Downlink Signal Level and Error Measurements for PACSAT-1

The PACSAT-l store-and-forward amateur radio satellite was placed into low earth orbit (LEO) on January 22, 1990 using the Ariane Structure for Auxiliary Payloads (ASAP). Most of the first year of operation was spent on application software development with full time operation of file server and file broadcast services beginning in late 1990. During 1991, both ground station and satellite-based software matured and stabilized such that the satellite sees a high volume of daily use both by individual amateur radio station operators and stations acting as gateways for terrestrial packet radio networks operating in the Amateur Radio Service. The purpose of this paper is to characterize system operation from the viewpoint of a PACSAT-l user. The results should be useful to system designers who would like to know what performance can be expected from similar systems. Among the topics addressed are: (1) the equipment configuration used during testing; (2) a comparison of expected and observed downlink signal strength; (3) an estimate of the downlink bit error probability; (4) a determination of the downlink efficiency, on a per-user basis, during typical file downloading operations; and (5) a brief characterization of downlink traffic according to type: file server, file broadcasting, and telemetry.