1. CubeSat Platform for SeaHawk
Clyde Space PDR Design

2. Presentation Overview
Abbreviations
Requirements
Platform Design, Functional Architecture and Budgets
Payload Interfaces
Subsystem Design
Discussion topics

3. Abbreviations OBC: On-board Computer
OBDH: On-Board data handling
PIM: Payload Interface Module
PPT: Peak Power Tracker
PLC: Payload Computer
RG: Rate Gyroscopes
RW(S): Reaction Wheels
SA: Solar Array
SADM: Solar Array Deployment Module
SS: Sun Sensors
STT: Star Tracker
UIM: Umbilical Interface Module
ADCS: Attitude Determination and Control System
ADM: Antenna Deployment Module
BAT: Battery
BCR: Battery Charge Regulator
C&DH: Command and Data Handling
CONOPS: Concept of Operations
CSS: Coarse Sun Sensor
FSS: Fine Sun Sensor
EPS: Electrical Power System
GPS: Global Positioning System
MTQ: Magnetorquer
MTM: Magnetometer

4. Requirements

5. Requirements Overview
Functional
What it does
Configuration
What it is composed of
Interfaces
Between parts & external world
Physical
Physical characteristics
Functional requirements are based on Concept of Operations and Mission Requirements.
Configuration, Interfaces, Physical requirements are based on interpretation of contract and subsequent communication.

6. Requirements Flowdown
CUSTOMER REQUIREMENT: The Platform shall support HawkEye Payload operations and science data downlinking.
DERIVED REQUIREMENTS ON:
Operations
Power
Physical
C&DH
ADCS
Communications
Based on interpretation of contract and communication till date.

7. Payload Ops Requirements
OPERATIONS REQUIREMENT: The Platform shall support HawkEye Payload operations and science data downlinking.
Platform shall support payload operations for at least 12 months, 24 months desirable.
Platform shall be able to operate between 400 and 540 km altitude.
Science observations will only be performed during sunlit part of the orbit, not during eclipse.

8. Power Requirements
POWER REQUIREMENT: The power subsystem shall provide power to all subsystems; Mission mode and Tumbling mode
DERIVED REQUIREMENTS:
Power Generation
Configuration TBD, currently assuming a configuration of
2x3U deployable and body mounted solar arrays.
Power Distribution
Provide power on 3V3, 5V, 12V, BattV buses
Provide over-current protection
Power Consumption
See later Power Budget slide

9. Physical Requirements
PLATFORM REQUIREMENT: The Platform shall be a 3U CubeSat capable of supporting the SeaHawk payload.
DERIVED REQUIREMENTS:
CubeSat Standard
Primary Structure needed
Support Payload Interfaces
Shall accommodate all necessary modules and components

10. C&DH Requirements
C&DH REQUIREMENT: The C&DH subsystem shall enable Command and Data Handling between Subsystems and Payload.
DERIVED REQUIREMENTS:
Onboard Computing
State and Mode management
Command distribution
Data routing
Telemetry and Housekeeping
Payload on and off switching
Data Routing
100 kbps I2C bus (OBC master)
2 Mbps SPI bus (HawkEye master)

11. ADCS Requirements
ADCS REQUIREMENT: The ADCS subsystem shall provide necessary pointing accuracy and stability for payload operations.
DERIVED REQUIREMENTS:
Pointing accuracy of at least 6o for binned operations.
Pointing accuracy of at least 3o for full resolution operations.
De-tumble and Pointing Modes required
Accuracy and Stability
Reorientation Time
Fine Sun sensors required
Reaction Wheels required

12. Communication Requirements
COMMUNICATIONS REQUIREMENT: The Communication subsystem shall provide spacecraft communications to support payload data downlink, spacecraft telecommand and telemetry.
DERIVED REQUIREMENTS:
Full duplex communication with VUTRX
High-speed downlink with STX
Antennas for all transmitters, receivers and transceivers
CCSDS Protocol for ground segment communications

13. Platform Design

14. Platform Design
Reference frames and orientation:

15. Platform Design Clyde Space Standard Structure
Stack configuration driven by payload requirements
Solar Cell configuration to meet power requirements
Deployable panels required
Body cells required for tumbling
Outer surface and solar panels accommodate:
Payload aperture
Coarse and Fine Sun Sensors
Antennas; GPS, STX, ADM
MTQ
Temp sensors

16. Functional Architecture – Power

17. Functional Architecture – Data

18. Power Budget
SubSystems & Ops Modes
STATE ASSESSMENT
SEPARATION: DETUMBLE
MISSION: SCIENCE ACQUISITION
MISSION:
SCIENCE DOWNLINK
MISSION: CALIBRATION
MISSION: DOWNLINK & ACQUISITION
MISSION: DOWNLINK & CALIBRATION
Config
Avg. Power (mW)
POWER On
300
ADCS
455
1070
2436
2386
1989
OBC
260
COMMS
314
100
513
Off
PAYLOAD ?
BATTERY CHARGING
TOTAL POWER CONSUMPTION (mW)
1329
1944
3096
3459
2549
3509
Required Power generation (30% maintenance margin)
1728
2528
4025
4497
3314
4562
Est. Power generation - 3U Single Deployed - Double Sided
Actual power generation (mW) (Direct from panels)
8000
Including 20% design margin (mW)
6400
Including 20% EPS Efficiency Margin (mW)
5120
Potential payload AND battery charging average power (mW)
3392
2592
1095
623
1806
558
Numbers are on orbit averages. High power items with low duty cycle such as high speed transmitter and payload change the power profile significantly. -> Detailed power budget (Peak power analysis and battery capacity) required.
Orbit details and CONOPS (e.g. downlink performance in eclipse) needed to proceed with detailed power budget
Power budget is tight.

19. Mass Budget
Preliminary mass budget
Payload mass?

20. Payload interfaces Power: Data: Physical:
EPS - HawkEye: 3V3, 5V, 12V and/or battV power bus connection (switchable)
Data:
OBC - PLC (OBC Master): I2C
PLC - High Speed Transmitter (Payload master): SPI (data), I2C(control)
Physical:
Mounting Brackets / Sub-structure
CSK Header or interface board?
Apertures
Alignment/On-orbit calibration
Harnessing / Routing
Environmental / EMC Coexistence

21. Subsystem Design

22. Subsystem Design Electronic Power System (EPS) 3rd generation EPS
Includes: BCRs, PPT, BAT
3V 5V 12V and raw battery voltage buses available
30Wh battery module
Watch-dog timer
Power switches and Over-Current protection

23. Subsystem Design OBC 166MHz Processor 8MB of MRAM and SRAM
Interfaces: I2C, CAN, UART, SPI, RS422/485
Watchdog timer

24. Subsystem Design Attitude Determination & Control Subsystem (ADCS)
Motherboard and daughterboard in Master-Slave configuration.
Motherboard:
FPGA based design with embedded control modes
Magnetic and inertial sensors
Coarse and Fine sun sensors
Magnetorquer actuation
Interface to daughterboard
Daughterboard:
3-axis Reaction Wheels Module

25. Subsystem Design S-band Transmitter (STX)
Transmission data rates up to 2 Mbps
Up to 0.8 Mbps science data capacity.
Hardware selectable frequency
2.4 – GHz (Amateur band)
2.2 – 2.3 GHz (Commercial Band)
QPSK or OQPSK modulation with Intelsat IES-308 based encoding
Configured via I2C, High-speed data via SPI

26. Subsystem Design VHF UHF Transceiver (VUTRX)
9600 baud GMSK, 1200 baud AFSK data rates
Hardware selectable frequency
420 – 450 MHz Transmit frequency
130 – 150 MHz Receive frequency
DTMF backdoor
EPS - Platform power cycle
GMSK or AFSK modulation with AX.25 protocol encoding/decoding
Configuration and data via I2C
[ISIS]

27. Subsystem Design GPS Dual Frequency GNSS receiver.
Differential GPS positioning
Interfaces: LVTTL, CAN, USB
Measurements and position up to 50 Hz.
[ISIS]

28. Design Issues

29. Design Issues Concept of Operations Power
Orbit determines platform design and payload support capabilities. What orbit do we want to operate in?
Launcher determines launchpod and the available space for the Cubesat and puts requirements on the primary structure. Which launchpod are we looking to use?
Platform only allows for sunlit operations. How are we going to do moon/flatfield calibration shots?
Power
Power Generation depends fully on the orbit. Orbit information is needed before we can proceed with platform design and solar array configuration.
Required powerbudget for HawkEye?
3V3, 5V, 12V and BattV available. Which do HawkEye need?

30. Design Issues Physical structure and Interface
Cubesat formfactor is limited to 100x100mm. Current Payload dimensions extend beyond this envelope. How is the Payload going to fit?
Platform uses CSK headers for module interfaces. Payload interface module is available but what is needed on it?
Umbilical connection needed for any outside connections after assembly? (Pre-flight configuration, debugging, etc)
Mounting of modules is done via standard brackets? Does the Payload match with those?
Payload orientation is limited by structure and interfaces. Which way are we going to orient the payload?
Cubesat structure does not include any controllable apertures. How are we going to perform outgassing?

31. Design Issues OBDH and C&DH Communications
The platform will switch the power supply to the Payload on and off. How does the payload switches between Full Resolution and Binned Operations?
Payload housekeeping data handling through VUTRX? What capacity/data rate for payload housekeeping data is needed?
OBC is designed for high efficiency processing of small amount of command an control data. How will the science data handling and dark frame subtraction be done?
Communications
CCSDS and AX.25 Protocol is used by the platform. Will this cause issues with the ground segment interface?
S-band Patch antenna positioning: Should be nadir pointing, will interfere with payload apertures.

32. Design Issues
ADCS
Platform will deform due to launch and operations. How do we plan to align/calibrate the ADCS with the observation axis?
Pointing accuracy and stability will not be perfect due to disturbances. How much pointing inaccuracy and instability can the payload correct for?
Required pointing stability for science and calibration?
Required pointing accuracy for moon pointing? (flatfielding)?
Platform contains a GPS. Is GPS time/position required by payload?
Is there a requirement for pointing axis rotation control?

33. Design Issues Environment Testing and Integration
How is the payload going to perform temperature monitoring?
Temperature operating range depends on Orbit. Similar platforms missions go from -20 to +50 °C.
Temperature variation vary based on concept of operations and selected orbit.
Magnetometers are sensitive to anything above 0.8 Gauss. Magnetic field strength of magnet that controls the shutter should be less than that at MTM location.
Permanent magnets will always interfere with attitude, should be avoided.
Testing and Integration
How will the payload be tested before shipping to, and platform integration at, Clyde Space?

34. Questions?