Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v10_3/v10_303.txt

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Subject: SPACE Digest V10 #303

SPACE Digest                                     Volume 10 : Issue 303

Today's Topics:
             NASA document abbreviations
        Re: Galileo Astronauts Honored at JPL
             Meteor Burst Communications
         space news from Oct 9 AW&ST, part 2
----------------------------------------------------------------------

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Resent-Date:  Sun, 03 Dec 89 19:22:13 EST
Resent-From: Harold Pritchett <[e-mail]>
Resent-To: Space discussion group <[e-mail]>
Date:         Wed, 29 Nov 89 11:42:13 SET
From: Hermann Schneider <[e-mail]>
Subject:      NASA document abbreviations

This message was originally  submitted by A6@ESOC to the SPACE  list at UGA. If
you  simply forward  it back  to  the list,  it  will be  distributed with  the
paragraph you  are now  reading being  automatically removed.  If you  edit the
contributions you receive into a digest, you will need to remove this paragraph
before mailing  the result to the  list. Finally, if you  need more information
from the author of this message, you should be able to do so by simply replying
to this note.

----------------- Message requiring your approval (11 lines) ------------------


I got the information, that there is a NASA document 'NASA GP1052' with
title 'Shuttle & Payload Acronyms & Abbreviations'. I am sure that many
readers of SPACE-L would appreciate to have this document. Can somebody
retrieve an electronic copy of this document and distribute it to this
List? At least I would be very thankful.

Regards Hermann Schneider
        (Communication Systems Programer)
        ESOC (European Space Agency's Operations Center)

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

Date: 2 Dec 89 22:12:16 GMT
From: psuvm![e-mail]  (Charles Hannum)
Subject: Re: Galileo Astronauts Honored at JPL

In article <[e-mail]>, [e-mail] (Stephen R Fleming)
says:
>
>>Time was then set aside for the
>>JPL employees to chat with the astronauts and to get their autographs.
>
>...Just think about this sentence for a second...
>
>I'm not a basher of the individual astronauts; I'd love to be one.
>But the thought of people at JPL, the *real* space-science heroes
>of the last couple of decades, clustering around a bunch of
>Right-Stuffers like teenage groupies...
>
>I dunno.  Maybe I'm getting cranky in my old age.  Let it pass.

If you'd been waiting (how many?) years to get your baby out into space,
you'd think the astronauts were God, too.

--
- Charles Martin Hannum II       "Klein bottle for sale ... inquire within."
    (That's Charles to you!)     "To life immortal!"
  cmh117@psuvm.{bitnet,psu.edu}  "No noozzzz izzz netzzzsnoozzzzz..."
  c9h@psuecl.{bitnet,psu.edu}    "Mem'ry, all alone in the moonlight ..."

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

Date: 4 Dec 89 02:01:48 GMT
From: philmtl!philabs!briar.philips.com![e-mail]  (Robert Casey;6282;3.57;$0201)
Subject: Meteor Burst Communications

copied from amateur radio packet:
From: K3UZZ@N2IMC
To: SPACE@ALLBBS
--------------------------------------------------------------------
The following article was reprinted from MIS WEEK Nov.20, 1989 with
permission from the author by K3UZZ @ N2IMC
--------------------------------------------------------------------

Meteors make uncommon carriers
by Michael Puttre

New York--"Look to the skies."

The slogan of Meteor Communications Corp. of Kent, Wash., is not a
warning against squid-faced alien fiends.  It calls attention to the
technology that is MCC's name sake.

Meteor-burst communications (MBC) uses meteors to send transmissions
between remote sites on the ground.  Building a network that relies on
shooting stars, the literary symbols of ephemerality, may sound like
the product of wishful thinking.  But many are looking to meteors as a
low-cost alternative to satellites.

As transient as they are, meteors arrive in the Earth's upper
atmosphere by the billions every day, mostly in the form of mote-like
micrometeors.  These visitors from space have only the briefest of
careers in the ionisphere, typically under three seconds.  However,
high-frequency radio waves can be bounded off of the ionized gasses
left behind in the meteor's fiery death dives.  And their abundance
makes it probable that there will be a meteor around when you want
one.

Getting there

A simple point-to-point MBC system is composed of a master station and
a number of remote transceiver sites.  When an MBC master station wants
to poll a remote site, it sends a continuous coded radio signal in the
30-to-50 MHz range.  Once a meteor shows up in the proper part of the
sky, the signal is reflected to a receiver at the remote site up to
2,000 kilometers distant.  Once the master signal is recognized, the
site transmits any data it has collected along the same path back to
the master station using the same meteor trail.  Sites can be relayed
to give an MBC system nearly unlimited range.  The actual performance
of an MBC system varies due to the effects of the Earth's rotation on
its axis and its revolution around the Sun.  At dawn, an MBC site is on
the Earth's leading edge in its movement through space.  More meteors
will then be in the atmosphere above the site.  In the evening, the
same MBC site will be on the trailing edge, so there will be fewer
meteors.  In the summer, there are four times as many meteors as there
are in the winter because of the density of particles in certain
regions of space through which the Earth passes.  One observer noted
that a transmission wait of two minutes at 4:00 a.m. in September
compares with a 10-minute wait at 4:00 p.m. in January.

The concept of MBC has been understood since the 1930's.  But at its
current level of performance, meteors will not threaten communications
satellites anytime soon.  In fact, the advent of commercial satellites
in the '50s and '60s dealt a virtual death blow to MBC.  When the U.S.
military, which had been the prime sponsor of MBC, diverted its R&D
money into satellites, it looked like meteors were out of the carrier
business.  But the technology has won out over satellites for extensive
networks.  The largest existing MBC network is also one of the oldest.
Back in 1975, the Soil Conservation Service arm of the Agriculture
Department defined a set of requirements for a system to measure snow
and rainfall in the 11 continental states of the American West.  The
SCS West Technical Service Center in Portland, Ore., was to be the hub
of a network of hundreds of widely scattered, unattended data
collection sites in remote, inhospitable terrain.

Data collection leader Garry Schaefer said that the SCS eventually
settled on MBC as the most cost effective solution.  A terrestrial
solution requiring a chain of line-of-sight relay stations was
discarded because of their maintenance cost.

MBC also won out against satellites for cost reasons and, ironically,
for reliability.  "We didn't want to be dependent on others for a
down-link," said Schaefer.  "We didn't want to have to wait for
irregular lease time to collect data."

The Snow Telemetry (Snotel) system today consists of two master
stations and 560 remote sites.  According to Schaefer, Snotel cost $5
million to build and costs $1 million a year to maintain.  "Satellites
would have cost a substantial magnitude more," he said.

Western Union performed the systems integrations for the Snotel MBC
system designed by a group of engineering consultants who broke away
from Boeing Corp.  These consultants would eventually incorporate
themselves, becoming Meteor Communications.  The company has installed
approximately 50 master sites and 2,000 remote sites to date, which
represents 95 % of MBC systems worldwide.

Wishing on a star

The very importance of satellites has reawakened military interest in
MBC.  Communications satellites would be high-priority--and highly
vulnerable--targets in wartime, and both Superpowers have developed the
capability to blow them out of orbit.

This capability is not likely to extend to meteors, and therefore the
military considers MBC systems "survivable." "It's a good back up for
any Star-Warsiness going on," said David Kocyba, VP marketing for MCC's
biggest customer.

However, Kocyba sees the real future of MBC as lying in the commercial
sector.  The trucking industry, for example, which represents a
potential market of tens of thousands of mobile terminals, could use
MBC to keep track of rigs on long-distance runs.  However, MBC has to
overcome its limitations before it can be considered for more
mainstream communications.

"The big drawback of the system is its relatively low throughput rate
of 100 to 400 words a minute," said Kocyba.  Upgrading antenna design
to allow the system to use even smaller meteors will increase
throughput.  Microprocessor enhancements will give MBC systems better
definition.

A new packet-switching system is currently being perfected to replace
the point-to point communications now used.  Automatic routing will
allow an MBC site to use one of many meteors rather than waiting for
one to connect it to a specific master station.  Kocyba said that some
packet-switching capability is now available to MCC customers, but that
the concept is still maturing.  Once thethroughput and networking
performance of MBC is sufficiently improved, many general-purpose
communications applications will be in reach.  "Voice mail is
possible," Kocyba said, adding that the burst technology inhibits
real-time voice capabilities.  It would not, however, inhibit facsimile
transmissions.  Long-distance emergency communications are another
application being evaluted.  Some sites in the Florida Keys are
reportedly looking at MBC as a back up for hurricane damage.

But even today, MBC proponents have a compelling argument to take the
technology seriously.  Noted SCS's Schaefer:  "Meteors are free."

1841z, 681 msgs, #10502 last @KD6TH-4 MailBox>
73 de WA2ISE

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

Date: 4 Dec 89 00:13:27 GMT
From: attcan!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: space news from Oct 9 AW&ST, part 2

[Current news from my spies:  Pegasus will fly a dress-rehearsal captive-
carry mission Dec 7, including everything but pushing the final button.
The latest captive-carry test did turn up some minor problems, which
are being fixed.]

[The following is the rest of the extensive planetary-missions coverage
in the Oct 9 issue, hitting the high spots only.]

JPL and JSC say that morale in NASA has improved considerably since Bush's
Moon/Mars announcement.  "This is the first time since President Kennedy...
that a President has told us clearly what he wants."

JPL outlines tentative approach to a manned Mars mission:

1996    Mars Observer 2, a followon to Mars Observer
1998    Mars Global Network, two launches landing penetrators at 24 sites
2001    two sample-return missions with small rovers
2003    two missions (for redundancy) each carrying a site-reconnaissance
    orbiter and a communications orbiter
2005    major rover to potential landing site
2007    another
2009    another
2011    sample-return missions, with small rovers, to 2 best sites
2015    manned launch from space station

Safety and scientific interest will determine the best landing site, but
the best spot would be an ancient lake bed (potential for fossils) with
nearby resources (e.g. near-surface permafrost) useful to the mission.
A manned mission is considered much more effective than robot missions.
[However, I note that quite a bit of the robotic buildup in the above
schedule is only tenuously related to the manned mission.  A cynic might
suspect the existence of a contingency plan which simply scratches the
"2015" entry off the schedule...]

All of the above missions except the final manned mission are assembled
on the ground and use Titan 4 launches.

Technologies being pursued for sample-return missions include aerocapture
at Mars, intelligent autonomous landing (the Viking landers were lucky:
current estimates put the chances of a successful blind landing as low
as 60%), and autonomous rendezvous and docking in Mars orbit.  [The
above-mentioned cynic might observe that aerocapture, although certainly
useful, would probably be unnecessary with on-orbit assembly... which
seems like a rather easier technology to develop.]

Technologies seen as significant problems for rover designs are autonomous
sample retrieval (locating and picking up a rock without help, currently
a research topic only), lubricants good to -140C, and power supplies that
do not require sunlight (unreliable due to Martian dust storms) or
batteries (which have problems with the cold).  (The probable solution to
the power-supply issue is RTGs.)

CRAF's penetrator propulsion system has changed from a solid rocket to a
liquid rocket to permit postponing choice of the impact velocity until after
a first look at the comet.  The penetrator design people would really prefer
to know now whether they have to deal with fluffy snow or solid ice, but
the current design should get at least 30cm into something as hard as sea
ice, enough to get the gamma-ray spectrometer into the surface at least.
The CRAF main bus is designed to be capable of carrying two penetrators,
although the current budget is for one; everyone would prefer to send two,
partly as a hedge against trouble and partly so a successful first impact
in a "safe" area could be followed by a shot at a more interesting area.

Cassini is planned for launch in April 1996 on a Titan/Centaur.  It will
use an Earth gravity assist, with encounter 26 months after launch.  An
encounter with asteroid Maja will occur between launch and Earth encounter,
and the possibility of a second asteroid encounter is being studied.
Cassini then proceeds to Jupiter, for a gravity assist there in Feb 2000.
Saturn arrival would be early in 2002.

Cassini's Titan probe would probably take 2-3 hours to descend on its
parachute, and there is hope of both data on surface hardness (from the
probe's accelerometers) and pictures from the surface (if the probe
survives impact).  The Cassini orbiter will also do Magellan's trick
of using its main communications antenna for radar mapping of Titan's
surface.

The Deep Space Network is gritting its teeth in preparation for Magellan,
which will tie up one DSN antenna almost continuously for eight months
with 3 terabits of radar data.  Some loss of data is likely if there is
an emergency on another spacecraft or a need for maintenance downtime on
the DSN, although an extended mission could fill in such gaps.  [There
is hope for an extended mission anyway, since the eight-month primary
mission will not do quite the entire surface.]

Magellan is in good general health but does have some problems.  One is
spurious signals in the star tracker, possibly caused by solar protons
or electrostatic discharges.  The problems seem to be correlated with
solar activity.  Pioneer Venus's similar tracker has similar problems.
The spurious signals are sufficiently away from expected star positions
that Magellan's attitude-control computer rejects them, but they do mess
up the attempt to determine Magellan's attitude accurately.  This is not
a trivial problem, since Magellan has to turn back and forth on each orbit
to use the same antenna for mapping and data transmission.  Magellan will
do a star calibration on each orbit, and can miss *one* calibration without
significant problems, but successive missed calibrations could hamper
communications and mess up the radar data.  JPL is developing software
filters for the attitude-control computer to reject well-out-of-bounds
signals and pick the best of the remaining ones; it is hoped that this
will suffice.

Magellan's attitude-control computer is also running too warm, which
could shorten its life.  The expected temperature was 40C, and it's
actually 58C.  A small error has been found in the thermal models, but
it doesn't account for the whole problem.  Nobody knows quite what is
going on; possibly the solar reflectors have become degraded, but they
have not done this on other missions.  Mission plans call for the
high-gain antenna to shield the computer bay in future, which should
keep things under control.

Finally, Magellan's thrusters are too warm, especially when the big
ones have the Sun shining up their nozzles.  Damage is not expected,
but one problem is that some of the hydrazine in the fuel lines might
decompose.  The resulting gas bubbles might cause erratic early firing,
a matter of some concern because the big thrusters are vital to proper
attitude control when Magellan fires its solid motor to enter Venus
orbit.  If studies of the problem suggest that hydrazine decomposition
is likely, the thrusters will be "burped" with a short firing beforehand.
Venus encounter date is Aug 10.

Voyager 2 has been running post-Neptune calibration tests before starting
interstellar-cruise phase.  The Voyagers will still be tracked every day,
but they will be reconfigured for a 160bps data rate (compared to 21600
at Neptune) so that DSN's smaller antennas can be used.  The major limit
on their lifetime is isotope decay in the RTGs, which will run them out
of power around 2017.  There is hope that they will reach the heliopause
(the edge of the Sun's atmosphere) by then; the distance to the heliopause
is very uncertain, but current guesses give each Voyager about an 85%
chance if no equipment failures occur.

Voyager 1's cameras will be used in February to make a mosaic of the solar
system from outside.  The star background will be supplied by the wide-angle
camera, with narrow-angle images of seven of the planets inserted.  Pluto
is too dim and Mercury is too close to the Sun (which will not be included).
The planet images will show them as bright stars only, but the general
colors should be right.

JPL's Voyager team will drop to 45-50 people next year, with no further
encounters to plan and run.  (The peak at Neptune was 230.)

West Germany's Kayser-Threde company has booked four microgravity flights
on Soviet recoverable spacecraft next year.  The agreement includes new
provisions for launch-site access.  This follows a successful protein
crystal growth experiment on Resurs-F in September, run by K-T on behalf
of Intospace.  Intospace is interested in all four 1990 K-T launch slots,
although no commitment has been made yet.  Payload definition deadline
is about six months before launch.  The short lead time is one of the
most attractive features of dealing with the Soviets:  "the West German
government finally allowed us to start negotiations with the Soviets
last April, things became serious in May, and we flew in September".
The biggest obstacle has been glacially slow approval processes in the
West German government, which made it necessary for K-T to invoke the
cancellation clause in an earlier deal for a 1989 launch slot.  (The
payload space was used by France's CNES instead.)  K-T also holds
reservations on Soviet launches in 1991 and 1992.

Arianespace is revising the 1989-90 Ariane launch manifest after an
electronics problem caused a one-month slip in launch V34, carrying
an Intelsat 6.  Other recent changes also contributed to revisions.
Intelsat is shifting another Intelsat 6 to a Titan, since it wants to
use up its two Titan launch reservations quickly, and will put a later
one on Ariane in return.  An Inmarsat bird scheduled for late next year
may not be ready, and there is a strong possibility that Italsat 1, set
for next autumn, may be late.  It's unusual for Ariane to be waiting
for payloads, rather than vice-versa.
--
Mars can wait:  we've barely   |     Henry Spencer at U of Toronto Zoology
started exploring the Moon.    | uunet!attcan!utzoo!henry [e-mail]

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

End of SPACE Digest V10 #303
*******************