ST5000 CACS Packet

Change Log
Version Date Comments
1.0 28-Oct-2004 Initial Release
1.1 18-Feb-2005 update Codes and CRC
1.2 10-Mar-2005 Move Qs to end
add state variables
renumber entries
1.3 28-Mar-2005 Move routing and packet codes before the CRC
1.4 30-Mar-2005 Add tracker ID
1.5 12-Dec-2005 Add NTRK to slot 12
1.6 12-Oct-2006 Switch to double-precision attitude

This section describes the telemetry packet that is sent out on the ACS I/O line to the CACS.

52 bytes (this includes the packet protocol bytes) at 10 Hz requires a comm bandwidth of 4160 bits per second.

ST5000 CACS Packet
Byte Item Notes
-4 Sync 1 (0x4a)
-3 Sync 2 (0x57)
-2 Sync 3 (0x50)
-1 Packet Length
0 Routing Code 10 (ROUTE-CACS)
1 Packet Code 16 (CACS-PACKET)
2 CRC (1/2) CCITT CRC 16 (x^16+x^12+x^5+x^1)
3 CRC (2/2)
4 Tracker ID TBD
5 spare
6 Frame Number (1/2) 16-bit unsigned int
7 Frame Number (2/2)
8 ACS State
9 ACQ State
10 LIS State
11 PIT State
12 # Stars Being Tracked Lose roll when this drops to 1
13 Software Input Bits
14 Digital Input Bits
15 Digital Output Bits
16 ACS Attitude Qx (1/8) 8-byte doubles in standard XDR/RPC format
24 ACS Attitude Qy (1/8)
32 ACS Attitude Qz (1/8)
40 ACS Attitude Qw (1/8)