Fundamental Technologies

Galileo Spacecraft Pages

Appendix A. EDR File Structure

Table of Contents

1. EPD Housekeeping Decom

Source: GLL-SRD 90-07-10, Rev. C, pp. 4.7-17 - 4.7-18 (June 1984)

RIMMOD 91 LRS Bits No. of Bits Channel No. Function
Any41 2129-2136 8S-1687 EP MISC S1
"47 2129-2136 8S-1688 EP MISC S2
"59 2129-2136 8S-1689 EP MISC S3
"03 2129-2133 5S-1690 EPD SCAN 1
"03 2134-2136 3S-1691 EP MTR POS - 0,1,2,3,4,5,6,7
"00 2161-2168 8S-1692 EP CMDS EX
"00 2177-2184 8S-1693 EP CM CODE
"00 21861 S-1694 EP PWR MON - NORMAL, INTER
"02 2129-2136 8S-1695 EP MOTOR T
"04 2129-2136 8S-1696 EPD SCAN 2
"10 2129-2136 8S-1697 EP LEMMS T
"16 2129-2136 8S-1698 EP CMS T
"22 2129-2136 8S-1699 EP ELECT T
"28 2129-2136 8S-1700 EPD INPUT I
"34 2129-2136 8S-1701 EP +60V
"40 2129-2136 8S-1702 LOG AMP T
"46 2129-2136 8S-1703 EP -15V
"52 2129-2136 8S-1704 EP +10V
"58 2129-2136 8S-1705 EPD +6V
"64 2129-2136 8S-1706 EPD +3V
"70 2129-2136 8S-1707 EP -3V
"76 2129-2136 8S-1708 EP -6V
"82 2129-2136 8S-1709 EP -10V
"00 21871 S-1710 EP BUS PAR - NORMAL, ERROR
"05 2129-2136 8S-1711 EPD SCAN 3
"09 2131-2136 6S-1712 EPD SCAN 4
"23 2129-2136 8S-1713 EPD MEM CS
"35 2129-2136 8S-1714 EPD LEMMS D

2. Spacecraft Clock (SCLK)

Each GLL telemetry frame shall contain a S/C time field. The SCLK shall have the characteristic that it can be directly used to determine time, identify all measurements, and to correlate events to within the time resolution of the S/C clock.

The SCLK shall mark the first bit of the frame synchronization code time and shall represent the time interval in which the CDS collected the instrument data contained within the frame. The SCLK is shown in Figure 5 and is described below.

Figure 5. Spacecraft Clock (SCLK)

Real-Time Image Count (RIM). This field is a 24 bit counter which shall be incremented each 60 2/3 s (corresponding to a real-time image cycle). This clock shall keep unambiguous account of time for 32 years. The starting value of the counter shall be initialized at launch and shall not be reset after launch except from the ground after an interruption of power to the CDS memories. The maximum value of the SCLK shall not roll over until attaining the value 16777215.

Mod 91 Count (MOD91). The MOD91 counter is an 8 bit counter which shall be incremented once every 2/3 s. This field shall range in value from 0 through 90, with 0 corresponding to the start of the real-time solid state imaging cycle. This field shall increment by one every LRS frame.

Telemetry mode changes shall occur synchronously with (1) the rollover of the MOD91 count from 90 to 0 and (2) incrementing the RIM by 1.

Mod 10 Count (MOD10). The MOD10 counter is an 8 bit counter which shall be incremented once each 66 2/3 msec. This field shall range from 0 through 9, with the change to zero synchronous to the incrementing of the MOD91 count. This field shall increment by 1 for each frame transmitted or recorded at a telemetry rate greater than 7.68 kb/s. The MOD10 count is synonymous with the Real-Time Interrupt (RTI) in the CDS.

Mod 8 Count (MOD8). The MOD8 counter is an 8 bit counter which shall be incremented once each 8 1/3 ms. The field shall range from 0 through 7. With the change to 0 synchronous to the incrementing of the MOD10 count.

This field shall normally be zero in any frame being created at telemetry rates less than or equaling 115.2 kb/s. For those frames being routed to the DMS at rates exceeding 115.2 kb/s, the counter shall increment by one for each frame placed onto the DMS.

Next: 3. EPD Subsystem Telemetry

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Updated 10/19/04, T. Hunt-Ward