Fundamental Technologies

Galileo Spacecraft Pages

CDS-Produced EPD Telemetry Record

Table 12. EPD Science Record Format vs. Format Number

Format
Number
Telem.
Alloc.,
bps
Accum.
Period, cycles
Rate
Channels
Chan.
Map
CMS PHA Events Hskpg/
Status, bits

Telem. Out,
bps
1,2,3,4,5 5 6356 1 12 40 5.08
6,8 10 3356 1 12 40 10.16
7 15 2451 1 12 40 15.24
9,10 20 2451 2 24 40 20.03
11 30 1356 1 12 40 30.48
12 40 1451 2 24 40 40.07

Packet TypeData SizeDescription
Packet 1 Rate Bin Data
    Map1401 bytes 
    Map2508 " 
Packet 2 CMS PHA and Housekeeping/Status Data
    Map135 bytes 
    Map265 " 

RECORD/PLAYBACK SCIENCE PACKET HEADER

Figure 1. EPD2 Record Mode Packet Header

Field NameData OffsetField Size Content/Description
Time Include Flag01 =1, 1st packet and every 16th thereafter
APID17=0A hex
Packet Size89=76, 152, or 228
Packet Sequence #177 0=127
Packet Time2432/0 * R-R-R-mf
EPD Minor Frame Data56/24 *608 76-byte EPD Record Packet
EPD Minor Frame Data664/632 *608 76-byte EPD Record Packet
EPD Minor Frame Data1272/1240 *608 76-byte EPD Record Packet

* The first number is for time included, the second is for time not included.

Time Included - This bit indicates if the time filed contains information. For the Record Mode data, time is included in the first packet of a new rate and every 16th packet thereafter. For those packets without the time, the packet is shortened by 32 bits.

Application ID - This 7-bit field generated by the CDS for all packets, and is used to identify the source of the data.

Size - This 9-bit field indicates the number of data bytes included in the packet.

Sequential Number - This 7-bit counter is incremented for each new EPD packet created.

Time - This 32-bit value will contain time reference data whenever the "Time Incl." flag is set. The format is "R-R-R-mf." This is the 24 least significant bits of the S/C RIM counter + spacecraft minor frame clock.

EPD2 REAL-TIME SCIENCE PACKET

Figure 2. EPD1 RT Mode Packet Header

Field NameData OffsetField Size Content/Description
Time Include Flag01=1, Always
APID17=31 hex
Packet Size89=401 Map 1, Rate Packet
=508 Map 2, Rate Packet
=35 Map 1, PHA/Hskg Packet
=65 Map 2, PHA/Hskg Packet
Packet Sequence #1770-127
Format ID2441:5 bps
2:10 pbs
3:15 bps
4:20 bps
5:30 bps
6:40 bps
Packet Time28281/2 R-R-R-mf
EPD RT Data56 Rate or PHA/Housekeeping Data

Time Included - This bit indicates if the time filed contains information. For the RT Mode data, time is included in every packet.

Application ID - This 7-bit field generated by the CDS for all packets, and is used to identify the source of the data.

Size - This 9-bit field indicates the number of data bytes included in the packet.

Sequential Number - This 7-bit counter is incremented for each new EPD packet created.

Telemetry Format - This 4-bit field indicates which CDS-EPD data collection mode was used to generate the record.

1: 5 bps2: 10 bps
3: 15 bps4: 20 bps
5: 30 bps6: 40 bps

Time - This 28-bit value will contain time reference data whenever the "Time Incl." flag is set. The format is "1/2 R-R-R-mf." This is a translation of the 28 LSBs of the spacecraft minor frame clock.

Continue

Return to SBand Mission Software Requirements table of contents page.
Return to Galileo EPD Handbook Table of Contents page.
Return to Fundamental Technologies Main Galileo Page.
Return to Fundamental Technologies Home Page.

Updated 11/2/04, T. Hunt-Ward
tizby@ftecs.com