Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V12_4/V12_467.TXT

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Subject: SPACE Digest V12 #467

SPACE Digest                                     Volume 12 : Issue 467

Today's Topics:
              Magellan Update - 10/17/90
              Re: Venus/Magellan, poles
               More on OSC and Pegasus
              Re: Man-rated SRBs
           Re: Pioneer 11 Update - 10/17/90
            Re: planetary north and names
             Re: Reflexes (teleoperators)
            Re: Ulysses Update - 10/16/90
             Pioneer 11 Update - 10/16/90

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription notices,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date: 17 Oct 90 22:03:26 GMT
From: julius.cs.uiuc.edu!wuarchive!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Magellan Update - 10/17/90


                    Magellan Status Report
                       October 17, 1990

     All spacecraft systems are performing nominally as Magellan
completes its 236th orbit.  The 7 star calibrations and 2 desaturations
of the past 24 hours were fully successful with nominal attitude updates.

     On two recent mapping passes, the two gyroscopes measuring the
spacecraft motion in the X axis gave differing values.  These miscompares
were very small (0.02 radians), but are possibly related to the solar array
drive problem since its position errors are also in the X axis.  The cause is
being investigated.

     The upload yesterday, to fill parts of AACS (Attitude and Articulation
Control Subsystem) Memory B with alternating 1's and 0's, inadvertently
overwrote a buffer area which was not supposed to be filled.  This was
corrected by uplinking a small memory patch.  The mapping sequence load and
radar parameter files were uplinked without problems.

     The radar system continues to operate normally, but there has been a
significant increase in the telemetry channel bit errors.  When the data is
lost, the computer fills the data record with zeros.  On orbit #598, for
example, about one-fourth of the record was zero-filled.  This degradation
of the SAR (Synthetic Aperture Radar) data was expected as Magellan
approaches Superior Conjunction.

     Fourteen new standard image swaths were produced by the SAR Processor
yesterday.  Five mosaicked images are being produced in the Image Data
Processing System to assess the radar system performance.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 18 Oct 90 01:33:07 GMT
From: swrinde!zaphod.mps.ohio-state.edu!samsung!munnari.oz.au!uhccux![e-mail]  (David Tholen)
Subject: Re: Venus/Magellan, poles

In article [e-mail] (Jeffrey R Kell) writes:

> I read all the (various) definitions of "poles" and longitude direction,
> spin, etc., but to ask a possibly silly question,  HOW do you determine
> where a longitude grid BEGINS?  Find Greenwich, Venus? ( ;-) )

The choice is arbitrary.  On the Earth, London was chosen because Britain
was the main seafaring nation of the time, so their choice is the one that
caught on.  On the sky, the vernal equinox represents a logical, but
arbitrary choice for the zero point of the right ascension grid.  For Pluto,
we've arbitrarily chosen the sub-Charon point to represent zero longitude.
Should Charon be proven to have a non-circular orbit, then the sub-Charon
point would wander around slightly, but the choice could be made more
explicit by specifying that zero longitude corresponds to the sub-Charon
point when Charon is at periapsis.

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

Date: 15 Oct 90 12:39:43 GMT
From: mvb.saic.com!ncr-sd!ncrlnk!ncr-mpd![e-mail]  (Mike McManus)
Subject: More on OSC and Pegasus


First of all, thanks for the replies to my post about info on Orbital Sciences
Corp.  Thanks to your help, my wife dazzled `em during her interview, and will
be starting work in their Boulder office next week (she sends her thanks).

Secondly, as to what they do in the Boulder office:  a little of everything,
but for the most part, it is controls and guidance work for both Pegasus and
the OSC/NASA TOS (Transfer Orbit Stage).  I have more info on the TOS, if
anyone is interested.

Lastly, some info from a glossy pamphlet my wife picked up on here interview
which discusses Pegasus.  I'm not going to quote the whole thing, but here's
the highlights (note that spelling errors are not my fault, blame them on
network spooks :-).

"System Description - The Pegasus flight vehicle is 49.2 ft. long and 50 in. in
diameter, and has a gross weight (excluding payload) of approximately 41,000
lb.  A delta wing with a 22-ft span and three 5-ft span moveable control fins
are mounted on the first stage.  Pegasus is carried aloft by a conventional
transport or bomber-class aircraft to level flight conditions of 40,000 ft. and
mach 0.8.   After release from the aircraft and ignition of its first stage
motor, the vehicle's autonomous flight control system provides guidance through
the required suborbital or orbital trajectory.  Pegasus can deliver spacecraft
weighing up to 900 lb. into low Earth orbits or launch payloads up to 1500 lb.
on suborbital, high Mach number cruise or ballistic flights.  Spacecraft as
large as 72 inches long and 46 inches in diameter can fit within the standard
Pegasus payload fairing.  In addition, Pegasus can accommidate three-axis,
gravity-gradient or spin-stabilized spacecraft or multiple smaller satellites
on a single launch."

There are several pictures, including an artist's rendition of "Deployment of
Pegasus from a commercial transport aircraft", which shows an aircraft with a
specialized mount on the bottom dropping Pegasus (maybe someday this will be as
common as sending US Mail on commercial airlines!).

Included on the glossies was what appears to be their "corporate battle cry":
"American Ingenuity Rises to the Challenge of Space".  Here, here!
--
Disclaimer: All spelling and/or grammar in this document are guaranteed to be
            correct; any exseptions is the is wurk uv intter-net deemuns,.

Mike McManus                        [e-mail], or
NCR Microelectronics                ncr-mpd![e-mail], or
2001 Danfield Ct.                   uunet!ncrlnk!ncr-mpd!garage!mikemc
Ft. Collins,  Colorado
[phone]   Ext. 378

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

Date: 15 Oct 90 03:09:09 GMT
From: van-bc!rsoft!mindlink![e-mail]  (Bruce Dunn)
Subject: Re: Man-rated SRBs

> [e-mail] writes:
> There are also a lot less things to go wrong in solids. There are no
> turbo pumps, no complex valves and plumbing, no cryogenic liquids to
> handle, no complex electronic control system to fail, just light and
> go. Admittedly the shuttle's SRBs are poorly designed, but in general,
> solids are the most reliable rockets we know how to build.


     I can remember reading an article written during the development program
for the Saturn rocket which bemoaned the fact that liquid fuel rockets had been
selected for the moon shot.  At that time, NASA was snarled in the development
problems of the F-1 engine and the thrust of the article was that solids were
simple, reliable, and easily scaled up and should have been selected for the
first stage of any moon vehicle.  How times change!
--
Did you hear the joke about the scientist whose wife had twins?
    - He baptized one and kept the other as a control.

Bruce Dunn   Vancouver, Canada    [e-mail]

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

Date: 18 Oct 90 11:39:25 GMT
From: att!cbnewsl![e-mail]  (james.f.burnell)
Subject: Re: Pioneer 11 Update - 10/17/90

In article <[e-mail]>, [e-mail] (Ron Baalke) writes:
>
>      The Pioneer 11 spacecraft emergency continues.  Yesterday, the 70 meter
> antenna in Spain used it high power transmitter at 400 kw, and Ames Research
> Center reported receiving telemetry intermittently for 8 minutes, 11 minutes,
> 8 minutes and 19 minutes.  The 70 meter station in Goldstone also provided
> uplink support at 400 kw.  The station was able to verify a 3-way downlink
> with the 70 meter antenna in Spain, although receiver lock remained
> intermittent.  The maximum AGC (Automatic Gain Control) was at -172 DBM.
> There was no telemetry data acquired during this pass.

Was the loss of the Pioneer 11 signal at this time expected, considering the
age of the spacecraft (loss of output of the RTG), limited power of its
transmitter and its extreme distance? Is the loss of signal premature, or is
a failure of some sort suspected?

Jim Burnell
AT&T Bell Labs

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

Date: 17 Oct 90 15:57:47 GMT
From: julius.cs.uiuc.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars![e-mail]  (Ron Baalke)
Subject: Re: planetary north and names

In article <[e-mail]> [e-mail] writes:
>Regarding two recent postings:
>
>Latin names on planets are useful when dealing with an international
>community of scientists. How can we use 'vernacular' names like 'Mariner
>valleys' in an international setting without being offensive? Look at
>medical terminology for all those squishy things inside us, or the latin
>names of genera and species of living things - latin is not really a dead
>language in science after all. Besides, it is just as easy to learn words
>like 'tessera' or 'tholus' as simple terms like 'graben' or 'caldera',
>without thinking of them as words in a foreign language.
>

The IAU has adopted a theme for Venus where most of its features are
name after women.  And if you look real close at the names, you will realize
that the feature are named after famous dead women.  The feature name has
two parts; the first part is the female name, the second part is the
feature.  Example: Aphrodite Terra.  Here is a list of the feature names
used for Venus.

Feature           Definition
-------------------------------------------------------------------------
Chasmata          Canyons
Colles            Small hills, knobs
Coronae           Ovoid-shaped features
Craters           Craters
Dorsa             Ridges
Lineae            Elongated markings
Montes            Mountains
Paterae           Irregularly shaped craters
Planitiae         Low Plains
Planum            High Plain
Regiones          Areas of moderate relief
Rupes             Scarps (a cliff or steep slope)
Tesserae          Polygonal ground, tiles
Terrae            Continents
Tholi             Domical hills

Incidently, using the Venera 15 and 16 data, the Soviets named two craters
Resnick Crate and McAuliffe Crater, after the two women in the Challenger
accident.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 16 Oct 90 21:58:14 GMT
From: visix![e-mail]  (Amanda Walker)
Subject: Re: Reflexes (teleoperators)

In article <[e-mail]>
[e-mail] (John Roberts) writes:
>I've often wondered about that. How can a conscious command from the brain
>suppress a reflex action that would normally be triggered before the stimulus
>even reaches the brain?

As I remember, some reflex arcs contain what could be called "cortical
overrides," or neurons which, when activated, inhibit the normal
reflex and allow the stimulus to be handled higher up in the nervous
system.  The only one I can think of is the infant suckling reflex,
but I'm pretty sure there are others.  The basic disadvantages of such
overrides are that (a) real-time response suffers, since the loop has
been lengthened again, and (b) most of them (aside from some infant
relfexes) can only be overridden when the stimulus is anticipated,
since they tend to "spring back".

However, reflexes have a whole range of reactions sites and associated
time delays.  Cerebellar motor skills, for example, are slower than
spinal reflexes but still faster than conscious processing.  Using our
current analogy, this is like being able to download code for specific
tasks into the remote (i.e., "training").

--
Amanda Walker                              [e-mail]
Visix Software Inc.                    ...!uunet!visix!amanda
--
Marching to a different kettle of fish.

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

Date: 17 Oct 90 16:23:59 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Ulysses Update - 10/16/90

In article <[e-mail]> [e-mail] (Magnus Olsson) writes:
>What kind of observations will Ulysses perform at Jupiter?

Much the same as it will perform in the polar regions of the Sun:  fields
and particles work.  It has no imaging system.
--
"...the i860 is a wonderful source     | Henry Spencer at U of Toronto Zoology
of thesis topics."    --Preston Briggs |  [e-mail]   utzoo!henry

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

Date: 16 Oct 90 14:57:15 GMT
From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Pioneer 11 Update - 10/16/90


                        Pioneer 11 Update
                        October 16, 1990

     The Pioneer 11 emergency continues.  The 70 meter antennas in Spain
supported downlink yesterday, and there has been no change to the status
of the spacecraft.  The same antennas will be used today to provide a
400 kw uplink.

     For those of you unfamiliar with Pioneer 11 or need their memory
jogged, here is an article posted by Peter Yee last spring when Pioneer
11 left our solar system.
------------------------------------------------------------------------

PIONEER 11 PASSES NEPTUNE'S ORBIT, LEAVES SOLAR SYSTEM
March 1990

     Pioneer 11 today will cross the orbit of Neptune and become
the fourth spacecraft to leave the solar system, providing a coda
to humanity's first major planetary explorations.  Pioneer 11
will join Pioneer 10 and Voyagers 1 and 2 in searching for the
heliopause, the point at which the Sun's electromagnetic
influence gives way to the galaxy's influence.

     As it crosses Neptune's orbit, Pioneer 11 will be 2.8
billion miles from the Earth.  Neptune's orbit currently marks
one measure of the expanse of the solar system because, for the
next 12 years, Pluto's eccentric orbit carries it inside
Neptune's path.  Some scientists refer to the heliopause as the
edge of the solar system.  By that definition, all four
spacecraft are still within the solar system.

     Launched in 1973, Pioneer 11 provided scientists with their
closest view of Jupiter, passing within 26,600 miles of the cloud
tops in December 1974.  The close approach and the spacecraft's
speed of 107,373 mph, by far the fastest speed ever reached by a
man-made object, hurled Pioneer 1.5-billion miles across the
solar system toward Saturn.

     Before reaching Saturn in 1979, Pioneer 11 reached an
inclination of 17 degrees above the solar equatorial plane, high
enough to illuminate the true character of the sun's magnetic
field.  Now 780 million miles above the ecliptic plane where most
of the planets orbit the sun, the spacecraft recently showed that
many of the solar cosmic rays in the heliosphere originate
outside the Sun's atmosphere in the interstellar gas, the space
between the stars.

     Pioneer 11 flew to within 13,000 miles of Saturn and took
the first close-up pictures of the planet.  Instruments located
two previously undiscovered small moons and an additional ring,
charted Saturn's magnetosphere and magnetic field and found its
planet-size moon, Titan, to be too cold for life.

     Pioneer 11, which will traverse interstellar space in the
same direction as the Sun moves, continues to return good data,
but in 3 years, operating the radio transmitter and scientific
instruments simultaneously will be difficult, says NASA Project
Manager Richard Fimmel.  Technical adjustments may extend the
craft's life through 1995.  Pioneer 10, with a stronger power
supply, may return data through the year 2000, which would extend
its original 30-month design life to 28 years.

     In June 1983, Pioneer 10 made history by becoming the first
human artifact to leave the solar system, travelling in the
direction opposite Pioneer 11's path.  Today, Pioneer 10 will be
4.5 billion miles from Earth.  Returning data to Earth at the
speed of light requires 6 hours, 36 minutes.  Pioneer 10
continues to search for the heliopause for very long-wavelength
gravity waves that would further understanding of Einstein's
Theory of Relativity and for evidence of a 10th planet.

     The Pioneers are managed by the Ames Research Center,
Mountain View, Calif., for NASA's Office of Space Science and
Applications.  The spacecraft were built by TRW Space &
Technology Group, Redondo Beach, Calif.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

End of SPACE Digest V12 #467
*******************