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Subject: SPACE Digest V12 #496

SPACE Digest                                     Volume 12 : Issue 496

Today's Topics:
            Re: RANGER spacecraft
             HST summary 10/22/90
              Galileo Update - 10/25/90
             Pioneer 11 Update - 10/25/90
           Re: --- Space Station Budget ---
              Magellan Update - 10/25/90
       Hubble to Observer Great White Spot (Forwarded)

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

Date: 24 Oct 90 15:55:45 GMT
From: mnetor!utzoo![e-mail]  (Henry Spencer)
Subject: Re: RANGER spacecraft

In article <[e-mail]> [e-mail] (Andy Clews) writes:
>Also I remember contact was lost with one of the Surveyor craft a couple
>of minutes before it was due to soft-land.  I wonder if it would
>eventually have made a soft-ish landing of its own...

That was Surveyor 4.  Depending on the exact nature of the failure, it may
have made a successful landing.  Surveyor landings were completely automatic,
with no ground control involvement in the late stages.
--
The type syntax for C is essentially   | Henry Spencer at U of Toronto Zoology
unparsable.             --Rob Pike     |  [e-mail]   utzoo!henry

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

Date: Thu, 25 Oct 90 20:35:09 EDT
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: HST summary 10/22/90


HST Update 10/22/90
Dr. Charles Pellerin and Dr. Edward Weiler
NASA Select
Selected details from broadcast

Some of this material seems to be of general interest, and I haven't seen much
of it on the list, so I thought it would be worthwhile to post a summary of
these parts:
..........................................

 - The cause of the spherical aberration seems to have been pretty much pinned
down. Elements in the null corrector (used to calibrate the shape of the
primary mirror) were spaced incorrectly by about 1.3mm. Elaborate measures
were taken to make the placement as accurate as possible, so it was not
suspected that an error of this kind could take place. To attain the ultimate
precision, measurement rods calibrated by the National Bureau of Standards
(now NIST :-) were used, and their position checked by an interferometer
(accurate to a fraction of a wavelength of light). An end cap with a hole in
the center was placed over the end of the measurement rod of interest, to
make sure the calibration was from the exact center of the rod. Unfortunately,
the person making that particular measurement, possibly through haste or
carelessness, got the lateral positioning of the interferometer wrong, and
calibrated from a shiny spot on the end cap, which stuck above the end of the
measurement rod. A comment was made that out of the thousands of people
contributing to HST, this error (and the failure to detect it) was
attributable to about three people working by themselves in an optics lab.
(I suspect those folks don't feel too good right now. :-) While in
retrospect an additional check on the null corrector would have been a good
idea, NASA still does not feel that a final integrated test for HST would have
been advisable, given the time and budgetary constraints, and the risk of
damage or contamination (I agree).

 - A graphic representation of point spread functions (target, actual, and
corrected) was shown.

 - The latest estimate is that 56% of the science that had been planned
for the near term (pre-WFPC2) can be accomplished. Since HST was already
oversubscribed by a factor of 10, now it's only oversubscribed by a factor
of 5. :-)

 - The other major problem is the jitter in the solar arrays. [It was stated
that these were provided by ESA - I hadn't realized that. Perhaps the same
company that designed Galileo's thrusters? :-) ] It is claimed that the
effect of the wobble has been overstated by the press - while the design spec
called for tracking to within the diameter of a dime at the distance from
Washington to New York, the wobble allows HST to track only to within the
diameter of a "Famous Amos" chocolate chip cookie. [No comment on choice of
units.] Most of the pictures released thus far were taken during the calm
periods in the orbit. It is hoped that the software fix (described in postings
by Ron Baalke) will be working in a few months. There are plans to replace
the solar panels in about 3 years, getting rid of the problem.

 - It is expected that WFPC2 will completely correct for the spherical
aberration. Tentative plans are being discussed to improve the performance
of the spectrographs, and perhaps perform an in-orbit repair of the Faint
Object Camera.

 - Because of atmospheric disturbance, the best images that can be obtained
from traditional ground-based telescopes (not using speckle interferometry,
etc.) have a resolution of about 1 arc second. The HST WFPC goal was .1 arcsec,
and it is meeting this target for bright objects. It was supposed to do this
for objects down to 28th magnitude, but because of the need to compensate
for the aberration, it will only work down to about the 25th magnitude, which
is about the limit for ground-based scopes.

 - The Saturn picture was discussed, mostly repeating information given in
newspaper articles. It was mentioned that this is the highest-resolution
image ever made of Saturn from the vicinity of Earth, and that unlike Voyager,
HST can take continuing sequences of pictures to observe long-term weather
patterns. I'm looking forward to the storm pictures.

 - Because of its brightness, it is now felt that Jupiter pictures should get
pretty close to the original expected resolution.

 - Imaging Venus in ultraviolet can record weather patterns.

 - An HST / Faint Object Camera picture of Pluto and Charon is compared to the
best ever taken from the ground. The HST picture clearly has higher resolution,
showing two distinct disks with considerable separation between them. WFPC2
may be able to pick up surface features on Pluto.

 - The target resolution for the Faint Object Camera is .06 arcsec, which it
too seems to be meeting for bright objects. The image of Supernova 1987A
with its circumstellar shell was shown.

 - There are plans to add an infrared telescope to HST in 6-8 years.

 - It was speculated that the Great Observatories will probably be able to
answer the question of whether black holes exist.

 - A detailed study of gravitational lenses such as the Einstein Cross can be
used to "weigh" galaxies, and to determine the relative distance of galaxies
and quasars.
.............................
    John Roberts
    [e-mail]

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

Date: 26 Oct 90 00:35:36 GMT
From: usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 10/25/90


                          GALILEO STATUS REPORT
                             October 25, 1990

     As of noon (PDT) Thursday, October 25, 1990, the Galileo spacecraft is
23,571,050 miles from the Earth and traveling at a heliocentric speed of
55,370 miles per hour; distance to the Sun is 109,203,570 miles (1.13 AU).
Round trip light time is 4 minutes, 19 seconds.

     Periodic radio receiver automatic gain control and tracking loop
capacitor tests were performed on October 19.  These tests provide continuing
trend data to characterize the receiver performance.

     The VE-9 (Venus-Earth-9) sequence stored on-board the spacecraft went
active as planned on October 22.

     A NO-OP command was sent on October 22 to reset the Command Loss Timer to
216 hours, the planned value for this mission phase.

     Six delta DOR (Differential One-way Ranging) navigation activities were
performed this week.  All were successful except for a single North/South pass
using the 70 meter antennas in Goldstone and Australia on October 22.  This
delta DOR was lost due to a hardware failure in Australia.  The delta
activities on October 21 and 25 included both North/South and East/West passes
using different combination of antennas from Goldstone/Spain/Australia. A
total of 13 of the planned 27 delta DOR activities are complete; 10 were
successful.

     A cruise science memory readout was successfully performed for the MAG
(Magnetometer) instrument on October 22.

     Commands were sent on October 24 to update the star scanner threshold
level in preparation for the planned star scanner intensity calibration later
that day.  The current threshold setting would allow collecting unwanted
intensity data from several dimmer stars and Jupiter.  This updated threshold
level guarantees collecting data from the intended stars.  In addition to
this calibration, other AACS (Attitude and Articulation Control Subsystem)
calibration data was collected for gyro drift, SBA (Spin Bearing Assembly) drag
torque and wobble; all data was collected successfully.

     The AC bus imbalance measurement exhibited minor activity fluctuating
1-2 DN and is stable near 48.4 volts.  The DC measurement by contrast dropped
60 DN from 17.5 volts down to 10.5 volts and then gradually increased to 12
volts. The 60 DN drop occurred during a period of no spacecraft activity.  All
other power-related and subsystem telemetry measurements are normal.

     The INS electronics was powered on and the Bay C/D heaters were turned
off on October 24. The INS electronics will normally remained powered (gyro
rotors off but activated for required inertial mode operation) to further
reduce the temperature excursions of Bay A CDS (Command Data Subsystem)
electronics.

     The first combined GDS/MRT (Ground Data Systems/Mission Readiness Test)
for Earth 1 was successfully completed Tuesday, October 24, with the Goldstone
Signal Processing Center.  Real time command and telemetry functions required
for Earth 1 support were demonstrated.  In addition magnetic tapes were
generated and provided to MIPL (Multimission Image Processing Lab) and DRS
(Data Records Subsystem) for interface validation.

     The Galileo Gravity Wave tests at the Goldstone 34 meter station were
completed on October 18 and 19.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 25 Oct 90 15:12:24 GMT
From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Pioneer 11 Update - 10/25/90


                            Pioneer 11 Update
                            October 25, 1990

     Pioneer 11 emergency continues, but things are starting to look much
better.  Apparently, the High Gain Antenna was slightly off Earth point
which was causing the communications problem for the past couple weeks.
Yesterday, the 70 meter antenna in Spain maintained telemetry throughout its
tracking pass.  The project at Ames Research Center reported all data was
usable. The average AGC (Automatic Gain Control) was -169.0 dbm with a SNR
(Signal-to-Noise Ratio) of 3.8 db.

     Early this morning the 70 meter antenna in Australia provided a command
pass support with 150 kw.  A total of 20 commands were transmitted.  Ames
reported that all 3415 block of telemetry received back was usable except
for one frame.  The average AGC was -166.8 dbm, SNR 3.5 db.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 25 Oct 90 18:43:20 GMT
From: hub.ucsb.edu!ucsbuxa![e-mail]  (Charles Frank Radley)
Subject: Re: --- Space Station Budget ---




+    o NASA should consider the possibility of an incremental
+      approach to Space Station:
+
+      ---begin man-tended capability
+      ---followed by manned capability
+      ---conclude with permanently manned capability

Why is congress telling us to do something we are already doing
as if it is a fantastic new idea ?
The schedule on my office wall, dated 27 March 1990 shows the
following:

      First element launch       3/95
      Man tended capability      11/95
      Permanent manned capability  1/97

What is meant by "manned capability" as opposed to  MTC or PMC ?

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

Date: 25 Oct 90 20:27:26 GMT
From: sdd.hp.com!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Magellan Update - 10/25/90


                     MAGELLAN STATUS REPORT
                        October 25, 1990

     The Magellan spacecraft continues to map Venus and has
completed its 295th mapping orbit. The sun-Earth-Magellan angle
is now down to 2.3 degrees as Venus and Earth enter superior
conjunction.

     At a meeting yesterdayit was decided to continue mapping
despite degraded communications caused by the sun's position
nearly between the two planets, difficulty in achieving the
required navigation precision and the spacecraft oscillations.
The oscillations are caused by a difference in commands to the
solar arrays by the sun sensors and the gyro.

     Based on the better-than-expected performance of the S-band
communications during the approach to superior conjunction, the
project decided to switch to the 1200 bits per second engineering
telemetry one week earlier than had been planned when the planets
come out of superior conjunction in November.

     Thirteen new image swaths were processed yesterday, bringing
to 193 the number of full resolution image swaths. The switch to
tape recorder track 4 from track 2 has greatly reduced the
problem of bad data frames.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 25 Oct 90 20:33:12 GMT
From: sdd.hp.com!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Hubble to Observer Great White Spot (Forwarded)

HUBBLE TO OBSERVE SATURN'S GREAT WHITE SPOT

     NASA's Hubble Space Telescope (HST) is now scheduled to
observe Saturn's newly discovered white spot in early November.
The "Great White Spot," now termed the "Wilber Spot" after
amateur astronomer Steuart Wilber from Las Cruces, N.M., was
discovered September 24.

     According to the Central Bureau for Astronomical Telegrams,
the Wilber Spot was over 10,000 miles across, larger than the
Earth, on October 1.  Twenty-one hours later it had grown an
additional 2,000 miles.  Currently, the spot has a diameter of
over 50,000 miles, is larger than the famous "Great Red Spot" on
Jupiter and covers much of one hemisphere of Saturn.

     Also in the last few weeks, the spot has become even more
complex.  New spots have been seen within the main feature and
two separate white, round spots have formed.  One side of the
main spot seems darkened, as if the Wilber Spot is a raised
feature casting a shadow.

     Dan Green of the International Astronomical Union's Central
Bureau for Astronomical Telegrams, Cambridge, Mass., has said
that the Wilber Spot seems "almost fluorescent" in appearance.

     In 1933, astronomers reported a phenomenon similar to the
present disturbance.  Since that time, no other Saturnian event
has approached this magnitude.  As seen from Earth, Saturn is in
the evening sky and sets before midnight in late October.

     HST's Wide Field Planetary Camera will record several images
per orbit, for two orbits per day, on 3 days.  The images will be
recorded in two colors, blue and near infrared.

     Observing times have been chosen with considerable care
because Saturn rotates rapdily  -  a "day" on Saturn lasts about
10 hours.  An added complication is that, over time, the angle
between Saturn and the Sun, from HST, is becoming smaller, making
observations progressively more difficult.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

End of SPACE Digest V12 #496
*******************