3440 (57

640 sec 3 min)

3440 (57

640 sec 3 min)

860 (14

160 sec 3 min)

28.672 sec

IRS data.- The 1000-bps IRS data were available to the MDS high-rate channel. The data were also routed to track 8 of both digital tape recorders for recording and subsequent playback. Two IRS data sources were formed and supplied to the MDS and DSS. There were 139 measurements allocated for the IRS data. Included were engineering data which were sampled frequently enough to include all measurements for data rates up to 33 1/3 bps, VO time, FDS memory readout, VIS commanded state, VIS actual state, and VIS A/PW data as well as the IRTMS and MAWDS status and A/PW data. Figure 108 is a block diagram of the IRS data format. An IRS minor frame consisted of 280 bits (28 10-bit words); an IRS major frame consisted of 4480 bits (448 10-bit words), which was 16 IRS minor frames. MAWDS engineering measurements were sampled once, IRTMS measurements were sampled 4 times, and MAWDS science measurements were sampled 15 times. VIS digital and VIS A/PW were sampled once out of every two consecutive IR science major frames. Each MAWDS telemetry measurement was represented as a 10-bit word (0 to 1023 DN); therefore, the maximum resolution of 1/1023 (±0.098 percent) was available. IRTMS and VIS engineering telemetry measurements were 9 bits plus the sign, for a maximum resolution of 1/511 (±0.196 percent).

Relationship of IRS data to engineering data.- Since the FDS was a synchronous system, a definite relationship existed between IRS and engineering data outputs. Some of these relationships were as follows:

66 VIS frames equal 1 IRS minor frame

4 IRS minor frames equal 5 engineering minor frames (1000 bps)

24 IRS minor frames equal 1 engineering minor frame (33 1/3 bps)

96 IRS minor frames equal 1 engineering minor frame (8 1/3 bps)

VIS data.- VIS telemetry data were routed to the DSS only. All line-retrace data plus every 7th pixel were routed to each of seven tracks of both I TR's. Six status words were assigned as carriers for line-retrace (flyback) data. Additionally, 5 bits were used for IRS data, and this was adequate to


(15 bus

FDS Status (15 bus)

data (10 bits)

Orbiter time (30 bits)

MAWDS digital status

MAWDS det 2

MAWDS det 3

MAWDS det 4

MAWDS det 5

MAWDS raster pos

IRTMS digital

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