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Subject: SPACE Digest V12 #3

SPACE Digest                                       Volume 12 : Issue 3

Today's Topics:
               Telescope mirror testing
       Re: RE  Hubble Space Telescope Update - 06/28/90
          Re: Reflections on Hubble and NASA
           Hubble Space Telescope Update - 07/02/90
             grim tidings for the future
         Re: Hubble Space Telescope Update - 06/28/90
         Re: Hubble Space Telescope Update - 06/28/90
             Perkin-Elmer and the Hubble
                (none)
               Re: Meaning of Palo Alto

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

Date: 3 Jul 90 05:21:02 GMT
From: uoft02.utoledo.edu![e-mail]
Subject: Telescope mirror testing

Here is some info I thought I would pass along.  In Astronomical
Optics by Daniel Schroeder he discusses in very excellent detail
telescopes, abberation and testing.  Yes testing.  (We keep hearing
from certain groups that it was obvious that they should have done
this or that.  While they were sitting around criticizing I was trying
ti understand more of what is going on.)  Anyway, he mentions that one
of the best tests of a mirror is using the Twyman-Green interferometer,
which is a modified Michelson interferometer.  Picture a standard
Mich. int.  Here the movable mirror is replaced with a positve lense,
called a null lense, and the test mirror.  The lens and mirror are
placed so that their optical axes coincide, with the focal point
of the lens coincident with the center of curvature of the mirror.  The
other change si to use a laser plus beam expander as the light source,
with the pinhole in the beam expander placed at the focal point
of the input collimator lens.  The beamsplitter divides the amplitudes
of the incident plaen wavefront, which, after refelction in the two
arms of the interferometer, returns to the beamsplitter.  A portion fo the
two beams is recombined at the beamsplitter and directed toward the output
lens and detector (D).   A good picture etc can be found in Malacara
(1978) Optical Shop Testing (Wiley:New York).  Note:  "It should
be evident from this discussion that the test using the T-G interferometer
is one of the null lens and mirror combination, not the mirror itself."
The lense must be independently tested.  This is what was done with HST.

Other interesting articles are Wetherell and Rimmer Appl Opt 11, 2817 (1972)
and "Instrument Handbooks" 1985 STscI.

Doesn't really add much but I thought others might find this of interest.
Besides, as Ron Baalke has pointed out they are not exactly sure where
the trouble is.  Speculation at this point is just that.


Robert Dempsey
Ritter Observatory
lens

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

Date: 2 Jul 90 13:55:50 GMT
From: xanth!xanth.cs.odu.edu![e-mail]  (Frank C. Paterra)
Subject: Re: RE  Hubble Space Telescope Update - 06/28/90


I remember reading a few years ago that some university in the
midwest determined that since all the R&D for hubble was already
paid for, it would be relatively cheap to build a clone.  Except
for the fact that they are missing the TDRS and ground station
support, they could have their very own *Great Observatory*.

If this is true (Seems reasonable), why doesn't NASA take their
lead and start building the replacement?  Of course you have to
convince everyone that they are to build a clone and not a new
design.


Rambling thoughts ...
Frank Paterra
[e-mail]
--
Frank Paterra
[e-mail]

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

Date: 2 Jul 90 15:20:55 GMT
From: uoft02.utoledo.edu![e-mail]
Subject: Re: Reflections on Hubble and NASA

In article <[e-mail]>, [e-mail] (Ronald Florence) writes:
> [e-mail] writes:
>
>  >   Lets draw a lesson from Hubble himself.  He first studied law and
>  > passed the bar.  He then enlisted and became an officer.  Later
>  > he turned Yerkes,  'a moribund institution', into a major research center
>  > and made many famous discoveries.  Pretty good for such a humble
>  > start in the wrong direction.
>
> The comparison between Hubble and NASA is valid, though in a slightly
> different way.  Hubble's autobiography shouldn't be trusted any more
> than his British accent, which was pure affectation.  Yerkes was
> hardly a "moribund" institution before Hubble's arrival.  Under Hales
> it was probably the premier institution for astronomical research in
> the United States.  Hubble dismissed the work of Shapley and his other
> predecessors at Mount Wilson as "of no significance", which is
> remarkably like the NASA press releases which described the Hubble
> Space Telescope as the most important event in astronomy since
> Galileo.
> --
>

I did not draw from his autobiography.  If you wish you might like
to read the Mercury Jan/Feb issue where this was the description
given by Donald Osterbrock, Ronald Brashear and Joel Gwinn.  By
1904 Hale had gone to California taking all the top notch astronomers
with him.  Frost inherited the directorship but just carried on.
E.E Barnard was one of the others - a very good observer but no
real scientific background.  The others were obscure astronomers.
By the time Hubble got there it was a "moribund institution".

Robert Dempsey
Ritter Observatory

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

Date: 2 Jul 90 23:17:29 GMT
From: usc!elroy.jpl.nasa.gov!forsight!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Hubble Space Telescope Update - 07/02/90


                         Hubble Space Telescope Update
                                 July 2, 1990

     The telescope has been slowly returned to nominal roll without major
thermal problems.  There has been a modest amount of activity in orbit, most
of it dealing with the Scientific Instruments (SI) rather than the focus.
Bootstrap activities continued as before with good Wavefront Sensor (WFS1)
measurements and bad WFS2 & 3 data.  The first attempt at using the Faint
Object Camera (FOC) to assist in characterizing the focus was not successful
-- possible pointing errors and a "take data" flag problem gave null results.
However, Wide Field Planetary Camera (WFPC) pictures were successfully taken.
All the SI related events went quite well with no anomalies or unexpected
events.  The Faint Object Spectograph (FOS) is in the process of turning on
their Blue Side High Voltage (HV) (successfully, so far), the FOC worked
well, despite not seeing stars, in its first focus support effort.  The
Goddard High Resolution Spectrograph (GHRS) was gathering HV dark count near
the South Atlantic Anomaly (SAA), The High Speed Photometer (HSP) was testing
the Photomultiplier Tube (PMT) detector, WFPC and the Fine Guidance Sensors
(FGS) continue to operate smoothly.

     Nothing new regarding the Pointing Control Subsystem (PCS) day/night
terminator instability fix.  There is high confidence that most of the
disturbance should be removed with the new flight software.  Expected time of
completion is early August (maybe late July).  The fix is expected to bring HST
stability to pre-launch expectations.  As for the rest of the PCS system, it is
clear that there are still problems with the Fixed Head Star Trackers (FHST)
but the problems do appear to be getting less frequent and understood quicker
than before.  The FHST's do appear to be the weakest link in the PCS, but there
is a growing understanding of how their operation can be made more reliable.
This problem is not expected to totally disappear until we get a few more
pointings under our belt (a month or two).  Flight operations has begun to load
the software to fix the "bit flips" in the FGS's caused by the SAA.  This
should remove the cause of some of the FGS acquisition failures.  A few FGS
failures are still ocurring for currently unknown reasons, investigations are
underway.

     In orbit activities are centered on setting up the new focus star,
epsilon Sco, for Wavefront Sensor (WFS) measurements.  In the past there have
been lot of problems getting good data off WFS2 & 3 (they do not see any
modulation of the signal in these two sensors).  The failure has been
attributed to a variety of causes, most recently an apparent inability to
properly center the star in the WFS aperture.  There have been a few more
pictures but nothing really new regarding the image quality.  Most of the
ground effort is directed at assessing the impact on existing science programs,
what can be done (if anything) to improve the existing focus, and once a focus
is established what should be done to better characterize the focus.

     FOC is taking images in support of focus efforts.  Their first attempt
was a failure, not because of anything within the FOC but because of a
possible pointing error and a command management problem that kept the
"take data" flag off during one of the FOC images (take data flag off =
closed shutter).

     FOS is in the process of turning on HV on the Blue side, so far (2 steps)
all is good.  Coarse Y-Base measurement went well.  Blue side HV finishes on
July 4.

     GHRS is doing a series of HV electronic dark count tests skirting the SAA.
All so far is going well.  Counts are lower than expected but the analysis
of the data has just begun.

     HSP is awaiting further testing of the PMT detector.  Ground hardware
tests seem to show that the cause of the problem is a minor "instability" in
one of the electronic components that should vanish with the application of
higher voltage.  The prediction is that no problems will exist when normal
operation voltage is reached.

     WFPC is in full operate mode.  Next images are scheduled for tomorrow.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

From: [e-mail]
Date: Mon, 2 Jul 90 21:20:23 MDT
Subject: grim tidings for the future


News flash:  shuttle fleet grounded due to design error on h2 pump system
News flash:  Hubble useless (almost) due to lack of testing on ground

What does all this mean?  It means that if we aren't careful, some group of budget
cutting myopics will seize this as a chance to lay waste to the entire U.S. space
effort for the rest of the decade.  Sound like overreaction? Could be, but I
didn't think the Challenger disaster would stop the program more than a year, but
I was wrong then, too.

                    Korac MacArthur (not bwebber)

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

Date: 1 Jul 90 23:19:37 GMT
From: amdahl!JUTS![e-mail]  (Kim DeVaughn)
Subject: Re: Hubble Space Telescope Update - 06/28/90

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
> In article <[e-mail]> [e-mail] (Phil Gustafson) writes:
> >...Various unnamed spokesmen say that the facility could not have
> >verified the the HST was within spec, but could have detected the
> >gross aberration currently present.
>
> In other words, it could not have checked the telescope for the sort of
> tiny errors that were likely possibilities, but could have checked for
> gross errors that nobody had any reason to expect.  At a substantial cost.
> What are the odds that Congress, if carefully given all the facts, would
> have authorized funding for this?

I usually agree with most everything you say Henry, but I have to differ on
this issue.  When developing anything as sophisticated and unique as the
HST, one *must* count on good ol' Murphy lurking around *every* corner.  And
plan accordingly.  The same can be said of any project where you are breaking
new ground.

Here, where we R&D very large mainframe machines, I and about 60 other
Engineers devote ourselves to ensuring that our machines are designed
correctly.  Possibily another 300 or more folks are involved in other forms
of testing (chip test, test equipment development, RAS testing, performance
testing, etc).  That is a *significant* percentage of the development
budget!

And believe me, we find all sorts of errors ... including the really gross
ones.  And even so, we still manage to miss a few.  But believe me, I would
never consider shipping a machine where we'd thoroughly tested both the CPU
complex and the I/O complex independently, but had never tested them hooked
together.  No way!

Why should the HST be viewed any differently?

The sign above my desk reads, "What you simulate, is what you get".  Words
to live by.

/kim

--
UUCP:  [e-mail]
  or:  {sun,decwrl,hplabs,pyramid,uunet,oliveb,ames}!amdahl!kim
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BIX:   kdevaughn     GEnie:   K.DEVAUGHN     CIS:   76535,25

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

Date: 2 Jul 90 20:48:13 GMT
From: mojo![e-mail]  (Doug Mohney)
Subject: Re: Hubble Space Telescope Update - 06/28/90

In article <[e-mail]>, [e-mail] (Phil Gustafson) writes:
>>Nice idea, but it's not quite that simple.  You have intrinsic problems
>>testing a flexible mirror in a gravity well when it's supposed to be
>>operational in space.  I.E. it wouldn't have looked right even if we
>>DID test it down here.
>
>This morning's New York Times says that the spooks offered their
>spy-telescope test facility to NASA, but the latter turned the offer
>down.  Various unnamed spokesmen say that the facility could not have
>verified the the HST was within spec, but could have detected the
>gross aberration currently present.
>

The 7/1 Washington Post said the same thing.

>I don't see much difference between testing a telescope designed to
>point down and one designed to point up  -- the spooks seem to have
>space telescope testing under control.  I'm just surprised that they
>loosened up enough to deal with NASA.

The Post went on to say that the Hubble was a very complicated relative of
the KH-9 spy satellite, with tighter focusing specifications. Since Perkin-
Elmer (now a Hughes subs...) did work on both KH-9 and Hubble, NASA felt
fairly confident that the job would be done without incident.

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

Date: 2 Jul 90 13:01:15 GMT
From: fernwood!portal!cup.portal.com![e-mail]  (Stephen R Fleming)
Subject: Perkin-Elmer and the Hubble

I'm confused.  I've been following the discussion on the Hubble, and
most of the fingers seem to be pointing at Perkin-Elmer for screwing up
the optics.  But I remember reading a lengthy article last year
(Discover?  Scientific American?  I don't remember where...) which gave
a well-written account of the mirror-polishing process at Perkin-Elmer
in Connecticut.  In the article, a major focus (pardon the pun) was how
wonderful the QA was and how P-E significantly -exceeded- NASA's specs
for the primary mirror.

So... was the article a puff piece planted by Perkin-Elmer's PR group?
Or did they do a great job of building to the wrong spec?  Or is it
some other mirror we're talking about?

+------------------------+---------------------------------------+
| Stephen Fleming        | In ten years, computers will just be  |
| [e-mail] | bumps in cables.       --Gordon Bell  |
| CI$:   76354,3176      +---------------------------------------|
| BIX:   srfleming       | My employers may disagree vehemently. |
+------------------------+---------------------------------------+

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

Date: 3 Jul 90 02:30:00 GMT
From: leah!rpi!rpitsmts![e-mail]  (Commander Krugannal)
Subject: (none)


   Subject:
     Someone asked about the AST being built here at RPI.
   I haven't heard a thing about it in a few years, but if I get the
   chance, I'll check it out.

   [e-mail]

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

Date: 2 Jul 90 18:04:09 GMT
From: mcsun!inesc!unl!unl![e-mail]  (Vitor Duarte & Sergio Duarte)
Subject: Re: Meaning of Palo Alto

In article <[e-mail]>, [e-mail] (Herman Rubin) writes:
>> > It stands for "tall trees", .....
>> This is incorrect, it is "tall tree."  It refers to a single tall pine/
>> I do not know if that tree is still standing.

>this is incorrect. the conventional derivation, which you have used:
>(palo from the root "pale" - modern "paling" for tree-like thingy;
> alto from the same root which begets "altitude")

>is frowned on by the residents, who prefer "old horse".
>followups to rec.pedant. now back to your published programme.

 I don't know if there was a tree or not over there, but a direct
 translation of Palo Alto is:
 Tall stick of wood.
 - Alto means Tall in spanish ( and portuguese by the way)
 - Palo is a stick a wooden one.

Therefore the people of Palo Alto should be called WoodenSticks :-)
--

               +--------------------------------------------+
                           Dept. de Informatica
                    Faculdade de Ciencias e Tecnologia
                        Universidade Nova de Lisboa

                    [e-mail] ; [e-mail]

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

End of SPACE Digest V12 #3
*******************