Bit error rate evaluation of GSTDN/TDRSS communication links
Previously cited in issue 08, p. 1191, Accession no. A82-22092
Coffey, R. E.↗
Engineering topics
Coffey, R. E.
Publications and source records attributed to Coffey, R. E..
Optimal GSTDN/TDRSS bit error rate evaluation using limited sample sizes
Statistical studies of telemetry errors were made on data from the Solar Mesosphere Explorer (SME). Examination of frame sync words, as received at the ground station, indicated a wide spread of Bit Error Rates (BER) among stations. A study of the distribution of errors per station pass, however, showed that there was a tendency for the station software to add an even number of spurious errors to the count. A count of wild points in science data, rejecting drop-outs and other system errors, yielded an average random BER of 3.1 x 10 to the -6 with 99% confidence limits of 2.6 and 3.8 x 10 to the -6. The system errors are typically 5 to 100 times more frequent than the truly random errors.
Coffey, R. E.↗
A bit transition density encoder for the Space Shuttle 2 MHz data channel
As a result of several unique factors, the 2 MHz data channel which carries science data from the various experiments aboard the Space Shuttle through the Tracking and Data Relay Satellite System (TDRSS) lacks sufficient bit transition density to satisfy the bit synchronizer requirements at the ground station. It is noted that six encoding techniques were examined, and all but one, a PN cover sequence (Reset Bit Scrambler) were dismissed because of incompatibility with system constraints. The rationale behind the particular PN sequence chosen, the way it was truncated, and the new sequence properties are presented. The properties of the raw data stream are analyzed, as are the encoded sequence properties, including transition density. Diagrams of the encoder and decoder are included.
Schoggen, W. O.↗