The refrigerator on the infrared camera on Hubble is broken and the camera is shut down, for now.
Better hope servicing mission 4 goes off on the revised schedule and is successful.
Currently functioning instruments on Hubble are just the old Wide Field Camera (2), which has one bad chip, and the Fine Guidance Sensors.
From stsci.edu:
"[doing software upgrade]...After the software was installed we attempted to restart the NCS, but it went into safemode before reaching a stable cooling situation. A project tiger-team, including the engineers who designed and built the NCS, has since made three more attempts to get the cooler started, all of which have failed. The leading theory is that small amounts of a contaminant, likely water ice, have been transported from benign spots to spots that interfere with the sensors and turbo machinery during the partial warm up of the system. Across the project, we have taken the decision to stand down from further attempts to restart the cooler. This will give the engineering staff some time to look more closely at the data and develop alternate turn-on sequences. It will also allow the entire system to warm up, which is likely to help with contamination control. The cooler will remain off through Servicing Mission 4 (we would have had to shut it off for the Servicing Mission to conserve power). It is likely that we will try again to restart it immediately after SM4.
The net result is that NICMOS observations planned for the next month will be deferred until after SM4. We expect that we will be able to get the NCS up and running after SM4, and so we will include all the remaining Cycle 15 and 16 NICMOS observations as we build the Long Range Plan for Cycle 17."
Basically they were doing a software patch in preparation for the new instruments to be installed during SM-4 (now scheduled for Oct 10 launch, weather permitting).
This required shutting down the NICMOS infrared camera.
The camera is actively cooled with a new no-refrigerant cooler, and the cooler failed.
They think it failed because of vapour condensation, possibly water ice - Hubble outgasses slowly, and the vapour tends to condense out on cool spots, like the NICMOS fridge. When it was shut off it warmed up, and the volatiles likely migrated, and apparently condensed out, either on the turbo or on the sensors, interfering with the cooler turnon.
If the conjecture as to the cause is correct, then it is probably fixable, most likely simply by letting it warm up and have the ice sublimate to somewhere else.
But, since the servicing mission is scheduled for Real Soon Now, they're not going to mess about, just shut the thing down and work on rebooting it during the engineering tests needed for the new instruments anyway.
If the conjectured cause is correct, then the problem may well have solved itself, and if the new Wide Field Camera (3) works as planned, NICMOS may not be needed again anyway.
Better hope SM-4 goes off on schedule though.
Bummernickles.
We still have NIC observations scheduled...
LOOK! Over there ->
Pretty Picture!
click for source
Old ACS image - kinda cheating... except it takes time to find these things in the data
Julianne explains much better than I could
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NICMOS goes a full octave further into the infrared than WFC3 will and is much more sensitive at all infrared frequencies, so it will definitely still be needed.
don't think so - WFC3(IR) is twice as sensitive as NICMOS
it only goes to 1.7 microns, but NICMOS only goes to 2.5 microns
which is about half an octave
or so the instrument handbook tells me - WFC3 has of course not flown yet
HST is a warm telescope and the thermal backgrounds are significant. For general use, NICMOS is most useful at H-band and shorter, and WFC3/IR was designed to limit its capability to shortward of 1.7 um. Although NICMOS works at K, the background is high enough that, for example, nearly all imaging surveys with NICMOS were done in J and H (F110W and F160W), not K.
WFC3/IR should be somewhat faster than NIC3, and has a much larger area and better sampling than NIC3 - about a factor of 10 increase in survey speed. However, NIC2 and NIC1 do provide finer pixel sampling that may be useful for some projects. Also, NICMOS is actually in the telescope and its performance is known rather than predicted. So I hope they are right and they can get it back.