Excerpted from CNN today:

Engineers at the Goddard Space Flight Center in Maryland have hit a snag in their efforts to bring the Hubble Space Telescope back on-line after a major equipment failure in space last month.

Hubble’s Science Instrument Control and Data Handling (SIC&DH) system went down September 27. This is the telescope’s on-board computer that coordinates commands to the various instruments and then downlinks the scientific data to the ground.

While that computer is off-line, most science observations are at a standstill.

The good news is that the computer was built with a fully redundant back-up channel called “Side B” designed to come on-line in the event “Side A” ever failed. Hubble team members at Goddard began a complicated process to switch over to “Side B” on Wednesday. This involved sending comprehensive software commands up to the telescope to essentially take control of Hubble’s suite of telescopes and other sensors through “Side B,” recalibrate all those instruments which went into safe-mode when the computer went down, start and stop gyroscopes, downlink data, and then check the data quality against some older “Side A” samples to make sure all is square.

Problems cropped up somewhere in that process Thursday night. We haven’t been told yet exactly what happened. The team is meeting today to discuss a further troubleshooting plan. We may get additional details later when that meeting ends. I am told they don’t expect the issue to be resolved today.

As noted, the switch-over process is extremely complicated, and it is probably to be expected that they would hit some sort of snag. Hopefully, they will work through it in the coming days and science operations can resume soon.

Even if the switch-over to “Side B” fails (and it is far to soon to go there), the Hubble design team had the foresight 20 years ago to build a spare SIC&DH system, which has been warehoused at Goddard all this time while the original instrument perked along just fine... (Please, everyone, let's just leave it at that and stay within the guidelines for this forum)

Keep your fingers crossed!

Glad to hear that there is spare hardware on the ground for advanced troubleshooting. Hot mockups can be unbelievably useful for this application; used to have them all the time for F-4 avionics systems.

One thing that's been puzzling me, and maybe someone knows this answer, is why the redundant SIC&DH box reportedly hasn't been powered up for all these years. You'd think that they'd do this periodically just to verify its serviceability for just this situation. I'm guessing that this was not done as a mission risk avoidance measure (sounds like the switchover process is pretty involved), or that we've not been given all the boring (to the general public) details of the maintenance routine.

Probably. Just look at how hesitant they are to turn on one itsy bitsy little microphone on Phoenix.

This is *never* done for a cold-spare system. You'd feel like an idiot testing side B only to find that it didn't work and side A broke in the meantime.

When MGS was lost, the side B MOC electronics had never been powered during flight at all.

Tread carefully everyone, very, very carefully.

Got it, Mike; thanks for the quick & informative reply! Interesting, never knew this was a basic UMSF design principle.

Dan, I am truly hip, believe me...

Does anyone know which CCD the HST is using?
Originally it was launched with a 2.56 million pixel CCD

It's more complex than that - it has several instruments, each of which will have one or more CCD's of their own.

For ACS, for example, there are a swath of different specs - http://adcam.pha.jhu.edu/instrument/overview/

HST has numerous CCDs in its instruments. I suppose you're referring to WF/PC-1? It was really a set of 8 CCDs (4 per plane) with a resolution of 800x800 pixels each.

Here's a list of the detectors currently onboard:

Indeed, I was talking about HST's best CCD... didn't want to elaborate too much in this "delicate" topic

That doesn't make any sense...Best is very dependent on what one is trying to do.

NASA is struggling to resuscitate the Hubble Space Telescope and could decide this week that it's too risky to try to revive it before astronauts arrive on a servicing mission next year. Some engineers fear an attempt to restart a faulty low-voltage power supply on Hubble's Advanced Camera for Surveys could present a risk to one of its cameras and to plans for repairing two others.
http://www.floridatoday.com/article/200810...317/1006/news01
Hubble Space Telescope Fails at the Right Time, one month later and could be catastrophe.

I wonder if they could use WF/PC2 and leave the ACS SBC off. What happened to NICMOS in all of this?

http://www.stsci.edu/hst/nicmos/localNews?...SafingAndStatus
But I guess this hasn't been updated since the SI C&DH anomaly happened.

Thanks! I wasn't really following this at that point.

Some more updates coming out today:
http://spaceflightnow.com/shuttle/sts125/081023hubble/

One software patch, one determination (hope?) that the glitch was a one-time event.

NASA's Hubble news site reports "The current primary camera on the Hubble Space Telescope is now back in active operation and will resume science observations shortly" and that Space Telescope Science Institute expect to release an image later this week after calibration.

More details here.

(First post after several months lurking - trust this info on Hubble instruments is OK to post)

Fantastic news so far. Now hoping for confirmation that the flight spare SIC&DH box is fully functional.

Wow, looks like WFPC/2's days aren't over after all.

Update...

http://www.flightglobal.com/articles/2008/...-telescope.html

Oh, great.

This is not a specific criticism, but a general one; I know the reasons for it have to be lack of personnel or money, and hopefully not lack of planning or foresight. I can't understand why this spare was not dragged out of storage periodically (maybe annually) and tested so that any problems could be identified & resolved long before it was needed. "Intermittent" problems are by FAR the most diffiicult to resolve because the symptom does not persist; it's too easy to end up chasing your own tail.

ESA also published a press report:
The NASA/ESA Hubble Space Telescope is back in business and HST science operations were resumed on 25 October 2008, four weeks after a problem with the science data formatter took the spacecraft into safe mode.

http://www.esa.int/esaSC/SEMQOV5BXMF_index_0.html

You answered your own question: this would have cost money. Also, the only thing extra this is costing now is time; if they had identified this 5 years ago it still would have been an intermittent problem and hard to fix.

Frankly I don't know very many astronomers who think HST is worth the money it costs to run any more, not even counting the cost of SM4, but apparently it's "too well-loved" by the public to just let die. You have to admire the STSCI's ability to do PR, if nothing else.

Oh, they have dragged it out a couple of times (but not for verification but to test various procedures before uplinking commands to live flight hardware.) It gets worse: on such occasions, it was noted that faults occurred with the flight spare during such operations...

Repair won't be easy: you're dealing with a box full of long-obsolete ICs. Perhaps with unlimited time and resources, they could have taken the modern approach of an all-software data handling system running on general-purpose hardware, just in case HST did not live up to its original design life of 15 years.

Thanks, Del.

<sigh>...I get it. I'm a bit slow about logistics issues for small programs like Hubble; used to military aircraft that usually have hundreds of end items to support, so the philosophy's a bit different.

Not seeing a happy ending here, but would be delighted to be proven wrong.

FlightGlobal's story is wrong, there is no need to build a new box.

http://forum.nasaspaceflight.com/index.php...27669#msg327669

If we ignore cost, how much of the observation capability cannot be duplicated by other telescopes? Long exposures in all wavelengths? IR & Near IR?

Don't forget that it is the only large ultraviolet telescope in operation.

In fairness, it's proven quite difficult to find much objective comparison between HST and ground-based capability; my earlier message was probably a little too hard-over. And like so many things it's probably a false dichotomy anyway, because if HST were shut down tomorrow, it's not like the money would be spent on ground-based telescopes.

The main justification for NGST is in the thermal infrared, measurements that are very hard to make from the ground because of atmospheric emission. NICMOS, so far as I know, has not been very successful for a variety of technical reasons and has probably been mostly supplanted by SIRTF anyway. I'm not sure about the role of UV; people seem to have concluded that with current detector technology it'll be hard to do a lot better than HST for a while.

http://www.stsci.edu/institute/conference/...HSLprogram.html is a good source of information.