Attitude Determination and Control Specifications

Transcription

1 Attitude Determination and Control Specifications 1. SCOPE The attitude determination and control sub system will passively control the orientation of the two twin CubeSats. 1.1 General. This specification establishes the design, construction, performance, development, and test requirements for the Attitude Determination and Control Subsystem, (herein referred to as the ADCS). 2. APPLICABLE DOCUMENTS The following documents of the exact issue shown shall form part of this specificaion to the extent specified herein. In the event of conflict between the requirements of this specification and any referenced document the order of precedence shall be 1. The contract, 2. This specification, 3. Referenced documents. 2.1 Government Documents. 2.2 Industry Documents. Cal Poly s P POD Payload Planners Document, Revision C (Document # ) GPS antenna requirements (Document # ) Antenna requirements (Document # ) Boom requirements (Document # ) 3. REQUIREMENTS 3.1 Item definition. The attitude control system consists of both passive and active control actuators (if torque coils are used). The passive control actuators include a gravity gradient boom and a nutation damper. The active control actuator, if decided upon, will be a torque coil wound along either the top or bottom surface of the CubeSat Illustrations or Functional Block Diagram. Science: GPS (Sensor) C&DH Power ADCS Actuators Structures

2 3.1.2 Interface Definition. The functional block diagram above shows the Attitude Determination and Control System (ADCS) relationship with the other subsystems Physical. GPS antenna shall be used as a sensor: If the Torque Coil is decided upon, the GPS will determine whether the CubeSat is Nadir pointing or Zenith pointing, to determine if rotation with the torque coils is necessary Each GPS will be tested, the one that receives a signal will be the active antenna and will determine our pointing If the GPS is Nadir pointing, then it will shut down and C&DH will activate the torque coils Power supplied to actuators Structural mountings for ADCS components The ADCS shall have the following physical interfaces: Electrical. Gravity Gradient Boom will be attached to the structure using Nutation Damper will be inserted into the body of the CubeSat using, Torque Coil will be wound around the edges of the structure, method Electrical interfaces will just be power interfaces between ADCS actuators and C&DH. Actuators will interface electrically with the Power and C&DH system using, Functional or Informational. The only data required for the ADCS actuators will be whether they are to be activated or turned off. 3.2 Characteristics. Other than the Torque Coil, all the rest of the ADCS actuators will only require a single use activation. The Torque Coil will require both an on and off input supplied to it

3 The following are the separate control modes that require analysis for attitude maintenance. Specifics. Control Mode Deployment Separation Gravity Gradient Deployment Antenna Deployment Reorientation (if torque coil is used) Operational times for each mode Performance Characteristics. The following list is the Attitude Control Dynamics actuators and there characteristics. Gravity Gradient Boom: Stainless Steel measuring tape style dimensions for boom length Length: Mass: Width: 1.23cm Thickness:.0178cm Lead tip mass with rectangular dimensions Dimension envelope: (xyz) 5cm X 10cm X 1.3cm Mass: Nutation Damper Dimensions: Mass: Torque Coil Required torque: Current: Mass: GPS Mass: ~4g Dimensions: (xyz) 1.8 X 1.8 X 0.45 cm Wiring: Reference GPS specs Disturbance Torques. Initial Calculations yielded the following disturbance torques. Torques need to differentiated between the coordinate directions (x, y, z)

4 Torques Maximum (N m) Gravity Gradient 7.176E 7 Aerodynamic 7.175E 7 Solar 5.9E 9 Magnetic Solar torque requires further analysis of the center of solar pressure Magnetic Torque requires further analysis of the residual magnetic dipoles Pointing Requirements. Science: non Nadir pointing accuracy Communications: Nadir normal pointing with accuracy Power: Solar Cells shall have the maximum area sun pointing accuracy Thermal: pointing with accuracy Physical characteristics Possible Orientation with redundant GPS patches. Mission success isn t dependent on orientation using this configuration CP Redundant GPS Patches x CG z Final Orientation using actuation (torque coil) if needed GPS Patch CP x CG Torque Coil z

5 3.2.4 Maintainability. No maintenance shall be required during the mission Environments Natural Environments The attitude control system will have to be able to compensate and or damp out for; Pressures ranging from 1atm to vacuum: Solar torques: Induced Environments. Aerodynamic torques: Thermal vibrations and cycling: Magnetic Torques and magnetic cycling effects: The attitude control actuators shall meet the requirements of these specifications during and after exposure to any logical combination of the following natural environments. Mechanical shock, including transportation, launch and use: Vibration, including transportation, launch and use: 3.3 Design and construction. The Attitude Control Dynamics design incorporates a passive gravity gradient and nutation damper, and an active actuator if the torque coil is decided upon. Construction and prototyping Parts, materials, and processes Parts and materials lists Wiring, Cabling, and Connectors Wiring, cabling and connectors Electronic parts and Printed Wire Boards. Electronic parts Cleanliness. Cleanliness control Outgasing and venting.

6 Outgasing and venting 4 QUALITY ASSURANCE PROVISIONS 4.1 General. This section describes the requirements for the verification process during design, fabrication, development, acceptance, and qualification test programs. 4.2 Quality conformance verification Quality conformance methods. The supplier shall verify all requirements of Section 3 by inspections, demonstrations, tests, or analyses as specified in Section 4 as follows: a. Inspection. b. Demonstration. c. Analysis. d. Test Test category definitions. a. Development Tests. b. Acceptance Tests. c. Qualification Tests.