Background:

The a portion of the control computer code is dedicated to running science sequences. These sequences can be in three states that have been identified: Running = 0x8000, Paused = 0x8800 or 0x0800, or Stopped = 0x0000. The mnemonic that indicates the state of a sequence can be found on the DPU_SEQUENCE page (IKDPSQST).

Some instances that would cause a sequence to pause would include: having a pause written into the sequence; an instrument mechanism overcurrent condition (RTS # 37 - Motor Overcurrent Response #1 will pause a sequence as the first command in the RTS); an ACS Fine Sunpoint re-acquisition, RTS 28, will also issue a pause command.

A sequence will be prematurely stopped when Actionpoint #42 detects the CHRON buffer as being full, and calls RTS#52 to stop a sequence that is being run. A stopped condition is different from a paused condition in that the next time a start sequence command is issued, i.e. from the timeline, the sequence will be started. A paused condition would not allow the new sequence to begin and must be cleared from the ground

A sequence that is paused can be resumed when directed by the EOF or OE (see recovery procedure, below). The sequence will pick up from where is was paused and continue to execute any nested sequences. The ATP will skip any timeline commands whose time had passed and continue with the current timeline command.

A list or RTS’s that pause or stop sequences are listed below:

14, 28, 34, 37, 40-42, 45-47, 49, 52

Key Telemetry:

On the pages, DPU_SEQUENCE, and INST_OV, the mnemonic (IKDPSQST) can be found that provides the current sequence status. The following values have been observed:

Also of value would be the sequence number and sequence ID (IKDPSQID). These can be found on the INST_OV page and the DPU_SEQUENCE page.

Recovery Procedure:

Once a sequence has been found that is prematurely stopped or paused, notify the OE and the EOF then begin troubleshooting. When a satisfactory cause has been determined, the sequence can be resumed as needed. The command to resume a sequence is

References:

TRACE C&DH FSW User’s Guide

http://tracedata.nascom.nasa.gov/~trace/cdhsw/trace/design/sc/pre_rts.htm

Instrument Operations Handbook - CC User’s Guide; Science Sequence Document

http://www.space.lockheed.com/TRACE/TRACElinks.html