Embedded Systems for Satellite Applications

CubeSats are just smaller versions of a full sized satellite. CubeSats are used for small payloads such as scientific experiments in space, earth

observations, and low rate

communications. The research

consists of an On Board Computer

(OBC) design that does the following: • Power control • Telemetry • Payload control • Data handling • Timekeeping • Memory integrity

References

[1] C. A. Hussmann, “Reliable design of micro-satellite systems using combined physics of failure reliability estimation models,” Master’s thesis, 2016

[2] X.-y. Zhang, Q. Guo, Y.-d. Li, C.-f. He, and L. Wen, “Total ionizing dose and synergistic effect of magnetoresistive random access memory,” arXiv preprint arXiv:1610.01285, 2016 [3] "MR4A16B Datasheet ", https://www.everspin.com, 2017. [Online]. Available: https://www.everspin.com/file/162/download

[4] "TMS570LS3137 Datasheet ", https://www.ti.com, 2015. [Online]. Available:http://www.ti.com/lit/gpn/tms570ls3137

Introduction

_Requirements

Survive low earth orbit enviroment consisting of:

• -20°C to 70°C temperature range • 12g acceleration

• 0.6 W of power

• Dose rate of 2825 rad (Si) [1] • 1% of mass outgassing

Microcontroller - TMS570

Digital Signal Processor - TMS320

• PCB design is successfully tested and verified • Microcontroller executes at 100 MHz

• OBC's nominal power consumption is 0.5W

• Windowed watchdog timer successfully resets the microcontroller • External watchdog timer functions independently

• Magnetic RAM functions at 20 MHz without any problems • FreeRTOS is able to manage the satellite

• Mission planner is able to schedule payload executions • Digital signal processor functions at 100 MHz

• Communications system is working on the digitla signal processor • Creates highly modular subsystems

• Makes it easy to replace subsystems • Provides power

• Provides sensor interface

• Allows OBC to control the satellite

• Dual lockstep CPUs for redudancy [4]

• 3MB NAND flash with hamming code for ECC • 256 kB RAM with hamming code for ECC

• Survives up to 5 krad (Si) • Has flight heritage

• Self-diagnostics

• -40°C to 125°C temperature rating • Windowed Watchdog Timer

• eFuses

• Attached to an external watchdog

List of Sensors

• Amateur radio band • 145.9 MHz downlink • 436 MHz uplink

• 12 kBit/s data rate

• QPSK with gold codes

• Convolution codes for FEC • OSI layers 1 and 2

• Attached to an external watchdog

System Bus Connector

• 2 MB ECC magnetic RAM • Non-volatile RAM

• Survives up to 40 krad (Si) [2] • 35 ns read/write [3] • 16 bit bus • -40°C to 85°C temperature rating • 10^120 write endurance • SEU > 100 MeV-cm^2 /mg • SEL > 84 MeV-cm^2 /mg

• FreeRTOS for operating system

• FreeRTOS+TCP for networking stack

• BCH code for protecting the file system • CRC8 for sensor message integrity

• Software Watchdog

• Mission planner for pre-planning payload execution • Attitude determination and Control System

• 2 x Gyroscopes • 2 x Magnetometer • 2 x Accelerometer • 1 x GPS • 2 x Temperature Sensor

Software

Power Regulation

• Independent regulators for each component

• Able to turn off components in an event of a failure

• Hybrid power supply for the microcontroller

• ESD protection

Results

Memory - MR4A16B

Embedded Systems for Satellite Applications

Author: Brosnan Yuen, Department of Electrical and Computer EngineeringSupervisor: Prof. Mihai Sima, Department of Electrical and Computer Engineering

This research was supported by the Jamie Cassels Undergraduate Research Awards, University of Victoria.