Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_0/V10_011.TXT

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Date: Fri,  1 Sep 89 05:25:27 -0400 (EDT)
Subject: SPACE Digest V10 #11

SPACE Digest                                      Volume 10 : Issue 11

Today's Topics:
           Re: Analysis of Martian "Face" Announced
           Voyager Interstellar Trajectory
           Re: RTG's and nuclear reactors.
              Re: BSB Satellite launch?
             Re: Voyager: Tape recorder?
             Re: How is Voyager powered?
            SPACE Digest, anyone?
               Re: Pluto fly-by
           Re: Analysis of Martian "Face" Announced
               Voyager's images
                  Re: Rings
----------------------------------------------------------------------

Date: 27 Aug 89 19:48:33 GMT
From: netcom!dlb!zygot![e-mail]  (Bruce Henderson)
Subject: Re: Analysis of Martian "Face" Announced


What sort of spacecraft will the Mars observer be?  does anyone have
any detail? If it has a synthetic aperature radar similar to Magellan,
then a lot of these conflicts over the way that this Geo-Structure on
Mars is put together.  I worked on an SAR system for the DoD, and they
can be very useful in obtaining 3D information about an object.


--
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Bruce Henderson                                       Software Engineer
zygot![e-mail]
"Sorry, Mathematica can't goon this much"
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

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Date: 27 Aug 89 17:46:13 GMT
From: [e-mail]  (Terry Hancock)
Subject: Voyager Interstellar Trajectory

>
>The answer was that in 8,000 years it will fly by Barnard's Star, in 20,000 or
>so it will pass Proxima Centauri, and then the Oort cloud.
>
    Okay, so this is completely wrong.  The announcer probably
confused talk about how long the probe would take to get to those
stars IF it were headed toward them.  As for the Oort cloud, well,
they'll have to fend for themselves on that one.

My QUESTION:
    What is the outbound assymptotic trajectory of Voyager as it
leaves the solar system?  By this, I mean which coordinates
(Equatorial, Ecliptic, or Galactic) will it approach asymptotically
as  viewed from Earth?

    I heard that it would pass a nearby star within ~1 ly, which
star is that? (clearly, the answer to the above will answer that
question in itself).

Thanks.
***************************
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Terry Hancock
[e-mail]
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Date: 27 Aug 89 20:09:07 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: RTG's and nuclear reactors.

In article <[e-mail]> [e-mail] (Jonathan Leech) writes:
>
>    Several people have mentioned problems with the Galileo RTGs
>having reduced power output due to the long launch delay, and there
>being no way to replace them.  Where are the RTGs for CRAF and Cassini
>supposed to come from, then, now that the missions are funded?    Is the
>plant to be reopened?
>--
    The problem with replacing the Galileo RTGs is not the
availability of RTGs, but the time required to install them.  Galileo,
despite launch delays has always been "a few months away from launch,"
(at least officially), so they didn't want to risk ripping it apart
and adding the new RTGs, just in case it really did get launched
on the then current schedule.  If they had known earlier that it
was going to be 1989 before they launched, they could have easily
replaced the RTGs in time.

    Ironically, CRAF and Cassini will be using the backup RTGs
from the Galileo program.  This is part of the way they planned to
do the missions cheaply.  This obviously puts a limit on how long
it can take before CRAF and Cassini get launched.  Fortunately they
are not scheduled on a Shuttle flight (they'll be launched with
expendable launch vehicles), and therefore probably won't be
subject to long launch delays like Galileo was.

    At least, this is how it was explained to me.

**************************
Terry Hancock
[e-mail]
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**************************
**************************
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------------------------------

Date: 25 Aug 89 20:33:50 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo!bnr-vpa!bnr-fos!bmers58!![e-mail]  (Henry Troup)
Subject: Re: BSB Satellite launch?

In article <[e-mail]> [e-mail] (Conor O'Neill) writes:
>
>Does anyone know the status of the BSB Satellite?
>
>The commercial operation of the satellite is still targetted at
>early next year.
>

I was in the UK about three weeks ago and saw all kinds of itty-bitty
under one metre dishes.  I was told that those are for satellite TV.
So what kind of DBS is already in use ? (Direct Broadcast Satellite).

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

Date: 27 Aug 89 20:22:00 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: Voyager: Tape recorder?

In article <[e-mail]> [e-mail] writes:
>I keep hearing of data being spooled to the tape recorder for later
>transmission to earth.  Surely they don't use a conventional mag.
>tape drive.  Wouldn't something solid state like a large array of
>eeprom be more robust?
>
    Remember that Voyager was built in the early 70's:  EEPROM wasn't
so great then as it is now.  Voyager does use a plain old magnetic
tape drive (though I'm sure it's quite different in design from
those used on mainframes on Earth -- due to mass considerations, and
the fact that it never has to load or unload the tape, just erasing and
rewriting over the same space on tape).  It's not the only probe to
use this system, either.

    There are of course other problems with various kinds of non-
volatile RAM.  Of course, with modern computers the amount of data
stored on Voyager's tape could probably be handled in ordinary RAM
space.  Of course, Voyager's computer can't -- early 70's, remember.

    This is what happens when it takes 10 or 20 years for a
spacecraft to get to its destination -- it's obsolete by the time
it arrives!

********************
Terry Hancock
[e-mail]
********************
********************

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

Date: 27 Aug 89 00:37:46 GMT
From: hpfcso!hpldola!hpctdlb!hpctdls![e-mail]  (Richard Katz)
Subject: Re: How is Voyager powered?

-Pardon me if these questions have already been asked -- I don't read
-this newsgroup.

-In a related question, does anyone know details of the computer(s)
-upon Voyager?  Is memory really implemented as ferrite core?  How much
-memory is available?

-       ATdhvaannkcse
-    -- Tim Olson
-    Advanced Micro Devices

This is from memory but I'm pretty sure it's accurate.  If anybody has
any references please correct me.  The memory in the Flight Data
System is CMOS RAM. The Attitude control system uses plated wire, not
core.  I believe the attitude control's memory is fairly small, a
couple of k words.

rich k.

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

Date: Sun, 27 Aug 89 16:40:29 PST
From: Peter Scott <[e-mail]>
Subject: SPACE Digest, anyone?
X-Vms-Mail-To: EXOS%"[e-mail]"

For those of you who read these postings through the SPACE Digest mailing
list, has it been getting through the last 5 days?  I haven't gotten
anything at my customary address, [e-mail], but tests
have shown that the net connection to andrew.cmu.edu has been fine.
I don't believe there's a moderator at the moment, my understanding is
that Ted left it on automatic; however, I have mailed space-request anyway.

Nitrogen volcanoes on Triton.  Wheeee....

Peter Scott ([e-mail])

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

Date: 27 Aug 89 17:47:00 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Pluto fly-by

In article <[e-mail]> I wrote:
>... Remember, also, that Jupiter will be in the right
>place only about once every 8 years (its orbital period).

Oops, correction:  12 years.  Don't know what I was thinking of...
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 28 Aug 89 00:47:18 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Analysis of Martian "Face" Announced

In article <[e-mail]> [e-mail] (Bruce Henderson) writes:
>What sort of spacecraft will the Mars observer be?  does anyone have
>any detail? If it has a synthetic aperature radar similar to Magellan...

Nope.  Mars Observer started out to be a relatively small and unambitious
mission.  It grew a bit along the way, and does have a moderately fancy
camera, but no radar.
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 27 Aug 89 21:55:50 GMT
From: [e-mail]  (Charles Daffinger)
Subject: Voyager's images


It has been mentioned earlier that the images taken of Mars (along with
two frames of the face ;-) are available on mag tape from NASA.  Is this
same type of service available for the Voyager images, either in raw form
B/W filtered images or in color/enhanced form?  What is the cost?
Mag tape + handling?  Where from? JPL?  How can one get an index to such
images?  What kind of restrictions are on such data?

Thanks,

-charles
--
Charles Daffinger  >Take me to the river, Drop me in the water<  [phone]
[e-mail]              {pur-ee,rutgers,pyramid,ames}!iuvax!cdaf
Home of the Whitewater mailing list:    [e-mail]

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

Date: 27 Aug 89 19:58:58 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: Rings

In article <Added.4YxL7Pa00Ui38=[e-mail]> [e-mail] (Samitha Amarasiri) writes:
>
>With the discovery of a ring on Neptune, it really looks like rings
>on the outer planets on the solar system is becoming the rule
>and not the exception. The two major differences between the
>'outer' and inner planets are the temperature on them, and gravitational
>pull by the sun. Could it be that either of these cause planets to
>have rings on them? Could the asteriod belt be a ring that never
>quite formed? Does this mean that Pluto will have a ring on it too?
>
>Please excuse the barrage of questions, I was watching 'Neptune up all
>night' and feel delerious with excitement.
>
>--  Samitha Amarasiri.
    Definitely we will think of rings as a rule for Gas Giants (though
we probably will expect a wide range in type, given what we've seen).  I
would like to add to your list of major differences, though:
    * Mass of the planets in question are much higher than
terrestrials, with correspondingly higher escape velocity.  Combined
with your point about the Sun's gravitational influence being less,
this results in larger "spheres of influence" for these gravity fields.
    * Gas giants -- the same accretion and hydrodynamic collapse
which resulted in these huge atmospheres, may have resulted in the
presence of ring systems.
    Personally, I doubt Pluto will have a ring -- it's a
qualitatively different system than the gas giant planets, and will
probably just act like a small terrestrial system (only MUCH colder,
:-)).
    To use a slightly different analogy, consider what on of the
great planet's systems would be like without the gas giant -- only
the moons.  Obviously, you'd expect tidal stresses to generate less
heat (probably Pluto and Charon are tidally locked, but they don't
weigh much -- so they wouldn't release as much energy in getting this
way).  And there wouldn't really be a deep enough gravity well to hold
any sizeable ring system -- and a small one would be correspondingly
short-lived (I think).

    As for the Asteroid belt being like a ring around the Sun,
there are some problems, the most notable being where the belt is
located -- outside the innermost planets.  A ring is kept from
accreting further by its proximity to the planet -- it is inside
of a certain radius -- the Roche limit, inside of which no
gravitationally bound moon can remain intact (those moonlets that do
appear in the rings are therefore held together by electromagnetic
forces -- like what holds a rock together on the Earth's surface,
or an icecube, or even you).
    The asteroids are outside of this limit for the Sun (the
Earth, inside of the Asteroid belts "average orbit" is a
gravitationally bound body, for example.  Presumeably it was the
presence of Jupiter which put an upper limit on the size of
gravitationally bound bodies in the asteroid belt.

*****************
*****************
Terry Hancock
[e-mail]
*****************
*****************
*****************

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End of SPACE Digest V10 #11
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