The In-Orbit Operation of Four Microsat Spacecraft--Four Years Later

More than four and one half years have passed since the launch of four Microsat spacecraft developed by the Radio Amateur Satellite Corporation of North America (AMSAT-NA) and other cooperating AMSAT groups. This paper documents the current status of the four Microsats with particular emphasis on AO-16 and DO-17. The software supporting the store-and-forward message system of AO-16 and LO-19 has changed significantly since launch, starting out as a real-time digital repeater, progressing to a connected-mode file server, and finally evolving to a broadcast-mode file server. A concise description of this software evolution is included along with long-term satellite usage data for AO-16. Statistics such as average bytes of directory and file data transmitted per day and the average time a user spends waiting for directory and file data requests to be serviced are included. In 1993, DO-17 was returned to service in the 2 m band after having been off the air for over 18 months. The temporary lapse in operations was caused by difficulties loading software after the failure of its 13 cm downlink transmitter modulator. Details of the recovery are summarized as an example of how operational problems have been addressed by an all-volunteer software development, command, and control team.