Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v16_6/v16no644.txt

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Date: Fri, 28 May 93 14:41:39
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #644
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri, 28 May 93       Volume 16 : Issue 644

Today's Topics:
     Can we use HST to look at possible Jupiter/comet collision?
    Comet Shoemaker-Levy, Possible Collision With Jupiter in 1994
                  Commercial Space News #23 [Part 2]
                  Hey Sherz! (For real!) Cost of LEO
               Hubble Servicing Mission Study Completed
                            Hubble vs Keck
                        Launch Vehicle Permits
                Liberal President murders spaceflight?
                      Meade Telescope For Sale
   Microlensing searches (was "detecting planets in other systems")
                  Privatizing scientific terminology
                            Space Raffles?
        Story Musgrave (Was: Carl Sagan, respected astronomer)
       Tom Wolfe's THE RIGHT STUFF - Truth or Fiction? (3 msgs)
    Voyager Discovers the First Direct Evidence of the Heliopause
                   Why a far side Science station.
               Why Government? Re: Shuttle, "Centoxin"

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
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    (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: Thu, 27 May 1993 16:55:05 GMT
From: Stupendous Man <[e-mail]>
Subject: Can we use HST to look at possible Jupiter/comet collision?
Newsgroups: sci.space

  Leigh Palmer must think I have a personal vendetta against him :-)
I don't - I'm just trying to point out the difficulties in using
HST in this particular case.  Leigh writes:

> I think that WFPC on Hubble is the natural instrument to use to
> observe these impacts. It is the highest resolution telescope
> available to do so

  This is true.

>  ... and there should be several events, perhaps with
> some action to be observed.

  This is a major problem.  The REAL interest is in the "action" -
the behavior of the cometary pieces and Jupiter's atmosphere with
time, right?  So we want good time resolution - say, video rate.
But HST can't give us that.  The WF/PC can take short-exposure
pictures of Jupiter, but not frequently.  Let me read a passage from
the "WFPC Instrument Handbook":

      "Commands to the WF/PC are processed at spacecraft 'major
       frame' intervals of 1 minute.  A filter may be returned
       'home' and another filter selected in one major frame.
       An exposure takes a minimum of one minute [not the actual
       shutter-open time, but the time between snapping picture
       and doing another operation], and a readout of less than
       4 CCDs takes a further minute.  A readout of all 4 CCDs
       of the WFC or PC takes two minutes."

  So, the WF/PC can take, at most, one picture every two minutes.
That's pretty slow for a high-speed impact, I'd say.  Don't
forget that HST will pass behind the Earth every forty minutes
or so, so one can get, say, twenty pictures, then a gap of forty
minutes, then twenty pictures, then a gap, etc.  And the gap
MIGHT come at impact of the biggest piece.

  I suspect that the best results will come from ground-based
telescopes at good sites using video-rate CCDs.  At Lick,
for example, someone used a video-rate CCD to monitor the occulation
of 28 Sagitarii by Saturn a few years ago.  It was an impressive
amount of data (figure 30 CCD frames per second for over an hour :-)

  I repeat, I suspect HST will do best to monitor the atmospheric
disturbances on an hourly/daily/weekly timescale AFTER the collision.
If, of course, there is a collision - let's hope so!

--
-----                                                    Michael Richmond
"This is the heart that broke my finger."    [e-mail]

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

Date: 28 May 93 00:04:39 GMT+12
From: Ross Smith <[e-mail]>
Subject: Comet Shoemaker-Levy, Possible Collision With Jupiter in 1994
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>                           COMET SHOEMAKER-LEVY (1993e)
>
>     According to IAU Circular 5800, about 200 positions of Comet
>Shoemaker-Levy (1993e) have been reported so far with about 50 of them
>coming during the past month.  Most of the observations were of the "center"
>of the nuclear train [last I heard the comet split up into at least 21 pieces].
>The current computations indicate that the comet made a close flyby
>of Jupiter at only 0.0008 AU on July 8, 1992 (this is within Jupiter's
>Roche limit), and will make an even closer flyby of Jupiter on July 25, 1994.
>
>     IAU Circular 5801 further discusses the orbital trajectory of the comet,
>and indicates that it is possible that half of the pieces of the comet may
>collide with Jupiter over a three day peroid in July 1994.  The surviving
>pieces may remain as satellites to Jupiter or be thrown closer to the sun on
>short-period heliocentric orbits.

Does anyone have any idea how big the pieces are? Are we talking about objects
comparable to the smaller known Jovian satellites (~20 km diameter), or little
bitty things barely bigger than ring particles, or what?

--
... Ross Smith (Wanganui, NZ) ............ [e-mail] ...
His philosophy was a mixture of three famous schools -- the Cynics, the
Stoics and the Epicureans -- and summed up all three of them in his famous
phrase, `You can't trust any bugger further than you can throw him, and
there's nothing you can do about it, so let's have a drink.'
                                                          (Terry Pratchett)

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

Date: 27 May 93 21:28:38
From: [e-mail]
Subject: Commercial Space News #23 [Part 2]
Newsgroups: sci.space

space markets might appear.  According to Goldin, the firms involved
would jointly perform a "market elasticity study" to determine where
the market is and what is needed in a new commercial launch vehicle,
defined as cost for access to space.  After this initial market
study, the firms would move into some type of joint vehicle
definition and technology study, focusing on what is needed for the
new launch system.
   What is most interesting is Goldin stated "They propose to...
focus on economic return instead of being driven by vehicle
performance specs and they are willing to share the risks and the
costs with the government."  This would be a major change in the way
of doing business.
   There are still major unknowns about this project -- who will
eventually be involved, the amount and direction of cost sharing
with the government, and the interaction with other, government
sponsored, vehicle development activities. The 5 firms involved are
being rather close-lipped, but seem unanimous in stating they are
still in the early stages of discussion about how to proceed for
this venture. It was reported McDonnell Douglas participated in
early stages of this discussion, but when the group approached Dan
Goldin, MDC backed out.  Other firms in the industry are supposedly
interested in this activity -- including some of the major
subcontractors and some of the smaller launch companies.  I expect
discussions will continue for some time within the industry before
any semi-formal arrangements are made for cooperative efforts.
   It is interesting to note this was first revealed by Dan Goldin
in a public forum.  The approach being taken by the 5 firms seems to
fit well with the Clinton administration's policy of involving
industry more directly in development of technology, and with
Goldin's new emphasis within NASA upon developing technology for
commercial application.
   I expect the firms desired to get NASA involved to support the
expensive and risky development of focused technologies for a future
commercial vehicle, if one is defined.  The approach outlined seems
to be more of a return of NASA to the "NACA" model of technology
development.  NASA will work with industry to identify key markets
and needed technologies, and work cooperatively to develop specific
technologies.  But NASA would not direct the development nor operate
any space transportation system developed for this market.
   Unfortunately, this tentative cooperative program seems to flying
directly in opposition to the planned USAF Spacelifter program,
which is focusing on the near-term government development of a new
20,000 lb. payload class launch system.  While some divisions have
apparently surfaced between factions in the USAF, the program seems
to be targeted towards a near-term vehicle to supplement the USAF
Titan-IV and MLV programs.
   It is rumored that the USAF has expressed great dissatisfaction
this market study is starting up, just when the USAF is planning to
spend about $55 M in FY94 starting the highly-focused Spacelifter
program.  Furthermore, the USAF plans upon turning the developed
vehicle over to a commercial operator after it has funded the
development and initial operations of the system.  Obviously, these
plans challenge any other "commercial" vehicle development.
   At the moment, there is little information released on how these
two programs might interact.  But I believe there is a dichotomy
between these two approaches that will have to be resolved before we
can see the development of a new commercial launch system.]

12-    SPACE TECHNOLOGY INDEXES THROUGH APRIL
   [The table below summarizes the results of the CSN/STI stock
indexes and pure-play portfolio through the end of April.  The Space
Technology Index again did quite a bit better than the market as a
whole, as represented by the S&P 500 index.  Part of this is due to
a 2.5 % drop in the overall S&P 500 index, while the firms who
contribute to the space indexes have not shown the same general
stock price drop. Part of this explanation may arise as many of
these firms have been quick to come out of the recession and are
aggressively pursuing new business, whereas the S&P 500 firms may
more generally reflect a continuing of the malaise of the current
recession.

   INDEX RESULTS THROUGH APRIL
                           Beginning  Beginning      1 Jan 93 to
                           1992       1993           30 Apr 1993
                           -------    --------       --------
   S&P 500                 416        436  (+4.7%)   440  (+1.0%)
   Space Tech Index        267        304 (+13.6%)   376 (+23.8%)
   Comm'l Space Tech Index 167        194 (+16.3%)   226 (+16.3%)
   Space Tech Pure Plays   147        169 (+15.4%)   198 (+17.0%)

   Firms contributing most to this month's rise in the stock indexes
are Comsat, General Instruments, and California Microwave, which
overcame significant downers from Qualcomm and Satellite Technology
Management.  It should be noted foreign firms included in the index
generally showed a double digit percentage gain traceable to the
drop of the dollar exchange against the yen.  However, this was not
generally reflected in the index totals due to the typical low
involvement of such firms in the space business as an overall part
of their activities, and their subsequent low weighting in the
index.  Within the foreign firms, Damiler Benz showed a significant
downer as they reported significant losses from their Deutsche
Aerospace activities over the past year.
   The increase in the overall space indexes is very encouraging,
although future months may reverse this trend.  Next month will see
an adjustment in the indexes as General Electric will be dropped
from the index as all of their space businesses have been sold to
Martin Marietta.]

FINAL NOTES -
   I've managed to catch up with the current piles of paper and
megabytes of data accumulating on my desk.  Unfortunately, this was
accomplished by judiciously tossing out news items not of general
interest.  Even with massive weeding though data files, this column
came out a bit longer than usual.
   Looking ahead, I've got articles in work on proposed changes in
the satellite navigation market, and on market impacts from
converting ICBMs into launch vehicles, plus other interesting stuff.
Now, if I can just find some free time to turn data into
articles.....
   And as always, I hope you folks find this stuff useful and
interesting -- Any and all comments are welcome.
-----------------------------------------------------------------
Wales Larrison                          Space Technology Investor
"Quam minimum credula postero"             P.O. Box 2452
                                        Seal Beach, CA 90740-1452

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

Date: 28 May 1993 13:19:18 -0400
From: Pat <[e-mail]>
Subject: Hey Sherz! (For real!) Cost of LEO
Newsgroups: sci.space


There was an editorial in this week's space news
by a soviet scientist? on teh BURAN.  He claimed teh Soviet Military
dropped support for teh program in 1983, and the science community
backed off a few years later.  this being before teh real big troubles.

pat

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

Date: 28 May 1993 13:01:55 -0400
From: Pat <[e-mail]>
Subject: Hubble Servicing Mission Study Completed
Newsgroups: sci.space,sci.astro,sci.space.shuttle

In article <[e-mail]> [e-mail] (fred j mccall 575-3539) writes:
>
>Still as wrong as it was the first time you said it.  They would have
>to fly a second mission to take this little 'cobbled together' tug of


What needs to be done is some analysis of weight budgts.

A while ago, someone kindly posted the Weights  for the HST service mission.

I seem to recall that Discovery was carrying  25K lbm of Hydrazine
which was listed as the Largest OMS fuel load carried to date.
I imagine the fuel is divided on the basis of Part :

    A) Circ Burn 1 :  After MECO at Perigee.

    B) TCM Burn   : In case of Engine Underperformance.

    C) Circ Burn 2 : an extra circularization burn, I think they no
            longer use this.

    D) HST Re-boost Burn : This is the big one.

    E) De-orbit Burn :  It's miller time.

    F) Emergency Burn : Emergency evasive action.

I'd guess A,B,E,F  run along the lines of 10KLbm.  does anyone know?
because if so, that means  that up to 15Klbm, can be devoted to
Extended mission supplies and an ESMT.
If anyone can help me out, i'd appreciate it.

pat

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

Date: 28 May 93 11:20:34 BST
From: [e-mail]
Subject: Hubble vs Keck
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Anita Cochran) writes:
> In article <[e-mail]>, [e-mail] writes:
>> In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
>> > In article <[e-mail]> [e-mail] (Phil G. Fraering) writes:
>> >>it would probably be cheaper to build another Hubble. Or to simply
>> >>write off the Hubble program entirely and build 2.5 more Keck
>> >>Interferometers. (Which could be done for the cost of fixing
>> >>Hubble).
>
>> > It wouldn't give you Hubble's UV or faint-object capabilities, even
>> > assuming that the Keck Interferometer works as well as projected.  The
>> > extent to which the new ground-based telescopes can (probably) equal
>> > or surpass Hubble is exaggerated; they do so in only one of several
>> > dimensions.
>

[Argument (mine) that Keck's larger collecting area will enable it to go deeped
than HST]

>
> Actually, having just gone through all of this for my HST proposal, Henry is
> correct.  The reason why HST wins, despite the 45 minutes per cycle and
> smaller telescope, is that the sky background is so much lower.
> A dark site on the ground has a sky background of 21.5 or 22 (very dark
> such as McDonald Obs) per sq arcsec.  With typical CCD plate scales,
> the background per pixel is around 22.5 mag.  Contrast that with
> the HST WFPC2 numbers of a sky background of ~27.2 mag/pixel.  Thus,
> to reach a given signal/noise, one can use shorter integration times
> on Hubble that on a comparable sized telescope on the ground.  As you
> point out, Keck is much larger but the sky background is a surface brightness
> and Keck just gathers more sky.  Additionally, with Keck, you have seeing
> effects which hurt you.  So, all in all, HST can reach pretty impressive
> limiting magnitudes.  Tyson and his co-workers have probably gone the
> deepest on the ground and have reached S/N=3 (I think) for m in the R band
> of 27.8 in 22000 sec with the 4-m CTIO prime focus.  We figure we can reach
> m=28.5 with S/N=4 in R in 18000sec on HST.  Yes, one has to reacquire
> each 45 minutes with HST but in practice, 22000 sec on the ground takes
> a long time too since one has to worry about airmass so it takes several
> nights.
>
> Incidentally, if one believes the specs in the call for proposal and instrument
> manual books, the FOC is not really the instrument that can go the faintest.
> WFPC2 can easily go fainter.  FOC could beat out WFPC1 but not the new
> instrument.  FOC has superior plate scale for some things and has a
> long slit mode but the detector is an outdated vidicon.

Thanks for the info. I don't have HST docs for the new instruments, and the
figures you quote for WFPC2 are impressive. I hope you get observing time for
the deep survey as I'd be interested in the results.

On the other hand though, you do have one clear problem, above and beyond the
technical ones, with HST that you don't have so much with Keck, and the other 8
m when they copme on line. Lack of observing time. With Keck it would not be
difficult to get several fields imaged deeper Tyson's during a couple of
observing runs. What are the chances that you'd get a similar large amount of
time of a facility like HST which is even more oversubscribed than Keck? In the
future, as long as the repair mission works, I can see HST doing a lot of
interesting ground breaking, but the bulk of the followup work will be done,
where possible, from the ground, with instruments like Keck or Gemini.


--
================================================================================
Dave Clements, Oxford University Astrophysics Department
================================================================================
clements @ uk.ac.ox.vax            |  Umberto Eco is the *real* Comte de
dlc      @ uk.ac.ox.astro        |           Saint Germain...
================================================================================

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

Date: Fri, 28 May 1993 14:49:26 GMT
From: SNYDER GARY EDWIN JR <[e-mail]>
Subject: Launch Vehicle Permits
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Mark Johnson) writes:
>[e-mail] (Henry Spencer) writes:
>
>>Transportation, which is part of the Dept. of Transport.  I'm told
>>they can be reached at [phone], although I haven't tried myself.
>
>>Anything that is capable of going above 100km needs an OCST permit.  Below
>>that, I think they bow out and it's mostly the FAA that has to be kept happy.
>>(The OCST minima are stated in more complex terms, but 100km is what they
>>boil down to, I'm told.)
>
>Actually, the criteria are even worse; OCST has jurisdiction over anything
>with a thrust time > 15 seconds. Yup, this means that the high power non-
>professional rocket guys had to get a waiver from OCST for this summer's
>LDRS rocket launch, here in Kansas. :-(
>--


Looking through "Space Mission analysis and Design" I saw that OCST is
the single point contact for all commercial expendable vehicles. My
question is what about non-expendable. My hp rocket was really
expensive, not to mention the GPS,hamradio,packet, and cpu payload.
This thing is not expendable

    Does a fully recovered/reused vehicle need a permit? How about a
really high flying sailplane with pressure suit and long burning, boost
motor?
    How do you get around the bureaucracy?
g.

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

Date: 28 May 1993 13:08:27 -0400
From: Pat <[e-mail]>
Subject: Liberal President murders spaceflight?
Newsgroups: sci.space

Did carter graduate from the Naval Academy?  if so, he was most likely
in some engineering program there.   Now granted the service academies
are not as good tech schools as the Name places,  but it's a technical
education,  and add in Nuke school,  that is  where most reactor people
in this country come from.

The military aviation program strongly influences  commercial aviation
in all forms,  the Navy nuclear program strongly influences
our commericial nuclear world.

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

Date: Fri, 28 May 1993 11:44:32 GMT
From: Jon Ciliberto <[e-mail]>
Subject: Meade Telescope For Sale
Newsgroups: sci.space

Meade 2045 4" Schmidt-Cassegrain Telescope For Sale

Compact, excellent optics, perfect for the beginner or as a
second scope for the experienced astronomer. Excellent for
astrophotography, and for use as a  1000mm telephoto lens. A
beautiful, professional scope.

    *    102 mm (4") Clear Aperture
    *    1000mm (40") Focal Length
    *    f/10 Focal Ratio
    *    1.1 arc second resolution
    *    Limiting visual magnitude: 12
    *    Limiting photographic magnitude: 14.5
    *    Motor Drive
    *    15 ft. near focus

The foam-lined case makes shipping a fairly simple operation.

Also, Heavy Duty tripod, which I will sell, but which would
be more difficult to ship.

Fork-type mounting; Setting Circles; Eyepieces (1.25" O.D.):
MA 9mm (111x)  and MA 25mm (40x); 2x barlow; filters;
Eyepiece holder/diagonal prism  assembly; 5 x 24 mm
Viewfinder; AC power cord; super tough carry case; table
tripod legs; camera piggy-back mount and T-Adapter; many
other features. Light  use, excellent condition.

Asking $475 plus shipping (UPS insured to the mainland
costs under $40 --negotiable).



--
..........................................................................
Jon Ciliberto                      .        [e-mail]
Graduate Assistant                 .                         [phone]
SHAPS Publications Office          .                              Moore 223

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

Date: 28 May 93 16:32:31 GMT
From: Ethan Bradford <[e-mail]>
Subject: Microlensing searches (was "detecting planets in other systems")
Newsgroups: sci.space,sci.astro

As Micael Richmond points out, the MACHO searches look at moderately
far away stars to find MACHOs between us and the lensed stars.  To be
detected at all, the MACHO has to be pretty far from us and from the
star -- halfway between is best.  Thus, the search will not find
objects in the LMC.

However, the French MACHO search expects to find objects at least down
to the size of Jupiter.  The Livermore searchers claim they might
detect objects down to 1/100 of Jupiter's mass.  The lower limit comes
from the angular size of the source star.  I don't know the lower
limit claimed for the OGLE project.

-- Ethan

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

Date: 28 May 1993 13:36:33 -0400
From: Pat <[e-mail]>
Subject: Privatizing scientific terminology
Newsgroups: sci.space,sci.astro

Well Cambrige has a Lucasian professor of Physics :-)

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

Date: Fri, 28 May 1993 15:55:26 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: Space Raffles?
Newsgroups: sci.space

In <[e-mail]> [e-mail] (David B. Lapadula) writes:

>I think I recall reading/hearing about some sort of Soviet venture where they
>tried to sell raffle tickets, with the lucky winner getting to go to MIR, or
>something like that. I recall that it was done w/a US partner.

>Did the whole thing turn out to be a sham? Misunderstanding between the
>Soviets (Russians?) and the US partners? Or what?

>Anyone know more about it?

As I (vaguely) recall, there was a prosecutor down here in Texas who
basically shut them down for running a lottery (which is illegal here
-- the U.S. partner was based here, I believe).  Lots of legal
wrangling, but I think they wound up giving up on it.

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

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

Date: 28 May 1993 14:29:19 GMT
From: Thomas J Gillen <[e-mail]>
Subject: Story Musgrave (Was: Carl Sagan, respected astronomer)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:

>Isn't Story Musgrave in this field? Does he have more than one doctorate?

    Story has the following degrees:

    1) B.S. Math and Statistics (Syracuse)
    2) M.B.A (UCLA)
    3) B.A. Chemistry (Marietta College)
    4) M.D. (Columbia, surgical internship at UK Medical Center)
    5) M.S. Physiology and Biophysics (University of Kentucky)
    6) M.A. Literature (University of Houston)

And, as if this wasn't enough, he has flown more than 17,000 hours in
160 types of aircraft.


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

Date: Thu, 27 May 93 23:49:12 EDT
From: Allen J Michielsen <[e-mail]>
Subject: Tom Wolfe's THE RIGHT STUFF - Truth or Fiction?
Newsgroups: rec.arts.books,sci.space

In [e-mail]> [e-mail] (Eugene N. Miya) writes:
>>[e-mail] writes:
>>>....Wolfe's most brilliant stroke, in my opinion, was the discovery
>>>of Chuck Yeager, who was, to most people, a footnote in the history books...

>Discovery?  Footnote?
>...Chuck Yeager wrote a bio with another writer in 1954.
>...This bio had many of the same pictures as the
>second bio "Yeager" with Leo J.  ...

I thought the first was a little disappointing.  Yeager (circa 1982) was
wonderful.  Great reading from a very comfortable personna.  It's also
interesting how it dovetails in with _Running_Critical_ by Patrick Tyler,
_Mayday_ by Michael Beschloss and _Deep_Black_ on issues and people.

But, don't forget the latest.
(And the precise title eludes me at this moment, sorry, but it's like this)

_More_Stories/Travels_from_the_Good_Life_ by C. Yaeger (& somebody probably)
It's currently on many discount stands and racks.  The book warehouse in
rochester ny has several hundred @ $4 (us) each.

al

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

Date: Fri, 28 May 1993 15:03:18 GMT
From: Richard Ottolini <[e-mail]>
Subject: Tom Wolfe's THE RIGHT STUFF - Truth or Fiction?
Newsgroups: sci.space,rec.arts.books

What is Mr. Yaeger doing now?  After the book/movie appeared he was in some
TV commercials and variety shows, but haven't seen him in a couple of years.

By the way, what is the status of the first seven astronauts and the twelve
moon walkers? (30 and 20 years ago)

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

Date: Fri, 28 May 1993 15:07:53 GMT
From: Richard Ottolini <[e-mail]>
Subject: Tom Wolfe's THE RIGHT STUFF - Truth or Fiction?
Newsgroups: sci.space,sci.space.shuttle,rec.arts.books

This book/movie evokes memories of the "Golden Age" of science and
exploration.  It hasn't really ended, but since the late 1960's much
of the public has been skeptical and ignorant about science.
The last time I felt this public enthusiasm was when I lived in
China some years ago.  They still believe in science and technology there.

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

Date: 28 May 1993 15:44:06 GMT
From: Steve Allen <[e-mail]>
Subject: Voyager Discovers the First Direct Evidence of the Heliopause
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]>
[e-mail] (Tim Schneider) writes:
>>watts.  However, these radio signals are at such low frequencies,
>>only 2 to 3 kilohertz, that they can't be detected from Earth."
>
>This is very interesting stuff.  However this point is somewhat unclear
>to me.  Could someone please elucidate?

Find a text on electromagnetic radiation and look for plasma frequency.

Whenever electromagnetic waves propagate through a medium where there
are free charges (read plasma) there is a cutoff frequency below which
those waves simply cannot propagate.  They are absorbed.
In cgs units this is
                  4 pi n_0 e**2
        omega_p**2 = --------------
                    m
where omega_p is the plasma freqency, n_0 is the density of charge,
e and m are the charge and mass on each particle, respectively.

The density of electrons in earth's ionosphere typically sets a cutoff
frequency of about 1MHz.  The density of electrons in the solar wind
near earth is less, allowing a lower cutoff for satellites outside
earth's environs, but not so low as to see 3kHz.
_______________________________________________________________________________
Steve Allen          | That was the equation!         |   [e-mail]
UCO/Lick Observatory | Existence!...Survival must     | If the UC were opining,
Santa Cruz, CA 95064 | cancel out programming! -- Ruk | it wouldn't use me.

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

Date: 28 May 1993 13:28:16 -0400
From: Pat <[e-mail]>
Subject: Why a far side Science station.
Newsgroups: sci.space

And if you have to go to the far side for a radio platform,  you
might as well stick a scope or two there.

Is the earth uniformly radio noisy?

I can see the US and Europe being real loud,  But over Big chunks of asia
 and the oceans,  it should be quiter,  or does the variation
not matter enough?

pat

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

Date: 28 May 93 16:50:42 GMT
From: Pat <[e-mail]>
Subject: Why Government? Re: Shuttle, "Centoxin"
Newsgroups: sci.space,talk.politics.space

A few billion here,  a few billion there,  and next thing you
know..... :-)

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

End of Space Digest Volume 16 : Issue 644
------------------------------