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Дата: 27 апреля 1998 (1998-04-27) От: Alexander Bondugin Тема: Mars Surveyor 98 Update - April 24, 1998 Привет всем! Вот, свалилось из Internet... 1998 MARS SURVEYOR PROJECT STATUS REPORT April 24, 1998 John McNamee Mars Surveyor 98 Project Manager The Pressure Modulator Infrared Radiometer (PMIRR) instrument failed to operate properly during orbiter solar thermal vacuum (STV) testing. A part failure in the 15V PMIRR power supply is the suspected cause. All other objectives of the orbiter thermal vacuum test were accomplished successfully. The plan is to break vacuum on Friday, April 24, troubleshoot the cause of the failure over the weekend, and reestablish vacuum conditions on Monday, April 27, if the team is confident the root cause of the failure has been diagnosed and fixed. Lander integration and test activities are proceeding on schedule with no significant problems. ElectroMagnetic Interference/Compatibility (EMI/EMC) testing of the lander spacecraft was completed successfully. For more information on the Mars Surveyor 98 mission, please visit this website: http://mars.jpl.nasa.gov/msp98/ Hа сегодня все, пока! =SANA=

Дата: 27 апреля 1998 (1998-04-27) От: Alexander Bondugin Тема: Third MGS Image Of Cydonia Region, Viking 1 Landing Site Available Привет всем! Вот, свалилось из Internet... The third image of the Cydonia Region taken by the Mars Global Surveyor spacecraft is now available on the MGS website: http://mars.jpl.nasa.gov/mgs/target/CYD3/index.html This is the raw image. Processed images will be available later today at the same site. Also available is an MGS image of the Viking 1 landing site: http://mars.jpl.nasa.gov/mgs/msss/camera/images/4_23_98_vl1_stereo_release/ind ex.html Captions to both images are appended below. Ron Baalke RAW IMAGE POSTED - April 24, 1998 10:00 AM Pacific Daylight Savings Time CYDONIA OBSERVATION #3 PHOTO CAPTION Orbit: 258 Range: 409.53 km Resolution: 3.46 m/pixel Image dimensions: 1024 X 9600 pixels, 3.5 km x 33.2 km Line time: 0.50 msec Emission angle: 29.90 degrees Incidence angle: 69.59 degrees Phase angle: 60.62 degrees Scan rate: ~0.15 degree/sec Start time: periapsis + 410 sec Sequence submitted to JPL: Wed 04/22/98 21:45:00 PDT Image acquired by MOC: Thu 04/23/98 12:23:02 PDT Data retrieved from JPL: Fri 04/24/98 09:00 PDT MOC Acquires High Resolution Stereoscopic Images of Viking One Landing Site Mars Global Surveyor Mars Orbiter Camera Release: MOC2-44A, -44B Mars Global Surveyor Mars Orbiter Camera Image ID: 577659262.25403 P254-03 (partial) 576862349.23503 P235-03 (partial) See also: Viking One Landing site (A)[Image] (B)[Image] (A) Viking Orbiter 1 027A63, showing outline of area including Viking Lander 1 location covered by stereoscopic images (B) Stereoscopic portions of MOC images 25403 (red) and 23503 (blue,green) reproduced at a scale of 7.5 meters/pixel (JPG = 676 KBytes) CAPTION Two MOC images of the vicinity of the Viking Lander 1 (MOC 23503 and 25403), acquired separately on 12 April 1998 at 08:32 PDT and 21 April 1998 at 13:54 PDT (respectively), are combined here in a stereoscopic anaglyph. The more recent, slightly better quality image is in the red channel, while the earlier image is shown in the blue and green channels. Only the overlap portion of the images is included in the composite. Image 23503 was taken at a viewing angle of 31.6њ from vertical; 25403 was taken at an angle of 22.4њ, for a difference of 9.4њ. Although this is not as large a difference as is typically used in stereo mapping, it is sufficient to provide some indication of relief, at least in locations of high relief. The image shows the raised rims and deep interiors of the larger impact craters in the area (the largest crater is about 650 m/2100 feet across). It shows that the relief on the ridges is very subtle, and that, in general, the Viking landing site is very flat. This result is, of course, expected: the VL-1 site was chosen specifically because it was likely to have low to very low slopes that represented potential hazards to the spacecraft. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO. Hа сегодня все, пока! =SANA=

Дата: 27 апреля 1998 (1998-04-27) От: Alexander Bondugin Тема: Cassini Update - April 24, 1998 Привет всем! Вот, свалилось из Internet... CASSINI SIGNIFICANT EVENTS FOR WEEK ENDING 4/24/98 Spacecraft Status: The Cassini spacecraft is presently traveling at a speed of approximately 136,000 kilometers/hour (~84,000 mph) relative to the sun and has traveled approximately 531 million kilometers (~329 million miles) since launch on October 15, 1997. The Cassini spacecraft has been flying for just over 6 months. Cassini's first planetary gravity assist, a technique used to increase spacecraft velocity, is approaching; the Venus-1 flyby scheduled for early Sunday morning, April 26th. The most recent Spacecraft status is from the DSN tracking pass on Thursday, 04/23, over Goldstone. The Cassini spacecraft is in an excellent state of health and is executing the C7 sequence nominally. Inertial attitude control is being maintained using the spacecraft's hydrazine thrusters (RCS system). The spacecraft continues to fly in a High Gain Antenna-to-Sun attitude. It will maintain the HGA-to-Sun attitude, except for planned trajectory correction maneuvers, for the first 14 months of flight. Communication with Earth during early cruise is via one of the spacecraft's two low-gain antennas; the antenna selected depends on the relative geometry of the Sun, Earth and the spacecraft. The downlink telemetry rate is presently 40 bps. Spacecraft Activity Summary: On Friday, 04/17, the third Periodic Instrument Maintenance activity (PIM) completed execution, as planned. This activity is carried out every three months by 11 of the 12 Orbiter instruments. All Instrument representatives reported successful completion of their PIM activities. Also on Friday, the realtime portion of an SSR Flight Software Partition maintenance activity was performed, as planned, completing the activity which had begun on Tuesday, April 14. On Saturday, 4/18, the Attitude and Articulation Control Subsystem's (AACS's) active vector was updated as part of the preparations for the upcoming Venus-1 gravity assist flyby. On Sunday, 04/19, and Monday, 04/20, there were no changes to spacecraft configuration. On Tuesday, 04/21, the Solid State Recorder (SSR) record and playback pointers were reset, according to plan. This housekeeping activity, done approximately weekly, maximizes the amount of time that recorded engineering data is available for playback to the ground should an anomaly occur on the spacecraft. On Wednesday, 04/22, the RPWS/RADAR minisequences for execution and playback were uplinked to the spacecraft. The RPWS activity is one which will search for lightning in the atmosphere of Venus using the Radio and Plasma Wave Scienceinstrument. The RADAR activity is an engineering test to verify the ability of the Cassini RADAR instrument to detect a signal reflected back from a target body (the surface of Venus). The data collection minisequence's activities will be carried out on Sunday, April 26 around the Venus closest approach point. The results of Sunday's activities will be returned to Earth in the playback minisequence, scheduled to occur the following Friday and Saturday nights (May 1 and 2). On Thursday, 04/23, there were no changes to spacecraft configuration. Upcoming events: Activities scheduled for the week of 4/24 - 4/30 include: Venus Flyby (04/25 thru 04/26), with closest approach occurring on Sunday morning (04/26), execution of the RPWS and Radar Venus activities (04/26), Pre-TCM 4 Memory Read Out of Mass Properties (04/27), SSR FSW Partition Maintenance (04/28), and an SSR Pointer Reset (04/30). Additionally, the first Solar and Earth Occultationswill occur (04/26). DSN Coverage: Over the past week Cassini had 10 scheduled DSN tracks occurring from 04/10 through 4/16. In the coming week there will be 16 DSN passes. Hа сегодня все, пока! =SANA=

Дата: 27 апреля 1998 (1998-04-27) От: Alexander Bondugin Тема: Lunar Prospector Update - April 24, 1998 Привет всем! Вот, свалилось из Internet... Lunar Prospector Status Report #29 April 24, 1998 - 1:00 p.m. EST (10:00 a.m. PST) The Lunar Prospector spacecraft continues to perform very well. A recent increase in solar activity has been associated with an increase in particle counts from the Alpha Particle Spectrometer (APS) over the last couple of weeks. This effect will be compensated for in the course of the ongoing data analysis. Current spacecraft state (00:00 4/23/98 GMT): Orbit: 1225 Downlink: 3600 bps Spin Rate: 11.96 rpm Spin Axis Attitude (ecliptic): Latitude: 83.2 deg Longitude: 94 deg Trajectory: Periselene Alt: 81.8 km Aposelene Alt: 118 km Period: 118 minutes Occultations: 46 minutes Eclipses: 46 minutes An attitude reorientation maneuver is scheduled for Monday, 4/27, with a maneuver test pulse firing scheduled for Friday, 4/24. Lisa Chu Thielbar Lunar Prospector Mission Office NASA Ames Research Center Moffett Field, Calif. 94035 Hа сегодня все, пока! =SANA=

Дата: 27 апреля 1998 (1998-04-27) От: Alexander Bondugin Тема: Physics News Update - April 23, 1998 Привет всем! Вот, свалилось из Internet... PHYSICS NEWS UPDATE The American Institute of Physics Bulletin of Physics News Number 368 April 23, 1998 by Phillip F. Schewe and Ben Stein THE STRONGEST GRAVITATIONAL FIELDS EVER MEASURED, corresponding to a spacetime warping of 30%, have been recorded by scientists using the Rossi X-Ray Timing Explorer (RXTE) satellite. By comparison, the proportional curvature of space is 100% at a black hole, but only about one part in a million near the sun's surface and one part per billion near the Earth's surface. RXTE was designed to monitor (over microsecond time intervals) the x rays coming from binary star systems in which matter from a conventional star is siphoned off into an accretion disk surrounding a nearby neutron star or black hole. In about 16 binary-star systems that contain neutron stars, blobs of gas in the disk are thought to spiral in toward the neutron star, picking up speed before they make a final plunge onto the surface. The x rays produced in this process are regularly dimmed when the hot gas is on the far side of the star. This leads to quasi-periodic oscillations (QPOs) in the x-ray brightness of the star. Also notable is the fact that the brightness variations only occur at certain well-defined rates, "pure tones" corresponding to special orbital periods for the gas going around the star. The spacetime encountered by the gas is so highly warped because the gas is able to skim within a few km of the neutron star, which itself is only about 10 km in diameter. At this week's meeting of the American Physical Society in Columbus, Ohio, Frederick Lamb of the University of Illinois (217-333-6363, f-lamb@uiuc.edu) described how the observed variations in the x-ray brightness can be used to deduce properties of the neutron star, such as its mass and size. At a press conference, Lamb and William Zhang of NASA Goddard concentrated on the binary-star system 4U1820-30, about 20,000 light years from Earth. The neutron star has a mass of 2.3 solar masses and orbits its companion star in only 11 minutes. Close observations of this system confirm a prediction made by Lamb and his colleagues Coleman Miller and Dimitrios Psaltis that the gas blobs would continue to spiral inward until they reached an "innermost stable orbit," where they would orbit before making the dive for the surface. This is a purely general relativistic (GR) effect; in Newton's mechanics, by contrast, the blob could have gotten arbitrarily close to the surface, providing it were going fast enough. The observations by Zhang and his collaborators now confirm Lamb's prediction, thus opening up a new "strong-gravitational field" era in GR studies. The measurements of the gas motion even provide hints as to the nature of the strong nuclear force sustaining the neutron star against further gravitational collapse. The new evidence indicates that the nuclear force is stiffer and more repulsive than has generally been thought. PLANETARY SYSTEMS IN THE MAKING have been discovered in the form of tenuous dust disks surrounding several more stars. Astronomers believe that our own solar system evolved out of such a disk of material left over after the formation of the sun. Previously a disk like this had been found around the star Beta Pictoris. Now a report in Nature (23 April) reveals disks around two more stars, Formalhut and Vega. Yet another, around the star HR4796A, was announced at a NASA press conference on 21 April. Formalhut's disk even has a dust-free inner zone which one would have expected if rocky planets formed there had swept all such material for their own use. The observations are possible because of new infrared detectors sensitive to the radiation emitted by the relatively cool dust. PHYSICAL REVIEW FOCUS is a new weekly online summary of selected recent or forthcoming articles in Physical Review Letters. (Physics News Update does this too, but Focus looks at articles in more depth.) The summaries are available on the American Physical Society website at this address: publish.aps.org/FOCUS? Hа сегодня все, пока! =SANA=

Дата: 27 апреля 1998 (1998-04-27) От: Alexander Bondugin Тема: Sky & Telescope News Bulletin - April 24, 1998 Привет всем! Вот, свалилось из Internet... SKY & TELESCOPE'S NEWS BULLETIN APRIL 24, 1998 HST ANNIVERSARY The Space Telescope Science Institute marked the eighth year of revolutionary astronomical data from the Hubble Space Telescope on April 17th by releasing an infrared image of Saturn taken earlier in the year by Erich Karkoschka (University of Arizona). The false-color view from Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) reveals details about the various cloud layers and hazes in Saturn's atmosphere. CASSINI PASSING VENUS After six months in space, the Saturn-bound Cassini spacecraft will have its first planetary encounter April 26th when it makes a pass over Venus at an altitude of 284 km. The planet's gravity will give the spacecraft a 26,280-kilometer-per-hour boost in speed. Launched last October, Cassini and the Huygens Titan probe, supplied by the European Space Agency, still have a long way to go before reaching the ringed planet. The spacecraft will make three more gravity-assist flybys -- a second pass by Venus, then one by the Earth, and then one by Jupiter -- before arriving at Saturn in 2004. SIGNS OF EXTRASOLAR PLANETARY SYSTEM Astronomers have found what they believe is a "missing link" for understanding the formation of planets around stars. Two teams of researchers noticed that the star HR 4796 in Centaurus is surrounded by a disk of material. Michael Werner, David Koerner, and Michael Ressler (Jet Propulsion Laboratory) and Dana Backman (Franklin and Marshall College) used the 10-meter Keck II Telescope atop Mauna Kea, Hawaii. Ray Jayawardhana (Harvard-Smithsonian Center for Astrophysics) and Charles Telesco (University of Florida) made their observations from Cerro Tololo in Chile. Although other stars are known to sport rings of dust -- which hint at planetary systems -- these new observations reveal that HR 4796 has a gap in the disk immediately next to the star. The absence of material strongly suggests that forming planets have swept this region clean. The cleared area has a diameter of about 100 astronomical units, slightly larger than our own solar system. FIRST VLT MIRROR INSTALLED The European Southern Observatory's Very Large Telescope took another important step toward completion on April 17th. The first of the 8.2-meter- wide mirrors was mounted in one of the four telescope structures atop Cerro Paranal in Chile. "First light" for the telescope is expected by the end of May. SUDBURY NEUTRINO OBSERVATORY GRAND OPENING Another observatory BELOW ground is nearly complete. The Sudbury Neutrino Observatory, located 2 kilometers beneath Sudbury, Ontario, will hold its inauguration ceremonies on April 28-29. The detector, designed to see neutrinos produced by the Sun's fusion reactions, uses 1,000 metric tons of heavy water in a 12-meter-diameter acrylic vessel. Distinguished guests for the subterranean festivities include Stephen Hawking, John Bahcall, and Nobel laureate Bertram Brockhouse. If you didn't get your invitation, you can still participate by watching the events live on the Internet. BOWER AWARDS On April 30th, Sir Martin Rees, Great Britain's Astronomer Royal, will be honored with the 1998 Bower Award and Prize in Science from Philadelphia's Franklin Institute. The prize of $250,000 is given annually to "a distinguished scientist for outstanding work in the life or physical sciences." The Institute also honored John C. Diebel, founder and chief executive of Meade Instruments Corp., with the Bower Award for Business Leadership. He was cited for "his courage, insight, and leadership of a commercial venture founded on the premise of making astronomy accessible and affordable to the public." The business award carries no cash prize. VENUS AND JUPITER ARE OCCULTED TOGETHER If you were lucky for clear morning skies earlier in the week, you may have witnessed the conjunction of Venus and Jupiter. The pair was joined by the waning crescent Moon on the morning of April 23rd. Even luckier observers in parts of Africa and southern Asia watched as the Moon occulted both Jupiter and Venus. Olivier Staiger journeyed to Ascension Island off the coast of Africa to see the event. According to Jean Meeus, there are 13 double occultations of bright planets between the years 1600 and 2200. (This does not include Uranus, Neptune, and Pluto.) The most recent was of Mars and Jupiter on February 8, 1951. The next will include Mercury and Mars on February 13, 2056. NAME A SPACECRAFT NASA and the Advanced X-ray Astrophysics Facility (AXAF) Science Center are sponsoring a contest to name AXAF, the third of NASA's "Great Observatories." The names Edwin P. Hubble and Arthur H. Compton are associated with AXAF's predecessors, the Hubble Space Telescope and the Compton Gamma Ray Observatory. But officials have yet to christen AXAF, which is currently slated for a December 1998 Space Shuttle launch. The winner will enjoy an expenses-paid trip to see the satellite take off from NASA's Kennedy Space Center. Contest rules are available on the World Wide Web at http://asc.harvard.edu/contest.html, by phone at 617-496-7941, or by writing to AXAF Contest, AXAF Science Center, Office of Education and Public Outreach, 60 Garden St., MS 83, Cambridge, MA 02138. You can also address queries to contest@cfa.harvard.edu by electronic mail. Entries are due by June 30th. THIS WEEK'S "SKY AT A GLANCE" Some daily events in the changing sky, from the editors of SKY & TELESCOPE. APRIL 26 -- SUNDAY * New Moon (exact at 7:41 a.m. EDT). APRIL 27 -- MONDAY * Early Tuesday morning the faint asteroid 1243 Pamela will occult an 8.2-magnitude star in Sagittarius for up to 9 seconds as seen from the central U.S. The occultation should happen around 8:51 Universal Time near the Mississippi Delta (3:51 a.m. Central Daylight Time), and around 8:54 UT in Michigan. See the finder chart in the April Sky & Telescope, page 94, or at http://www.skypub.com/occults/occults.html. APRIL 28 -- TUESDAY * The thin waxing crescent Moon occults the 1st-magnitude star <b style="color:black;background-color:#ffff66">Aldebaran</b> in broad daylight today for much of North America. The Moon will be only 30 degrees east of the Sun, so it may not be easy to find even with a wide-field telescope unless the air is very clear. For a timetable see the January Sky & Telescope, page 97, or http://www.skypub.com/occults/lunocc98.html. * After the Sun sets, <b style="color:black;background-color:#ffff66">Aldebaran</b> can be easily seen shining below or to the lower right of the Moon in the western sky. APRIL 29 -- WEDNESDAY * Early on Thursday morning, the oddly shaped asteroid 216 Kleopatra will occult a 10.8-magnitude star in Scutum for up to 16 seconds. Observers in the Northeast have the best chance to see this event. You may need an 8- or 10-inch telescope to keep the faint star in steady view. Kleopatra displayed a silhouette almost four times longer than wide during a 1991 occultation that was timed by 10 amateurs (see Sky & Telescope for January 1992, page 73), so interest in this event is high. A finder chart is in the April Sky & Telescope, page 94, and at http://www.skypub.com/occults/occults.html. APRIL 30 -- THURSDAY * The crescent Moon shines this evening in the feet of Gemini in the western sky. High above the Moon are Gemini's head stars, Pollux and Castor. A similar distance to the Moon's left is Procyon. MAY 1 -- FRIDAY * This evening the Moon is almost midway between Pollux (to its upper right) and Procyon (to its lower left). MAY 2 -- SATURDAY * Binoculars show the Beehive star cluster, M44 in Cancer, about 5 degrees to the right of the Moon this evening. ============================ THIS WEEK'S PLANET ROUNDUP ============================ MERCURY is barely above the eastern horizon as dawn brightens. It's far to the lower left of Venus and Jupiter. VENUS shines brightly low in the east-southeast during dawn, with Jupiter just to its upper right. Venus is 7 times brighter than Jupiter. They're moving apart by about 1 degree per day. MARS is hidden behind the glare of the Sun. JUPITER appears close to Venus in the east-southeast during dawn; see above. SATURN is hidden behind the glare of the Sun. URANUS and NEPTUNE, magnitudes 6 and 8, respectively, are in Capricornus low in the southeast just before dawn. See the finder chart in the May Sky & Telescope, page 96. PLUTO, magnitude 13.8, is near the Ophiuchus-Scorpius border. It's well up in the southeast by midnight. A finder chart is in the May Sky & Telescope, page 97. (All descriptions that relate to the horizon or zenith are written for the world's midnorthern latitudes. Descriptions that also depend on longitude are for North America. Eastern Daylight Time, EDT, equals Universal Time minus 4 hours.) More details, sky maps, and news of other celestial events appear each month in SKY & TELESCOPE, the essential magazine of astronomy. See our Web site at http://www.skypub.com/. Clear skies! SKY & TELESCOPE, P.O. Box 9111, Belmont, MA 02178 * 617-864-7360 (voice) Copyright 1998 Sky Publishing Corporation. S&T's Weekly News Bulletin and Sky at a Glance stargazing calendar are provided as a service to the astronomical community by the editors of SKY & TELESCOPE magazine. Widespread electronic distribution is encouraged as long as these paragraphs are included. But the text of the bulletin and calendar may not be published in any other form without permission from Sky Publishing (contact permissions@skypub.com or phone 617-864-7360). Illustrated versions, including active links to related Internet resources, are available via SKY Online on the World Wide Web at http://www.skypub.com/. In response to numerous requests, and in cooperation with the Astronomical League (http://www.mcs.net/~bstevens/al/) and the American Association of Amateur Astronomers (http://www.corvus.com/), S&T's Weekly News Bulletin and Sky at a Glance are available via electronic mailing list too. For a free subscription, send e-mail to skyline@gs1.revnet.com and put the word "join" on the first line of the body of the message. To unsubscribe, send e-mail to skyline@gs1.revnet.com and put the word "unjoin" on the first line of the body of the message. SKY &