Background:

The quadrant selector high temperature safing sequence is another chained failure sequence designed to protect the quadrant selector motor from overheating and possibly burning out. If an overheating condition occurs, it is likely to be either a stuck motor or operational heater misconfiguration or failure. If the motor temperature reaches 55 ° C for 60 seconds, AP #29 will initiate RTS#45 which will reset the quad selector, turn off the bulk of operational heater power to the instrument body (zones 1-3) and activate AP#30. After an additional, two minutes, the motor temperature is still above 55 ° C, the reset is not likely to have worked so RTS#46 will pause all science sequences and turn off power to all mechanisms.

Note: As of 1/28/98, the C&DH on-line documentation is incorrect and has not been updated to reflect the correct sample period of 60 and 120 seconds)

RTS45: Quadrant shutter high temperature response #1

WATCHPOINTS sampled:

Instrument Quadrant Selector Motor

ACTIONPOINT logic:

If ( ITTETH3 > 55 degrees C (for 12 or more consecutive samples) )

Execute QS_TEMP1

file: qs_temp1.atf

00:00:00 /ICQSRS

00:00:00 /ICHTDCDB ZONE=1, DUTY=0, LOW=0, HIGH=0

00:00:00 /ICHTDCDB ZONE=2, DUTY=0, LOW=0, HIGH=0

00:00:00 /ICHTDCDB ZONE=3, DUTY=0, LOW=0, HIGH=0

00:00:00 /SWNOOP

00:00:00 /SWNOOP

00:00:00 /LCAPSTATE QS_TEMP2, ACTIVE

RTS46: Quadrant shutter high temperature response #2

WATCHPOINTS sampled:

Instrument Quadrant Selector Motor

ACTIONPOINT logic:

If ( ITTETH3 > 55 degrees C (for 24 or more consecutive samples) )

Execute QS_TEMP2

file: qs_temp2.atf

00:00:00 /ICSQPAUS

00:00:00 /SWNOOP

00:00:00 /ICPWMEOF

Key Telemetry:

ITTETH3 - quadrant selector motor temperature

Instrument: Quad Shutter High Temperature #1 Sensed

Value #1: The Actionpoint number that failed its limit.

Value #2: The RTS number that was requested.

Value #3: The number of consecutive failures that triggered this Actionpoint

Value #4: Unused.

Recovery Procedure:

Analysis will have to be performed as to why the temperature remained so high for so long. I&T testing has revealed software bugs in the past dealing with the way encoders are being read and it is just as possible to have a hardware failure. At the direction of the EOF, mechanism power may be restored using TI_me_on. This procedure will also send each mechanism to it’s home position so if it not desired to move the quad selector, this needs to be removed. Operational heater power may be restored using TI_th_init and TI_th_all_on or TI_th_set.

References:

TRACE C&DH FSW User’s Guide

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

Instrument Ops Handbook

For mechanism documentation on-line, see:

http://www.lmsal.com/TRACE/cal/index.html/

qs_doc.txt