SeismoSat – Critical Design Review

1. SeismoSat – Critical Design Review

2. Group Members • Lan Gao – Weight & Balance • James (JuHeon) Lee – EPS & OBDH • Aditya Vishwanathan – Structural & Telecoms • Ding Yan – Thermal Analysis

3. Table of Contents • List of Components • Mechanical • Mass and Balance analysis • Disturbance and Control Stability analysis • Structural, Thermal analysis • Electrical • Power Analysis • Communication Throughput analysis • Software • Software Latency and Throughput analysis • Fault analysis • Final Design

4. List of Components

5. Key Changes and Notes • Passive Control: Magnets • Stanford University has Clarified that Passive Control was sufficient • Boom Length Decreased to ~ 20cm • Long boom length was to distant sensor away from electronic noise. With proper filters, we can afford to reduce boom length

6. Key Changes and Notes (Cont.) • Magnetometer Sensor Length Decrease • Reduced to lower satellite’s weight • search coil’s size with respect to the additional amplification need was simulated. To decide on its new size.

7. Key Changes and Notes (Cont.) • Change in Material: Carbon Fibre Side Panels • Reduces weight significantly • Does not significantly effect the overall structural strength • CPU uses PIC18F452 • Familiar to work with • Rad-Hardening not necessary for a proof of concept work • Has all the functionality needed.

8. Mechanical – Mass Analysis Total Mass = 3.544kg A reduction of approx. 1kg

9. Mechanical – Balance Analysis Centre of Mass Moment of Inertia

10. Mechanical – Control

11. Mechanical – Disturbance Gravity Gradient Solar Pressure

12. Mechanical – Disturbance (Cont.) Aerodynamic Drag

13. Mechanical – Control Stability Angular Acceleration with Passive Control:

14. Mechanical – Structural Analysis

15. Mechanical – Structural Analysis (Cont.)

16. Mechanical – Thermal Analysis

17. Electrical - Power Analysis

18. Electrical - Communication Throughput Analysis • COMPONENTS: • Antennas • Satellite: Four monopole steel tape UHF antennas • Ground Station: ISIS Yagi UHF antenna • Tekk T-Net Mini (Half duplex crystal controlled radio) • Baypac BP-96a Modem

19. Electrical - Communication Throughput Analysis (Cont.) DOWNLINK ANALYSIS: • Demodulation Information • Data Rate: 9600 bps • BPSK

20. Electrical - Communication Throughput Analysis (Cont.) UPLINK ANALYSIS: • Demodulation Information • Data Rate: 1200 bps • AFSK

21. Software – Software Latency and Throughput analysis • Sources of Latency: • Clock Cycles to execute each assembly command • Time taken to complete one assembly command is generally 100 ns (period of the internal clock cycle) • 9600 BAUD Rate in communication between the Modem and the RS-232 • 9600 BAUD Rate is equivalent to, at the longest 9600 bits per second; meaning the maximum delay of 104 ms per bit transfer/receive

22. Software – Fault Analysis • Sources of Error • Over Saturated commanded per timer interrupt • The SPI and RS-232 commands which are executed within the Timer interrupt can pose a significant delay; to the point of creating an infinite interrupt loop. • RX Pin sharing • Switching the RX pin between Tekk and GPS can cause mismatches and switching errors unless the timing as been defined properly • Payload error due to external interference • A general source of error, where external hardwares, radiation and the likes can either generate noisy signals, or even corrupt data.

23. Final Product