Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_3/V11_336.TXT

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Subject: SPACE Digest V11 #336

SPACE Digest                                     Volume 11 : Issue 336

Today's Topics:
          NASA Prediction Bulletins:  Space Shuttle
            Re: Re: Dyson spheres?
              Magellan Update - 04/30/90
              Galileo Update - 04/30/90
                   Antenna
                  Re: Radar
               Re: Sex in space
           NASA Prediction Bulletin Format
Re: Not-so-Silent Running (Was Re: a bunch of other irrelvant things)
----------------------------------------------------------------------

Date: 28 Apr 90 03:41:24 GMT
From: ncis.tis.llnl.gov!blackbird![e-mail]  (TS Kelso)
Subject: NASA Prediction Bulletins:  Space Shuttle


The most current orbital elements from the NASA Prediction Bulletins are
carried on the Celestial RCP/M, [phone], and are updated several times
weekly.  Documentation and tracking software are also available on this
system.  As a service to the satellite user community, the most current
elements for the current shuttle mission are provided below.  The Celestial
RCP/M may be accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data
bits, 1 stop bit, no parity.

STS 31
1 20579U 90 37  A 90117.10416666  .00002331  00000-0  25599-3 0   432
2 20579  28.4724 214.4778 0006679 321.4080 256.4255 14.84204124   381
HST
1 20580U 90 37  B 90115.92007935 -.00019413  00000-0 -22999-2 0   416
2 20580  28.4631 222.0038 0005784 272.7940  87.2151 14.84112255   202
--
Dr TS Kelso                           Assistant Professor of Space Operations
[e-mail]          Air Force Institute of Technology

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

Date: Mon, 30 Apr 90 18:18:00 EDT
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Re: Re: Dyson spheres?


>From: usc!elroy.jpl.nasa.gov!aristotle![e-mail]  (Peter Scott)
>Subject: Re: Dyson spheres?

>In article <[e-mail]>,
>[e-mail] (John Roberts) writes:
>>  [...]
>> Ignoring the infrared feedback, one can calculate the maximum mass of a
>> nonreflecting, nonrotating sphere that can be supported by light pressure
>> from the sun.  [...]
>> Incidentally, to the inhabitants of the sphere, the sun would be "down",
>> with the local force of gravity about 1/3000 of that on earth.

>?  Are you saying that the gravitational attraction exerted on a particle
>on the inner surface of the sphere is g/3000?  I thought that gravitational
>attraction inside a spherical shell was 0.  Yeah, I know it's approximately
>the same answer, but still... what gives?

Patrick Brewer has it right - I'm talking about the gravitational attraction
of the sun. Since the sphere is not rotating, you are subject to the pull of
the sun, which is felt as weight. Picture a scene from the old Saturday
morning cartoons - a character is held up by the stream from a geyser. The
pressure of the flowing water holds him up, but he still feels weight.
Similarly, if you live in a room on the Dyson sphere described, you will tend
to drift toward the inner side. If you are in a space suit sunbathing on the
inner surface, then fall asleep and lose your grip, in an hour you will
have moved about 19km toward the sun (from sqrt(2) * 1AU). Eventually you will
either fall into the sun or pass very close by - I forgot the formula to
determine how long the fall will take.

Note the conclusion: you could build a Dyson sphere held up by light pressure,
but it would be a crummy, low-density one, and might adversely affect the
center star.
              John Roberts
              [e-mail]

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

Date: 1 May 90 00:12:54 GMT
From: usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Magellan Update - 04/30/90



                     MAGELLAN STATUS REPORT
                         April 30, 1990

     The Magellan spacecraft is now 103 million miles from Earth and
nearly 21 million miles from Venus as of Monday, April 30. The cruise
continues with all subsystems performing well. The spacecraft is
traveling at 66,824 mph relative to the sun.

     Cruise sequence 22 was uploaded and is being executed
perfectly. It changed to a new star pair for star calibrations.
They are now Beta Gruis and Alpha Aquilae.

     Five of the seven daily star calibrations were fully
successful with an average attitude update of 0.05 degrees. Two
of them, on Tuesday and Thursday, were partially successful, with
only single star updates, due to the rejection of Beta Gruis on both
occasions by the star scanner unit's foreground filter. The
spacecraft team is analyzing the playback data for those events.

     Last week also saw the completion of memory readouts of all
command data system redundant memories in both the A and B sides.
No parity errors were found.

     SPACECRAFT
     Distance from Earth (mi)             102,942,136

     Velocity Heliocentric                66,824 mph

     One-way light time                   9 mins, 12.5 secs

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |    Go Lakers!

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

Date: 30 Apr 90 23:02:55 GMT
From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 04/30/90



                     GALILEO MISSION STATUS
                         April 30, 1990

     The Galileo spacecraft is almost 92 million miles from Earth
today, so that a radio signal takes 16 1/2 minutes to go up to
the spacecraft and return.  Its speed in orbit around the Sun is
71,230 mph, and it has traveled almost 341 million miles since
launch.

     Two weeks of spacecraft tracking have confirmed that the
four-day trajectory correction maneuver completed April 12 went
extremely well.  The next maneuver, currently being designed,
will start May 11 and take two days.

     The spacecraft health countinues to be generally excellent.
Normal cruise activities this week have included Sun-pointing
turns, propulsion system maintenance, and science observations by
the magnetometer, dust and ultraviolet instruments. These
activities are governed by a new operating sequence, transmitted
to the spacecraft last Friday and covering the period from April
23 through June 10.

 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |    Go Lakers!

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

Date:    Mon, 30 Apr 1990 8:22:17 EDT
From: [e-mail]
Subject: Antenna
X-Vmsmail-To: SMTP%"[e-mail]"

Yes, radar does just fall off as the square of the distance.  You can't
just plug the transmitter power into the inverse square law and get a
valid number, that's true.  You multiply the transmitter power by the
antenna gain, and plug THAT into the inverse square law.  Nothing fancy
at all; the stuff radiated from a directional antenna is the same as the
stuff radiated by an omni.  It's just that more is radiated in some directions
than others (and if you know the beam width, it's pretty easy to calculate
the antenna gain, which will be left as an excercise to the reader).  I am
a EE.  I really am.  This stuff is a lot easier than you think.
--scott
   (Engineer-In-Charge, Radio Techwood International)

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

Date: 30 Apr 90 14:57:06 GMT
From: att!cbnewsl!moss![e-mail]  (Forrest Gehrke,2C-119,7239,ATTBL)
Subject: Re: Radar

In article <[e-mail]>, [e-mail] (John Nordlie) writes:
> A lot of discussion is going on about the power dissapation of
> radar signals over distance.  One fact that I have not seen
> mentioned is that the inverse square law is being applied
> to radar signals as if they were point sources, radiating energy
> equally in all directions.  This is not the case with radar (or
> just about any other radio transmission).  Radar is radiated from
> an antenna in a highly directional beam.  Simply plugging in the
> transmitter power and distance into the inverse square equation will
> not give you an accurate estimation of signal strength.
> The width and shape of the beam must also be taken into consideration.
> I am not an EE, so I don't know what equations you need to solve
> this problem.  Any radio-types out there know?



All that has changed when a radio signal is emitted from an
array (whether this is a parabolic dish or whatever) is the
effective radiated power has been raised in the chosen
direction, (often referred to as the gain of the array).

This gives us a signal which will reach out further for a
given power source than we would have been able if the
the source had been isotropic.  The inverse square law
still holds, (especially so in space).  But you are
correct in thinking that the shape of the beam must
be taken into account.  Columnation at radar frequencies
is nothing like achievable with lasers.  As a result
polarization effects must be taken into account when
estimating the distance a detectable signal might reach.
Calculating this is a bit sticky.

Forrest Gehrke [e-mail]

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

Date: 30 Apr 90 16:00:47 GMT
From: sdd.hp.com!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Sex in space

In article <[e-mail]> [e-mail] (Chris May) writes:
>... a friend and I are interested in knowing whether anyone has
>had sexual intercourse while in orbit...

Nobody has admitted to it. :-)  I consider it rather unlikely:  workloads
are heavy, privacy is nonexistent, and the sponsoring agencies are prudish.
(For example, there are married couples among the US astronauts, but they
do *not* fly together.)  It's just possible that it might have been tried
on the US shuttle as a highly-unauthorized private venture. :-)

>... Would the offending couple be booted from the
>astronaut program if caught?

Very probably.  At the very least, their chances of flying again would be
zero.  Flight assignments are decided by office politics, and incurring
the wrath of the higher-ups is bad news.
--
If OSI is the answer, what is |     Henry Spencer at U of Toronto Zoology
the question?? -Rolf Nordhagen| uunet!attcan!utzoo!henry [e-mail]

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

Date: 30 Apr 90 11:44:46 GMT
From: ncis.tis.llnl.gov!blackbird![e-mail]  (TS Kelso)
Subject: NASA Prediction Bulletin Format


As a service to the satellite user community, the following description
of the NASA Prediction Bulletin's two-line orbital element set format is
uploaded to sci.space on a monthly basis.  The most current orbital elements
from the NASA Prediction Bulletins are carried on the Celestial RCP/M, (513)
427-0674, and are updated several times weekly.  Documentation and tracking
software are also available on this system.  The Celestial RCP/M may be
accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data bits, 1 stop
bit, no parity.

==============================================================================

Data for each satellite consists of three lines in the following format:

AAAAAAAAAAA
1 NNNNNU NNNNNAAA NNNNN.NNNNNNNN +.NNNNNNNN +NNNNN-N +NNNNN-N N NNNNN
2 NNNNN NNN.NNNN NNN.NNNN NNNNNNN NNN.NNNN NNN.NNNN NN.NNNNNNNNNNNNNN

Line 1 is a eleven-character name.

Lines 2 and 3 are the standard Two-Line Orbital Element Set Format identical
to that used by NASA and NORAD.  The format description is:

Line 2
Column     Description
 01-01     Line Number of Element Data
 03-07     Satellite Number
 10-11     International Designator (Last two digits of launch year)
 12-14     International Designator (Launch number of the year)
 15-17     International Designator (Piece of launch)
 19-20     Epoch Year (Last two digits of year)
 21-32     Epoch (Julian Day and fractional portion of the day)
 34-43     First Time Derivative of the Mean Motion
        or Ballistic Coefficient (Depending on ephemeris type)
 45-52     Second Time Derivative of Mean Motion (decimal point assumed;
           blank if N/A)
 54-61     BSTAR drag term if GP4 general perturbation theory was used.
           Otherwise, radiation pressure coefficient.  (Decimal point assumed)
 63-63     Ephemeris type
 65-68     Element number
 69-69     Check Sum (Modulo 10)
           (Letters, blanks, periods = 0; minus sign = 1; plus sign = 2)

Line 3
Column     Description
 01-01     Line Number of Element Data
 03-07     Satellite Number
 09-16     Inclination [Degrees]
 18-25     Right Ascension of the Ascending Node [Degrees]
 27-33     Eccentricity (decimal point assumed)
 35-42     Argument of Perigee [Degrees]
 44-51     Mean Anomaly [Degrees]
 53-63     Mean Motion [Revs per day]
 64-68     Revolution number at epoch [Revs]
 69-69     Check Sum (Modulo 10)

All other columns are blank or fixed.

Example:

NOAA 6
1 11416U          86 50.28438588 0.00000140           67960-4 0  5293
2 11416  98.5105  69.3305 0012788  63.2828 296.9658 14.24899292346978

Note that the International Designator fields are usually blank, as issued in
the NASA Prediction Bulletins.

--
Dr TS Kelso                           Assistant Professor of Space Operations
[e-mail]          Air Force Institute of Technology

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

Date: 30 Apr 90 10:50:40 GMT
From: mcsun!ukc!icdoc!syma![e-mail]  (Nick Watkins)
Subject: Re: Not-so-Silent Running (Was Re: a bunch of other irrelvant things)

In article <[e-mail]> [e-mail] (Tom Egelston) writes:
>In article <[e-mail]> [e-mail] (Nick Watkins) writes:
>>Have you heard of a Rocket called Saturn V ? There are 2 still available
>>for your contemplation if you haven't ...
>
>     Only two?!?!?!?  Last I checked, there was one at Kennedy, Johnson, and
>one at Huntsville.  Has someone sprayed a fresh coat of paint on one and
>"borrowed" it?   ;-)
One is an engineering mockup (Huntsville I think). Other two are Apollo
18's & 19's, with Apollo 20's going to launch Skylab (or some similar
permutation).

Good article by David Baker in an ancient copy of Spaceflight covered
other Apollo hardware, perhaps a keen netter would like to revise it.

Nick

"Get your ticket for that wheel in space while there's time " - IGY,
Donald Fagen
--
Dr. Nick Watkins, Space & Plasma Physics Group, School of Mathematical
& Physical Sciences, Univ. of Sussex, Brighton, E.Sussex, BN1 9QH, ENGLAND
JANET: [e-mail]   BITNET: [e-mail]

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

End of SPACE Digest V11 #336
*******************