propulsion, and avionics subsystems user provides thruster number or DOF, and duration laptop sends command by RF satellite receives packet, translates data SIH reads command, computes thrust durations PIH reads duration vector, commands thrusters Test Results commanded thruster fires for correct duration software interrupt handlers function as expected

85 Future Work in Software Further integration receive metrology data monitor tank and battery levels Ensure flexibility of testbed easy swapping of controllers ability to select maneuver or array various methods of global control hierarchy master/slave system individual metrology data acquisition during SIH or background array execution planned by user, on laptop, or on one or more satellites

86 Systems Integration George Berkowski

87 Systems: Integration Approach Test each subsystem independently Ensure functionality of each subsystem Physically integrate subsystems into structure Address spatial allocation conflicts within SPHERE Optimize position of avionics cards and wiring Test each subsystem after integration into the SPHERE Ensure functionality of each subsystem after integration Verify subsystem interfaces Test overall functionality of integrated SPHERE

88 System Integration Tests Integrate propulsion, avionics and power Ability to control thrusters / verify propulsion board Add a communications capability Allow remote thruster control Incorporate metrology functionality into SPHERE Ability to calculate position Check interference issues: thruster noise Transmit metrology data to ground station Capacity to transmit large data stream for analysis Incorporation of metrology data with maneuvering Closes control loop Shows functionality of fully integrated testbed

89 1-g, 2-D Test Device Should simulate as closely as possible the effects of microgravity in a 1-g environment Must provide 3 degrees of freedom (restricted to 2-D movement) 2 translational DOF (along x- and y-axes) 1 rotational DOF (about z-axis) Must allow for minimal physical modification of the article to be tested

90 1-g, 2-D Test Device Air bearing levitation vehicle Three CO 2 tanks feed three pucks via a single regulator A SPHERE satellite sits atop the square mounting plate for testing Can also run off of in-house lab air supply

91 SPHERES Integration Results Accomplishments Open loop control of single satellite Limited position and attitude determination of satellite Every system integrated and functional (metrology system needs refinement) Integration highlighted necessary flight hardware design modifications Frictionless 2-D air-bearing Issues discovered Tolerance buildup Quality of manufactured boards Wire / Tubing buildup Conflicts with subsystems; mainly propulsion and metrology Too much electrical interference with propulsion Too much acoustic interference with thruster firings

92 Program Plan

93 Summer/Fall 1999 Schedule

94 Flight Hardware Procurement Begin procurement of long lead items Propulsion tanks Continue prototype testing/refinement Dynamic model CG, moment of inertia Rewire prototype Metrology refinement & integration Flight hardware procurement in earnest after prototype testing/refinement Payload Systems

95 Phase D/E Activities Flight hardware integration Physical integration Recalibration Operations planning KC-135 operations training Acceptance & safety reviews Flight Data Analysis/Compilation Final Review

96 Schedule

97 Preliminary KC-135 Ops Plan Typical Parabola Each satellite calculates position from metrology data Formation Flying maneuver (Avionics, Software) Command acquisition (start of zero-g) Appropriate thrusters fire for formation flying (Propulsion) Satellite to Ground Communication (STG) Uplink command (Communications)

98 Preliminary KC-135 Ops Plan

99 Summary

100 Summary: Today Accomplishments Demonstration of operational subsystems (except for metrology) Demonstration of open loop controlled movement Issues to be resolved Electrical interference Software to close the loop Internal clutter

101 Summary: Tomorrow Proceed with flight hardware procurement and assembly Resolve remaining interface issues Complete metrology development Systems check-out on KC-135 Verify functionality of testbed Limited control algorithm testing

102 Questions?