ST5000 HRTB Packet

Change Log
Version Date Comments
1.0 19-Jan-2007 Initial Release
1.1 31-Jan-2007 Add FWHM

This section describes the "high rate track box" packet that is sent out on the ACS Echo line to the TM. In normal telemetry, track boxes are subcommed with an 8-frame period; any given track box appears every 8th frame. The HRTB contains all 8 track boxes in every frame, usually sent at 10 Hz. This packet was designed to provide detailed real time data, allowing post-flight re-analysis of tracking algorithms.

589 (5+8+8*72) bytes (this includes the packet protocol bytes) at 10 Hz requires a comm bandwidth of 46720 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 8 (ROUTE-ST5K2)
1 Packet Code 18 (HRTB-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 Current X-position 1/4 Floating point centroid
12 Current Y-position 1/4 Floating point centroid
16 Current Peak Value ADUs
17 Current Mode Most common value
18 Current Flux 1/2 ADUs
20 Track box row 1 unsigned bytes
27 Track box row 2 unsigned bytes
34 Track box row 3 unsigned bytes
41 Track box row 4 unsigned bytes
48 Track box row 5 unsigned bytes
55 Track box row 6 unsigned bytes
62 Track box row 7 unsigned bytes
69 Target Status Enumerated
70 Target Amplitude 1/2 ADUs
71 Target Amplitude 2/2
72 Current FWHM (1/4) Floating point pixels
76 spare
77 spare
78 spare
79 spare