Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_0/V15NO054.TXT

Internet Message Format | 1993-07-13 | 39KB

Date: Fri, 31 Jul 92 05:02:32
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #054
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri, 31 Jul 92       Volume 15 : Issue 054

Today's Topics:
                A 12 mile tether that generates 5000v?
                   Biogenesis (was: ETs and Radio)
                        censorship, yet again
                         ET's, life in space
                       Fwd: ET's, life in space
                      Magellan Update - 07/30/92
                             NASA Select
                       shuttle --ufo? (2 msgs)
                       TOPEX/Poseidon Press Kit

    Welcome to the Space Digest!!  Please send your messages to
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    (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: 30 Jul 92 19:10:32 GMT
From: Fil Feit <[e-mail]>
Subject: A 12 mile tether that generates 5000v?
Newsgroups: sci.space

Hi all.

Can someone explain how that works?  I saw reference to this on the AP
wire, and they must think this is perfectly normal, since no-one is
bothering to explain it.

Is there an article on this some kind soul can direct me towards?

Thanks,

--f2
----------------------------------
  Hey, Mother Earth, won't you bring me back down,
  safely to the sea?

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

Date: 30 Jul 92 16:44:02 GMT
From: "Richard A. Schumacher" <[e-mail]>
Subject: Biogenesis (was: ETs and Radio)
Newsgroups: sci.space

Obvoiusly Mr. Wallace wants to have the exact story of biogenesis
handed to him. We'd all like to see it, but the chemists and
biologists have not yet worked it out. In the meantime, us lay
people (of whom Mr. Wallace most certainly is one) will either have
to be content with the partial answers and plausibility arguments
that the professionals find compelling, or undertake serious reasearch
on their own. Trotting out old arguments or well-known current
problems to the Net does not constitute research.

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

Date: 30 Jul 92 17:49:51 GMT
From: Jim Mann <[e-mail]>
Subject: censorship, yet again
Newsgroups: sci.space

In article <[e-mail]> [e-mail]
(Richard Schroeppel) writes:
> I think Doug is wrong.  As a US taxpayer, I hereby invite Henry Spencer
to
> offer me whatever perspective he has on the politics of space in the
US.
> I will also note that Henry is a directly interested party, since the
outcome
> of the election will influence his prospects for eventual space travel.
> As an interested party, he is certainly entitled to participate in the
debate,
> and perhaps even to complain that many disinterested parties (who don't
pay
> taxes, and don't care about space) are allowed to vote, while he isn't.
> I must also ask Doug why he wants to muzzle Henry.  Is it because you
don't
> like the analysis?  Is it too close to the truth?

I agree to the extent that I think he has every right in the world
to offer his (often good) advice on what to do.  However, as
one of the taxpayers paying for the US space program, my vote
(and the vote of any other taxpayer) should count for more.
I must admit that I do bristle a bit at those who aren't paying for
something telling us how we have to spend money. But then, I bristled
the same way when I had a (US) college student (who wasn't paying taxes
yet) try to explain to me that taxes should be raised to pay for
some service he wanted and (he claimed) couldn't afford. (This was 10
minutes after he told me how he was spending $15 (1978 prices) per week
on comic books.)

--
Jim Mann       [e-mail]  Stratus Computer

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

Date: Thu, 30 Jul 1992 19:46:00 GMT
From: "Robert S. Hill" <[e-mail]>
Subject: ET's, life in space
Newsgroups: sci.space

>In <[e-mail]> [e-mail] (Tom) writes:
>>>>Given that for evolution of life to start, a simple living organism must
>>>>come together from amino acids etc. by accident; and that for any
>>Not accident.  Think in statistics.  Given umpteen billion gallons
>>of warm, super gunky sea, what are the possibilities that any one
>>group of amino acids could form self-replicating protiens...

In article <[e-mail]>,
[e-mail] (russell wallace) writes...
>I *am* thinking in statistics. If the smallest possible self-replicator
>is 1000 amino acids in size, and there is only one self-replicator of
>that size, and supposing there are 20 possible amino acids, then the
>odds against any 1000-amino acid chain being a self-replicator are
>20^1000 to 1. Against this statistic, the total number of molecules that
>can have been formed in the visible universe since the beginning of
>time is insignificant.

Any time I see the phrase `the odds against X,' a little alarm bell
goes off in my head.  Let's postulate a situation and do the combinatorics.

Suppose the `reaction vessel' contains 1E6 molecules of each of 20
amino acids.  Suppose that our magic polypeptide contains 1000 amino
acids, 50 of each kind for simplicity.  Let C(N,n) mean the combinations
in N objects taken n at a time (since it's a little hard to make double-
height parentheses on my terminal). ^ is exponentiation operator.

   Prob(magic molecule) = C(1E6,50)^20 / C(2E7,1000)

I think I have this formula right.  Probability mavens, please correct
me.  The denominator is the number of 1000-link polypeptides that can be
selected from our reaction vessel.  The numerator is the number of them
that are this one kind of active molecule.  I evaluate this probability
to be 1E-23 _not_ 20^(-1000).  (First time I've used logs to do a
computation since high school.)

There are about 1E17 seconds in 2 billion years (oops, I mean 2E9 years
for non-USAns).  So if you have one chain spontaneously form and fall
apart per second (arbitrary assumption), that gives you 1E17
`statistical trials' in two billion years.  If you have 1E6 of the
`reaction vessels' such as I've described, you have a good shot at
forming your molecule.

Of course, I haven't _proved_ a darned thing, but I think that the
`horrendous odds against' argument is pretty shaky.

- Bob Hill
---------- ---------- ---------- ---------- ---------- ---------- ----------
   [e-mail]           ***MY individual opinions ONLY***
---------- ---------- ---------- ---------- ---------- ---------- ----------

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

Date: Thu, 30 Jul 1992 14:29:52 -0400
From: David O Hunt <[e-mail]>
Subject: Fwd: ET's, life in space
Newsgroups: sci.space

> I *am* thinking in statistics. If the smallest possible self-replicator
> is 1000 amino acids in size, and there is only one self-replicator of
> that size, and supposing there are 20 possible amino acids, then the
> odds against any 1000-amino acid chain being a self-replicator are
> 20^1000 to 1. Against this statistic, the total number of molecules that
> can have been formed in the visible universe since the beginning of
> time is insignificant.
> Russell Wallace, Trinity College, Dublin
> [e-mail]

Ah, but you're making the mistake that there is only one such acceptable
sequence.  If you look at real proteins with structure, the structure is
the main key to their functionality.

I'm remembering off the cuff here, so please don't flame me about not
having numbers and sources:

It's been shown that if one considers structure and not sequence, the
probability that a biologically active protein will be formed increases
by many orders of magnitude.


David Hunt - Graduate Slave | My mind is my own.          | Towards both a
Mechanical Engineering      | So are my ideas & opinions. | Palestinian and
Carnegie Mellon University  | <<<Use Golden Rule v2.0>>>  | Jewish homeland!
============================================================================
Email:  [e-mail]            Working towards my "Piled Higher and Deeper"

Cthulhu for President - Why vote for the lesser evil!

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

Date: 31 Jul 92 02:58:15 GMT
From: Ron Baalke <[e-mail]>
Subject: Magellan Update - 07/30/92
Newsgroups: sci.space,sci.astro

Forwarded from the Magellan Project

                       MAGELLAN STATUS REPORT
                          July 30, 1992

1.  Magellan continues to operate under the M2206 command
    sequence, which consists of only starcals (star
    calibrations) and desats (desaturations of the reaction
    wheels).  No radar mapping is being performed.

2.  Yesterday spacecraft controllers repeated the power cycle
    test of Transmitter B.  This mode replicated the
    conditions experienced by the transmitter when is was
    first used in January.  At that time the performance was
    perfect until the temperature reached 30 degrees C, then was
    affected by the signal spur.

3.  During this week's tests, however, the spur appeared
    immediately at turn on, drawing power from the carrier and
    preventing the DSN (Deep Space Network) station from locking
    onto the signal.  This appears to rule out this mode of
    operation for mapping in September.

4.  Transmitter B has been left on and is being allowed to
    continue warming as the telecommunications engineers watch
    for a stable regime for transmitting data.  During the
    period following Superior Conjunction in June, science
    data was being received at 115 kbps with the transmitter
    at 57 degrees C.  Transmitter B is presently at 42.9
    degrees C.

5.  This effort is directed at filling  the only significant
    gap in Magellan's global coverage of Venus, a 10-day
    mapping segment at the end of the cycle.  The prime
    mission goal of obtaining global gravity coverage between
    September 1992 and May 1993 is not affected by the
    transmitter problem because only the X-band carrier signal
    is required.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Most of the things you
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | worry about will never
|_____|/  |_|/       |_____|/                     | happen.

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

Date: 30 Jul 92 17:22:14 GMT
From: John Roberts <[e-mail]>
Subject: NASA Select
Newsgroups: sci.space

I tried to record the replay of the TOPEX press conference on NASA Select
at 1:00 AM EDT. The pictures and graphics were certainly very impressive.
Unfortunately, there was no sound. :-)  Apparently the NASA Select people
were aware of the problem, because the replay was abruptly cut off after
about 25 minutes. (My guess is that it was accidentally *recorded* with
no sound.)

That made me wonder - is there a "NASA Select operations" phone number that
a viewer could use to reach operations and tell them "there's no sound"
or "you're playing the tape backwards"? Occasionally I'm up late enough that
such a number would be useful, and assuming replays are from NASA Headquarters,
it wouldn't cost me much to give them a call (definitely worthwhile for an
important press conference).

NASA Select's been having some really interesting material lately, including
the Geotail launch, video of the "Rocky IV" rover (including some shots
of the stereo display screen), and many press conferences, plus the usual
historical material, "Launchbox" for kids, JPL computer animation movies,
and so on. According to Peter Yee's posts of NASA Daily News, the noon
broadcast of the NASA Today show is live - I hadn't realized that. There
seems to be an increasing trend toward replaying the press conferences in each
of the four-hour time slots, which is very useful to me. Is it true that there
are plans to cover the launch of an Ariane with a US-related payload?

In a recent press conference that I saw replayed on NASA Select, Administrator
Goldin was asked about cooperation between the US and Russian space programs.
Among the items I had heard elsewhere, he mentioned the plan to dock a Shuttle
to Mir, in order to use the living space and life support of Mir, along with
the scientific resources of the Shuttle. The thing that surprised me was the
planned duration of the rendezvous - I *think* he said four months!

Heard this morning on network news - Congress decided to continue funding for
SSF, but at half a billion dollars less than the Administration had requested.

John Roberts
[e-mail]

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

Date: Thu, 30 Jul 92 16:58:52 GMT
From: EL GATES <[e-mail]>
Subject: shuttle --ufo?
Newsgroups: sci.space,sci.space.shuttle

In article <[e-mail]> SPS@helios (Bill Jamerson SPS Pres.) writes:
>a friend of mine reports having seen on WCMH evening news from Columbus,oh,
>a report about the space shuttle seeing something like unto a UFO while up
>earlier this year. He thinks it was either the last Columbia mission or
>the Endeavor mission (more likely).
> The footage shown (taken from orbit by the shuttle) was a shiny object
>apparently in orbit below the shuttle, which suddenly darted in a different
>direction. immediately following, the footage showed a flash of light
>originating form below where the object had been.  THere was some speculation
>that it may have been a UFO.
>  Did anyone else see or hear about this? if so, what else do you know?
>  If someone from NASA could give us any info, that would be greatly
>appreciated.
>  THank you.


The video you are refering to was shown on Hard Copy and Larry King
(I believe).  I've seen this video and the objects in question are
simply ice.  These objects change direction because one of the
manuevering jets on the shuttle was fired (this can be seen in the
video as a flash right before everything changes direction).
There is nothing in the video that suggests to me that it is an ETI
spaceship.


El

[e-mail]

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

Date: Thu, 30 Jul 1992 14:34:30 -0400
From: David O Hunt <[e-mail]>
Subject: shuttle --ufo?
Newsgroups: sci.space,sci.space.shuttle

The general consensus (discussed extensively on sci.skeptic) is that these
are two pieces of ice, or possible glare on the camera.

David Hunt - Graduate Slave | My mind is my own.          | Towards both a
Mechanical Engineering      | So are my ideas & opinions. | Palestinian and
Carnegie Mellon University  | <<<Use Golden Rule v2.0>>>  | Jewish homeland!
============================================================================
Email:  [e-mail]            Working towards my "Piled Higher and Deeper"

Democracy is based on the theory that the people know what they want...and
they deserve to get it - GOOD AND HARD!

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

Date: 31 Jul 92 00:59:25 GMT
From: Ron Baalke <[e-mail]>
Subject: TOPEX/Poseidon Press Kit
Newsgroups: sci.space,sci.astro

PUBLIC AFFAIRS CONTACTS


Brian Dunbar
Headquarters, Washington, D.C.
(Phone:  [phone])


Mary Hardin
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  [phone])


CONTENTS


General Release.............................................................1

Mission Overview And Science Objectives.....................................3

Satellite Tracking..........................................................4

TOPEX/POSEIDON Satellite....................................................5

Science Instruments And Spacecraft..........................................6

Mission Phases..............................................................8

Mission Timeline............................................................9

Spacecraft Specifics.......................................................10

U.S.-French Cooperation....................................................10

Mission Management.........................................................11



RELEASE 92-126

U.S., FRANCE SATELLITE TO STUDY OCEANS AND CLIMATE

    On Aug. 10, the United States and France will undertake a mission to
help provide a new understanding of Earth's environment by determining
how the global system of the Earth's oceanic currents influence climate.

    The means to this end is the TOPEX/POSEIDON satellite, a joint
mission of NASA and France's space agency, the Centre National d'Etudes
Spatiales (CNES).

    "TOPEX/POSEIDON is an investment in our future," said NASA's
Program Scientist Dr. William Patzert.  "Without TOPEX/POSEIDON, there is
no possibility of meaningful long-term climate forecasts."

    "TOPEX/POSEIDON sets a precedent for international studies of global
change," said Patzert.  "In a future of limited resources, it is imperative
that all nations work together to study our atmosphere and oceans.  We will
have to share our understanding to develop common solutions.  Climate knows no
national boundaries."

Ocean Topography

    TOPEX/POSEIDON will use the global perspective available only from
space to develop maps of ocean topography showing the barely perceptible
hills and valleys of the sea surface.  This effort will significantly expand
the knowledge developed from shipboard research which was limited to specific
locations.

    From the TOPEX/POSEIDON data, scientists will calculate the speed
and direction of ocean currents worldwide to better understand how the
oceans transport heat from the Earth's equatorial region toward the poles,
thus regulating global climate.

    The spacecraft's six scientific instruments are designed to function
for 3 to 5 years.  The resulting data base will help scientists develop more
precise long-term climate forecasts, understand and predict the timing of
the El Nio phenomenon and better comprehend the ocean's role in
regulating overall global climate.



    TOPEX/POSEIDON will be launched from the Guiana Space Center in
Kourou, French Guiana, aboard an Ariane 42P expendable launch vehicle.
The satellite will be placed into an orbit 830 miles (1,336 km) above the
Earth, inclined 66 degrees to the Earth's equator.  Launch is scheduled for
7:08 p.m. EDT.  The launch window is 44 minutes in duration.

International Cooperation

    The TOPEX/POSEIDON launch will help commemorate 1992 as the
International Space Year.  The joint science team includes 38 principal
investigators from nine countries including the United States, France,
Australia, South Africa, Germany, Norway, Japan, the Netherlands and the
United Kingdom.  Data from TOPEX/POSEIDON eventually will be made
available to global change researchers around the world for their analysis.

    TOPEX/POSEIDON is the second major satellite in NASA's Mission to
Planet Earth, a coordinated, long-term program to study the Earth as a
complete environmental system.  Mission to Planet Earth began in
September 1991 with the launch of the Upper Atmosphere Research
Satellite and continued last March with the ATLAS-1 Space Shuttle mission.

    The next element of Mission to Planet Earth is the Italian-built
LAGEOS II satellite, scheduled for launch aboard the Space Shuttle Columbia
in October.  LAGEOS II will be used to study the dynamics of the Earth's
crust.

    The U.S. portion of the TOPEX/POSEIDON project is managed by
NASA's Jet Propulsion Laboratory, Pasadena, Calif., for the agency's Office of
Space Science and Applications.  The French portion of TOPEX/POSEIDON
is managed by CNES' Toulouse Space Center, Toulouse, France.


MISSION OVERVIEW

    TOPEX/POSEIDON will be launched by the European Ariane 42P
rocket from Kourou, French Guiana.  The spacecraft will be placed in a
nearly circular orbit with an altitude of 830 miles (1,336 kilometers),
inclined 66 degrees from the equator.  This relatively high altitude will
minimize atmospheric drag on the spacecraft, reduce the effects of gravity
field variations and simplify maneuvers needed to maintain the orbit.

    The satellite's orbital period is 112 minutes.  TOPEX/POSEIDON will
repeat the same ground track every 10 days (127 revolutions), allowing
scientists to measure changes in the sea surface topography using a
sampling technique that matches changes in the global ocean currents.

    This mission builds upon the knowledge gained from three previous
ocean-observing satellites Q GEOS-3 in 1975, Seasat in 1978 and Geosat in
1985 Q which demonstrated that altimetry could measure ocean circulation.
Like these prior missions, the primary instrument on-board the
TOPEX/POSEIDON satellite is a radar altimeter.

    The altimeter is similar to aircraft radar, but the satellite altitude
and the required height precision are many times greater.  The
TOPEX/POSEIDON altimeter bounces radar pulses off the sea surface and
measures the time it takes the signals to return to the satellite.  A
microwave radiometer will correct for any errors in the time delay that is
caused by water vapor in the path through the atmosphere.

    The adjusted round-trip travel time is used to calculate the distance
between the spacecraft and the sea surface.  When this distance is combined
with the measurements of the satellites exact location in space, scientists
will first determine the height of the sea surface relative to the Earth's
center and then calculate fluctuations in currents and tides.

SCIENCE OBJECTIVES

    The primary objective of the TOPEX/POSEIDON project is to make
precise and accurate global observations of the sea level for several years,
substantially increasing understanding of global ocean dynamics.  Members
of the TOPEX/POSEIDON science team will share their data with scientists
working with the World Ocean Circulation Experiment (WOCE).  Together
they will be able to determine the general circulation of the ocean and its
variability.

    The satellite also will increase understanding of how heat is
transported in the ocean.  The ocean absorbs the sun's heat and
redistributes it.  Active currents such as the Gulf Stream carry warm water
from the tropics to the poles where it cools and sinks into the deep ocean.

    Without this circulation, the difference in temperature between
equatorial and polar waters would be much greater than it is today.  How the
water circulates in the ocean determines the speed at which the heat is
transported and how the exchange of energy regulates the world's climate.

El Nio

    Another short-term climate change influenced by the ocean is the
phenomenon known as El Nio.  Every 3 to 7 years, usually beginning
around Christmas time, there is a dramatic rise in the sea surface
temperatures in the eastern Pacific Ocean.  At the same time, atmospheric
patterns shift, causing severe environmental consequences around the globe.

    The El Nio event of 1982-83 was the worst so far this century.
Massive flooding and landslides killed hundreds of people in Ecuador and
Peru and caused millions of dollars in damage along the Southern California
coast.  Cyclones left 25,000 people homeless in Tahiti and severe droughts
plagued the southern hemisphere, especially Australia, Indonesia, the
Philippines and South Africa.

    TOPEX/POSEIDON will improve our knowledge of upper-ocean
circulation in the tropical Pacific, which is essential for reliable
prediction of these El Nio events.

    The ocean also is influenced by gravity and the Earth's rotation.
If the Earth did not rotate, the shape of the resting ocean would conform to
the Earth's gravity, a condition scientists refer to as the geoid.  But the
Earth is not still, and ocean currents raise or lower sea level from the
geoid.  The elevation of sea level relative to the geoid is called ocean
topography.

    Sea currents contribute to the low hills and shallow valleys in the
ocean which are similar to the high and low pressure systems that occur in
the atmosphere.  Sea water flows around these hills and valleys just as winds
blow around the highs and lows of atmospheric surface pressure.
TOPEX/POSEIDON will measure these changes in ocean topography, and
scientists will calculate the speed and direction of ocean surface currents.

SATELLITE TRACKING

    TOPEX/POSEIDON is equipped with instruments that enable
scientists to accurately pinpoint the satellite's location.  Precise orbit
determination is crucial because errors in locating the spacecraft would
distort the sea level measurement calculated from the altimeter readings.

    TOPEX/POSEIDON will measure the distance from the satellite to the
sea surface within 1.2 inches (3 cm).  Three independent tracking systems
will determine the position of the spacecraft within 4 inches (10 cm).  The
first, the NASA laser retroreflector array (LRA) will reflect laser beams from
a network of 10 to 15 ground-based laser ranging stations under clear skies.
    The second, for all-weather, global tracking, will be provided by the
CNES Doppler Orbitography and Radiopositioning Integrated by Satellite
tracking system receiver (DORIS).  This device uses microwave doppler
techniques (changes in radio frequency corresponding to relative velocity)
to track the spacecraft.  DORIS consists of an on-board receiver and a global
network of 40 to 50 ground-based transmitting stations.

    The third system utilizes an on-board experimental Global Positioning
System (GPS) demonstration receiver to precisely determine the satellite's
position continously by analyzing the signals received from the U.S Air
Force's GPS constellation of Earth orbiting satellites.

    TOPEX/POSEIDON also will fly over two verification sites so that
scientists can compare data taken on the ground to the readings obtained
from the satellite.  These sites are located on the Texaco Harvest Oil
Platform off Point Conception, Calif., (the NASA site) and near Lampedusa
Island in the Mediterranean Sea (the CNES site).  Throughout the mission,
comparisons of the information collected at these sites will ensure that the
satellite's instruments are calibrated very precisely.

THE SATELLITE

    The TOPEX/POSEIDON spacecraft is based on the existing
Multimission Modular Satellite (MMS) bus, modified to meet the needs of
this mission.  Built by Fairchild Space, the satellite is comprised of the MMS
and an instrument module which houses the sensors.

    The MMS command and data handling subsystem contains the main
computer on-board TOPEX/POSEIDON.  It interprets and executes
commands and receives data from all subsystems and sensors for
transmission to the ground.  The command and data handling subsystem
houses three tape recorders used for engineering telemetry and science
data storage.  Each tape recorder will record for about four revolutions or 8
hours of data before playback.

    This subsystem also provides telecommunications using a steerable
high-gain antenna dish and two omni antennas.  During normal operations,
the satellite communicates with the ground via the Tracking and Data Relay
Satellite System (TDRSS).  This link handles all commands, science data,
engineering telemetry and the operational orbit tracking for navigation and
mission planning.

    The attitude determination and control subsystem maintains the
proper spacecraft attitude during mission operations and points and
stabilizes the satellite during all orbit adjustments.  It also will
automatically "take charge" to put the satellite into a "safing" mode if
it detects a problem with its own performance or if it does not receive
the periodic "I'm OK" signal from the on-board computer.

    The spacecraft's electrical power subsystem contains the solar array
and three batteries.  The solar array is the main power source and the first
item to be deployed, 2 minutes after separation from the launch vehicle.
After deployment, the on-board controller rotates the array so that the
panels face the sun.

    The batteries provide power from about 10 minutes before launch
until the solar array takes over.  The batteries also are used to keep the
instruments operating while the spacecraft is orbiting the night side of the
Earth.

SCIENCE INSTRUMENTS

    TOPEX/POSEIDON carries five scientific instruments.  Three are
provided by NASA and two by CNES.

The Dual-Frequency TOPEX Radar Altimeter (ALT)

    The primary instrument onboard the satellite is the dual-frequency
NASA radar altimeter (ALT).  Provided by NASA and managed by the
Goddard Spaceflight Center, the altimeter was built by the John Hopkins
University's Applied Physics Laboratory.  The instrument is designed to
measure the height of the satellite above the sea at two frequency channels,
13.6 GHz and 5.30 GHz.  This is the first altimeter to use two channels to
correct for measurement errors caused by free electrons above the Earth's
atmosphere.

The TOPEX/POSEIDON SPACECRAFT

TOPEX Microwave Radiometer (TMR)

    The companion TOPEX microwave radiometer, developed by NASA's
Jet Propulsion Laboratory, Pasadena, Calif., operates at three frequencies
(18 GHz, 21 GHz and 37 GHz)  The radiometer measures water vapor, which can
delay the return of the radar pulse to the spacecraft, along the path viewed
by the altimeter and corrects the altimeter data.  The 21 GHz channel is the
primary channel for water vapor measurement.  The 18 GHz and 37 Ghz
channels are used to remove the effects of wind speed and cloud cover,
respectively, in the water vapor measurement.

Single-Frequency Poseidon Altimeter (SSALT)

    SSALT is an experimental precision altimeter designed by CNES and
built by Alcatel Espace.  This instrument is being flown as an experiment to
validate improved solid-state technology, which results in smaller, lower-
power and lower-weight altimeters for future missions.

    SSAlt uses the same antenna as the NASA altimeter but operates at a
single frequency of 13.6 GHz.  During the first 6-month verification phase,
the SSALT will operate about 12 percent of the time to assess its
performance.  For the remainder of the mission, NASA and CNES will
determine an antenna sharing plan to optimize data collection.

Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS)

    The DORIS tracking system will provide important tracking data for
precision orbit determination using microwave Doppler techniques.  This is
a proven system manufactured by the French aerospace firms, Dassault,
CEPE and STAREC, and was first flown by CNES on the SPOT-2 satellite.

    The system is made up of an on-board receiver and a network of 40 to
50 ground transmitter stations.  Operating in all weather conditions, DORIS
receives signals at two frequencies (401.25 MHz and 2036.25 MHz) which
allows the total electron content of the ionosphere to be estimated.  This
allows the removal of SSALT altitude errors introduced by traveling through
the ionosphere.

Global Positioning System Demonstration Receiver (GPSDR)

    The GPSDR is an experimental receiver developed by JPL and
manufactured by Motorola to provide a unique tracking data type for
continuous precision orbit determination.  This new technique
simultaneously measures the satellite's position relative to the U.S. Air
Force's Global Positioning System and ground stations.  By adding the
ground stations, the exact locations of which have been precisely measured,
the new system promises to revolutionize orbit determination by providing
continuous satellite tracking with a potential accuracy of 4 inches (10 cm)
or better.  The GPS receiver operates at 1227.6 MHz and 1575.4 MHz.
MISSION PHASES

    The French-provided Ariane 42P launch vehicle, manufactured by
Arianespace, is a three-stage, liquid-propelled rocket, approximately 215
feet (60 meters) long, with two strap-on first-stage solid propellant motors.
The first two stages of the core vehicle are powered by hydrazine and
nitrogen tetroxide.  Stage three contains cryogenic liquid oxygen and
hydrogen.  The vehicle equipment bay is located between the third stage
and the payload compartment, and its inertial reference system and
computer conduct the ascent attitude control, guidance and sequencing.

    The spacecraft arrived at the Centre Spatial Guyanais in Kourou,
French Guiana, on June 23 to undergo a series of performance tests prior to
launch.  Five days before launch, the encapsulated satellite will be mated to
the launch vehicle.

    After that, the satellite will continue functional testing and battery
charging cycles in preparation for flight.  Final configuring for the launch
is achieved 90 minutes before liftoff, with the exception of the tape
recorders and transmitters.

    Transmitter A is turned on 2 hours before launch.  Two tape recorders
are commanded to record at launch minus 20 minutes.  At launch minus 10
minutes, the satellite is switched to internal battery power and the umbilical
disconnect process, which takes about 40 seconds, begins a minute later.

    After the umbilical is disconnected, real-time monitoring of the
satellite's functions will be conducted through the satellite's telemetry
transmitter.

Tracking During Launch

    Launch vehicle telemetry is coordinated primarily through the Guiana
tracking facilities at Kourou.  After injection (which occurs approximately 17
minutes after launch), real-time satellite telemetry is available through the
NASA tracking station at Bermuda.

    Telemetry also is recorded on two satellite tape recorders for later
playback.  Several critical events, including injection, the orientation
maneuver, satellite separation and solar array deployment occur while the
Bermuda station is tracking the satellite.

    Madrid is the first Deep Space Network (DSN) station to track the
satellite after launch.  This pass starts 20 minutes after launch
(approximately 1 minute after separation) and continues for 12 minutes.
The DSN 26-meter antennas are the primary method of communicating
during the first day.

    Beyond that, the DSN only will be used as an emergency method of
communicating.  For the balance of the mission, the primary method of
communicating between the satellite and the ground will be via the
Tracking and Data Relay Satellite System (TDRSS).  The first TDRSS contact
is established approximately 1 hour after launch.

MISSION TIMELINE

Mission Elapsed Time    Event
L-1 day    Launch vehicle propellant loading
L-09:30:00    Satellite functional tests
L-06:30:00    Battery cycling
L-02:00:00    Satellite Transmitter A ON
L-02:00:00    Final RF tests
L-01:30:00    Configure Satellite for Launch
L-00:20:00    Configure tape recorders/trackers
L-00:10:00    Set internal battery power
L-00:09:00    Start umbilical demate
L-00:06:00    Begin Ariane automatic launch seq.
L-00:00:09    Release Ariane inertial platform
L-00:00:00    LIFTOFF
L+00:01:28    Solid separation
L+00:03:19    Stage 1 burn out
L+00:03:48    Payload fairing jettisoned
L+00:05:30    Stage 2 burn out
L+00:17:38    Stage 3 shutdown/Orbit Injection
L+00:19:28    Separation
L+00:21:28    Solar Array Deployment
L+00:26:28    High Gain Antenna Deployment
L+00:27:28    GPS Antenna Deployment

Assessment Phase

    The assessment phase begins when the satellite separates from the
Ariane rocket.  For the first 45 days after launch, the satellite's sensors
and instruments will undergo check-out and assessment.  The first spacecraft
maneuver is scheduled for 7 days after launch to refine the satellite's
orbit.  Up to six additional maneuvers will be performed to attain the
precise observational orbit.

Initial Verification Phase

    This phase occurs after the assessment phase and gives the project
team time to calibrate the instruments against ground data they are
receiving from the two laser verification sites.  This phase lasts about 6
months.



Observational Phase

    The key objective of the observational phase is the production and
distribution of the Geophysical Data Records which contains sea surface
height, sensor corrections and geophysical information.  The science data
team is responsible for distributing and archiving these sensor and
geophysical data products.

SPACECRAFT SPECIFICS

Design lifetime:    3 years prime; 2 years extended mission
Length:    18 feet (5.5m)
Width:    9.2 feet (2.8m)
Solar panel:    28.5 feet x 10.8 feet (8.7m x 3.3m)
Power:    2,100 Watts
Mass:    5,500 pounds (2,500kg)

U.S.-FRENCH COOPERATION

    TOPEX/POSEIDON is only one area in which the U.S. and French
space programs are cooperating.  French scientists are principal
investigators or co-investigators on NASA's Galileo and Wind spacecraft and
the Upper Atmosphere Research Satellite.

    There has been substantial collaboration on several Spacelab missions,
including Space Life Sciences-1 in 1991 and the ATLAS-1 and International
Microgravity Laboratory-1 missions in 1992.

    There has been substantial collaboration on several Spacelab missions,
including Space Life Sciences-1 in 1991 and the ATLAS-1 and International
Microgravity Laboratory-1 missions in 1992.  The agencies are cooperating
in development of the Visual and Infrared Mapping Spectrometer to fly on
NASA's Cassini mission to Saturn in 1997.

    U.S.-French cooperation extends back to joint solar studies in the
1960s.  In 1978, CNES provided the ARGOS data collection system that flew
on the TIROS-N satellite and subsequent satellite search-and-rescue
equipment based on ARGOS technology.  In 1985, French payload specialist
Patrick Baudry flew on Space Shuttle mission 51-G, which deployed three
satellites.


MISSION MANAGEMENT

NASA Headquarters

Daniel Goldin            Administrator

Aaron Cohen            Acting Deputy Administrator

Dr. L.A. Fisk            Associate Administrator,
                    Office of Space Science and Applications

Alphonso V. Diaz        Deputy Associate Administrator
                    Office of Space Science and Applications

Dr. Shelby G. Tilford    Director, Earth Science and Applications Division

Dr. W. Linwood Jones    Program Manager

Dr. William Patzert    Program Scientist


Centre Nationale d'Etudes Spatiales

Dr. Jean-Louis Fellous    Program Manager

Michel Dorrer            Project Manager

Dr. Alain Ratier    Program Scientist

Dr. Michel Lefebvre    Project Scientist
                    Jet Propulsion Laboratory

Charles Yamarone Jr.    Project Manager

Dr. Lee-Lueng Fu    Project Scientist
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Most of the things you
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | worry about will never
|_____|/  |_|/       |_____|/                     | happen.

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End of Space Digest Volume 15 : Issue 054
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