Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V09_4/V9_441.ZIP/V9_441

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Subject: SPACE Digest V9 #441

SPACE Digest                                      Volume 9 : Issue 441

Today's Topics:
               Space Telescope
      Re: Rendezvous with Rama (was Re: Re: Asteroid Encounter)
               Space Telescope
           Re: UFOs and other bunk (getting tiring
           Re: DO IT YOURSELF SPACE-PROBES?
             Re: heavy launchers
            Re: NSS Hotline Update
              Re: Amroc on NASA
               Re: SPACE Digest V9 #423
       Apollo anniversary press conference (Forwarded)
      Re: manned vs. unmanned (was: Priorities at NASA?)
----------------------------------------------------------------------

Date: 15 May 89 13:54:19 GMT
From: oravax![e-mail]  (Douglas Harper)
Subject: Space Telescope

Does anyone know to what frequencies of light the space telescope will
be sensitive?  Also, how is UV photometry done?  Aren't most
photosensors insensitive to UV?  Do UV sensor work on a different
principle from optical sensors?  Do they merely employ different
materials?

Any enlightenment would be appreciated.

--
Douglas Harper              |      "Confess, or we bring the rabbit back in."
Odyssey Research Associates | oravax![e-mail]       ARPA
301A Harris B. Dates Drive  | {allegra,rochester}!cornell!oravax!harper  UUCP
Ithaca, NY 14850-3051  USA  | [phone] extension 276

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

Date: 15 May 89 15:20:05 GMT
From: calvin![e-mail]  (John Sahr)
Subject: Re: Rendezvous with Rama (was Re: Re: Asteroid Encounter)

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Wayne D. T. Johnson) writes:
>>It would be interesting to know how far an earth based radar can reach with
>>the accuracy to detect killer rocks?
>
>For radars of practical size with practical power output, the range is
>zero on an astronomical scale.  The trouble is that radar return is an
>inverse *fourth power* function of distance, since the inverse-square law
>gets you once in each direction.  And you thought inverse square was bad...
>Arecibo, with the biggest dish on Earth (not even vaguely steerable) and
>a monstrously powerful custom-built transmitter, can get useful radar
>echos from *planets*... but it's not easy.  The biggest conventional
>radars on Earth have trouble tracking inert objects out at Clarke-orbit
>distances, one-tenth of the way to the Moon.  For a 100m rock at
>planetary distances, forget it.  Optical tracking is much better -- it's
>only inverse-square, since the Sun supplies the illumination.

Actually, the "inverse fourth power law" only applies to point targets,
that is, targets which are much smaller than the radar beam.  Other types
of targets are inverse square laws, such as ionospheres, which fill the
radar beam, and there are even a few inverse cube laws, such as E-region
backscatter (fills the beam one direction, but not two directions (sometimes)).

Asteroids are "inverse fourth power" objects, as Henry states.

Arecibo also does duty as an incoherent scatter (atmospheric) radar.  For
ball park estimates, these radars could spot a Canadian dime at a distance
of a thousand kilometers or so.  I'll point out that although the Arecibo
dish is not steerable, the antenna is somewhat steerable, because the
feed can be moved around.  There is another big radar in Peru, whose "dish"
is somewhat _larger_ than Arecibo's, the Jicamarca Radio Observatory near
Lima.  However, Arecibo has higher gain because of its higher radar operating
frequency, and there are other important differences.

Food for thought: suppose the maximum killer asteroid speed is 100 km/s.
If the entire sky is examined once a day, then to have at least a one day
warning for a "bullseye" asteroid, you need to be able to spot them when they
are about 8e6 km away, which is about 20 times the distance to the Moon.

Arecibo gathers signals from Io over about an hour. "But Io is really
far away, so that's pretty good, right?"  Well, no doubt about it, radar
observation of Io is neat, but Io is right where you expect it to be, and
it is as big as the Moon, and it isn't moving very fast, or rather, its
speed is known precisely ahead of time.  None of the above are true for
asteroids, and it makes a big difference for radars.  In fact, if all
you knew about Io was that it was "out there," it probably wouldn't be
found (by radar).  Yet Galileo found Io with a binocular power telescope,
and even he happened to be looking at Jupiter at the time---he knew where
to look.  Asteroids are solitary wanderers.

More food:  the mass (kinetic energy) of an asteroid varies as r^3,
while its radar cross section varies as r^2 (r is the asteroid radius).
From the inverse-fourth power law for point targets, the range R at which
an asteroid of radius r is first detectable varies as r^(-1/2).  If you
think about it, this says that you'll always start seeing asteroids at
about the same distance, at least the ones that are worth seeing.  I won't
go into it, but this has implications for the utility of Stealth technology.

Upshot: current radars are not even close to being able to usefully spot
the next author of a Meteor Crater or even of a Hudson's Bay.  Optical
searches are still the way to go.

>Mars in 1980s:  USSR, 2 tries, |     Henry Spencer at U of Toronto Zoology
>2 failures; USA, 0 tries.      | uunet!attcan!utzoo!henry [e-mail]


--
John Sahr,       Dept. of Electrical Eng., Cornell University, Ithaca, NY 14853
ARPA: [e-mail]; UUCP: {rochester,cmcl2}!cornell!calvin!johns

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

Date: 15 May 89 18:45:35 GMT
From: sgi![e-mail]  (Brian McClendon)
Subject: Space Telescope

This may be old news, but in a small article in Sunday's (5/14) SJ
MercNews, They mentioned that the Hubble Space Telescope was getting
bumped back 3-5 months to make room for two military launches.

Excuse me for being impatient, but that _REALLY_ sucks.

            - brian

   --------------------------------------------------------------------------
   Brian McClendon [e-mail] ...!uunet!sgi!rudedog!bam 415-335-1110
   --------------------------------------------------------------------------

   "Fuse Exxon" - me

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

Date: 14 May 89 21:20:00 GMT
From: m.cs.uiuc.edu!s.cs.uiuc.edu![e-mail]
Subject: Re: UFOs and other bunk (getting tiring


/* Written  4:08 pm  May 13, 1989 by [e-mail] in s.cs.uiuc.edu:sci.space */
/* ---------- "UFOs and other bunk (getting tiring" ---------- */
}From: portal!cup.portal.com![e-mail]  (Mark Robert Thorson)
The original settlers of America didn't come to destroy a millenia old culture,
(on both sides of the Atlantic), but they did nonetheless.
/* End of text from s.cs.uiuc.edu:sci.space */

Sorry to disagree with you, but the Spaniards certainly intended to destroy
the cultures they found, and at best the North Americans settlers were
indifferent to such destruction. You should read some accounts of what was
done to the Mayan, Inca, and Aztec cultures and their records. They were
very deliberately erased from the face of the planet by their conquerors.

Alan M. Carroll                "And there you are
[e-mail]           Saying 'We have the Moon, so now the Stars...'"
CS Grad / U of Ill @ Urbana    ...{ucbvax,pur-ee,convex}!s.cs.uiuc.edu!carroll

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

Date: 10 May 89 17:05:44 GMT
From: tektronix!sequent!mntgfx![e-mail]  (Mike Butts @ APD x1302)
Subject: Re: DO IT YOURSELF SPACE-PROBES?

From article <[e-mail]>, by [e-mail] (Paul Flaherty):
> The OSCAR satellites (as opposed to Oscars, which are milsats) are built by
> any of a number of organizations within the amateur radio community.  Their
> primary mission is to provide reliable VHF and UHF communication between
> properly equipped amateur stations, although two satellites (OSCARS 9 and 11,
> built by the University of Surrey) are planetary science experiments.
>
> We build the world's cheapest satellites.

The May 1989 issue of QST (an amateur radio magazine you can find in many
libraries) carries a detailed article "Microsat: The Next Generation of
OSCAR Satellites", part 1 of 2, p.37-40.  AMSAT-NA plans to launch 4 Microsats
into sun-synchronous polar orbits, piggybacking on a single launch vehicle this
year.  Microsats are 10 Kg cubes, about 230 mm on a side.  I recall hearing at
a seminar that they cost only about $40K each.  They said the satellites are
stabilized using permanent magnets and spun by photon pressure on one side of
the antenna masts.  Simple!

The primary goal is to implement a digital store-and-forward message handling
packet-radio satellite system available worldwide.  It is also a demonstration
of what how small spacecraft can get using modern microelectronics.  The computer
has a NEC V40 (8088 clone) with 8MB of RAM disk.  The structure has been flight
qualified for any of the world's currently available launchers.  One of the
Microsats will carry a speech synthesizer, which will broadcast telemetry and
messages receivable by school children using common scanners.  The article goes
into detail on the conception, and on the power, radio and computer systems.
Next month's article will carry operational details.

--
Michael Butts, Research Engineer       KC7IT           503-626-1302
Mentor Graphics Corp., 8500 SW Creekside Place, Beaverton, OR 97005
...!{sequent,tessi,apollo}!mntgfx!mbutts  OR  [e-mail]
Opinions are my own, not necessarily those of Mentor Graphics Corp.

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

Date: 15 May 89 17:18:56 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: heavy launchers

In article <[e-mail]> [e-mail] (John McKernan) writes:
>>... The Saturn V was expensive, hand-built,
>>and non-recoverable because of the decision in the mid-60s to throw it away!
>>When Congress capped Saturn V production at 15...
>
>It's hardly surprising that congress refused to guarantee long term funding
>for the Saturn program, few if any large procurment contracts are or have
>been long term. If the "experts" would have told congress to stick with the
>Saturn V post Apollo, congress most likely would have funded more of them...
>The Saturn V was fairly expensive and a lot of people thought changing to a
>fully reusable (that was the original plan) vehicle would save money...

You've missed my point slightly, I fear.  Note the date I gave.  This
particular decision was made long before the shuttle was seriously looked
at, and long before any serious post-Apollo planning was done.  The fateful
decision was made in the middle of Apollo, over NASA's strenuous objections.
The NASA administrator of the time -- Webb? -- had to fight hard just to
get authorization for 15.  It wasn't a refusal to guarantee long-term
funding, it was a specific decision that there would be no long-term
Saturn program at all.

Many people date the decline of the Saturn V to NASA's post-Apollo decision
not to retain Saturn V launch capability.  This is wrong; the original
Congressional decision to terminate production after 15, made much earlier,
was the real killer.  The loss of production capability made the inability to
launch the last two Saturn Vs a relatively minor issue.  (Admittedly it
would be useful now to have them, but realistically it just wouldn't have
happened.)
--
Subversion, n:  a superset     |     Henry Spencer at U of Toronto Zoology
of a subset.    --J.J. Horning | uunet!attcan!utzoo!henry [e-mail]

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

Date: 15 May 89 17:20:00 GMT
From: m.cs.uiuc.edu![e-mail]
Subject: Re: NSS Hotline Update


Tom Neff writes:
>[ that's one annoyance about these NSS screeds, they appear to be
>  written down to the shoe clerk level.  Mustn't let annoying details
>  interfere with the phone tree! ]

Tom, I'm annoyed too at the level of the presentation, but, in
fairness to NSS, consider:
    - what we're seeing is a transcript of a 2-minute recorded
      phone message.  There's a limit to how much detail you can
      put into a couple of minutes of voice.
    - the message is aimed at a public of much less sophistication
      than you or I.  In fact, it isn't composed for USENETters,
      and Jordan posts it here to let us know what the NSS hotline
      is saying.
I don't really see how the message could be much less simplistic than
it is, and still fit the required format.  Broadcast material,
speeches, and the like, when put in writing, always suffer by
comparison with material that was intended for print media.

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

Date: 15 May 89 13:24:27 GMT
From: tank!shamash!com50!questar![e-mail]  (David Becker)
Subject: Re: Amroc on NASA

" Letter to the Editor, Ad Astra, April, 1989
" From James C. Bennet and George A. Koopman of American Rocket Company
" ...
" In addition to numerous
" malicious actions directed against American Rocket Company, NASA has
" done substantial damage to Transpace Carriers, Conatec, Space
" Industries, Astrotech and many other small, entrepreneurial ventures.
" They have also threatened several large aerospace companies with
" economic sanctions when those companies expressed interest in entering
" and participating in commercial space ventures.

Where can I look up details about this?  Or post if you know them.
--
David Becker
and another bug bites, and another bug bites   another bug bites the dust
[e-mail]

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

Date: 15 May 89 18:10:53 GMT
From: cfa!cfa250![e-mail]  (Steve Willner)
Subject: Re: SPACE Digest V9 #423

From article <[e-mail]>, by [e-mail]:
> I also seriously wonder if it is possible to hide a warhead at all. I
> wonder how much neutrino flux you get out of weapons grade Uranium,
> Tritium and Plutonium?

Not much.  Without looking them up, I think U(238) and Pu(239) are
both alpha emitters, which decay without neutrino emission.  (Though
there may be some neutrinos emitted later in the decay chain.)
Tritium emits a neutrino (actually an anti-neutrino) when it beta
decays.  U(235) decays at least partly by spontaneous fission (maybe
an alpha decay mode, too, but I don't know the branching ratios).
The fission process itself doesn't emit neutrinos, but the fission
products generally beta decay rapidly, each beta decay emitting an
anti-neutrino.

However, it's easy to show that the total emission is trivial.
Assume the mass is about 20 kg of fissionable material.  (About the
right order of magnitude for a small plutonium device.)  This is
about 5E25 atoms.  Instant decay of all of them would produce far
fewer than this number of neutrinos.  However, the Sun bombards each
square centimeter with something above 1E36 neutrinos each second
(above the Cl(37) detection threshold of a couple of MeV).  It takes
a giant tank (thousands of gallons) containing chlorine several
months to detect the solar flux.

I suspect that gamma emission may be the most sensitive way of
detecting warheads, but I'm not familiar with the details.  I would
be surprised, though, if effective ranges were longer than a few
meters.

Sorry this posting doesn't contain more specific numbers, but the
neutrino concept seems to be off by so many orders of magnitude that
I don't want to bother looking everything up.
--
Steve Willner            Phone [phone]         Bitnet:   willner@cfa
60 Garden St.            FTS:      830-7123           UUCP:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [e-mail]

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

Date: 16 May 89 01:23:47 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Apollo anniversary press conference (Forwarded)

David W. Garrett
Headquarters, Washington, D.C.                       May 15, 1989


N89-42

MEDIA TELEVISION ADVISORY

     In preparation for the 20th anniversary of the first manned
lunar landing, the Apollo 11 astronauts will participate in a
press conference in Wash., D.C., May 26, 1989.  The conference
will begin at 10:30 a.m. EDT in the NASA Headquarters 6th floor
auditorium, 400 Maryland Avenue, S.W.

     TV cameramen are advised that camera-to-talent distance will
be 40 feet for this conference.  It is suggested that cameramen
be equipped with 14X or greater zoom lenses.

     Media reps planning to attend this conference must contact
the Headquarters newsroom by May 22 to gain admittance to the
conference.  The conference will be carried live (monitor only)
on NASA Select television, Satcom F-2R, Transponder 13, at 72
degrees West Longitude, 3960.0 MHz, audio 6.8 MHz.

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

Date: 12 May 89 20:43:22 GMT
From: att!mcdchg!ddsw1!corpane![e-mail]  (John Sparks)
Subject: Re: manned vs. unmanned (was: Priorities at NASA?)

<[e-mail]> <[e-mail]>
Sender:
Reply-To: [e-mail] (John Sparks)
Followup-To:
Distribution:
Organization: Corpane Industries, Inc.
Keywords:

In article <[e-mail]> [e-mail] (Doug Borsom) writes:
>A few weeks back I posted a request for arguments in favor of the
>manned space program.
>Two follow-up postings
>In fact, not one person responded to my original posting with an
>argument in favor of the manned space program.
>
>Maybe the subject of my posting simply isn't of interest to
>subscribers to this news group.  But the appearance is that there
>are no good arguments for a very expensive manned space program.

I think you got the idea when you stated that the subject is not of any
interest. Not that most of us out there aren't interested but rather that we
are probably *tired* of arguing about it. You see, you just missed the
incredible 'manned-unmanned' debate by about 2 months.

It was very heated and informative. I didn't save the articles but perhaps
someone out there did and could mail them to you.

I venture to speculate that most people didn't respond to your posting because
they didn't want to stir up the whole mess again.

--
John Sparks   |  {rutgers|uunet}!ukma!corpane!sparks | D.I.S.K. 24hrs 1200bps
[not for RHF] |          [e-mail]         | 502/968-5401 thru -5406
If a town has one lawyer, he starves; if it has two lawyers, they both get rich

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

End of SPACE Digest V9 #441
*******************