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Designing a Communications System for Eagle

Explore EagleSat's communications system design, research objectives, packet radio communications, link budget analysis, and future development plans. Learn about the system diagram, current status of the project, and the potential for improved range and connectivity.

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Designing a Communications System for Eagle

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  1. Designing a Communications System for Eagle Lisa Ferguson Dr. Gary Yale, Dr. Ed Post Arizona Statewide Symposium Announcements April 12, 2014

  2. Overview • System Definition • Research Objectives • Design Process • Packet Radio Communications • Friis Equation / Link Budget • Current Status • Future Development

  3. Communications System Definition • Responsible for up-linking commands to and down-linking data from the satellite • Provides a means of contact and control from the ground station • Comprised of a ground segment and a space segment

  4. Research Objective Develop a communications system that will establish a communication link over amateur radio frequencies between EagleSat and the satellite ground station at Embry-Riddle on the Prescott campus.

  5. Design Process • Requirements Definition • System Design • Develop Prototype • Preliminary Testing • Final Prototype • Validation

  6. Data Packet Protocol – AX.25 w/out Acknowledge • AX.25 Packet Radio Protocol • Packet will not be resent or rejected if containing errors • Error correction will be attempted by the computer software • All packets down-linked from satellite will be attempted to be received by the ground station • UI packet

  7. AX.25 UI Packet Structure Receiver Call Sign Sender Call Sign Control Bit PID Data Checksum SSID

  8. Current Status • Prototype developed and in operation for > three weeks • PCB designed and ready for fabrication • On schedule for testing on HASP

  9. Schematic

  10. Communications System • Software written in C • Control via On-board Computer (OBC) PIC 24FJ256GA110-16 MIPS processor • Modem converts audio tones to digital signals for both transmit and recieve • Audio tones 1200 / 2200 Hz • Non-return-to-zero inverted signals

  11. System Diagram GPS PIC24F Modem Transceiver Payload EPS

  12. Link Budget • Used to determine the amount of power necessary to establish a connection between a satellite and the ground station • Satellite transmit power is 500 mW • Final link budget TBD

  13. Friis Equation R ~ Ae Gt Gr Pt Pr

  14. Range vs Antenna Gain Plot

  15. Results of Friis Equation Analysis • Preliminary calculations suggest that the range possible and the range needed for communication do not correlate • Increased power and antenna gain will improve range and connectivity • Link budget will be calculated to include all factors

  16. Future Development • Complete Link Budget • Integrate with HASP payload • Fly on HASP • Integrate with EagleSat • Test • Launch 2016

  17. Thank You • Dr. Gary Yale • Dr. Ed Post • Mr. Jack Crabtree

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