Return-path: X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl@andrew.cmu.edu (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests) ID ; Sat, 27 Oct 1990 01:47:12 -0400 (EDT) Message-ID: Precedence: junk Reply-To: space+@Andrew.CMU.EDU From: space-request+@Andrew.CMU.EDU To: space+@Andrew.CMU.EDU Date: Sat, 27 Oct 1990 01:46:41 -0400 (EDT) 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 space+@andrew.cmu.edu. Other mail, esp. [un]subscription notices, should be sent to space-request+@andrew.cmu.edu, or, if urgent, to tm2b+@andrew.cmu.edu ---------------------------------------------------------------------- Date: 24 Oct 90 15:55:45 GMT From: mnetor!utzoo!henry@uunet.uu.net (Henry Spencer) Subject: Re: RANGER spacecraft In article <3665@syma.sussex.ac.uk> andy@syma.sussex.ac.uk (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 | henry@zoo.toronto.edu utzoo!henry ------------------------------ Date: Thu, 25 Oct 90 20:35:09 EDT From: John Roberts 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 roberts@cmr.ncsl.nist.gov ------------------------------ Date: 26 Oct 90 00:35:36 GMT From: usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov!baalke@apple.com (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 | baalke@mars.jpl.nasa.gov ___| | | | |__) |/ | | |___ Jet Propulsion Lab | baalke@jems.jpl.nasa.gov /___| | | | ___/ | |/__ /| 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!baalke@ucsd.edu (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 | baalke@mars.jpl.nasa.gov ___| | | | |__) |/ | | |___ Jet Propulsion Lab | baalke@jems.jpl.nasa.gov /___| | | | ___/ | |/__ /| M/S 301-355 | |_____|/ |_|/ |_____|/ Pasadena, CA 91109 | ------------------------------ Date: 25 Oct 90 18:43:20 GMT From: hub.ucsb.edu!ucsbuxa!3001crad@ucsd.edu (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!baalke@ucsd.edu (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 | baalke@mars.jpl.nasa.gov ___| | | | |__) |/ | | |___ Jet Propulsion Lab | baalke@jems.jpl.nasa.gov /___| | | | ___/ | |/__ /| 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!baalke@ucsd.edu (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 | baalke@mars.jpl.nasa.gov ___| | | | |__) |/ | | |___ Jet Propulsion Lab | baalke@jems.jpl.nasa.gov /___| | | | ___/ | |/__ /| M/S 301-355 | |_____|/ |_|/ |_____|/ Pasadena, CA 91109 | ------------------------------ End of SPACE Digest V12 #496 *******************