Update on ACIS Operations
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Transcript of Update on ACIS Operations
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20101
Update on ACIS OperationsUpdate on ACIS Operations
I. New Patch for ACIS Flight SWII. Control of the ACIS FP temperature
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20102
Update to the ACIS Flight SWUpdate to the ACIS Flight SW
• ACIS flight SW has been updated three times during the mission in 2000, 2004, & 2008• We are preparing the fourth patch for uplink in Spring 2010• This new patch contains two new items:
1) Fixes a bug in a subarray mode – the list of bad pixels and columns onboard is misinterpreted if the subarray starts in a row other than row 1
2) Prevents Back End Processor (BEP) from crashing when one of the Front End Processors (FEPs) is powered down - there have been several occurrences when radiation levels have been high, that ACIS was commanded by the stored command load to start the first science observation of the orbit, it started collecting the bias data, but then received a high radiation shutdown signal from the satellite, but ACIS waits for the bias maps to be collected before stopping the science run, but before the bias maps are collected a command is sent which powers down the FEPs, this caused the BEP to crash in the past
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20103
Control of the ACIS FP TemperatureControl of the ACIS FP Temperature
• Desired temperature -119.7 C, FI/BI CCDs go out of gain spec at -119.2C/-118.2 C
•Mean T of science observations• ACIS DH heater turned off in April 2008• SIM FA6 heater turned off in August 2009
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20104
Controlling the ACIS FP TemperatureControlling the ACIS FP Temperature
FP is contained in the “Camera Body”
DH heater is on the “Camera Body”
• Camera Body used to be held at -60 C, it now floats between -65 and -70 C
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20105
Exploded View of ACIS HWExploded View of ACIS HW
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20106
Restrictions on Spacecraft AttitudeRestrictions on Spacecraft Attitude
• unfortunately there are no other heaters we can turn off which would help to keep the FP cold• must now consider imposing restrictions on the satellite’s orientation during observations (which is already done for several other systems on Chandra)
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20107
Impact of Current Restrictions on Spacecraft Pitch Angle Impact of Current Restrictions on Spacecraft Pitch Angle
• restrictions imposed in 2005 significantly increased the amount of time spent at tail-Sun attitudes, pitch>115• unfortunately this is a hot attitude for the ACIS FP temperature
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20108
Chandra in the Shuttle Bay Before LaunchChandra in the Shuttle Bay Before Launch
• thermal properties of the back surfaces of SIM are changing with time
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 20109
Chandra in the Shuttle Bay Before LaunchChandra in the Shuttle Bay Before Launch
• heating on the back surface of the SIM, heats the ACIS Camera Body• heating of the shade for the radiator, heats the radiator
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201010
Earth in the ACIS Radiator FOVEarth in the ACIS Radiator FOV
•Earth in the ACIS radiator FOV has a significant impact on the FP temperature• The complex shape of the shade has been approximated by a simpler shape, we are working on a more realistic model• we recently included reflections off of the interior surfaces of the shades
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201011
ACIS FP Temperature vs. Earth Solid Angle Without ReflectionsACIS FP Temperature vs. Earth Solid Angle Without Reflections
Adams-Wolk (SAO)
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201012
ACIS FP Temperature vs. Earth Solid Angle With ReflectionsACIS FP Temperature vs. Earth Solid Angle With Reflections
Adams-Wolk (SAO)
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201013
Future Strategies to Keep the ACIS FP ColdFuture Strategies to Keep the ACIS FP Cold
1) Earth in the ACIS radiator FOV2) Sun on the back surfaces of the SIM and the radiator shade
There are two reasons the ACIS FP temperature gets warm now:
Our only option now is to impose restrictions on the spacecraft attitude, but that will be difficult because:
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201014
Backup MaterialBackup Material
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201015
Chandra’s Changing Orbit and Implications for the FP TemperatureChandra’s Changing Orbit and Implications for the FP Temperature
•Chandra’s orbit is changing such that in 2012 the inclination will be at its highest value in the mission and the perigee will be at it lowest• the solid angle of the Earth in the ACIS radiator FOV will also reach missions highs in 2012• other mission constraints such as momentum management and thermal issues frequently conflict with keeping the ACIS FP cold during perigee passages
Davis (Chandra FOT)
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201016
The FP Temperature during Recent Perigee PassagesThe FP Temperature during Recent Perigee Passages
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Example of a good perigee passage
Adams-Wolk (SAO)
Chandra X-Ray Observatory CXC
Paul Plucinsky EPI Cal 201017
The FP Temperature during Recent Perigee PassagesThe FP Temperature during Recent Perigee Passages
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sciencecal
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Example of a bad perigee passage
Adams-Wolk (SAO)