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Fundamental TechnologiesGalileo Spacecraft Pages |
EPD Rate Channel Data Processing
Table 3. EPD Rate Channel Packet
| Byte # | Description |
| 1 | b0: Update flag (MSB) 1: new; 0:old b1, b2: Spin quadrant 00:A; 01:B; 10:C; 11:D b3: New spin 0:same; 1:new b4: Map ID 0=MAP1; 1=Map2 b5-b7: Motor position (LSB) 000:Pos.0;...111:Pos. 7 |
| 2, 3, 4 | Rate Channel 1 (24 bits) |
| 5, 6, 7 | Rate Channel 1 (24 bits) |
| 8, 9, 10 | Rate Channel 3 (24 bits) |
| ... | ... |
| 143, 144, 145 | Rate Channel 48 (24 bits) |
| 146 | HV Monitor Value |
| 147-151 | Housekeeping/Status |
| 152-211 | 12 PHA events (20 bits each) and 30 bytes of
filler, or 24 PHA events (20 bits each |
Once the data is retrieved by the CDS, it must sequentially go through the 24-bit rate channel values and add them to the proper rate channel bins defined in the CDS memory. The addition algorithm for this may be fairly simple (see Appendix A for more details, but determining which bin to address is not so straightforward. This task will be addressed in section 7.
The motor position, spin quadrant, and motor direction (in the science record status byte), all represent the values present during the quadrant that was just completed. In other words, the motor and spin parameters match up with the rate channel data that is also present in the data for that minor frame. One could expect, therefore, that in a minor frame data packet in which the "new spin flag" is set, the spin quadrant will equal "D."
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Updated 11/2/04, T. Hunt-Ward
tizby@ftecs.com