MEMORANDUM
TO:
Distribution
DATE:
March 21, 2002
SUBJECT:
Questions and Answers from 21 March 2002 TIPS Meeting
HD Perspective
Presenter – Rodger Doxsey
No questions.
SM3b/SMOV3b Update
Presenter – Carl Biagetti
Q: Would the NICMOS cool-down schedule slip affect the ERO release plan?
A: Yes. The original plan was to have a single press release together with ACS, but now we might have to
delay the release of ACS results or have 2 separate press releases. The decision will be made tomorrow.
ACS Update
Presenter – Guido De Marchi
Q: What is the timescale for the ACS/WFC Amplifier B Bias level decay?
A: The timescale is about 24 hours.
Q: When investigating the possibility of achieving a lower temperature for ACS, will the engineers also
look at the implications to the entire system and how it will affect the aft shroud temperature?
A: Yes, the engineers will look into how the entire system will be impacted by a change in the operating
temperature for ACS.
Q: What is the turnaround time for the data to get to us?
A: The data takes a few hours to get to the ground and about 40 minutes to go through OPUS.
Q: When will the ACS GTO program start?
A: The bulk of the program will begin when ACS is properly aligned with FGS, possibly by mid April.
Basic science observations, however, will start a bit before then.
NICMOS/NCS Update
Presenter – Larry Petro
Q: Is the gradual speed decline of the turbo alternator anticipated?
A: The speed decline is anticipated since the fluid density increases with decreasing temperature. This is
normal.
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Q: The actual and the model cool-down rates were plotted against time. Would a plot of the cool-down
rates versus temperature provide better comparisons?
A: We have not done that comparison yet, and it will be next.
Q: Could the slower than expected cool-down rate simply mean that the cool-down model used was
wrong?
A: We may have more parasitic heat loss in the system.
Q: Given the longer than expected cool-down rate, does it mean that NICMOS and the entire system have
to be on all the time?
A: The current plan is to keep NICMOS cool at all times.
Q: What is the warmest temperature that NICMOS can operate at?
A: At this point we do not have detailed calculations yet, but the cooler (around 82 – 83 K) the better. The
team will need to establish not the temperature requirements but the critical requirements for scientific
performance at operational temperature above our current expectation.
Q: Can we manually speed up the cooling process?
A: The cooling system is at maximum performance right now, and there is nothing we can do to speed up
the cooling process at this point.
STIS Update
Presenter – Paul Goudfrooij
Q: What is the current temperature range for the MAMAs?
A: It is not clear at this point. From looking at the dark frames, the temperature seems to be the same as
before the servicing mission. We will need to wait for a few weeks, until all other systems are up, before
we can get a better read on the MAMA temperatures.
FGS/Pointing Update
Presenter – Ed Nelan
Comment: The small-amplitude periodic jitters could be due to the new solar arrays or they could be from
heating and cooling from the other parts of the spacecraft.
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