Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_3/V15NO353.TXT

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Date: Thu, 29 Oct 92 05:00:09
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #353
To: Space Digest Readers
Precedence: bulk


Space Digest                Thu, 29 Oct 92       Volume 15 : Issue 353

Today's Topics:
        active planetary probes; should someone update the FAQ
                       AUSROC II Launch Update
                 Collision with Comet P/Swift-Tuttle
                       Comet Collision (4 msgs)
                        HRMS for ETI (2 msgs)
                         nasa shake up rumor?
                       re HRMS for ETI (2 msgs)
      Sen. Al Gore on the American Space & Aeronautics Programs
            Smith-Tuttle Comet a threat to earth? (3 msgs)
                             Solar Sails
          Strategy for new generation of telescopes (2 msgs)

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

Date: 28 Oct 92 17:30:14 GMT
From: Henry Spencer <[e-mail]>
Subject: active planetary probes; should someone update the FAQ
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Nick Haines) writes:
>...What is Hiten?

Hiten, aka Muses-A, is the Japanese engineering-test mission that has been
batting around the Earth-Moon system for a year or two.  It's not a science
mission, and has nothing to do with Geotail et al.

Actually, I exaggerate slightly...  Hiten has one science instrument, a
German dust detector, which has been returning some interesting results:

---------
11.05       Iglseder H.*   Grun E.   Munzenmayer R.   Svedhem H.
                Cosmic Dust and Beta-Meteoroids in the Earth-Moon System: More
                Than Two Years of Operation of the Munich Dust Counter MDC

On 24 January 1990, ISAS (The Institute of Space and
Astronautical Science) launched a space engineering satellite
HITEN (MUSES-A Mission) from Kagoshima Space Center, Japan (JKCS)
into a highly elliptical orbit around the Earth with perigees
between some thousand and 100,000 km, and apogees between 300,000
and 1.53 million km. The Munich Dust Counter (MDC) is a cosmic
dust experiment on board the spacecraft HITEN. After a short
introduction describing the experiment setup and the measuring
principle, the results of two years of operation of the MDC will
be discussed. From these micrometeoroid measurements a summary of
the following results will be presented: (1) Determination of the
mass, velocity, and angular distribution of cosmic dust particles
and beta meteoroids in the Earth-Moon system. (2) Detection of
pro- and retrograde beta meteoroids in the solar system. (3)
Accurate measurements of the cumulative particle flux of cosmic
dust particles and beta meteoroids. (4) Evidence of different
types of cosmic dust particles like apex particles, beta
meteoroids, and particles with high inclinations. (5) Focussing
and defocussing effects by the Earth and the Moon. (6) Evidence
of swarms, groups, and random particles. Enormous variations of
the instantaneous particle fluxes and impact rates of
micrometeoroids. (7) No significant indications for stable dust
clouds near the Lagrangian points L4 and L5 (Kordylewsky-clouds).
(8) Indications of the existence of interstellar particles. (9)
Finally the spatial distribution of 351 cosmic dust particles is
shown in geocentric and heliocentric coordinate systems. The
directional distribution is also given, showing the different
populations of cosmic dust particles.
---------
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 28 Oct 92 18:01:09 +0930
From: [e-mail]
Subject: AUSROC II Launch Update
Newsgroups: sci.space

Reprinted from The Advertiser, Friday, October 23, 1992, p.1

Rocket blast-off ends in big bang
---------------------------------

by Zac Donovan

     Australia's re-entry into the space race ended in a huge cloud of smoke
and flames at Woomera yesterday - and a $400 valve has been blamed.

     Ausroc II, an unmanned 6 m rocket designed and built by amateur enthusiasts
from Melbourne's Monash University, was engulfed in flames when a launch was
attempted about 10:25 am.

     The largest liquid-fuelled rocket built in Australia was expected to climb
12 km, hit a top speed of 1600 km/h and travel about 25 km from the Woomera
launch site in South Australia's Far North.

     Instead Ausroc II, which took four years and $200,000 to get to the launch
pad, exploded in a ball of flames and smoke.

     Project scientists said the small valve apparently did not open to let
liquid oxygen accelerant mix with kerosene fuel. The fuel ignited into a
brilliant orange flame that without the oxygen mixture was unable to propel
the rocket.

     When the kerosene flame burnt back to the liquid oxygen, it exploded the
top half of the rocket off the launch pad.

     Despite the setback, range officials believe the attempt will heighten
public interest and boost plans to launch commercial satellites from Woomera.

     Woomera range manager Mr. Bob Dyer said the failure was to be expected in
the rocket industry.

     "The fact that they got as far as they did was a real boost to this
place," he said.

     The bid follows a proposal by the Southern Launch Vehicle consortium to
launch $21m communication satellites from Woomera by 1994.

     The SLV group, headed by British Aerospace Australia, has said it was
likely to seek government funding for initial launches.

     Mr. Dyer said yesterday the use of Woomera for the Ausroc II rocket bid
could help convince the Federal Government to invest in the SLV program.

     "People will start to talk about Woomera again and I hope that filters
back to the right people," he said.

     "The equipment is still here and the range is in perfect condition; there
is no reason not to start using it again."

     The State Government believes the SLV project could create 2000 jobs and
inject $100 million into SA.

     Ausroc program co-ordinator Mr. Mark Blair said yesterday the team of 12
amateur rocket builders would be "spurred on" by the failure.

     "You learn far more from your mistakes than you do from your successes,"
he said.

     At the end of the countdown yesterday, the rocket failed to take off.
About five minutes later it exploded.


Previous AUSROC updates can be obtained by anonymous ftp to
audrey.levels.unisa.edu.au in the space/AUSROC directory.

--
Steven S. Pietrobon,  Australian Space Centre for Signal Processing
Signal Processing Research Institute, University of South Australia
The Levels, SA 5095, Australia.      [e-mail]

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

Date: Tue, 27 Oct 1992 00:52:35 GMT
From: "<[e-mail]>" <[e-mail]>
Subject: Collision with Comet P/Swift-Tuttle
Newsgroups: sci.astro,sci.space

This discussion about Swift-Tuttle is getting out of hand on several
fronts. Below is an extract the text of the IAU Circular 5636 which contains
ALL of the "hard" information on the matter.

Some Newspaper reports have misquoted various astronomers,
implying they say it WILL hit when they only amplify and interpret
Brian Marsden's comments in the circular. In particular Duncan
Steel would not have told anybody that P/Swift-Tuttle will
collide, just that it has a serious chance of doing so,
and the consequences of such a collision.

 Brian Marsden, is the Director of the
Central Bureau, and an Assistant director of the Smithsonian
Astrophysical Observatory. He is the person several posters
have said appeared on one or other talk/ News shows on US TV,
I am sure.

Another sociological aspect of this phenomenium is that the media
 took so long
to get onto it. Note the date on the notice is October 15.
Thus discussion on these Newsgroups about it was on
the Weekend of Oct17-18.
============================================
                                               Circular No. 5636
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.

PERIODIC COMET SWIFT-TUTTLE (1992t)
     Orbital computations by the undersigned, and also by S. Nakano,
Sumoto, Japan, have so far failed to link all the observations, even
when allowance is made for nongravitational forces.  Although a
reasonable fit can be made to the 1862 (except October) and 1992
observations, the resulting transverse nongravitational component is
so large that the resulting eighteenth-century perihelion time is 15
months too late.  Alternatively, although the three perihelion times
can be well represented without any consideration of nongravitational
forces at all, there are strong systematic errors, amounting to more
than 1', in 1862 and 1992.  The gravitational orbital elements below
satisfy the observations in 1992 and in Oct. 1862 very well, and they
also represent the presumed 1737 perihelion time within 1 day.
Backward computation of this solution reveals few candidates for
earlier appearances of the comet, although the one of -68 fits within
1 year (there being 15 revolutions between then and 1862), and the
comet of +60 may also belong.  Future extrapolation gives the next
return to perihelion as 2126 July 11, although the problem with the
computation of the nongravitational forces must introduce some
uncertainty; a change by +15 days could cause the comet to hit the
earth on 2126 Aug. 14.  It therefore seems prudent to attempt to
follow P/Swift-Tuttle for as long as possible after the present
perihelion passage, in the hope that an adequate independent orbit
determination, uncontaminated by nongravitational effects, can be made
from mid-1993 (at r = 3 AU and far to the south) to, say, 1998 (when r
= 15 AU and an assumed nuclear absolute magnitude of 14 yields an
apparent magnitude of 26).

                    Epoch = 1992 Dec. 4.0 TT
     T = 1992 Dec. 12.323 TT          Peri. = 153.013
     e = 0.96359                      Node  = 139.456   2000.0
     q = 0.95812 AU                   Incl. = 113.430
       a = 26.31666 AU     n = 0.007301     P = 135.00 years

1992 October 15                (5636)              Brian G. Marsden

Tony Beresford
AARNET [e-mail]

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

Date: Wed, 28 Oct 1992 10:03:30 GMT
From: Colleen Anderson <[e-mail]>
Subject: Comet Collision
Newsgroups: sci.space

[e-mail] writes:
>I caught the end of a newsclip on SKY TV this a.m. which said that
>NASA "scientists" (probably the techs. that actually do the real work)
>had tracked a comet on collision course with the earth - I think it
>was due to hit us in 2016. Anyone else hear this, or was I just fantasising
>it !
       I heard about it from a friend the other night.  He said that
scientists said a comet which will soon be making a pass (or has just made
one) near our planet will actually collide in 2145 with Earth.  I am highly
dubious and would like to know more.  I also believe that, depending on size
of course, by then we should have no problem in deflecting it.
Colleen
--
It's not how much I know that counts but how much I'm trying to learn.
The Crimson Bunion

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

Date: Wed, 28 Oct 92 13:10:18 GMT
From: Glen K Moore <[e-mail]>
Subject: Comet Collision
Newsgroups: sci.space,alt.sci.planetary

Would a comet collision be so bad? Presumably the damage would primarily be
a loss of crops for a season (apart from the damage at the impact site). Food
could be put aside in many countries but in many others there could be
massive starvation with a resultant loss of population (perhaps half of the
worlds total?).
Mankind should survive but with a reduced population. Many other species may
be lost and perhaps others which survive may even multiply.
For the first time in history a real attempt could be made on a global scale
to cooperate. External threats may unite us against a common threat
and force us to face the challenges and problems of food distribution.
We are hardly as helpless as the dinosaurs!

After the changes of the past few years it is impossible to guess the world
perspective 130 years into the future.

Glen
[e-mail]

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

Date: 28 Oct 92 14:59:05 GMT
From: "Richard S. Brice" <[e-mail]>
Subject: Comet Collision
Newsgroups: sci.space

>
> >There is a greater change of dying from a train wreck or a car accident than
> >getting plowed by the comet.
>
At the macro level, i.e. the interaction of planets, stars and comets, the
universe seems to behave in almost clocklike manner; chance and probability
have only a small role.     ^^^^^

Would anyone care to comment on how probability plays a role in the
future interactions of earth and comet P/S-T and how much of the
script is already written into the clock?

R. Brice
MCC Corp

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

Date: 28 Oct 92 16:18:29 GMT
From: "C. Taylor Sutherland III" <[e-mail]>
Subject: Comet Collision
Newsgroups: sci.space,alt.sci.planetary

Or just blast the shit out of it when it gets close enough.


--
         We're not hitchhiking anymore.  We're riding!
             -The Immor(t)al Ren & Stimpy-
         The Fly Boy  <| E-MAIL:  [e-mail] |>
+--<| My life is a math question with one equation and 42 unknowns. |>--+

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

Date: Wed, 28 Oct 1992 13:09:39 GMT
From: Paul Dietz <[e-mail]>
Subject: HRMS for ETI
Newsgroups: sci.space,sci.bio

In article <[e-mail]> [e-mail] (David M. Palmer) writes:

>One way to estimate P(life | suitable planet), while adjusting for the
>weak local anthropic principal ("how strange that we should be on
>a planet which has life---NOT!" :-)) is to look at how long it took life to
>evolve, and compare that to the length of the 'window of opportunity'
...
>It turns out that life occurred just about as soon as the Earth was
>tolerable, like within 100 million years (this number is approximate, I
...
>accreted.)  This is very near the start of the window, which is roughly
>5 billion years long as a rough number.


The last statement cannot be supported, since we don't know what
conditions are required for life to originate.  It could be that they
would exist only soon after the formation of a planet.  For example,
perhaps deposition of organic material from space is required.

Another thing one can do is to look at how long it took humans to
appear -- about 4.5 billion years.  The earth will not be habitable
much longer (due to the increasing brightness of the sun with time),
perhaps as little as a few hundred million years.  The late appearance
of humanity is weak evidence that the evolution of intelligence, or,
indeed, multicellular life, takes a long time, perhaps much longer
than the average lifespan of a biosphere.

    Paul

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

Date: Wed, 28 Oct 1992 17:32:16 GMT
From: Henry Spencer <[e-mail]>
Subject: HRMS for ETI
Newsgroups: sci.space,sci.bio

In article <[e-mail]> [e-mail] (Paul Dietz) writes:
>... The earth will not be habitable
>much longer (due to the increasing brightness of the sun with time),
>perhaps as little as a few hundred million years...

This claim depends on many assumptions, and is a fairly weak basis for
reasoning about expected lifetimes of biospheres.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

Date: 28 Oct 92 15:21:41 GMT
From: Greg Moore <[e-mail]>
Subject: nasa shake up rumor?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
>
>It won't be ten years since Clinton will be a one term president. At the
>end of which (if we are successful lobbying Congress) we will have an
>operational SSTO at which point we may not need the government any more.
>
    Wow Allen... I'm impressed.  Not only will DC-1 decrease launch
costs dramtically, take us to the moon, and more... it'll eliminate our
need for a government? :-)


P.S.  Will it do windows and slice bread?
>  Allen
>
>--
>+---------------------------------------------------------------------------+
>| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
>|  [e-mail]     |  nothing undone"                                       |
>+----------------------179 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: Wed, 28 Oct 1992 09:52:06 GMT
From: "H. Evans (WMA" <[e-mail]>
Subject: re HRMS for ETI
Newsgroups: sci.space

From what I remember of the course in Measurment, Error and Truth,
the probability (as measured) of intelligent life forming on another
planet is 1 (with an error of 1).  Not much of a help, but we have only measured
one instance of intelligent life forming (and that is disputable :-)).
Of course, if evidence of life is found, then the error in the measurement will
decrease to 1/sqrt(n).

Any attempts to pin down the probability more than this is idle speculation but
fun.

Hugh.

P.s. if you put an infinite number of monkeys on an infinite number of planets...

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

Date: Wed, 28 Oct 1992 16:41:02 GMT
From: Nick Haines <[e-mail]>
Subject: re HRMS for ETI
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (H. Evans (WMA)) writes:

   From what I remember of the course in Measurment, Error and Truth,
   the probability (as measured) of intelligent life forming on
   another planet is 1 (with an error of 1).  Not much of a help, but
   we have only measured one instance of intelligent life forming (and
   that is disputable :-)).  Of course, if evidence of life is found,
   then the error in the measurement will decrease to 1/sqrt(n).

   Any attempts to pin down the probability more than this is idle
   speculation but fun.

Not at all. We are not completely ignorant of the processes which are
necessary to generate life, or multicellular life, or intelligent
life. Ignorant, but not completely so. Therefore we have more
information than simply the observation `there is intelligent life
here'. By your argument, we could state that the probability of life
on Mars, the Moon, or Ceres is 1 (with an error of 1). The idea is to
identify those conditions which can lead to life (e.g. the occurence
of suitable clay minerals in an organic-rich water-rich environment,
possibly) and then make an educated guess as to the likelihood of
those conditions.

Nick Haines [e-mail]

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

Date: 28 Oct 92 18:34:09 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Sen. Al Gore on the American Space & Aeronautics Programs
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Patrick Chester) writes:

>=                    STATEMENT BY SENATOR AL GORE
>=                     Goddard Space Flight Center
>=                       Monday, October 19, 1992

>Gore butters up spaceflight enthusiasts, flem at eleven.

Actually, Gore is buttering up Shuttle enthusiasts. In the first part of
his speech he talks about reducing the cost to orbit but when you get to
where he plans to spend the money, it's all for Shuttle. There will be
no money for cutting costs but plenty of pork.

>= I'm talking from first-hand experience.  As Chairman of the Senate
>= subcommittee that writes NASA's authorization bill, I have battled
>= every year with the Administration on priorities in aerospace.

>What is his REAL record? Anyone? Back to our sound bite.

Not good. Gore was at the forfront of people working to protect Truly
when he was fired. His efforts on his sucommittee shows that he simply
doesn't care about space very much (asside from Mission to Planet Earth.

>Maybe NASA's budget should be increased a bit more. At least cut the pork from
>all of their projects.

From Gore's statements and actions one must conclude that he opposes 'better,
cheaper, faster' and therefore won't increase budget or reduce pork.

>=      Right to the point, Dan Quayle and the National Space Council
>= have failed to act decisively on the issue of developing a new rocket
>= program.  The blame must lie squarely at their feet.

>He may have a point here.

Quayle and the Space Council have shown tremendous leadership on new
launch programs. SSTO for example, wouldn't have happened without the
personal interest of VP Quayle.

Gore doesn't have a point here.

>=      As proposed by the Space Council, the U.S has been actively
>= attempting to develop not one, not two, but three -- yes, three new,
>= costly, and technically complex orbital launch systems:

First, Gore shows here that he simply doesn't understand science or
engineering all that well. If he did he would know that the best way
to cut costs is to fund several efforts.

Second, all together I agree that NLS is a bad idea we could develop
ALL these ideas for about 15% of NASA's budget. Given that this is
the sort of research NASA is chartered to do, it hardly seems costly.

>= Plane, and the Single Stage Rocket Technology program, which still
>= has no price tag.

>Allen, could you enlighten everybody to the Delta Clipper's price, please?

DC-Y should cost $2 to $4 billion with another billion or so needed beyond
that to take to market. Over four years it is hard to see why Gore
could possibly consider this costly.

>= even given the fact that the Space Plane and the Single Stage
>= Technology program may provide significant benefits only in the
>= long-term future.

>I don't know about the NSP, but DC-X is going to be test-flown in a few months.
>Guess long-term to Gore is anything longer than 4 years.

NASP is a long term research effort. It's a pity that Gore considers long
term research a bad idea.

SSRT is a moderate risk high payoff project which, if it works, will
reduce costs by an order of magnitude during a Clinton administration.

>=      The findings of the Advisory Committee on the Future of the U.S.
>= Space Program, the so-called "Augustine Committee", offer a good road
>= map.

Which is very strange. The number one recommendation of the Advisory
Committee was that a Heavy Lift Vehicle (which he opposed above)
should be the highest priority for NASA.

>My main bitch about waiting for manned exploration is that we've *been* waiting
>for nearly 20 yrs to start. At least let us return to the Moon, dammit.

Any you will continue to wait under Clinton.

If you loved NASA under Truly, your going to love the next 4 years.

   Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------178 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 28 Oct 92 15:25:36 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Smith-Tuttle Comet a threat to earth?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (J. D. McDonald) writes:
>
>>Speed relative to Earth is 50 km/s
>Lord Almighty! 1/6 the speed of light!!!!!! ???????

You're off by three orders of magnitude. Light speed is roughly
300,000 km/s.

Gary

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

Date: 28 Oct 92 15:47:20 GMT
From: Curtis Roelle <roelle@uars_mag.jhuapl.edu>
Subject: Smith-Tuttle Comet a threat to earth?
Newsgroups: sci.space

[e-mail] (Nick Haines) writes:

  [re: a post in article <[e-mail]>
   by [e-mail] (Steinn Sigurdsson)]

>I keep reading this, and have a couple of questions to ask:

>1. S-T crosses Earth orbit twice every 120 years. The risk of
        ^^^^^^^ ^^^^^ ^^^^^ ^^^^^
This business about P/S-T crossing Earth's orbit twice each time around
has appeared in at least one other post.  It is not clear whether Nick
Haines is talking about the orbital plane or the orbital path.

Obviously P/S-T crosses Earth's ORBITAL PLANE twice, but that does not
imply that it crosses the ORBITAL PATH twice.  My understanding is
that the Perseids are the only meteor stream known to be associated
with this comet.  Earth passes through this stream each August.
Therefore, the comet crosses the orbital path of earth only once.  If
P/S-T crossed earth's orbit twice during its orbit as stated above,
then the Perseids would be a biannual event, which it is not.

Curt Roelle -- [e-mail]

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

Date: 28 Oct 92 17:02:20 GMT
From: Ed Russell <[e-mail]>
Subject: Smith-Tuttle Comet a threat to earth?
Newsgroups: sci.space

>  the risk of encounter is 1e-6

The probability of impact must be calculated with respect to the
uncertainty in the orbit of the comet due to the astrometrics and
the action of non-gravitational forces.  This comet is a particular
comet on a particular path  - not a hypothetical comet on a
hypothetical path.

To determine the probability of impact during a given time period
simply integrate the density of the distribution of the error in
the location of the comet over the cross section of the Earth's orbit
over the time period in question.

It will vary depending on the expected distance that the comet is from
Earth during that time period - and thus is not a constant over equal
time periods.  For instance the apparent risk of an impact by S-T today
is much lower (nil) than it will be on Aug 14, 2116 given our present
state of knowledge of the S-T orbit.


======================================================================
Ed Russell

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

Date: Wed, 28 Oct 1992 16:55:04 GMT
From: Jeff Greason ~ <[e-mail]>
Subject: Solar Sails
Newsgroups: sci.space

Well, so solar sails are just "driven by radiation pressure".  I'd heard
that (as well as solar wind) before.

However, If you look at the original post, you'll see my concern --
radiation pressure seems 2-3 orders of magnitude too small to be useful
for drive.  Recalling that F=P/c for light pressure, and that power
density P is roughly 1.4kW/m^2 at Earth orbit, you get a pretty trivial
4.7 MICRONEWTONS per square meter.

Even if you are satisfied with 0.001G (0.01m/s^2) of acceleration, this
means your sail material must mass less than 0.5 GRAMS per square meter.
Is this feasible?  I recall seeing some discussion on solar sails for the
proposed 1992 solar sail race to Mars -- surely someone can post, or
email me, some hard numbers on this?  I'm just having difficulty convincing
myself that solar radiation pressure is strong enough for this purpose.

Disclaimer:  All opinions expressed are my own, and do not reflect the
     position of Intel, Portland State University, or Zippy the Pinhead.
============================================================================
Jeff Greason                  "You lock the door ... And throw away the key.
  <[e-mail]>   There's someone in my head, but it's not me."
  <[e-mail]>                -- Pink Floyd

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

Date: 28 Oct 92 15:33:45 GMT
From: Imaging Club <[e-mail]>
Subject: Strategy for new generation of telescopes
Newsgroups: sci.space,sci.image.processing

The current issue of the Economist has a very interesting, lengthy
article on the new generation of large telescopes that is coming
along.  The main point of the article is that these new ground
telescopes are going to make the Hubble space telescope technology
obsolete, althought Hubble will continue to provide valuable
service especially after the shuttle mission with the "fix."  The
plan is to use image processing to make ground corrections for all
the image aberrations caused by the changing atmosphere.  The
technique is to create artificial stars high in the atmosphere by
bouncing a laser beam off various layers.  Since the expected apparent
position of the artificial star is known, ground observers can make real
time corrections (many times per sec.) when the artificial star's image
shows up at the telescope slightly off, correcting the images of everything
else in the field.These corrections are made by mechanical movements of
the mirror or component portions of the mirror.  This is a fascinating
article with some amazing technology being described.  If anyone would
like me to air mail them a copy, let me know.  It's too long to retype
and I don't have OCR (or intelligent character recognition) at this
location.  This article has nothing to do with Wang imaging products.

[e-mail]

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

Date: 28 Oct 92 17:40:50 GMT
From: Henry Spencer <[e-mail]>
Subject: Strategy for new generation of telescopes
Newsgroups: sci.space,sci.image.processing

In article <[e-mail]> [e-mail] ("Imaging Club") writes:
>... The main point of the article is that these new ground
>telescopes are going to make the Hubble space telescope technology
>obsolete...

This is the usual ill-informed claim, I'm afraid.  Hubble has three or four
different edges over ground-based astronomy, and the new big ground-based
telescopes are only addressing one of them.  The most obvious case in point
is that ground-based ultraviolet astronomy is largely impossible, and no
amount of smart optics is going to fix that.

From the Economist I had expected better.

A more accurate statement is that Hubble's edge over ground-based telescopes
is not as large as it was intended to be.  That's largely a result of the
interminable delays in the project (of which the shuttle grounding was only
the most recent).  Its gestation period was nearly 25 years, and the basic
design was frozen 15+ years ago.
--
MS-DOS is the OS/360 of the 1980s.      | Henry Spencer @ U of Toronto Zoology
              -Hal W. Hardenbergh (1985)|  [e-mail]  utzoo!henry

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

End of Space Digest Volume 15 : Issue 353
------------------------------