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By Daniel Fischer Every page present in Europe & the U.S.!
| Ahead | Awards 
The latest issue!
| An experimental German companion. Current mission news: MGS (latest pictures!) + Cassini + Galileo + NEAR |
on a special TV channel for the SRTM (see below)! It's on DFS-2 Kopernikus, 28.5 deg. East, 11.595 GHz V, in analog PAL, with audio at 7.02 MHz and 6.65 MHz. There will be daily half-hour programs starting at 14:30 UTC: details!
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Endeavour up, mast out, radar onEver since Endeavour's slightly delayed liftoff into perfect Florida skies at 17:44 UTC on Feb. 11th, the Shuttle Radar Topography Mission is proceeding like clockwork: The 60 meter mast with the 2nd radar receiver antenna extended just as planned, in just 17 minutes - the longest rigid structure ever deployed in orbit. And the radar has already started its 9 days of intense Earth mapping - with scientists still fighting for a 10th day that was originally in the timeline but dropped recently to get a contingency day for retrieval of the mast. Only if the mission progresses extremely smoothly and enough resources remain, NASA might be willing to add a tenth day of radar operations.
SRTM countdown ticks on as struggle over data rights loomsOn February 10th everything is looking just perfect: NASA is working no more technical issues with either Endeavour and its payload, and the weather forecast for the 11th now stands at 90% for a go. Meanwhile, however, the situation regarding the access of civilian scientists to the expected bonanza of Earth radar data has become quite confusing. The Shuttle Radar Topography Mission is largely paid for by the U.S. military, and the National Imagery and Mapping Agency (NIMA) is the owner of the data and the Digital Terrain Models (DTMs) of most of the world that will be generated from them. Several sources report that there will be a kind of three-class system for access to those DTMs:
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Astro-E burns up after rocket's first stage failsA month after a flurry of Chandra results were presented (see Update #167 first stories) and less than 24 hours after XMM-Newton's first results were celebrated (see last Update lead story), X-ray astronomers have to mourn the loss of the Japanese Astro-E satellite (see Update # 172 story 4) that would have completed an unprecedented trio of complementary observatories: The $105 million satellite did not reach a proper orbit and has probably already burned up in the atmosphere. After two 24-hour delays the M-5 booster had finally lifted up at 01:30 UTC on Feb. 10th from the Kagoshima Space Center, located on the southern tip of the Japanese island of Kyushu.But then the $62 million M-5 rocket obviously suffered a control system breakdown during the first stage of flight - according to early reports graphite on the rocket's nozzle appeared to have fallen off about 40 seconds after launch. The nozzle failure allowed the M-5 to lose its proper orientation during launch. That meant the rocket could not gain enough velocity to place Astro-E into the correct orbit around Earth. The later two stages of the rocket then tried to correct the problem but failed, leaving Astro-E in a far lower than intended orbit, probably taking it only half-way around the Earth. The U.S. astronomers involved in the mission initially thought the launch had been successful. "We broke out the champagne, literally," says one. But they were a little puzzled about why they weren't getting info through the usual sources. It was only an hour later before they knew that there was a problem - because Astro-E did not make contact with a tracking station 90 minutes after liftoff. Astro-E has never been heard from since launch, despite many subsequent attempts to contact it: The botched launch seems to have left it in an orbit 400 by only 80 km high which would have put the satellite on a trajectory straight back into the atmosphere. The Japanese prime minister has already called for an investigation into this latest of several space disasters. |
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Proton flies again, as Zvezda launch is set for JulyThe first Proton rocket since the accident in October (see Update # 154) has carried an Indonesian TV satellite into a perfect orbit on Feb. 12th, one day after a U.S.-Russian conference in Moscow had settled on the July 8...14 window for the launch of the Zvezda ISS module. There has to be yet another successful Proton launch, though, before the valuable module is allowed to fly on the rocket. Meanwhile the independent American Aerospace Safety Advisory Panel has warned that NASA's race to become "faster, better and cheaper" has left its human spaceflight team too small and too inexperienced to safely cope with the high rate of shuttle flights that will be needed to build the ISS... |
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What we know about ErosWhen the first attempt to get into an orbit failed in December 1998, the NEAR science team could at least reprogram the spacecraft to make some scientific observations during the fly-by - to learn more about the famous Near Earth Asteroid as such and to understand its size, mass and gravity field for better orbital maneuvers in the future. In all 222 images were obtained, covering slightly more than 2/3 of Eros, with a resolution approaching 400 meters in some locations.Eros turned out to be an elongated, cratered body with a linear feature extending for at least 20 kilometers as well as 5 large craters up to 8 km in size - about as big as physically possible on a body with a size of 33 x 13 x 13 kilometers. During the fly-by the trajectory of NEAR was changed by the gravity field of Eros just enough to be measurable: A mass of 7 +/- 2 x 10^12 metric tons could be calculated from all radio and optical tracking data which, together with the volume estimate from the images, yields an average density of 2.5 +/- 0.8 g/cm^3. This is similiar to the bulk density of asteroid 243 Ida and suggests a similar interior structure or composition (Eros and Ida both belong to the asteroidal spectral class S). Small bodies such as Eros are either fragments from a collision or 'rubble piles' of discrete fragments: The presence of the long linear feature (of unclear nature) favors the former model, i.e. that Eros is structurally homogeneous. Also its crater density is between the low value of Gaspra and the saturated surface of Ida, which would make Eros rather young: Its parent bodies disrupted only recently. But there is also the possibility that Eros' "crater clock" has been reset during a recent impact that made one of the large craters and obliterated all smaller ones: The expected hi-res images from NEAR should provide clearer answers. (Yeomans & al./Veverka & al., Science of July 23rd, 1999, p. 560-564) |
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| Cassini's pictures of 2685 Masursky (see Update # 171 small stuff) don't resolve the asteroid's body but have scientific value nonetheless: "Its reflectivity indicates that it may not, in fact, be an S-type asteroid like Gaspra, Ida and Eros, a puzzling result given its dynamical association with the Eunomia family of S-type asteroids." Next stop for Cassini: Jupiter in December - and "starting in October, the Imaging Team will begin making a 3 month long, planetary blockbuster movie of Jupiter's swirling atmosphere, its rings and orbiting satellites": something Galileo couldn't deliver! |
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More silence from Mars, but effort far from overInitial analysis of data taken on Feb. 8th by radio telescopes in the Netherlands and Italy has shown no obvious signal from Mars Polar Lander, but exhaustive review of the data is continuing with a final report due next week. Analysis of data taken at Stanford University in California is ongoing with no signal detected so far, while a telescope at Jodrell Bank in the UK was not able to collect any data due to high winds."Our plan for the next week is to temporarily end active efforts to listen for a signal," said Richard Cook, project manager for Mars Polar Lander at JPL. "We are evaluating several scenarios for future listening attempts that could take place at the end of this month." Mission managers are also reviewing information about the Mars relay link between MGS and the lander. |
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Picosatellites end brief but successful missionThe smallest satellites ever placed into orbit (see last Update story 4) have concluded their pioneering mission: Engineers at The Aerospace Corporation made the decision on Feb. 10 to close out the mission of the two 'picosatellites' that are connected with a tether, because power aboard the tiny spacecraft began to diminish. The first milestone achieved during the operations period from Feb. 6th to 10th had been their release from OPAL (Orbiting Picosatellite Automated Launcher), the "mother ship". OPAL in turn had been released by JAWSAT, the Joint Air Force Academy Weber State University Satellite (see Update # 172 story 7), launched Jan. 27th from a new commercial spaceport at Vandenberg Air Force Base (see Update # 170 story 3), a first from that site.A major achievement, in addition to getting the picosats launched successfully and released from their mother satellite, was demonstrating that they could be located and tracked. This presented a significant challenge because they offered a diminutive profile, kept so by omnidirectional patch antennas that do not protrude from the picosats.The insertion of thin strands of gold in the tether connecting the two satellites was a key factor in enabling them to be located by radar and tracked by the U.S. Space Command's Space Surveillance Network. Another achievement was establishing communications from the 50-meter dish antenna at the SRI International ground station at Menlo Park, Calif. |
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Students discover rare black hole candidate during routine assignmentWhat started out as a routine observing project with a small campus telescope has turned into the discovery of a possible black hole. The black hole candidate is part of a binary star system in which the two components revolve around each other every 91 days. If confirmed, this will be the longest-known orbital period for a black hole binary by a factor of about 10 - and the first system known to undergo eclipses from Earth's viewpoint. The investigation of this system, the variable star BG Geminorum, began in 1992 when undergraduate students were asked to monitor its brightness changes with Wellesley College's 0.6-meter telescope at the school's Whitin Observatory.Five years' worth of data were were eventually compiled - and the resulting light curve piqued the interest of a binary star expert who recognized this object as an interesting binary in which the lighter secondary is being stretched out by the strong gravity of the more massive primary. The stretching is so extreme that material from the secondary is actually flowing towards the primary. Spectra taken next revealed emission from hot gas orbiting the primary star, and that gas appears to be eclipsed by the cooler secondary once in each orbital period. Likewise, the secondary, estimated from its spectrum to contain half the mass of the Sun, is eclipsed half a cycle later. The eclipses imply that the binary system orbits in a plane tilted at nearly 90 degrees to the line of sight - a rare arrangement. But the big surprise was yet to come: The secondary star races around the primary at 75 km/s, and using Kepler's Laws of Motion, the students estimated the mass of the primary to be about 4.5 times the mass of the Sun. One possibility is that the primary is a normal hot star emitting most of its light in the UV, but the alternative is that the primary is a dark compact object. To test the first possibility, the astronomers have applied for time to obtain UV spectra with the HST. However, such a star would have a hard time heating the surrounding gas to the high observed temperature. If the ultraviolet does not show a hot star spectrum, the best alternative is that the primary star is actually a black hole whose gravity fuels the hot gas - or that it is a neutron star with a massive stable disk, a model rarely discussed but thought to be viable by some. If BG Gem is confirmed to contain a black hole, it will open up an important new window on how black holes are fueled. Its orbital period, 91 days, is nearly 10 times longer than any other known black hole binary candidate: This, along with its favorable inclination, will allow future observers to make slow, accurate measurements of the hot accretion disk as it is orbited and eclipsed by the secondary. |
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195th Meeting of the American Astronomical Society in Atlanta in January, which had also featured in Updates # 166 (1st story), 167 (all stories), 168 (first 3 stories), 170 (last 3 stories) and 172 (first 3 stories) as well as as smaller items in between - and see also S&T's coverage of the conference. |
Peak in CMB spectrum now "unambiguous"The latest generation of cosmic microwave background telescopes, namely TOCO and BOOM/NA, is now clearly detecting a peak in the angular spectrum of the Big Bang's echo radiation, with a peak amplitude of between ~70 and 90 microKelvin. Such a peak is consistent with the currently popular inflation-inspired flat (see Update # 168 story 1 sidebar 3), cold dark matter plus cosmological constant models of structure formation in the Universe: Paper by Knox & Page.A long review of current cosmological data & thinking: Science News. Anomaly!The "ice bombs" from above (see Update # 170 story 4) remain a mystery while the "lunar impact" (see Update # 172 last story) is a dud (see article at right) - how about three new topics from the astronomical fringe to ponder:
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New star catalog from Hipparcos!It is called "Tycho-2", and it contains the positions, proper motions, brightness and colours of 2 539 913 stars, determined from data by the Tycho detector on ESA's astrometry satellite as a valuable by-product of its main mission. This unique catalog includes 99% of all stars down to magnitude 11 - and everything is available on CD-ROM as well as online: Access Page, details and ESA Science News.Iridium's rescue moves aheadas a group of investors led by telecommunications pioneer Craig McCaw provides $74.6m in interim financing for the bankcrupt satellite telephone company: SpaceViews, Space Daily.Worth reading:
The last word on the 'lunar impact'"After new pictures of the possible meteorite impact on the moon (see Update # 172 last story) have been examined at DLR it seems quite clear now that all photographs in question show indeed only optical artefacts, as many amateurs have suspected before. In addition, the visual TLP observation turned out to be carried out at a different time." ( S. Molau on IMO News of Feb. 10, 2000)
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All other historical issues can be found in the Archive.
The U.S. site of this Cosmic Mirror has been visited
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Compiled and written by Daniel Fischer
(send me a mail to [email protected]!), Skyweek
