Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V12_0/V12_006.ZIP/V12_006

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Date: Tue,  3 Jul 1990 02:09:32 -0400 (EDT)
Subject: SPACE Digest V12 #6

SPACE Digest                                       Volume 12 : Issue 6

Today's Topics:
        Re: Testing of Hubble Space Telescope
           Payload Status for 07/02/90 (Forwarded)
        Re: Testing of Hubble Space Telescope
              Re: MOL (yes, yet more...)
         Re: Hubble Space Telescope Update - 06/29/90
           Re: What Spherical Aberration is
            Re: How to fix the HST
                Hubble Trouble
              looking for graduate study

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Date: 2 Jul 90 20:57:37 GMT
From: zaphod.mps.ohio-state.edu!uwm.edu!ogicse!milton!unicorn![e-mail]  (Worth Henry A)
Subject: Re: Testing of Hubble Space Telescope

In article <[e-mail]> [e-mail]
(Brad Templeton) writes:
>I can believe that a full sytem test of the HST would have been too expensive.
>
>But I refuse to believe that a test that would have detected real BONEHEAD
>errors like a 1/2 wave curvature error would have been expensive.  In fact,
>any astronomer with mirror making experience could have done it for $10, given
>a hallway and a chance to sit at the focus, couldn't they?

     Individual testing would not help if the problem was a mis-communication
of the specs from within NASA and/or the designer's organization; the
individual component testing would most likely have been to the same incorrect
figure. The design surely went through many design revisions, and as every
experienced engineer or programmer knows, change control is not a trivial
problem (such a problem was the cause of the Apollo 13 explosion). Before
crucifying PE, let's give the review board a chance to find the actual point
of failure.

PS - Did any of you happen to catch Sen. Gore's hearing on C-SPAN, It was
rather interesting, Gore seemed determined to trap the NASA reps. into
saying that the experiments that might replace those affected would be 2nd-rate,
thus justifying, instead, a cut in the HST's operating budget. Just what we
need, a perfectly usable n-billion dollar instrument orbiting in a sleep mode,
because Congress thinks that experiments not originally scheduled in the
first couple of years are 2nd-rate and not worth the operating costs.
What does this portend for the HST's future even if all the problems are
quickly corrected, or even if there had been no problems? :-(

HW
7/1/90

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

Date: 2 Jul 90 16:09:15 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Payload Status for 07/02/90 (Forwarded)


    Daily Status/KSC Payload Management and Operations 07-02-90.


    - STS-35 ASTRO-1/BBXRT (at OPF) -

    Experiment monitoring continues.  BBXRT liquid argon
    servicing will also be performed today.


    - STS-37 GRO (at PHSF) -

    Test batteries will be discharged today.


    - STS-40 SLS-1 (at O&C) -

    Module and experiment mechanical operations will be active
    today along with STT MLI installation.


    - STS-41 Ulysses (at Hanger AO) -

    At the VPF, preps for CITE testing will continue today.


    - STS-42 IML-1 (at O&C) -

    Rack, floor, and module staging is continuing.


    - Atlas-1 (at O&C) -

    Pallet brackets, temperature sensors, and cables will be
    installed today.


    - STS-46 TSS-1 (at O&C) -

    EMP paper closure continues.


    - STS-47 Spacelab-J (at O&C) -

    Rack 5, 7 and 11 staging continues.


    - HST M&R -

    GSE cables will be installed today.

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

Date: 2 Jul 90 17:23:24 GMT
From: optilink![e-mail]  (Clayton Cramer)
Subject: Re: Testing of Hubble Space Telescope

In article <[e-mail]>, [e-mail] (Brad Templeton) writes:
> I can believe that a full sytem test of the HST would have been too expensive.
>
> But I refuse to believe that a test that would have detected real BONEHEAD
> errors like a 1/2 wave curvature error would have been expensive.  In fact,
> any astronomer with mirror making experience could have done it for $10, given
> a hallway and a chance to sit at the focus, couldn't they?
> --
> Brad Templeton, ClariNet Communications Corp. -- Waterloo, Ontario 519/884-7473

My first telescope mirror was 1/2 wave -- but then again, it was 3" f/4.5,
and I was using cruddy equipment.

I would have been quite willing to test it for $20. :-)
--
Clayton E. Cramer {pyramid,pixar,tekbspa}!optilink!cramer
Amtrak subsidies: adults playing with choo-choos.
----------------------------------------------------------------------------
Disclaimer?  You must be kidding!  No company would hold opinions like mine!

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

Date: 2 Jul 90 12:58:09 GMT
From: cs.utexas.edu!titan![e-mail]  (Donald Heskett)
Subject: Re: MOL (yes, yet more...)

MOL was to have been placed in a low earth orbit, and the 'system' was
to have consisted of a single MOL and its astronaut transfer vehicles.
This would have resulted in very poor, and easily defeatable, coverage.

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

Date: 2 Jul 90 18:50:23 GMT
From: sdd.hp.com!usc!cs.utexas.edu!news-server.csri.toronto.edu!csri.toronto.edu![e-mail]  (Wayne Hayes)
Subject: Re: Hubble Space Telescope Update - 06/29/90

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>                      Hubble Space Telescope Update
>                               June 29, 1990
>
>     Since June 26 there has only a little activity in orbit but, as I am
>sure most of you aware of by now, a lot of action on the ground.

This is the lynching, right?  :-)

>spherical aberration is the only mirror problem -- in all other respects the
>mirrors are perfect.
>4 cm, the circle of least confusion is ~1.5 arc second, if you were to
>assume that the error is in the primary mirror and that the center of the
>mirror is correct, then there will be ~2 micron error at the edge.
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^ !!!!!!
>of real image quality we are talking about ~70% of the encircled energy in
>~0.8 arc second radius and ~12% in 0.1 arcsec (spec was 70% in 0.1 arcsec
>radius).

Well, if Ron's as-usual-hard-facts-only post is any indiction, most of
us are making FAR, FAR to big a stink about the mirror problem.  All the
other problems seem iron-out-able, and some kind of corrector plate or
replacement mirror (hopefully the secondary) will be up by 1993 at the
latest.  As Eugene Miya pointed out, we made an oops, we learned, there
wasn't much other choice, and now we go on.  Let's just hope that we can
convince the funders (polititians?) that the problem is not as big as
the media and USENET has so far made it out to be.  For now we get only
twice Earth-bound resolution; soon it'll be the 10 we hoped for.

Thanks Ron, yet again, for sticking to the facts.

--
Mathematics: That branch of Human Thought which takes a finite set of trivial
axioms and maps them to a countably infinite set of unintuitive theorems.

Wayne Hayes    INTERNET: [e-mail]    CompuServe: 72401,3525

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

Date: 2 Jul 90 12:26:18 GMT
From: ncrlnk!ncr-mpd![e-mail]  (Mike McManus)
Subject: Re: What Spherical Aberration is

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>   In article <[e-mail]> [e-mail] (Craig E. Smith) writes:
>   >        Does anyone know if it is possible to correct for spherical
>   >aberration, or at least reduce its effects significantly, by the
>   >use of advanced computer image analysis techniques.
>
>   Yes and no and somewhat.  Under good conditions, when you have a fair idea
>   of what you're looking for, and it's a simple shape, and it's bright against
>   a dark background, yes.

This is kind of a half-baked idea, but indulge me for a minute...

Let's assume that the problem with the HST mirrors is a design problem (as
current speculation seems to point to).  That means that they should know (1)
what the *theorectical* design parameters should be (as designed), and (2) what
the actual parameters are (as built).

Knowing these 2 things, I would think that one could come *very* close to
post-processing observed data to produce what they should have gotten, had the
mirrors been built as designed.  This would not require comparing images at
all, since trying to match the "real" image and observed image is near
impossible anyway.

So am I missing something?  Assuming that (1) and (2) are known, what's the
problem with post-processing of images?

--
Disclaimer: All spelling and/or grammar in this document are guaranteed to be
            correct; any exseptions is the is wurk uv intter-net deemuns,.

Mike McManus                        [e-mail], or
NCR Microelectronics                ncr-fc![e-mail], or
2001 Danfield Ct.                   uunet!ncrlnk!ncr-mpd!garage!mikemc
Ft. Collins,  Colorado
[phone]   Ext. 307

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

Date: 2 Jul 90 14:29:32 GMT
From: att!cbnewsh![e-mail]  (lawrence.m.geary)
Subject: Re: How to fix the HST

In article <[e-mail]> [e-mail] (Francis Vaughan) writes:
>
>Build a robotic installation machine. The machine is latched to

Minor problem: No one one earth knows how to do this yet, and it's unlikely
that anyone will have one ready by 1993.

That aside, you don't just plop a corrector into a telescope and make it
good. Telescope designs are highly optimized, and as you pointed out,
a corrector can cause problems as well as solve them.

The idea of putting individual correctors on each instrument is better
because the separate correctors can be optimized for the axial or off axis
position of each instrument. A single, big corrector would probably ease
problems with some of the instruments while making things worse for others
off the optical axis.

Two other problems with individual correctors, though. A) They'll have
to replace ALL the instruments. I haven't heard that they are actually
considering that, only the WFPC. B) You've got to put the new instruments
back into their slots *just right* or they will be out of alignment. Maybe
there are relay mirrors that can be collimated to account for any slop
in instrument insertion, but I don't know.
--

Larry Geary: [e-mail] | Dislexics of the world, untie!
         [e-mail]         |

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

Date: 2 Jul 90 21:21:11 GMT
From: frooz![e-mail]  (Steve Willner, OIR)
Subject: Hubble Trouble

Here is some information on the HST status and some comments of mine.
The information came from a talk given here on 6/29.  The speaker got
his information directly from a briefing to the Science Working Group.

The image problem is about a half wave of spherical aberration.  (My
impression was that this means wavefront error, but I cannot refute the
claim it means surface error.  If so, the wavefront error would be one
wave.)  Other aberrations (coma and astigmatism) have not been seen in
the Faint Object Camera, where they would appear, but tests are not
sufficient to say that these aberrations are identically zero.  The
spherical aberration is definitely in the telescope system and not the
instruments, but it is to early to identify the cause.  (See below.)

The net effect is that only 10% of the light falls within the
originally planned central spot size.

The effects of the poor image quality will depend on the instrument.
The Fine Guidance Sensors will be little affected, so most of the
astrometry science will still get done.  The High Speed Photometer will
have to use larger apertures and thus will take in larger backgrounds,
but only the most difficult projects will be affected.  The two
spectrographs (Faint Object Spectrograph and High Resolution
Spectrograph) will have to use wider slits or else lose light falling
outside the narrow slits.  Using wider slits degrades the spectral
resolution.  Many science projects - those that don't use the highest
resolution on the faintest objects - can still be done, though.  The
cameras (Wide Field/Planetary Camera and Faint Object Camera) will be
the worst affected.  At best, image restoration might be able to derive
full-resolution images from the 10% of the light still within the
central spot, but at least a factor of 10 (2.5 magnitudes) in
sensitivity will thereby be lost.  Ultraviolet imaging will be possible
at spatial resolution comparable to ground-based telescopes in visible
light.

There are actuators on the primary mirror intended to correct its shape
for residual astigmatism, if any.  These actuators have not yet been
turned on.  They will be only slightly effective in correcting for
spherical aberration and certainly cannot be causing the problem.

No decision has been made on how to treat approved projects that now
turn out to be impossible or how to distribute time that will
presumably be made available by their cancellation.  Since the time
available was over-subscribed by a factor of ten, there will still be
lots of worthwhile things to do.  Imaging was 40% of the approved
time.  (This figure may have been WF/PC imaging only.)

NASA already planned to replace some instruments in 1993, and design of
the new instruments has been underway for some time.  It should be
possible to correct the spherical aberration in the new instruments,
though with varying degrees of difficulty.  For the new imager
("STIS"), the correction is trivial.  For the infrared instrument
("NICMOS"), correction should be possible in the current design.  The
new spectrograph ("?") will need some design changes.  With the new
instruments, the originally expected performance should be achieved (as
far as now known).

Lots of things that might have gone wrong seem to be working.  Power,
communications, and telescope scheduling are better than expected.
Because of the bad images, telescope alignment may be cut short and the
science mission begun early.

---------What follows is from me, not from the talk-------------------

There are at least three possible causes of the spherical aberration:
surface error in the primary, surface error in the secondary, or
installation of the instruments at the wrong distance from the primary
mirror.  Speculation now centers on the first two, but it's my own
impression that the lack of coma favors the third.  We shall see.

Many people have complained about the lack of testing of the two
mirrors as a system.  Such testing should not have been necessary,
since the theory of geometric optics is well understood.  Further, such
tests would not necessarily have shown all possible problems.  Until we
know more, it is premature to assert that such tests ought to have been
done.  (There were certainly management problems with HST.  It just
isn't clear that this particular decision was one of the wrong ones.)

The problem of image restoration is rather different than the radio
case.  An optical detector measures the wave "intensity," not the
"amplitude."  The difference is that phase information is lost.  Some
degree of reconstruction should certainly be possible, but it is not
clear how much.  Since any reconstruction costs signal-to-noise, the
faintest objects will not be reconstructable.   However, there are lots
of bright objects where HST resolution will be valuable.  On the other
hand, it may be better to do spectroscopy for now and wait for STIS.

There are still a lot of facts unknown.  Let's be careful about jumping
to conclusions.
-------------------------------------------------------------------------
Steve Willner            Phone [phone]         Bitnet:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [e-mail]

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

Date: 2 Jul 90 18:00:21 GMT
From: usc!sdd.hp.com!samsung!xylogics!bu.edu!dartvax![e-mail]  (R. Aileen Yingst)
Subject: looking for graduate study

Greetings!

I'm looking for a graduate school with strong programs in geology and/or
planetary science.  I'll be graduating next year with a Physics modified with
geology major and would like to start school hunting with the hope of
studying planetary/space science or just plain geology.  E-mail responses to
the above address and thanks very much in advance.

aileen
--
|R. Aileen Yingst                             Dartmouth College Class of 1991|
| Internet:[e-mail]         UUCP: ...!eleazar!aileen    |
|        Snail mail:  HB 4444, Dartmouth College, Hanover, NH 03755          |
|    "You may be big....but I'm small!"    --Daffy Duck                      |

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End of SPACE Digest V12 #6
*******************