Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_5/v11_594.txt

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Subject: SPACE Digest V11 #594

SPACE Digest                                     Volume 11 : Issue 594

Today's Topics:
         Atlantis has a leak like Columbia's
           Re: gravity and the hubble lens
     Re: Is there a backup HST mirror ??? (see sci.astro)
            Re: HST focus problem
               Hubble telescope optics?
         Re: Hubble Space Telescope Update - 06/28/90
          The HST was risky from square one
             Re: Space telescopes
              Unofficial hubble trouble
           Re: Hu Space Telescope Update - 06/24/90
         RE  Hubble Space Telescope Update - 06/28/90

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
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----------------------------------------------------------------------

Date: 29 Jun 90 18:18:22 GMT
From: sam.cs.cmu.edu![e-mail]  (Vincent Cate)
Subject: Atlantis has a leak like Columbia's

I was just watching NASA sellect and the tests this morning on
Atlantis have shown a leak so it will not be flying soon.
It seems they do not have spare "umbilicals" to connect
shuttles to tanks.  They took Endevour's for Columbia.
I think they said it would take over a year to make another
one.  Things look very bad.

   -- Vince

------------------------------

Date: 29 Jun 90 19:14:10 GMT
From: earthquake.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: gravity and the hubble lens

In article <[e-mail]> [e-mail] (Lord Snooty @ The Giant Poisoned Electric Head       ) writes:
>if the problem is really microgravity (rather than a defective spec)
>i would have thought that, given accurate surface profile measurements
>and six years of computer time, the effects of gravity changes on the
>performance would be well understood. after all, the bulk modulus of
>the material is known...

I bet it's not known to anywhere near the precision that the Hubble's
mirrors were ground to... 8-(

Space isn't just dangerous, it's devious.  Designing things to operate out
there is a constant hassle, and we're still discovering new problems that
can appear.

--
  == George William Herbert  ==       Quantum Mechanics can explain everything
 == JOAT for Hire: Anything, ===  except Madonna, Flame Wars, and NASA's space
=======Anywhere, My Price.=======   Policy.  We're working on the first two...
 ==   [e-mail]    ==  :::"Gee, I Hope that wasn't a hostage...":::
  ==  ucbvax!lilac!ocf!gwh   == The OCF Gang: Making Tomorrow's Mistakes Today

------------------------------

Date: 29 Jun 90 08:51:43 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Is there a backup HST mirror ??? (see sci.astro)

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Fraering Philip) writes:
>>... they _can_, if neccesary, bring HST back to Earth to be fixed?
>
>It's theoretically possible but nobody wants to try it, especially
>after the structural parts have been in space for years.  Heaven only
>knows how a 3G reentry and potentially-rough landing would mess up
>the optics.

Nope, sure wouldn't want messed up optics would we!

Surely the real question is, what harm could retrieving HST do that
couldn't be FIXED on the ground afterwards.  Who cares if the mirror
mounts go out of alignment; there's plenty of time to realign them
before launch.

There were dozens of different abort modes designed into the HST launch
mission where the Shuttle re-entered and landed with HST still in the
bay.  If it weren't possible to do this safely (at least for the orbiter
and crew) they wouldn't have allowed HST as a payload.

If they bring it down they might well have to detach the solar panels
first -- I cannot find any reference to a re-furl capability.  (Maybe
I should call a re-furl agency? groan).  But those panels are a pain
in the butt anyway!  We could re-launch it with properly designed arrays
that don't waggle 10 inches for 10 minutes out of every 90.

If it turns out the primary has the aberration, I despair.  Rename it
the Edsel Space Telescope (EST) and chalk it up to [ha!] experience.

But if it's the secondary, come on!  Start grinding and schedule a
retrieval mission.  This is too much money to waste.
--
If the human mind were simple enough to understand,   =))  Tom Neff
we'd be too simple to understand it. -- Emerson Pugh  ((=  [e-mail]

------------------------------

Date: 29 Jun 90 20:04:10 GMT
From: [e-mail]  (Kevin William Ryan)
Subject: Re: HST focus problem


   In regards to post-processing the HST images to remove the spherical
abberations, I would have to say that this is neither easy nor robust in any
general sense.

   First things first: the spherical abberation will likely vary across the
field.  This means that the distortion function is shift-variant.  Standard
Fourier techniques require a linear shift-invariant transfer function for a
successful inversion.  Secondly, the abberation may lose information - in
that certain spacial frequencies will not be recorded well.  This lowers the
signal level.  Since noise is (roughly) white noise, that is, of roughly
constant level at all frequencies (this is very rough, but a good approximation
of most systems), the S/N ratio will be considerably lower.  After a point
you lose the information completely.  I suspect that the higher frequencies
will be lost entirely - never even recorded.  Remember that the focus spot
size is considerably larger than it was supposed to be - light outside
the current aperture of the detectors is lost.

   Finally, successful inversion requires a well-known distortion function.
Since the resolution of the Hubble even now is at or past the limits of
most ground based scopes, it will be _hard_ to get an accurate reading of
the mirror distortions.

   I suspect that, perhaps using maximum entropy methods, a partial inversion
of the distortions can be done.  But I don't think, based on my work with
inverting distortions, that it will improve matters enough for HST to be
terribly useful...

                                                 kwr

Internet: [e-mail]

------------------------------

Date: 28 Jun 90 12:51:14 GMT
From: philmtl!philabs!briar![e-mail]  (Robert Casey)
Subject: Hubble telescope optics?

Heard on the News about the optics in the Hubble space telescope.  Either the
big mirror or the secondary was cut to a wrong spec.  Question:  Didn't they
test it on the ground?  Thought crossed my mind that maybe the index of
refraction is different for vacuum vs air, but mirrors shouldn't care about
that.  Though there must be some lenses on the instruments the mirrors aim the
light at.  Might turn out that someone designed these lenses with values for
air, instead of vacuum.  (didn't change the default values in some software).

Can they do any interesting science before the shuttle goes up to fix it?

------------------------------

Date: 29 Jun 90 23:47:01 GMT
From: cs.utexas.edu![e-mail]  (Donald A. Varvel)
Subject: Re: Hubble Space Telescope Update - 06/28/90

In an earlier posting I stated that earthbound telescopes maintain
their figure in a variety of orientations, and could therefore
be expected to perform similarly in space to how they perform on
earth.  I asked in what way the HST was different?  Thinner glass?

My premise seems questionable at least.  Several people pointed
out to me that mirror support systems for large telescopes are
complex and push the mirrors in different ways and in different
places depending on where they are pointed.  I had based my
statement on experience with small amateur telescopes, and some
dimly remembered reading about larger instruments.

Apparently the optics and mounting of any large telescope
constitute a system that can only be tested definitively as a
unit.  I am beginning to believe that there *was* no clear-cut
way to test the HST.

Thanks to the people who emailed information.

-- Don Varvel ([e-mail])

------------------------------

Date: 30 Jun 90 01:15:58 GMT
From: agate!brahms.berkeley.edu![e-mail]  (Greg Kuperberg)
Subject: The HST was risky from square one

It may seem now as if the Hubble Telescope is a priceless asset to this
nation and to science, and some bozos down at Perkin-Elmer have nearly
ruined it.  It may look like the proper course of action is to form a
marauding lynch mob that will terrorize NASA for the next two years.

But let's face it:  Launching satellites is a risky business.  NASA's
record on a par with that of every other space agency or company.
People will make many mistakes in the course of any large engineering
project.  The difference between space projects and most other
enterprises is that smaller mistakes have larger consequences.
Catastrophic error is NASA's toughest enemy.

A telescope that definitely works is not what we ordered for
$2,000,000,000.  What we bought was a telescope that might work, but
also might get destroyed during launch or malfunction in space or might
have been built to the wrong specifications.  If you think that it was
worth the money in the first place, then your main response to the
latest bad news should be: "We tried and we failed.  Back to the drawing
board."
-----------------------------------------------------------
The Tail Gunner

"A well-regulated militia being necessary to the security of a free state,
the right of the people to keep and bear arms shall not be infringed."

------------------------------

Date: 30 Jun 90 04:41:41 GMT
From: uokmax![e-mail]  (Robert W Murphree)
Subject: Re: Space telescopes

SummarThe Most Science for the Least Bucksy:

Expires:
References: <[e-mail]>
Sender:
Followup-To:
Distribution:
Organization: Engineering Computer Network, University of Oklahoma, Norman, OK
Keywords:Hubble,

In article <[e-mail]> [e-mail] (John Nordlie) writes:
>An atricle I read in Sky & Telescope before the launch of Hubble
>indicated that many scientists thought that the idea of "putting
>all your eggs in one basket" by sending up one very complex and
>expensive space telescope was a very bad one.  They said that
>a larger number of smaller, less complicated machines could do
>more science at less risk.  The recent troubles with Hubbles'
>mirrors seem to bear out this opinion.  My question is this:
>could a number of small, simple space telescopes be built from
>off-the-shelf components do the work of the now "useless" WFPC
>on Hubble?  For example: if you took a Celeston 16" 'scope, a CCD
>imager, a computer, and the various sub systems of a satellite and
>built a small space telescope, could this device gather data that
>would justify the expense of launching it?  Amsat and the University
>of Surrey have demonstraited that good space science can be done
>on a very limited budget.  What do you think?
>
>
>
While it is true that NASA seems to prefer megamegabuck projects at the
expense of smaller, more timely, more manageable projects, there was some
reason for the size of the project.  From what I can tell, high resolution is
linked to apature -smaller UV telescopes like IUE are very useful and result
in large numbers of publicattion.  but to get .07 arc seconds of resolution
you do in fact need a big mirror.  That fact, not just the  politics and
beauracracy of it contributed to the long delay.  In fact, scientists have
wanted a large, optical telescope for a long time.  But to get the high
resolution it had to be so big and so expensive that it just now arrived.

In fact in recent years, I notice some small, cheap missions are on the way.
COBE, a few light sats (180 kg) to be launched in the early 90's, the
Mariner Mark I and II series for planetary exploration are all budget rate
science missions.  JPL has been toying with microsats since brilliant pebbles
started to miniturize spacecraft.  Whether all of this will survive the
Space Station era as the missions of the 80's suffered under the shuttle era
remains to be seen.  Ocaisonally  reason does prevail at the NASA.
c>
>
>=======================================================================
>John Nordlie   |   I tried to think of something intelligent to say.
>               |    " Urgh..", I managed.
>               |               - Harry Harrison 'A Stainless Steel Rat
>               |                                 is Born'
>=======================================================================

------------------------------

Date: 29 Jun 90 19:26:12 GMT
From: osu-20.ircc.ohio-state.edu![e-mail]  (Robert Bunge)
Subject: Unofficial hubble trouble

A friend of mine who writes an astronomy column for a local newspaper talked
to some NASA officials yesterday.  It happens that he is very knowledgable
about mirror testing and optics, and was able to get some interesting infor-
mation that I haven't seen in the common press.

It is believed the secondary mirror is 1/2 wave over corrected.  It was
suppose to be 1/20 wave.  Information at the time of the testing seemed to
indicate that it fell within those tollerences.  This, according to the
person he talked to, points to a problem with the testing equiptment or `
set up that Huges used.  As earlier posting in this net said, the images
are about 2" across.  I made a 4-inch telescope that resolves 1.5" double
stars cleanly.  The guy also said the defects were "textbook", which also
suggests a mistake during manufacture.

Apparently, they are ready worried about the fall-out from this - both from
the public and from Congress.

Bob Bunge
[e-mail]
----------------------------------
All information above is subject to change even before I finished writing it!

------------------------------

Date: 28 Jun 90 16:29:50 GMT
From: usc!snorkelwacker!bu.edu!mirror!otto!jimi!herbert![e-mail]  (Doug Phillipson 5-0134)
Subject: Re: Hu Space Telescope Update - 06/24/90

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>
>                           Hubble Space Telescope Update
>                                 June 24, 1990
>
>     In the past three days not a lot has happened with the Hubble Space
>Telescope (HST) other than a lot of focus testing.  Currently, the telescope is
>in a "new focus" position that has given "the best image quality yet."  Analysis
>of the out of focus images and the "in focus" images is in progress.
>Preliminary analysis indicates there is improvement in the image.  All else
>is quiet with all other spacecraft subsystems.
>

    How is focusing accomplished.  Must you snap a picture then do some
image processing on it or do you have a more interactive method. Also
how real time can the images get. Is there a "video link" to watch live movement?

Inquiring minds want to know.

Douglas Phillipson (EG&G)  (Long singatures waste net time)

------------------------------

Date: 29 Jun 90 15:29:00 GMT
From: cs.utexas.edu!sdd.hp.com!apollo![e-mail]  (Peter Nelson)
Subject: RE  Hubble Space Telescope Update - 06/28/90



 [e-mail] (Ron Baalke)

>     At least one of the two mirrors in the Hubble Space Telescope (HST) was
>built in the wrong shape and will not work properly. The flaw most seriously
>affects the Wide Field and Planetary Camera (WFPC) and the Faint Object Camera
>(FOC) which use visible light but doesn't affect as heavily four other
>instruments which do not depend heavily on crisp, clean visible images. The
>WFPC, that was to do 40 percent of the scientific work, will not be usable and
>the FOC will not work as hoped.



>    The mirrors were not tested together before launch because that would have
>cost hundreds of millions of dollars. Even after HST was assembled the system
>was so delicately balanced it could not be calibrated and tested under the
>influence of Earth's gravity.

>     Ground controllers may be able to compensate for some of the problems,
>but a permanent correction will have to wait two or three years for astronauts
>to visit the craft and replace some of the parts.  Corrective optics on a
>second generation of instruments currently under construction may compensate
>for the spherical aberration, and could be available for launch in 1993, 1996
>and 1997.

  Does someone have the whole story on this?  The above posting, from
  a NASA site yet, still leaves key questions unanswered.

  Just what WAS the manufacturing flaw?

  I'm also confused about why it wasn't tested.  At one point, above, the
  poster implies it was cost, and later he implies it was a result of the
  Earth's gravity.  Is he saying, in other words, that it would have had
  to shipped up on an earlier shuttle flight to test?  [be specific, dammit;
  is there some special school they send government-workers to learn
  a new vague English dialect ("Vaguelish") ? ]

  Did anyone take measurements of the mirror and use computer modeling
  to try to account for the effects of gravity?

  What did the cost of testing have to do with anything, anyway?
  Testing is part of ANY engineering project; if you can't afford
  the testing you can't afford the project!   There may be certain
  kinds of tests that *cannot* be done, but the poster, above, implied
  that these tests COULD have been done but it was decided not to
  because of cost.   Did the people who approved the $1.5 billion
  KNOW they were approving a project which was deliberately not
  testing certain key components?   I assume HST was a line-item
  in NASA's budget; did Congress know they were approving a project
  that was skipping the testing of certain key parts?  ( I am definitely
  going to ask my Congresscritter!)

                                                     ---Peter

------------------------------

End of SPACE Digest V11 #594
*******************