Background:

AP#24/ RTS #40

ACTIONPOINT logic:

If ( Instrument Front Survival Heater Temperature > 50 degrees C AND

Instrument Fore Flange Temperature > 50 degrees C AND

Instrument Primary Mirror Temperature > 50 degrees C

(for 60 or more consecutive samples)) Execute TELE_TEMP

The purpose here is to protect against a general overheating of the telescope body. The three thermistors checked are located at the front, middle and rear of the main telescope tube. For nominal full sun orbit conditions, telescope temperatures will range between 20-30 (TBC) degrees C. If the above temperatures reach 50, then it is possible that some type of software control failure has occurred and the heaters have been left on.

The critical parameter here is the primary mirror temperature, IOMIRRORTEMP. At ~43(??) degrees, the bonding compound between the mirror and it's base plate begins to breakdown which could cause a shift in the mirror position.

Key Telemetry:

Event Message:

1024 - Instrument: Telescope High Temperature Sensed (ActionID, RTSID,

fails)

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.

From inst_thermal page:

Instrument Front Survival Heater Temperature - IOFRSRHTTEMP

Instrument Fore Flange Temperature - IO4FLNGTEMP

Instrument Primary Mirror Temperature - IOMIRRORTEMP

Recovery Procedure:

1. Reset action point #24 to ACTIVE (/LCAPSTATE AP=24, ACTIVE)

2. After the cause has been determined thermal control will have to be re-established. TI_th_init can be used to restore operational heater deadbands and duty cycles and TI_th_all_on can be used to turn on heater zones 1-6 (excludes zone 7 - CCD). TI_th_set may be used to interactively change a deadband, duty cycle or on/off status of one or more heaters.

References:

TRACE C&DH FSW User’s Guide

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

Instrument Ops Handbook