[X] My Assistant

[ilbasso]

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!

[nprev]

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.

[centsworth_II]

...the redundant SIC&DH box reportedly hasn't been powered up for all these years....I'm guessing that this was not done as a mission risk avoidance measure...

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

[mcaplinger]

why the redundant SIC&DH box reportedly hasn't been powered up for all these years...

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.

[ElkGroveDan]

Please read http://www.unmannedspaceflight.com/index.p...;showtopic=5444
Specifically

"The hubble servicing mission is off topic"

Tread carefully everyone, very, very carefully.

[nprev]

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...

[Guest_PhilCo126_*]

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

[djellison]

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/

[Del Palmer]

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

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:

CODE

                ACS         WFPC2         NICMOS         STIS
Wavelength
range (nm)

        WFC: 370-1100        115-1100    800-2500      FUV-MAMA:115-170
        HRC: 200-1100                                  NUV-MAMA: 170-310
        SBC: 115-170                                   CCD: 200-1100
  
Detector(s)

        SITe CCDs, MAMA    Loral CCDs    HgCdTe         CCD, MAMAs

Image format

        2×2048×4096        4×800×800     256×256        1024×1024
        1024×1024                        256×256        1024×1024
        1024×1024                        256×256        1024×1024

[Guest_PhilCo126_*]

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

[tedstryk]

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.

[peter59]

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.

[tedstryk]

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

[mcaplinger]

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.

[tedstryk]

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