5.7 Events and Conflicts during Operations

This is a summary list of special events and conflicts between instruments that occurred during the Operational Phase of the mission (some of which have already been mentioned):

Revolution	Event
79	First revolution after PV Phase.
94	PHT-FCS1/TRS2 change in illumination behaviour/brightness increase.
116	AOCS calibration led to shorter science window. Some loss of
	science due to system crash.
137	ISO pointing performance tests using ISOCAM.
152	Soft geomagnetic disturbance with no impact on science.
161	Tests of the SWS virtual fourth aperture.
173	Tests of LWS parallel mode.
196	As soon as AOS was achieved at the start of the revolution, it was seen
	that ISO had gone to survival mode and that both the Earth warning
	and forbidden regions had been traversed by ISO -
	ISO had viewed the Earth for about 2 minutes. All temperatures were
	out of range (high) and all scientific operations for the revolution
	were therefore suspended.
197	Recovery procedures implemented.
198	Normal operations resumed within 36 hours. No damage was done to the
	satellite.
204	LWS switch-off rolled back 60 minutes.
217	Some LWS tests made during the revolution to verify a command changing
	the LWS biases.
220	Many small problems affecting a large number of observations. First there
	were problems with the PPM (Earth constraint was approached closely),
	then a guide star was not found, and PHT-P2 suffered from latch-up problems
242	Over four hours of observations lost due to problems with the Goldstone
	antenna.
256	Goldstone problems led to loss of over one hour observations.
263	Goldstone problems led to loss of over one hour observations.
264	ISOCAM and SWS measurements made for ISO pointing tests. Special
	ISOCAM mode had to be used for the one hour test.
267-268	Goldstone problems led to loss of over ten hours observations.
274	Spacecraft problems (automatic on-board reset) led to the loss of half the
	revolution.
290	Improved SSO tracking algorithm implemented.
294	The opening of the science window was delayed by 2h 30m due to a
	planned delta-V maneouver (to keep the phase of the orbit correct) and
	second DLCM, both at the start of the revolution.
301	Nearly six hours of science lost due to spacecraft problems.
317	Long ($\sim$6 hours) calibration observation of Uranus affected for 90 min by
	short Goldstone dropout.
327	Improved Sun ephemerides.
330	Goldstone problems led to 5 observations (80 min) lost.
343	Loss of communications with ISO for 45 min from Goldstone due to
	high winds.
356	Tests of LWS wheel subsystem plus minor Goldstone problems.
364	ISO went into survival mode at the start of the revolution, leading to
	a loss of two hours science.
365	Some Goldstone problems leading to loss of 85 min science time.
368	STR calibration updated.
372	Goldstone power failure led to the loss of 5 hours observing. Satellite
	went into perigee with ISOCAM in wrong mode.

Revolution	Event
373	No anomaly observed with ISOCAM, but one hour observing lost due to
	one minute of loss of contact with the satellite.
378	LWS activities halted until further notice due to FP interchange wheel
	problem (positioning difficulties). Next two revolutions could not be
	replanned. This time was devoted to LWS observations, that were lost.
384	Straylight rejection measurements for SWS.
398	Many telemetry problems due to a thunderstorm around Madrid and
	Goldstone problems led to the loss of over 100 min science time.
410-412	Tests of ground system for the 366 day year problem (1996 was a leap
	year). On revolution 411 this caused the loss of one hour of science.
413	Telemetry problems in Madrid and Goldstone caused the loss of two hours
	of science.
417	Various problems caused the loss of just over one hour of science.
432-435	Manual LWS checks and tests were made to try and solve the wheel problem.
442	LWS operations re-start with one test observation completed successfully.
447	Real re-start of LWS operations with 30 observations completed nominally.
452	Sun ephemerides recalculated four times per revolution, instead of once
	per revolution to improve ISO pointing accuracy.
470	Lots of minor Goldstone problems lead to the loss of $\sim$1 hour of science.
484	Lots of problems at handover leading to 67 min science lost.
522	Loss of over six hours science due to LWS problems (microprocessor and reset).
528	Non-nominal behaviour of SWS led to the loss of 78 min science.
566	Loss of 75 min of science due to a CTV problem.
571	CAM-CVF observations in the Mission Data Base temporarily `blocked'
	from the automatic scheduling routines to prevent the strong increase in
	band 3 dark currents observed in SWS observations performed
	in the following 30 min.
575	Loss of 100 min science time (SWS observation) due to non-availability
	of Goldstone.
578	Fire alarm drill on station, Instrument Controller left post as per procedure.
	No events happened during this time.
602	Almost four hours of science lost due to spacecraft attitude problems -
	one observation was up to 1.5 degrees off.
603	Many problems with PHT-P2 latch-ups affecting 85 min science.
	Science observations using PHT-P2 detector suspended.
613	Start of PHT-P2 latch-up tests. Also, many telemetry drops but little impact
	on the science time.
614	Lots of telemetry drops due to a thunderstorm around VILSPA.
620	Two hours of observations lost due to Goldstone problems.
623	Two hours of observations lost due to Goldstone problems.
637-641	400 min of PHT science time affected or lost due to PHT-P2 latch-up
	problem.
646	Loss of 81 min science time due to Goldstone problems.
659	End of PHT-P2 latch-up tests.
661-662	PHT straylight tests during eclipse.
664	Start of long ($>$140 min) eclipses.
668	Loss of 90 min of observations due to Goldstone problems.
672-673	Special PHT straylight measurements during eclipses.
676	Automatic scheduling of CAM-CVF observations resumed. Mission
	Planning software was updated so that SWS observations were not
	scheduled any more until after 30 min of a CAM-CVF measurement.
678	Last revolution for which the eclipses lasted longer than 140 min.

Revolution	Event
684	Resumption of PHT-P2 observations.
688	200 min observation lost due to Goldstone problems.
719	LWS wheel tests.
721	$\sim$82 min lost due to problems on instrument start-up.
722	Solar flare caused loss of most of the science time due to enhanced
	glitch rate.
732	284 min science lost due to Goldstone problems.
756	Problems with guide stars caused 60 min of science to be lost.
757	Third DLCM and an orbit correction maneouvre carried out at the start of
	the revolution.
	Problems with Goldstone led to the loss of 185 min science.
764	OTF set to 2$^{\prime}$$^{\prime}$ for all instruments.
777	100 min of science lost due to a combination of errors, plus on the 1997-1998
	year change the wrong year entered in the system.
843-844	$\sim$90 min of science lost as orbit geometry causes VILSPA antenna to point
	directly at the Sun (ISO in the VILSPA-Sun line).
851	Problems with a guide star (blemish on CCD) causes 4h 45m of science
	to be lost.
875	Liquid helium depletion at 21:07 zulu on 8 April 1998.
876-880	Some SWS observations carried out as bands 1 and 2 are still useable.
881-887	Start of SWS post-He observations. SWS used all these revolutions.
888-907	SWS observations interleaved with the Technology Test Phase (TTP).