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Subject: SPACE Digest V11 #589

SPACE Digest                                     Volume 11 : Issue 589

Today's Topics:
             Re: F-117 at Oshkosh
              Voyager Update - 06/28/90
       Re: NASA Headline News for 06/26/90 (Forwarded)
     Re: Is there a backup HST mirror ??? (see sci.astro)
     Re: Is there a backup HST mirror ??? (see sci.astro)
           Re: What Spherical Aberration is
           Re: Receiving Hubble Photos - directly?
           Re: Anyone Know What MOL Is/Was?
            Re: HST focus problem
           Re: What Spherical Aberration is
               Re: model rocket staging

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription notices,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date: 28 Jun 90 19:21:03 GMT
From: dsac.dla.mil!dsacg3.dsac.dla.mil!dsacg2.dsac.dla.mil![e-mail]  (Tom Ohmer)
Subject: Re: F-117 at Oshkosh

From article <[e-mail]>, by [e-mail]:
>          Just a BTW the F-117 is scheduled to do a fly-by
>      at the EAA convention in Oshkosh between 27 July and
>      2 August. []
(I sent something similiar to this to sci.military, but have not seen it yet)
I heard that an F-117 would do a fly-by over the 19-22 July U.S. Air &
Trade Show at Dayton International Airport, Vandalia, OH.  Any one know
which day(s) this will happen (as THAT is the day I want to be there :-)?

--
Tom Ohmer @ Defense Logistics Agency Systems Automation Center,
            DSAC-AMB, Bldg. 27-6, P.O. Box 1605, Columbus, OH  43216-5002
UUCP: ...osu-cis!dsac!tohmer   INTERNET: [e-mail]
Phone: [phone]   AutoVoN: 850-9210   Disclaimer claimed

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

Date: 29 Jun 90 04:56:44 GMT
From: usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Voyager Update - 06/28/90


                     Voyager Mission Status Report
                            June 28, 1990

                              Voyager 1

     The Voyager 1 spacecraft continues to collect routine cruise science data.
One frame of high-rate Plasma Wave (PWS) data was recorded on June 19. On
June 15 and 18 Ultraviolet Spectrometer (UVS) observations were performed on
HD 199579 and HD 200120.  On June 15 the Signal-to-Noise Ratio (SNR) at the
70 meter antenna in Spain varied from -0.5 to -2.1 db below the predicted
value; following a switch in masers the SNR improved significantly.  On
June 18 telemetry data from the 70 meter Goldstone antenna was severely
degraded due to a Ground Communications Facility (GCF) problem.  Telemetry
was replayed successfully the following day.

     On June 18 a new sequence in the Computer Command Subsystem (CCS) began
execution and the Attitude and Articulation Control Subsystem (AACS) Sun
Sensor Heater B test was conducted.  AACS Sun Sensor Heater B was powered on
for one hour to verify it's operation; the temperature/power profile for the
heater operation was as predicted.

     A pre CCSA Refresh CCS checksum was scheduled on June 21 using the 34
meter Goldstone antenna (DSS 15).  Due to problems at DSS 15 this data was not
recovered.  DSS 15 appeared to be in lock however, Test and Telemetry Subsystem
(TTS) was unable to obtain sync on the CCS telemetry.  Real-time commands
were transmitted to initiate the CCSA refresh activity and to reset the CCS
status telemetry.  Successful completion of the refresh, which included the
area of memory in which the Command Processor and Error routines reside, was
verified by the received checksum value; the CCS status telemetry reset was
also successful.

     Memory compares of the full AACS, CCS, and Flight Data Subsystem (FDS)
memory readouts performed on June 8 have been completed and verify the memory
contents are as expected.



                              Voyager 2

     The Voyager 2 spacecraft continues to collect routine cruise science
data.  One frame of high-rate PWS data was recorded on June 19.

     On June 18 the Data Capture and Staging (DACS)/TTS 2 was observed to not
be processing science data.  Following analysis, the problem was found to be
in DACS 2.

     There is currently no visibility into near-real time UVS data on
Voyager 2.  The UVS investigators are looking at the new cosmic ray data but
have not yet completed their software development; they will also be looking
at the new ultraviolet data.

     Several of the Low Energy Charged Particles (LECP), Plasma (PLS),
Planetary Radio Astronomy (PRA) and PWS status channels continue to be
incorrect on Voyager 2.  Other data indicate that all of the Fields,
Particles & Waves (F&P&W) instruments are on and operating normally.
Quicklook science data for the Cosmic Ray (CRS) instrument have been
formatted for the new ultraviolet format and the four channels look good.


                  CONSUMABLE STATUS AS OF 6/28/90

    P R O P E L L A N T    S T A T U S          P O W E R

                     Consumption
             One Week    Propellant Remaining     Output     Margin
  Spacecraft  (Gm)                (Kg)            Watts      Watts

   Voyager 1    5             36.4 + 2.0          370         59
   Voyager 2    5             39.5 + 2.0          374         66

      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 29 Jun 90 03:31:59 GMT
From: mailrus!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: NASA Headline News for 06/26/90 (Forwarded)

In article <[e-mail]> [e-mail] (David Smith) writes:
>>>orbiter Endeavor currently under construction
>>... Weren't we all supposed to remember that as the Endeavour with a 'u'?
>Maybe they just came to their senses and translated the name into
>American.

I note that you're from somewhere called "Palo Alto".  What's the
American translation of that (Spanish) placename?

The name of OV-105, in *any* language -- English, American, Swahili, or
Tibetan -- is "Endeavour".
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."      -John Osterhout |  [e-mail]   utzoo!henry

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

Date: 29 Jun 90 03:47:00 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Is there a backup HST mirror ??? (see sci.astro)

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.

The original HST plans called for bringing it back to refurbish it and
fit new instruments.  That was quickly scrapped in favor of doing the
work in space.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."  -John K. Ousterhout |  [e-mail]   utzoo!henry

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

Date: 29 Jun 90 03:44:41 GMT
From: swrinde!zaphod.mps.ohio-state.edu!samsung!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Is there a backup HST mirror ??? (see sci.astro)

In article <[e-mail]> [e-mail] writes:
>Note that there is no way to change either mirror without bringing the
>telescope back to earth.

Correction:  there is no currently-defined procedure for doing so, and
the telescope was not designed for it.  That doesn't mean it can't be
done.  Some of the repairs to Solar Max were on things not designed to
be repairable either.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."  -John K. Ousterhout |  [e-mail]   utzoo!henry

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

Date: 29 Jun 90 03:50:48 GMT
From: swrinde!zaphod.mps.ohio-state.edu!samsung!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: What Spherical Aberration is

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.  When things aren't so happy, no.  Only the most
fortunate astronomical work falls into the first category.  HST's cameras
(which are only 2 out of the 6 instruments, remember) won't quite be
useless in visible light, but close.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."  -John K. Ousterhout |  [e-mail]   utzoo!henry

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

Date: 29 Jun 90 03:19:23 GMT
From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Receiving Hubble Photos - directly?

In article <[e-mail]> [e-mail] (Allen Baum) writes:
>A friend of mine would like to recieve pictures from the Hubble Space Telescope
>directly from the downlink, much as one can currently do with weather satellite
>pictures.

There is one big difference here:  the weather-satellite data is designed
for easy decoding by simple receivers.  The HST data... isn't.  To put it
mildly.  It's high-speed digital data in complex formats.  I wouldn't
call it impossible, but it's an order of magnitude harder than getting
weather-satellite pictures.  Then you have to pick a time when HST is
transmitting an image, as opposed to (say) photometer data or just
engineering telemetry saying "I am now 73% of the way to lining up on
the next target".
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."      -John Osterhout |  [e-mail]   utzoo!henry

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

Date: 29 Jun 90 03:15:58 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Anyone Know What MOL Is/Was?

In article <[e-mail]> [e-mail] (john reece) writes:
>Where was the hatch located with respect to the astronauts seats, and
>how were they supposed to move around inside the capsule to get to it?

As I recall, the hatch was set between the two seats (which were roughly
together at the bases, but well apart at the head ends).  The seats may
have been relocated outward a bit for the MOL Gemini.  I dimly recall a
comment to the effect of "everyone was amazed that it could be done".

>I remember reading about how the Gemini astronauts had to practically
>be shoehorned into their seats, and how it was so cramped astronauts had
>difficulty after EVAs getting back into the vehicle on their own.

It wasn't quite that bad.  It was crowded, but not so bad that (for
example) they couldn't take off their spacesuits -- some of the crews
did exactly that.  This was admittedly a cumbersome and lengthy
procedure.  The problem with getting back in after an EVA was not
lack of room, but the problem of keeping yourself and a great mass
of loosely-coiled umbilical inside while reaching up -- in a decidely
stiff spacesuit -- to pull the hatch down and close it.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."      -John Osterhout |  [e-mail]   utzoo!henry

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

Date: 29 Jun 90 09:10:51 GMT
From: unmvax!nmt.edu![e-mail]  (Daniel Briggs)
Subject: Re: HST focus problem

In article <[e-mail]>, [e-mail] (Alan Filipski) writes:
>
> Couldn't this be corrected by digitally post-processing te image?
> By looking at stars you can evaluate the point spread function
> at each point of the field. The distortion of non-point objects
> could be modeled as a linear combination of these point spreads.
> As long as this function is invertible (which seems likely)
> you could reconstruct the image you want from the distorted image.
>
> This is a standard image-processing technique.  Could it be used here?

Several people have speculated on this general topic.  The basic gist
of the discussion seems to be, "it will probably help a little, but
not a whole lot.  The SNR will drop abysmally, and it will only work
for simple objects...."

Perhaps I am being dense here people, but it is not obvious to me why
this should be so.  For example, the technique described above goes by
the name CLEAN, in radio interferometry circles.  This technique does
indeed suffer from some of the woes mentioned above.  (And at least
one person made explicit reference to it earlier.)  However, CLEAN is
a *non-linear* algorithm!!  In the radio case, we sample the fourier
transform plane incompletely.  The algorithm literally has to make up
data where we didn't measure it.  As a consequence, it is not
tremendously robust, although it works pretty well for bright & simple
objects.  The optical people are in an entirely different boat
however, so arguments based on CLEAN variations do not apply.  A CCD
completely samples the image plane.  Image reconstruction algorithms
to work on this data are *linear*, and generally a whole lot more
bullet proof.  Now I grant you, a lot of this will depend on the form
of the transfer function in the fourier transform plane.  If it drops
extremely sharply, then I guess that it would screw up the SNR in the
high spatial frequency components.  (Yes, I know that a wide halo in
the image plane == sharp peak in the transform plane.  The question
is, how sharp??  How wide is the usable wings?)  Note also, btw, that
the form of the transfer function will not change from observation to
observation.  (It will essentially depend only on the mirrors, at
least as far as the WFPC is concerned.)  This can be measured by the
STScI people, and coded into their deconvolution algorithm.  There is
no question that this horrible mess will degrade the data quality
badly, but I am not convinced yet that all is lost for the WFPC.  If
anyone gets hard numbers on the telescope PSF or transfer function,
please post them!
--
This is a shared guest account, please send replies to
[e-mail] (Internet)
Dan Briggs / NRAO / P.O. Box O / Socorro, NM / 87801  (U.S. Snail)

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

Date: 29 Jun 90 16:15:15 GMT
From: uvaarpa!murdoch!astsun.astro.Virginia.EDU![e-mail]  (Greg S. Hennessy)
Subject: Re: What Spherical Aberration is

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.

Yesterday I was doubtful, but after thinking about it a bit, I would
say that much of the errors can be corrected for. Note, there are
things that HST won't be able to do, but I would say that the images
could be restored. I am POSITIVE a lot of people in Baltimore are
giving it a whole lot of thought. Give them some time, and you would
be amazed at what they do.



--
-Greg Hennessy, University of Virginia
 USPS Mail:     Astronomy Department, Charlottesville, VA 22903-2475 USA
 Internet:      [e-mail]
 UUCP:        ...!uunet!virginia!gsh7w

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

Date: Fri, 29 Jun 90 15:50 EDT
From: [e-mail]
Subject: Re: model rocket staging
Sender: [e-mail]
Reply-To: [e-mail]
X-Envelope-To: [e-mail]

        In a previous issue, [e-mail] (Fred Walter) writes:

>With all this discussion on model/amateur rockets to the moon (but no
>actual figures being posted, such as the weights of the rocket engines) one
>wonders whether or not it'd actually work.

        It probably won't work, but stranger things have happened.  As to fig-
ures being posted, I have some data from a computer simulation that I've been
running for the past week.  I'd be happy to post it, but I'd rather anyone who's
   interested contact me and I'll e-mail it to them.

>Some comments:
>
>       1) If you are doing staging, the materials holding the stages
>          together will add weight that must be taken into consideration.

        True, but the materials in most staged model rockets consists of a small
cardboa
   rd tube and a piece of tape.  The weight of these is *probably* negli-
gible on the scale of an `N' engine.  This is only a guess, but an educated one
based on a few previous flights of two stage model rockets.

>       2) How will you ensure that the stages separate properly?
>          Without damaging the upper stages ? While properly igniting the stage
>
        above it?

        The solutions to these problems can be found in any model rocketry book.
To sum
   them up: you tape the upper and lower stage engines together.  The lower
engine ignites the upper, and the upper engine blows off the lower when it's
ignited.

>       3) Where will the lower stages end up falling ? On houses/people ?
>          Or will you be launching from over water ? Will the discarded stages
>          have a parachut on them to slow them down on their return, to
>          try and ensure they don't kill anything ? How will this be
>          handled ?

        Let the lower stages fall free.  They'll have a high surface area and
low mass, hence a fairly low terminal velocity.  This is a common way of re-
covering lower stages of model rockets or small, lightweight rockets.

>       4) If you try and put multiple rocket motors together side-by-side
>          in a stage, how do you compensate for the fact that their
>          thrusts won't be excactly the same ? How do you ensure they
>          all ignite at the same time ? Failure to handle either of these
>          will result in an off course rocket.

        Aye, there's the rub!  In short, you pray.  Lower impulse engines (A-D)
have a 20% error for the commercial types and 10% for competition types (I don't
   know about larger engines.)  You ignite them at the same time by hooking them

up to your own specially-built ignition system, and hope all the igniters go
off.  I'd be willing to assume that the rocket's course would be affected more
by high-altitude winds than engine differences, though.
        The primary problem is going to be building a model that can withstand
the aerodynamic pressures without being reduced to its component parts.  If you
use metal in the structure, I believe it ceases to become a model in the eyes of
   the NAR (but I'm really just guessing, so no flames, please.)  If anyone can
build and fly a paper and balsa rocket past the speed of sound, I'll print this
   message and eat it.  :-)

                                -Thomas D. Blersch
                                 [e-mail]  (I think I've got
                                                           it right, now.)



        `:-|  (Spock smiley with raised eyebrow.)

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

End of SPACE Digest V11 #589
*******************