From: Marc Postman (postman@stsci.edu)
Date: Thu Jun 29 2006 - 07:01:19 PDT
Begin forwarded message:
> Colleagues,
>
> Here is a brief update on what will be happening with ACS over the
> next few days if everything goes as planned.
>
> Cheers,
> Ken
>
> ----------------------------------------------------------------------
> --
>
> 1) The Anomaly Review Board (ARB) is reasonably convinced that the
> ACS suspend was caused by an open +15V circuit in the low voltage
> power supply (LVPS) on Side-1. This is not 100% certain, since
> currently it appears that a shorted +15V circuit could also produce
> the on-orbit behavior under certain conditions.
>
> 2) The ARB has determined that a switch to Side-2 electronics should
> restore ACS capabilities if the Side-1 LVPS is at fault.
>
> 3) The ARB has recommended that we go ahead with the side switch.
>
> 4) A Flight Readiness Review (FRR) is being held Thursday, just
> before our STScI science staff meeting. If the FRR board gives
> its approval to go ahead with the Side-2 switch, then the following
> sequence of activities [5-9] will occur.
>
> 5) Pending FRR board approval, new flight software will be loaded into
> EEPROM late Thursday / early Friday, and ACS will be brought to
> life
> briefly on Side-2. This will include a check of the memory,
> copying
> the FSW into RAM, a check of the TECs, and transition to full
> operate
> mode. The MAMA Interface Electronics, mechanisms, and the CCD
> electronics will be powered. If all is well, ACS will be safed
> for the
> upcoming SMS intercept on Sunday.
>
> 6) After SMS intercept, ACS will be brought out of safe mode, the
> TECs will be returned to their nominal (current) operating
> temperatures, and several memory/dump tests will begin. This will
> take most of the day Monday.
>
> 7) We'll get our first internal bias/dark/flat exposures Tuesday,
> July 4, with the remaining orbital verification calibration
> observations to follow during the week. The WFC TEC temperature
> setting will be lowered early in this process from -77 C to -81 C
> to improve WFC performance.
>
> 8) Science observations will be interleaved with calibration
> exposures,
> either in sequence or in parallel. The first ACS GO observation
> should occur late Tuesday night (~9:30 PM - around the time of
> fireworks!).
>
> 9) The ACS Team will be analyzing the data as soon as they come in,
> and we'll update the staff when further information becomes
> available.
>
-----------------------------------------------------------------
Marc Postman Email: postman@stsci.edu
STScI - CMO Phone: +1-410-338-4340
3700 San Martin Drive Fax: +1-410-338-4796
Baltimore, MD 21218 U.S.A. http://www.stsci.edu/~postman
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