Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_5/V11_575.TXT

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Date: Wed, 27 Jun 1990 02:36:08 -0400 (EDT)
Subject: SPACE Digest V11 #575

SPACE Digest                                     Volume 11 : Issue 575

Today's Topics:
        Flame at ET base (WAS: Re: 10 psi overpressure
         Hu Space Telescope Update - 06/24/90
            Re: Sounds Of Earth recording
               Re: 10 psi overpressure
             Re: BBXRT servicing.
        Re: More on NASA 91 Appropriation Vote
           Re: NSS protests Chinese launch pricing
              Re: SPACE Digest V11 #563
        GIOTTO (was Re: ESA-brief summary of activity)
               RE: Biosphere II
              Gravity measurment

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: 25 Jun 90 18:08:59 GMT
From: usc!samsung!rex!rouge![e-mail]  (Fraering Philip)
Subject: Flame at ET base (WAS: Re: 10 psi overpressure

Okay, then. What _is_ the flame at the base of the ET?

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

Date: 25 Jun 90 17:37:24 GMT
From: swrinde!zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Hu Space Telescope Update - 06/24/90


                           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.

     Nothing new on the analysis of the 10 Faint Object Camera (FOC) images.
Efforts are underway to fix a FOC take data flag software error (the take
data flag now goes on if the Fine Guidance Sensors (FGS's) drop to gyro
control) and begin using the FOC to support focus activities along with the
Wide Field Planetary Camera (WFPC).  More FOC images will be taken later this
week.

     The only Pointing Control Subsystem (PCS) news concerns FGS dropouts and
the focus efforts.  Dropouts from both fine lock and coarse lock were occurring
with some regularity this weekend.  Analysis appears to show a good correlation
between the frequency of the FGS dropouts and mirror motion.  When the focus
was at its worst it was difficult to maintain coarse track, as the focus
improved coarse track became possible but not fine lock.  Further improvement
in the focus brought regular acquisition in fine lock.

     The focusing effort was the only major HST activity for the past three
days -- both in onboard activities and long range planning.  Beginning on
June 21 the mirror was moved to a number of focus positions, ranging from +12
waves to -12 waves from the June 20 focus position, with no tilting or
decentering.  After each movement wavefront sensor (WFS) and WFPC images were
taken.  The primary purpose of this focus series was to provide diagnostic data
on the HST/WFPC pupil function.  As with earlier focus runs the WFS data has
been plagued with data quality problems:  WFS1 data has been quite reliable,
WFS2 data has been, in general, quite poor, and WFS3 data has been of mixed
quality.  All WFPC images have been useful.  It appears that in the process
the Optical Telescope Assembly (OTA) team identified a new "better" focus and
the secondary was positioned at this new point.  It appears that all the mirror
motion, possibly with the exception of the last one, has been in focus and not
tilt or decentering.  Quantitative analysis of all the images is in progress.
There is a major effort to bring the FOC on line to support future focus
efforts, this will allow them separation of the  Scientific Instrument (SI)
focus/aberration problems from those of the OTA.  Beginning on June 28 a
switch to the star epsilon Sco will occur.  This star has the advantage of
not disappearing in a few days (as iota Car will) and will allow a return
(after this first focus effort) any time before early October and do
desorption focus runs.  Unfortunately, switching stars requires that steps
2 and 3 of the Bootstrap procedure be redone, adding an extra 48 hours.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |     Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___  Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /| M/S 301-355        |
 |_____|/  |_|/       |_____|/  Pasadena, CA 91109 |

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

Date: 25 Jun 90 19:19:39 GMT
From: tristan![e-mail]  (Loren Petrich)
Subject: Re: Sounds Of Earth recording

In article <[e-mail]> [e-mail] writes:
>
>
>Many of you netters may recall the Sounds Of Earth recording aboard
>the Voyager spacecraft.  It was, to my knowledge, never released publicly.
>I do have a very poor recording that is about to fail.  Does anyone
>know of a way to get a copy of this (even if temporarily to make a
>copy).  I would be very appreciative.

    If you can't get a new copy, you can always make a copy of
your old copy onto a tape. I think any big enough stereo system will
allow tape->tape and record->tape copying. So just make a couple of
copies of your prize, and keep at least one as a "backup".

    If you have trouble getting set up, you may want to have some
audiophile friend to help you out (I probably wouldn't qualify as an
audiophile -- although I have a lot of audio components, I see them as
a means, not as an end. One reason I got my CD player is that it
provides good sound with no fuss.).

                                ^
Loren Petrich, the Master Blaster             \  ^  /
    [e-mail]                  \ ^ /
One may need to route through any of:               \^/
                        <<<<<<<<+>>>>>>>>
    lll-lcc.llnl.gov                   /v\
    lll-crg.llnl.gov                  / v \
    star.stanford.edu                 /  v  \
                                v
For example, use:
[e-mail]

My sister is a Communist for Reagan

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

Date: 25 Jun 90 20:04:44 GMT
From: mojo![e-mail]  (Doug Mohney)
Subject: Re: 10 psi overpressure

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
>
>Nope.  For one thing, there has never been a polar shuttle launch, and
>never will be unless the USAF does a remarkable about-face.

I'm going back to AvWeek. One of the DoD missions flew a weird flight path to
put it in a reasonable orbit to drop off a spy-sat. The path took it close over
the East Coast and the launch, if I remember correctly, was at night.

>NASA point-blank refuses to put destruct charges aboard the orbiter.

I seem to recall that the charges went in by the SSMEs and when I read it,
I said "Oh. I wonder what the guys up front think."

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

Date: 26 Jun 90 03:30:00 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: BBXRT servicing.

In article <[e-mail]> [e-mail] (Francis Vaughan) writes:
>Why does the device need to remain cold? I have no trouble with sensors
>that need to be cold to get enough signal to noise ratio and the like,
>but the continual servicing of the BBXRT seems to imply that the system
>will be damaged if it is allowed to warm up.

It's not uncommon to have sensors that are delicate enough that they are
not rated to survive more than one or two encounters with the thermal
expansion and contraction involved in warming up and then cooling down
again.  These things are often made of strange, uncooperative materials
that we don't know how to fabricate very well.
--
As a user I'll take speed over|     Henry Spencer at U of Toronto Zoology
features any day. -A.Tanenbaum| uunet!attcan!utzoo!henry [e-mail]

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

Date: 26 Jun 90 05:47:51 GMT
From: agate!agate![e-mail]  (William Baxter)
Subject: Re: More on NASA 91 Appropriation Vote


In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
   In article <[e-mail]> [e-mail] (William Baxter) writes:

>>We can all write to Bob Traxler and thank him for not allowing NASA to
>>begin another large, ill-defined project

>Before posting statements like this perhaps you should read what the
>spending was requested for.

I did.  That's why I said it.  Read the 90 day report again, Allen.

>studies are to be evaluated by people outside NASA including groups like SSI
>and individuals like Dr. Andy Cutler (famous NASA cheerleader :-) ).

Andy agrees with me.

>>He [Rep. Traxler] has taken an important step toward reform of NASA.

>If you feel that way, please write him and say so. However, your letter will
>be interperted as a letter opposed to any manned space at all.

Traxler did the right thing.  We should reward him with positive
reinforcement.  At the same time, we can expose him to pro-space ideas.
He may not have recieved many letters which differentiate between
"pro-NASA" and "pro-space."

--
William Baxter

ARPA: web@{garnet,brahms,math}.Berkeley.EDU
UUCP: {sun,dual,decwrl,decvax,hplabs,...}!ucbvax!garnet!web

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

Date: 26 Jun 90 16:23:16 GMT
From: clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: NSS protests Chinese launch pricing

In article <[e-mail]> [e-mail] (Craig E. Ward) writes:
>The National Space Society has been unfairly trashed by a vocal minority of
>this group for being too pro-government and anti-private enterprise, but when
>NSS does make a public statement supporting private enterprise, these same
>people continue to complain.

Statements opposing cheap launch services do a considerable disservice to
satellite suppliers and other *private enterprises* that want cheaper
access to orbit.  The US space industry is not just the US launch industry.
Indeed, much of the US launch industry is about as close to the government
as it can get without actually being a government agency.

>Chinese launches are cheap because the Chinese government is willing to divert
>resources from other sectors of their economy to subsidize launch services.

Can you substantiate this claim?  The extent to which Chinese launches are
cheap because of subsidy, as opposed to being cheap because their costs
are low, is *most* unclear.  Nobody who's seen any details on the Chinese
launch facilities and practices disputes that their costs are lower than
those of Western launches.  Claims that it's all due to subsidies should
be backed up with numbers.

>... How can start-up companies like AMROC or SSI compete with that?

Dunno about Amroc and SSI, but OSC/Hercules already *is* competing with
that -- at least one small satellite formerly booked on Long March is now
booked on Pegasus.


On the whole, I am inclined to agree that the Chinese are *probably*
subsidizing launches somewhat, for the sake of hard currency and market
share.  Numbers are notably lacking, however, and most of the mindless
China-bashing ignores their genuinely lower costs.  Furthermore, the
implicit claim that Western launch industries would be in great shape if
only China weren't muddying the waters is silly.  There is increasing
overcapacity in the launch business, relative to the current market,
now that the post-Challenger backlog is starting to clear.  Even if
China is totally excluded, many people have predicted that at least
one of the three big US launch companies will die or get out of the
commercial-launch business in the next decade.  All three would be in
very bad shape already if it weren't for their lucrative government
contracts.  (Did somebody say "subsidy"? :-))  What the launch business
needs most is more customers... which probably won't happen until the
prices drop.
--
As a user I'll take speed over|     Henry Spencer at U of Toronto Zoology
features any day. -A.Tanenbaum| uunet!attcan!utzoo!henry [e-mail]

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

Date:     Tue, 26 Jun 90 13:37:39 MDT
From: [e-mail] (John M Harres)
Subject:  Re: SPACE Digest V11 #563

[...]
> Brits3-) :-)), which was the "fat Saturn" design. As we've seen, the
> most popularly publicized concepts don't always make it to the real world
> (just look at the F-19..er..F-117A concepts!), so I'm curious as to what
[...]

Well, as far as I knew, the F-117A is quite operational.  Otherwise, why would
they have 59 of them already?

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

Date: 26 Jun 90 10:14:38 GMT
From: mcsun!ukc!icdoc!syma![e-mail]  (Andy Clews)
Subject: GIOTTO (was Re: ESA-brief summary of activity)

From article <[e-mail]>, by [e-mail]
(M.S.Bennett  Supvs= Prof Pendry):
> On 2 July 1990 Giotto will pass within 23000 km of Earth, and the
> Earth's gravitational field will be used as a 'slingshot' force to
> propel the spacecraft on towards its new target.

I know it's a bit late to ask this, but is there any chance of Giotto
being visible from the Earth during it's fly-by? Are there any
predictions of its flight path and visibility against the night sky?
Inquiring minds want to know....


--
Andy Clews, Computing Service, Univ. of Sussex, Brighton BN1 9QN, England
JANET: [e-mail]   BITNET: [e-mail]

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

Date: Mon, 25 Jun 90 16:43 EDT
From: "Michael N. Davis" <[e-mail]>
Subject: RE: Biosphere II


I don't know if this helps but my space calendar's picture for this
month shows a night picture of Biosphere II in Arizona showing two people
looking in at the large plants inside.  It appears that the photographer
was standing on top of one module looking down on the next and the people.

Apparently some progress is being made.

_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_
Michael N. Davis, System Manager, NC A&T State University, Greensboro, NC 27411
BITNET: DAVISM@ATSUVAX1

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

Date: 25 Jun 90 17:54:49 GMT
From: mcsun!ukc!icdoc!mvax.cc.ic.ac.uk!sund![e-mail]  (M.S.Bennett Supvs= Prof Pendry)
Subject: Gravity measurment

The following is taken from Earth observation quarterly No.27 October 1989.




Aristoteles will be moving along a heliosychronous orbit (where the satellite
crosses the equator at 6:00 am in the direction of the North pole), at an
altitude of aproximately 200 km. This is sufficiently low to give the
gradiometer instruments suitable sensitivity to detect the variations in the
gravity field over the Earth's surface (as these variations are less detectable
as altitude increases).

Accelerometers mounted on a satellite can be used, as the key components of an
instrument called a 'gradiometer', for the determination of local gradients of
the gravity field onboard the satellite. Accelerommeters such as CACTUS
(developed by ONERA, France) have already measured, for instance, aerodynamic
and solar radiation forces on satellites, but have only recently acquired the
high resoloution needed to perform fine measurments of gravity gradients. It is
well known that, orbital motion being a type of free fall, a perfect
accelerometer placed at the center of mass would give a zero response. However,
if it is shifted to any point kept at a fixed distance from the center of mass,
the signal delivered is a measure of the change in gravitational acceleration
along the direction of the shift, ie. the gravity gradient. The square
arrangement of GRADIO ( the name given to the Aristoteles gradiometer conceived
by ONERA), combined with the orientation of the two highly sensitive axes of
the accelerometers parallel to the side of the square, allows the gravity
gradient along those directions to be determined by subtracting the signals of
the accelerometers placed at the ends of each side. The plane of GRADIO is
perpendicular to the orbit plane and the satellite's attitude is precessed
along the orbit, so that one of the highly sensitive axes stays perpendicular
to the orbit plane while another rotates to track the center of the Earth.

As usual with very high-precision instruments of inertial class, a number of
corrections must be applied to GRADIO signals in order to draw full benefit
from its inherent accuracy. One has to consider error parameter, such as
accelerometer misalignment or scale factor non-linearities. It should also be
noted that all masses in the satellite generate a 'self-gravitation', which the
accelerometers will detect because of their high sensitivity.

An onboard electromechanical calibration device ensures a considerable
reduction of such errors. However, the demonstration of such gradiometric
accuracy to the level of 1e-2 Eotvos units (1 EU = 1e-9 s^-2), i.e. 1e-11 s^-2,
necessary to satisfy the Aristoteles mission objectives, imposes a quite
elaborate error bubget modelling.

In order to optimise the data-preprocessing algorithms (in particular the
reconsititution of the local gravity gradient tensor) and to validate the
mission performance budgets (simple error budgets imperfectly accounting for
all error sources), computer simulation of Aristoteles data reductions have
proved necessary. These simulations will reproduce the evoloution along the
orbit of the Earth's gravity gradient on a resoloution scale of 100*100 km,
using available models. The actual resurring frequency of GRADIO measurments is
also simulated, so that harmonic analysis of deviations between the
reconstructed and original gravity gradients provides a reliable input to
further scientific simulations of the later parts of data processing. The
latter, to be carried out by scientific groups, is aimed at evaluating the
final performance of the Earth's gravity potential reconstitution process.

/------    -------    -----\       /------   |  ======================  |
|          |          |      \    |          |  M. Sean Bennett         |
\-----\    |----      |       |    \-----\   |  UKSEDS TECH.OFF.        |
       |   |          |      /            |  |  Janet:[e-mail]  |
------/    -------    -----/       ------/   |  Bitnet-                 |
                                             |  [e-mail]  |
                                             |  ======================  |

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

End of SPACE Digest V11 #575
*******************