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Subject: SPACE Digest V11 #66

SPACE Digest                                      Volume 11 : Issue 66

Today's Topics:
              Galileo Update - 02/16/90
               maintaining L5 position
               Re: Recreation in Space
           Re: Why we would need a planet.
          RE: NASA Select TV & Operacio 9000
           Approaching light speed in space travel
              Re: NSS STATEMENT
               Viewing shuttle launches
----------------------------------------------------------------------

Date: 20 Feb 90 04:48:00 GMT
From: zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 02/16/90


                  GALILEO
               MISSION STATUS REPORT
            FEBRUARY 16, 1990

     As of noon Friday, February 16, 1990, the Galileo spacecraft is 36,987,350
miles from the Earth, 2,151,150 miles from Venus and is traveling at a
Heliocentric velocity of 90,063 miles per hour. Perihelion will occur on
February 25. Roundtrip light time is 6 minutes, 30 seconds.

     Venus flyby was successfully accomplished late on February 9, 1990. Radio
tracking data indicated the delta velocity achieved by the gravity assist was
as expected.  The spacecraft velocity was increased by nearly 5000 mph.
Spacecraft performance during the flyby was as expected and within predicted
values.

     During the post-Venus closest approach phase, an apparent anomaly occurred
involving the Solid State Imaging system (SSI). The anomaly resulted in
several hundred (approximately 760) unplanned SSI shutter actuations. CDS and
SSI memory readouts were performed and subsequently the SSI was powered-off
and its replacement heater powered-on to assure the health and safety of the
instrument.  Intensive anomaly investigation was initiated. Later that day
mission and spacecraft risk assessment by the Project personnel concluded it
was safe to power-on the SSI again and continue with the imaging sequence
planned for late February 10th. Careful review of the anomaly timing indicates
there is high confidence that 14 of 16 images planned during this phase were
properly executed.

     The SITURNS to lead the sun by about two degrees were
successfully completed on February 10, 13 and 15.

     Part B of the EV-6 sequence memory load went active as planned on February
12. This EV-6 memory load contains the spacecraft events needed to accomplish
the DMS MRO activity. It is pointed out that the DMS MRO is a special
experimental technique which basically plays back the stored tape recorder data
into the CDS at 7.68 kbps and then data is transmitted to Earth at 1.2 kbps
consistent with the telemetry link performance.  Since a single compressed
image being returned contains a little over 3 x 106 bits and the imaging data
is transmitted to Earth at 256 bits/sec. (imaging data portion of the 1.2
kbps), the time to retrieve a picture from the telemetry standpoint only is
roughly 3.6 hours.

     The DMS MRO activity began as scheduled on February 13. To maximize the
downlink performance, the spacecraft's S-Band ranging channel was turned off
and the DSN diplexer was bypassed (station is listen-only mode) thereby
improving the performance margin by about 1.8 db.

     The Venus-Earth 1 sequence memory load was transmitted and properly
received by the spacecraft without incident on February 16. The VE-1 sequence
controls spacecraft activities from February 19 through March 26.  This
sequence includes two major first time events such as Low Gain Antenna (LGA)
LGA-2 to LGA-1 switch and downlink telemetry operation at 10 bps.

     The AC/DC bus imbalance measurements profile during this last week was
not much different from that observed for the last three weeks. The AC
measurement continued to fluctuate between about 45 and 48 volts (AC) and
about 19 and 21 volts (DC).

     The GDS successfully supported the Venus Encounter and subsequent
playback of selected data from the spacecraft tape recorder via CDS Memory
Read Out (MRO). Support of MRO operations required manual reconfiguration
of the Deep Space Network (DSN) telemetry system at the tracking stations
for each of the frequent spacecraft data rate changes (twice every 45 minutes).
The DSN NOCC and tracking station operations personnel are to be commended for
excellent "heads-up" operational support that was able to accomplish the
required reconfigurations with no loss of playback data. The two significant
GDS problems occurring during Venus support were as follows:

     1. An error in CDS sequencing memory management (generated by the SEQTRAN
program) for the Venus sequence caused parameters for the SSI control
Spacecraft Expanded Block (SEB) to be overwritten before CDS execution of the
block was complete.

     2. Playback of the selected images over the 70 meter antenna in Goldstone
on Tuesday was interrupted when high winds forced stowing of the 70 meter
antenna.  About one-half of the first image was lost (temporarily since it
will be played back later). A 34 meter antenna in Australia was called from a
Pioneer pass (at rise time) to provide Galileo support in time for playback of
the remaining two images.


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

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

Date: 19 Feb 90 06:51:01 GMT
From: portal!portal!cup.portal.com![e-mail]  (Martin J Brown-Jr)
Subject: maintaining L5 position

I am posting the following for someone who does not have USENET access.
You may post your answers, which I will relay to him, or you may email to
him if you have BIX access, or you may email to me [e-mail] and
I will pass it on.

*******************

.
.
This question comes from a non-astrophysicist.
.
.
I have read that L5 in the Earth-Luna system is a gravity "plain", not a
"well".   Since L5 is defined as the point where Earth's gravity, Luna's
gravity, and centrifugal force exactly balance, any perturbation from
the sun will cause a space habitat to wander across the surface of
the L5 "plain".
.
So my question is:  can anyone give me any general concept of how much
energy would be required to overcome the sun's perturbations and to
keep an L5 habitat at or near the mathematical L5 point (Earth-Luna)?
.
In order not to limit anyone's answer, I haven't included details about
the habitat.   If it helps, you may assume the habitat's mass is
250,000 tons (small, as habitats go), and that it is a cylinder of
600' diameter.   You may orient the diameter in whichever direction
you prefer, and you may choose whatever length you prefer.
You may assume that "stationkeeping" means anything within 100 kms of
the mathematical L5 point.   You may assume that the habitat is
rotating at 3 rpm.
.
If you know about solar sails (I don't!), can you estimate how
large a solar sail might you need to do this??
.
ANSWERS TO WITHIN ONE ORDER OF MAGNITUDE WOULD BE FINE!
.
SO WOULD "INTUITIVE" ANSWERS!
.
Thank you, Bill Wright (BIXname = KATHWRIGHT)


********************

Thanx

                             - MJB -

                    USENET: [e-mail]
                       BIX: mbrown

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

Date: 19 Feb 90 16:35:27 GMT
From: MATHOM.GANDALF.CS.CMU.EDU![e-mail]  (Donald Lindsay)
Subject: Re: Recreation in Space

In article <[e-mail]> [e-mail] (Richard Brittain) writes:
>A few months ago a rather good spoof of a NASA technical report on the subject
>appeared in alt.sex.


I'm still waiting for the NASA SUTRA.

--
Don        D.C.Lindsay     Carnegie Mellon Computer Science

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

Date: 20 Feb 90 03:48:04 GMT
From: voder!dtg.nsc.com![e-mail]  (Lord Snooty @ The Giant Poisoned Electric Head )
Subject: Re: Why we would need a planet.

In article <[e-mail]>, [e-mail] (Brian or James) writes:
>How likely is it that space living Islamics would consent to dismantling Mecca?

Dunno, but the high-tech alternative may be more attractive (as well as
a lucrative income source for the aware entrepreneur): 3D-rotating prayer
mats. This neatly solves the orientation problem of zooming over Mecca at over
20,000 mph while kneeling.

It begs the question of the definition of local time, of course.    :-)
--
...........................................................................
Andrew Palfreyman    [e-mail]    Albania before April!

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

X-Delivery-Notice:  SMTP MAIL FROM does not correspond to sender.
Date: Mon, 19 Feb 90 14:29 GMT
From: RITA HAYWORTH <[e-mail]>
Subject: RE: NASA Select TV & Operacio 9000

From : [e-mail]
Date : Feb/19/1990

Sorry, it was a missprint. Of course it is 9000 hours (375 days)

jordi Iparraguirre
  CS Student at U.A.B.     [e-mail]

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

Date:     Mon, 19 Feb 90 23:55 EST
From: <[e-mail]>
Subject:  Approaching light speed in space travel

Scott ([e-mail]) writes:
>There is yet another major problem ... with the relativistic time dialation,
>  piloting a vessel safely at such speeds will become quite a pain.  Not only
>  will the computer become enormously slow at reacting to potential dangers,
>  but these objects will be very difficult to detect due to high speed, large
>  blueshift, and relativistic "tunnel vision".
        It is hard to see what you mean here.  The computer will not
slow down at all - at least not for those on the ship.  However, one
does have to worry about light travel time.  For example, consider a
ship travelling at 0.5c.  It sends out a radar signal that reflects off
of an asteroid that is 1 ly in front of the ship the instant the signal
is sent out.  By the time that the ship receives the reflection, 2/3 of
a ly will have been travelled already by the ship.  There is some time
to react, but not overly much.  At higher speeds, the available reaction
time goes down even more.  Travelling at the speed of light means that
the ship hits the asteroid before the occupants are even aware of its
existence.  Makes one wonder how a starship can effectively maneuver at
warp speeds. :-)

>Who knows what would be considered a "dangerous" object when the ship is
>travelling
>  so fast.  Maybe even a thin interstellar gas/dust cloud would wear on the
>  hull over years of travel (millions of years if you're talking other galaxies
>  here)!  Not everything out there is ionized or has a magnetic field, so you
>  can't just put up an electro-magnetic shield.
        Larry Niven covers stuff like this in his various Known Space
stories, especially World of Ptavvs.  Basically, use a Bussard ramjet
with a lightyear size magnetic scoop and fusion heating up the gas/dust in
front of the ship.  This would ionize anything, and then the magnetic
fields can contain it.  Of course, E.E. Smith just uses the interstellar
gas/dust as a friction source to keep his inertialess ships from hitting
infinite speeds.  :-)

 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
|  Arnold Gill                          |
|  Queen's University at Kingston       |
|  BITNET:    gill@qucdnast             |
|  INTERNET:  [e-mail]  |
 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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

Date: 19 Feb 90 09:54:37 GMT
From: agate![e-mail]  (William Baxter)
Subject: Re: NSS STATEMENT

In article <[e-mail]>, aws@vax3 (Allen W. Sherzer) writes:

>Official Notice from the National Space Society, February 14.

>The so-called "space activist alert" in regards to Mr. Scott Pace
>which has appeared on this bulletin board (as well as others) is
>not a National Space Society action.  Individuals who have
>initiated this alert are acting in their own right and not on the
>behalf of the National Space Society.

True.

>Furthermore, NSS considers this action to be completely
>unjustified and detrimental to the creation of a spacefaring
>civilization.  Scott Pace served as the Executive Vice President
>of NSS and Chairman of the NSS Legislative Committee for the past
>two years.  In this capacity Scott was responsible for
>championing support for space in Congress including commercial
>space programs.  HR 2674, the Commercial Space Transportation Act
>was reviewed by the committee during this time and was supported
>by NSS through written testimony to the House subcommittee on
>Space Science and Applications.

True.  Careful wording avoids the statement that Scott Pace actually
supported HR2674 in his capacity as NSS Legislative Committee chairman,
which would be false.

>Mr. Pace has recently resigned from his posts within the National
>Space Society because he has taken a position within the federal
>government.  In his new position, Scott is working to promote
>space commerce.  It is counter-productive to the National Space
>Society's efforts to support commercial space to pursue Mr.
>Pace's transfer or detachment from this position or to otherwise
>harass him.

In other words, although he has resigned his positions at the NSS, he
maintains close ties with the organization.  The NSS views are Scott
Pace's views, even now.

The point is this:  Those of us working to remove Mr. Pace from his
new position are doing so precisely because it will interfere with "the
National Space Society's efforts to support commercial space," a
euphemism for preventing the development of commercial space industries
for the forseeble future.  If we succeed, the remaining NSS leaders will
find it difficult to use the NSS as a stepping stone to positions of
administrative power as Mr. Pace has tried to do.  And since many of the
people who have supported HR2674 over NSS resistance are also working to
remove Scott Pace from his new position, their fears are well justified.

Help remove Scott Pace from a position of influence.  Write your letters
to the Secretary of Commerce today:
Robert A. Mosbacher
Secretary of Commerce
14th Street at Constitution Ave.
Washington, DC 20230


----
William Baxter

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

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

Date:         Mon, 19 Feb 90 09:50:39 EDT
From: Jerry Davis <[e-mail]>
Subject:      Viewing shuttle launches

This may be of interest to those of you who wish to attend future
shuttle launches.  It was taken from the 18feb90 edition of _The Atlanta
Journal and Constitution_ with excerps form _The Hartford Courant_,
authored by Steve Silk (paraphrased by me).

 The next launch is scheduled for late February; another for late April.
 For a complete list of liftoffs, write NASA, BOC-155, Kennedy Space
 Center Fla. 32899.  Those who plan well in advance can write for a
 special pass permitting them onto Space Center grounds for the closest
 view of a launch (~seven miles from the pad).  About 2,000 passes are
 issued free for each launch date.  They are parceled out on a first come
 first served basis.  For reservations or more information, write:

              NASA Vehicle Passes
              PA-PAS
              Kennedy Space Center, Fla.  32899

 For information about visiting the Space Coast area of Florida, write:

              Brevard County Tourist Development Council
              P.O. Box 1969
              Cocoa, Fla.  32923    or call 800-872-1969

 Local officials allow people to park on Route 1 in Titusville.  Binoculars
 are a must as it is 15 miles away.  You may park there 24 hrs. before a
 launch.  Additionally, the article points out that many viewers prefer
 to watch the SRB's drop off.  This can be seen from spots along ~20 miles
 of beachfront.  The preferred spot is Jetty Park in Port Canaveral.

I've never been there, I'm just passing along information.  Eugene you may
want to add this to your list :).  Apologies to the author for any botches.

Jerry

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

End of SPACE Digest V11 #66
*******************