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

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

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

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.

Design Process Requirements Definition System Design Develop Prototype Preliminary Testing Final Prototype Validation

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

AX.25 UI Packet Structure Receiver Call Sign Sender Call Sign Control Bit PIDDataChecksum SSID

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

Schematic

Communications System Software written in C Control via On-board Computer (OBC) PIC 24FJ256GA 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

System Diagram GPS Payload EPS PIC24F Modem Transceiver

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

Friis Equation R PtPt AeAe GtGt GrGr PrPr ~

Range vs Antenna Gain Plot

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

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

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