Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_2/V11_205.TXT

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Subject: SPACE Digest V11 #205

SPACE Digest                                     Volume 11 : Issue 205

Today's Topics:
              Galileo Update - 03/30/90
               Galileo Updates
   Re: "Brilliant Pebbles" vs. "Smart Rocks" (was Re: Railgun ...)
       Re: SUSI (Was Re: Austrailian Reduced Wobble telescope)
              Re: Ejection seats
               Re: Solar Cells
----------------------------------------------------------------------

Date: 31 Mar 90 00:13:58 GMT
From: jarthur!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 03/30/90


                              GALILEO
                      MISSION STATUS REPORT
                         March 30, 1990

     As of noon Friday (PST) , March 30, 1990, the Galileo spacecraft
is 75,701,420 miles from the Earth, 12,872,890 miles from Venus
traveling at a heliocentric velocity of 82,650 miles per hour. The
spacecraft continues at a steady 3.15 rpm in a cruise mode-dual spin.
Round trip light time is 13 minutes, 28 seconds.

     Three SITURNS to lead the sun were successfully performed on March 26,
28, and 30.  Spacecraft performance for these activities was as expected
and without incident.

     The Venus-Earth (VE-2) sequence load went active as planned on March 26.
This sequence controls spacecraft activities to April 23 and contains 12
SITURNS, 1 Retropropulsion Module (RPM) flushing event, several cruise
science memory readouts (MROs) for the Magnetometer (MAG), Extreme
Ultraviolet instrument (EUV), and Dust Detector Subsytem (DDS). During early
April, from April 9 through April 12, time windows have been established for
the planned TCM-4A (Trajectory Course Maneuver).

     Commands were sent on March 28 to reconfigure the Command and Data
Subsytem (CDS) and Telemetry Modulation Unit (TMU) for 40 bps coded telemetry
data transmission.  The data rate switch from 10 bps to 40 bps was
accomplished without incident and involved commanding the CDS spun critical
controllers to route the generated 40 bps data stream to the TMUs.  TMU
commands were sent to reset the telemetry modulation index value to a level
compatible with the 40 bps data rate.  Subsequent to the data rate switch,
telemetry link performance was as expected and near predicted levels.

     A massive power failure for about 5 hours occurred at the Signal
Processing Center (SPC-40) in Canberra, Australia, on March 28.  The power
loss resulted in the loss of planned cruise science MRO data reception from
MAG, EUV and DDS instruments.  Later that same day, a planned SITURN was
performed from the VE-2 stored sequence without flight team monitoring since
the 70 meter antenna (DSS-43) was still down.  Upon resumption of DSS-43
tracking coverage, later that day, telemetry data indicated that the
spacecraft executed the SITURN properly and that spacecraft performance was
as expected and without incident.  Science Team members pointed out that
nearly all DDS and MAG science data collected for the last three weeks was
still retrievable if a real time MRO could be performed on March 29.  To
assess the risk of doing a MRO, a careful review of the VE-2 scheduled
spacecraft activities was performed; the risk was found to be acceptable and
the MROs were successfully completed.

     When the power failure occurred, the station immediately switched to
generator power but was unable to properly configure any links due to damage
to the Network Configuration Facility and other interface related problems.
It was reported that the power outage was due to a failure in a 22 kv
commercial power distribution transformer.  During this power failure voice
communication with the station was available.

     The Energetic Particles Detector (EPD) instrument was powered again on
March 29, the first time since the Venus flyby, in preparation for planned
motor maintenance activities.  Prior to instrument turn on, however, Delay
Action Commands (DACs) were transmitted on March 28 to reset the EPD input
current threshold limit to a level consistent with expected instrument
operation in order to preclude science safing system fault protection
execution.

     The AC/DC bus voltage imbalance measurements have fluctuated slightly.
The DC measurement has ranged between 20.9 and 21.62 volts; the AC measurement
has ranged between 47.8 and 48.7 volts.  All other power-related measurements
(bus voltages, bus currents and shunt currents) and  other subsystem
measurements have all been as expected.

     Impact to both TCM-4A and TCM-4B has been eliminated in the current
version of the Deep Space Network (DSN) schedule for elevation bearing rework
throughout the DSN network.  Although this schedule is contingent on
satisfactory bearing conditions at DSS-43 and DSS-63 (70 meter antennas at
Australia and Spain, respectively) following their inspections, it will allow
work to proceed on the basis of what is known at present and relieves the
immediate concern for Galileo.

     New software for the DSN Telemetry Processor Assembly (TPA) that provides
consistent telemetry time tagging between different support configurations went
into "soak" on March 29th and is now being used for Galileo support.

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

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

Date: 30 Mar 90 11:33:34 GMT
From: shelby!csli![e-mail]  (John Kallen)
Subject: Galileo Updates

Are the Galileo Updates archived? If so, are they accessible by anonymous
FTP? I'm interested in tracking the probe given the data provided by
Yee and Balke (btw, thank you for keeping us in touch with the status
of the probe)
_______________________________________________________________________________
 | |   |   |    |\ | |   /|\ | John K{llen           Computer: kom-pyu'-t:r (n)
 | |\ \|/ \|  * |/ | |/|  |  | PoBox 11215            device to speed and
 | |\ /|\  |\ * |\ |   |  |  | Stanford CA 94309      automate errors.
_|_|___|___|____|_\|___|__|__|[e-mail]__________________________

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

Date: 29 Mar 90 14:25:28 GMT
From: att!tsdiag![e-mail]  (Dave Tiller N2KAU)
Subject: Re: "Brilliant Pebbles" vs. "Smart Rocks" (was Re: Railgun ...)

In article <[e-mail]> [e-mail] (John F Nixon) writes:
[e-mail] (Mike Pelletier) writes:
->Whence this silly nomenclature "Brilliant Pebbles"?
-
->Whatever happened to the succinct, professional sounding "Smart Rocks"?
-
-Actually, I am proposing "Savant Sand" as an SDI weapon....
[e-mail]                    ...steinmetz!atl.decnet!jnxion

How about:

    -Intelligent Igneous
    -Loquatious Limestone
    -Precocious Perovskovites
    -Brainy Boulders
    -Cerebral Coral

Any more?
--
David E. Tiller         [e-mail]  | Concurrent Computer Corp.
FAX:  [phone]      Ph: [phone] (w) | 2 Crescent Place, M/S 117
UUCP: ucbvax!rutgers!petsd!tsdiag!davet        | Oceanport NJ, 07757
ICBM: 40 16' 52" N      73 59' 00" W           | N2KAU @ NN2Z

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

Date: 23 Mar 90 02:51:48 GMT
From: munnari.oz.au!csc!ccadfa!usage!metro![e-mail]  (Robert Minard)
Subject: Re: SUSI (Was Re: Austrailian Reduced Wobble telescope)

From article <[e-mail]>, by [e-mail]:
>
>         Awhile back on the Discovery Channel, I saw a piece on these guys
> down under at one of the universities that had crafted an optical telescope
> that had the capability to adjust for the wobble of stars due to the air.

Sounds like you're talking about us!

The Chatterton Astronomy Department of the University of Sydney has
built a prototype of one such instrument and is completing
a full scale version called SUSI (Sydney University Stellar Interferometer)
this year.

The instruments are optical interferometers formed by
combining the light from two computer-controlled plane mirrors
at either end of a "baseline".  The mirrors are called "siderostats" because
they reflect starlight towards the centre of the baseline, where the
two beams are combined in a maze of mirrors, periscopes and beamsplitters.

Two of these mirrors are piezoelectrically driven to compensate for
the small rapid (~10 ms) wavefront tilts introduced by the atmosphere.
The tilts are measured by splitting off some of the light and focusing it
onto position detectors each containing four photomultiplier tubes.

Another important aspect of the combination process is that the distances
travelled by the two beams are adjusted dynamically so that they travel
roughly equal distances (to within a few wavelengths) before
being combined.

When the wavefronts are parallel they are allowed to interfere and the strength
of the interference (the "visibility") is measured.   This measurement
allows us to determine the angular diameter of the star.

The prototype first measured visibility on 1 October 1985 and the
angular diameter of Sirius was measured during February/March 1986
as 5.63 +/- 0.08 marcsec confirming a result obtained by the
Narrabri Intensity Interferometer (that's another story) but
requiring substantially less observing time.  The result was published
in Nature ("New determination of the angular diameter of Sirius",
J. Davis and W.J. Tango, Nature 323, pages 234-235).

The specifications of the prototype and SUSI are as follows:

            prototype        SUSI

baseline:        11.4 m            5 to 640 m
wavelengths:        442 nm            400 to 900 nm
angular resolution:    8 marcsec        .05 to 15 marcsec
siderostat diameter:    100 mm            140 mm

Note:    marcsec = milli arcsec = 5 x 10^-9 rad

The angular resolution is a function of the baseline length, and is the
same as for a conventional telescope  with a diameter equal to the
baseline (can you imagine a telescope 640 m in diameter?).  The
downside is that we don't form images of the star, we only obtain its
visibility and because our input aperture is so small we don't have
anything like the sensitivity of large telescopes.  However
no other optical instrument being constructed has such resolution and
similar resolution at radio wavelength cannot be achieved by ground-based
antennas because the diameter of the earth does not provide a long enough
baseline.
--
Robert Minard                      Telephone: [phone]
Chatterton Astronomy Department,          Facsimile: [phone]
School of Physics A28,                  Telex: AA 26169 UNISYD
University of Sydney, NSW 2006, AUSTRALIA.    ACSnet: [e-mail]

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

Date: 30 Mar 90 22:05:30 GMT
From: skipper![e-mail]  (Al Bowers)
Subject: Re: Ejection seats

In article <[e-mail]> [e-mail] (John Roberts) writes:

>>Subject: Hermes crew escape system

>> For the European Hermes spaceplane it was decided (according to newspaper
>> reports) to buy the russian ejection seats developed for Buran.
>> The ejection seats will enable the crew to eject during the first 90 seconds
>> of the flight, placing them 500 m away from Hermes in 2 seconds.
>> Ejection will be possible up to 30 km altitude and a velocity of
>> 3000 km/h.

>That's a pretty abrupt trip! Are US ejection seats comparable? What's the peak
>acceleration? (It would have to be 25g minimum, probably greater.)

>I presume the crew are ejected head first, in a sitting position. Higher
>accelerations have been employed in a rocket sled, but I don't think the
>force was applied in this direction.

Your 25g estimate is in the ballpark.  Older seats generated up to 40g
and had consequent higher injury rates.  The Ari Force publishes their
ejection seat statistics every year and two years ago the sucessful
ejection rate was ~85% or so.  Another 10% or so caused some
debilitating injury such that the pilot was not flight capable within
a month.  The remaining were fatalities.  These stats were only for
seats used within the envelope prescribed for them.  There was one
freak accident in which an F-16 jock on an FCF (functional check
flight) out over water ejected at the edge of the envelope.  About
10000 ft msl, 700 knots (just supersonic), the seat was specified for
subsonic below 10000 ft.  During the ejection the pilot broke both
arms and collar bones.  Chute deploy worked fine, unfortunately the
pilot was unable to inflat his life vest and drowned.

--
Albion H. Bowers  [e-mail]  ames!elxsi.dfrf.nasa.gov!bowers
         NASA Ames-Dryden Flight Research Facility, Edwards, CA
                  Aerodynamics: The ONLY way to fly!

                     Live to ski, ski to live...

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

Date: 30 Mar 90 02:13:15 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Solar Cells

Since the "31% efficient" GaAs photovoltaics are really two distinct
layers of cells with complementary spectrum coverage, I would first
check the WEIGHT vis a vis current technology.  Understand that this is
much more efficient per surface area, but how much weight do we save.
--
"UNIX should be used          ::   Tom Neff <[e-mail]> or
 as an adjective." -- AT&T   ::    ...uunet!bfmny0!tneff (UUCP only)

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

End of SPACE Digest V11 #205
*******************