|
By Daniel Fischer Every page present in Europe & the U.S.!
| Ahead | Awards 
The latest issue!
| A German companion! (SuW version) Current mission news: MGS (latest pictures!) + Cassini + Galileo + NEAR |
|
| |
Controversial deorbiting of Compton beginsDespite protests from many circles, NASA is going ahead with its 4-step-process of sending the big Compton Gamma Ray Observatory satellite on a fiery crash into the Pacific Ocean. NASA controllers will fire CGRO's thrusters four times to lower the observatory's orbit. After each burn, mission trackers at Goddard Space Flight Center will determine the observatory's exact position and, if necessary, adjust the descent. The engine burns will occur at: 1:54 UTC on May 31, 2:41 UTC on June 1 and 5:37 and 7:05 UTC on June 4 - and within one hour the satellite should be destroyed. A test burn of Compton's thrusters has gone well on May 28.Unlike most satellites, Compton is too large to burn up entirely in the atmosphere during re-entry. More than 6 tons of metal debris is expected to fall to the Earth's surface (or rather a remote part of the Pacific Ocean, 4000 km SE of Hawaii). The debris fragments will range in size from the size of a small stone to several hundred kilograms. To ensure the safety of aircraft and surface vessels in or near the target impact area, Debris Hazard Warning Areas were established well away from land. Shipping and air traffic in the area have been notified to ensure that craft will not be in the vicinity of the impact area. NASA decided before Compton was launched that, due to the observatory's size, it would be returned to Earth by controlled re-entry when the mission was over. "Extensive research showed that it was significantly safer to perform a controlled re-entry than any other method of dealing with the satellite," the space agency says - but many scientists inside and outside the Compton project feel that the decision is rather based on irrational fears after the Mars disasters of 1999. Most supporters of Compton have conceded defeat already - the campaign to save the satellite had started too late and astronomers were too lazy... |
| |||||
NEAR Shoemaker observations link Eros to primordial solar systemNew data from NASA's Near Earth Asteroid Rendezvous (NEAR) mission indicate asteroid Eros may be a primordial relic left over from the solar system's formation. The NEAR team had gathered the information after a powerful explosion on the sun had zapped Eros with X-rays on May 4: The half-hour solar flare caused elements on Eros' surface to emit X-rays which gave the X-ray/Gamma-ray Spectrometer (XGRS) a fingerprint of the asteroid's chemical composition. Analysis of X-rays from an area roughly 6 km across on Eros indicated it has an elemental composition similar to the most primitive rocks in the solar system, the chondritic meteorites.The XGRS scientists will spend the remainder of the mission collecting data from other parts of Eros to determine if their latest findings are consistent across the approximately 21-mile-long asteroid. If more data confirm Eros is primordial, the asteroid can be seen as a link between the chondrite meteorites found on Earth and the history of the solar system's formation. The latest XGRS data show that the surface of Eros does not have an excess of heavy or light materials, and that the relative abundance of elements is similar to that in chondrites. But it is possible that other areas on Eros were exposed to some melting and differentiation, or that the surface composition has been altered by the constant hail of micrometeorites in space. |
| |||||
Some of the best images of planet Mercury from the groundhave been obtained during tests of a novel imaging system that will eventually yield high-resolution pictures of the planet's tenuous atmosphere. This will be done by observing Mercury simultaneously through a filter system with just one Angstrom bandwith and in white light: Thousands of short exposures will be taken and, based on the white-light view, the best frames will then be chosen for adding up in the computer. This can not be done with the narrow-band images alone because their signal/noise ratio will be extremely bad, but with the guidance provided by the brighter white-light images, eventually a sharp composite picture can be hoped for.For trying out the white-light part of the system, Mercury was observed on August 29, 1998, with the 60-inch at Mt. Wilson Observatory in California, shortly after sunrise before the Sun's heating of the atmosphere distorted the images. In order to obtain a clear photograph, images were taken with very short exposures, 1/60th of a second, continuously for 90 minutes, 340 000 pictures in total. The trick was then to find the best 30 to 60 that could be added together to create a time exposure of sufficient duration (0.5 to 1 second) in order to capture detail on Mercury's surface. Maximum-entropy processing sharpened the result further - which shows a face of the planet not observed by Mariner 10. |
| |||||
The complex rotation of Neptune's NereidIt's certainly not one of the popular moons in the solar system, but even Neptune's tiny Nereid can be an intriguing object: In the 1980's this moon showed strong brightness variations, but when Voyager 2 saw it from some distance in 1989, its light was steady. Now the astronomers that had found the brightness fluctuations in the first place are presenting many more observations, 224 photometric measurements, stretching from 1987 to 1997 - and the mystery is far from over. Nereid does display large-amplitude brightness variations with a total amplitude of 1.8 mag., on time scales ranging from a few hours to roughly a year, just not when Voyager was there.Perhaps there were large-amplitude long-term variations, but they were hidden by the large phase effects and the short duration of Voyager's observations? The new lightcurve also allows other conclusions: Nereid's variability is caused by high contrast albedo features, i.e. a dark hemisphere, along with rotational modulation. And the character of the brightness variations changed around 1991 from fast and large-amplitude to comparatively slow and low-amplitude, demonstrating that the direction and magnitude of Nereid's rotational angular momentum vector is changing on time scales comparable to its orbital period. Behind all this could be chaotic rotation (as seen only in Saturn's Hyperion so far), but the math is far from clear. |
| |||||
The first U.S. rocket with a Russian enginehas launched successfully late on May 24th, after numerous delays, and carried a European communications satellite into orbit: The maiden flight of the Atlas IIIA with one powerful Russian-built RD-180 engine in the first stage has made history. For one, it was the first launch of the new Atlas 3 family of boosters - and it was the first time an American booster has used a Russian rocket engine. The RD-180 replaces the MA-5A engine and four solid-propellant strap-on boosters used in the older Atlas IIAS, giving the Atlas IIIA about 10% additional payload capacity.The RD-180 was designed and built by NPO Energomash in Russia and is marketed by RD AMROSS, a joint venture between Energomash and Pratt & Whitney in the U.S. RD-180 engines will also be manufactured in the U.S. in the future, primarily for Atlas launches of military payloads. The 1st payload, Eutelsat's W4 satellite, will primarily be used to provide direct television broadcasts to Russia, but a secondary beam from the satellite will also provide television and broadband Internet access for sub-Saharan Africa. |
|
Atlantis back after ISS repairs, orbit raisingDespite threatening weather, space shuttle Atlantis has returned to the KSC on time on May 29th, capping a successful ISS maintenance mission. It was the 14th nighttime landing in Shuttle history and the 22nd consecutive mission to end with a landing at KSC. The space station is now almost as new - and, after three Atlantis maneuvers, in an orbit 44.4 km higher than before, with an apogee of 382.5 and a perigee of 369.1 km. Atlantis will now be processed for the next Shuttle flight in early September to return to the International Space Station with another crew for the outfitting and supply of the Service Module Zvezda that should have arrived on July 8.From May 30: Fla. Today (also on astronaut complaints that the ISS doesn't have enough windows), AFP. May 29: Status # 21, CNN, AP ( earlier), AFP, BBC, SPIEGEL, Welt, RP, Spaceflight Now, Space.com, SpaceViews. May 28: Status # 20 and 19, Fla. Today, AP, Spaceflight Now, Space.com, SpaceViews. May 27: Status # 18 and 17, Fla. Today ( earlier), AP ( earlier), SPIEGEL, Spaceflight Now, Space.com, SpaceViews. May 26: Status # 16 and 15, CNN, Fla. Today, SpaceViews, BBC, Space.com, AP, Spaceflight Now. May 25: Status # 14, 13, BBC, Fla. Today, Spaceflight Now, Discovery, Space.com, AP, SpaceViews, SPIEGEL. May 24: Status # 12, AFP. The next three shuttle missions, also going to the ISS, are currently set for Sept. 8 (STS-106), Sept. 28 (STS-92 with the Z-1 Truss) and Nov. 30 (STS-97 with the PV Module P6) - if Zvezda really launches on July 8: KSC schedule. Russia defends its role in ISS: Space.com. ISS not out of the woods, even when Zvezda comes? CNN. First ISS crew starts final training in Baikonur: AFP. Russia & China resume their space talks, though the agenda is mysterious: Space.com. French still eager for Mars Sample ReturnDespite the major shakeup and delays NASA's Mars program is facing (see Update # 189 story 2), the French space agency is still hoping to sign a Memorandum of Understanding about a big joint Mars Sample Return Mission by the end of this year - a major investment is contained in a long-term budget plan just released. The inevitable delays would actually have an advantage as a more powerful Ariane 5 could be used that's to enter service in 2006. (AW&ST of May 22, p. 33-4)Liquid water on Mars: the story from meteorites - small amounts of water were available near the surface of Mars during the past several hundred million years: PSR Discoveries. Mysterious Martian ridges in MGS pictures defy explanation: Spaceflight Now. Visual highlights from MGS: Space.com. Dust devils reviewed in a long article by Carr. |
Clusters cleared after thruster problems fadeEngineers at Astrium (formerly DASA's space infrastructure unit) have carried out tests with the thrusters of several satellites, including the Cluster science spacecraft, and found all key parameters within limits - the Cluster launches on July 12 and August 6 can go ahead. (AW&ST of May 22, p. 21)A Cluster PR event in Italy: ESA Science News. Chandra sees SN 1987A heating upImages from the X-ray observatory show how a shock wave is smashing into the outer parts of the ring around the supernova at a speed of 4500 km/s (where a brightening is also taking place in the optical - see Update # 175 small stuff): MSFC Press Release, SpaceScience, Discovery, Space.com, SpaceViews, Spacefl. Now, BBC, RP.Chandra clocks super-fast wind from a galactic center, thanks to "the most detailed X-ray spectrum ever taken of a galaxy with an active black hole": Chandra Press Release, BBC, Space.com. An intensive observing campaign to follow up ISO discoveriesof unknown celestial objects starts now, with a dozen ground-based telescopes (mainly on the Canary Islands) as well as later with XMM - thousands of sources detected by the IR satellite are still without counterparts at other wavelengths: ESA Science News.VLTI expertise center opens in LeidenThe Nova-ESO VLTI Expertise Centre (NEVEC) has now opened in Leiden, NL: As a joint project of the Netherlands Research School for Astronomy (NOVA) and ESO, NEVEC will develop in the coming years the expertise to exploit the unique interferometric possibilities of the Very Large Telescope (VLT): ESO Press Release.
|
All other historical issues can be found in the Archive.
The U.S. site of this Cosmic Mirror has been visited
since it was issued (the German site has no counter).
Compiled and written by Daniel Fischer
(send me a mail to [email protected]!), Skyweek
