The PCsat Mission and Cubesat Design Notes

There are growing opportunities for Universities to gain educational access to Space. The Naval Academy has used the Department of Defense Space Test Program for its PCsat and Sapphire projects and the Stanford Cubesat program offers a unique opportunity to get numerous small student satellite payloads into space. As a spin-off of our PCsat project, we have investigated several off-the-shelf solutions to the Telemetry, Command and control portion of small satellites that can greatly simplify small satellite and CubeSat designs. This permits students to concentrate on the various payloads and other aspects of the project without starting from scratch with a comm. system. This simple comm. System based on AX.25 packet radio is being flown this summer in the Naval Academy’s Personal Communications Satellite (PCsat) which will demonstrate downlinks receivable on Hand Held Transceivers (HT’s) with only a whip antenna. Further these simple downlinks can be easily fed into the Internet for live worldwide distribution of data. These designs are all based on the amateur radio standard on-air AX.25 packet network protocol that is implemented in a number of off-the-shelf modems (called Terminal Node Controllers or TNC’s). The following paragraphs describe three such hardware devices and the remainder of this paper describes how TNC’s and the AX.25 protocol were used on PCsat