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By Daniel Fischer Every page present in Europe & the U.S.!
| Ahead | Awards 
The latest issue!
| A German companion! (the latest updates) Current mission news: MGS (latest pictures!) + Cassini + Galileo + NEAR |
Saturn, Jupiter and Mercury are so close to the Sun now that SOHO's coronagraph is seeing them all. Get the very latest SOHO views (updated every half hour or so) here!
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Artificial degradation of GPS signals stopped!It's the news that users of the Global Positioning System have been waiting for for years: On May 1st the DoD, owner of the navigation satellites that the system is based on, turned off 'Selective Availibility' (SA), an artificial degradation of the navigation signals - the position information even a simple handheld GPS receiver is delivering has since jumped up by an order of magnitude. "The decision to discontinue Selective Availability is the latest measure in an ongoing effort to make GPS more responsive to civil and commercial users worldwide," President Clinton said in a statement: "This increase in accuracy will allow new GPS applications to emerge and continue to enhance the lives of people around the world."The Global Positioning System had been invented by the U.S. military for the military which had - and still has - protected access to a special high-precision navigation signal. From the beginning the GPS satellites had been broadcasting a civilian signal as well, however, that had found countless applications since. To deny critical targetting information to 'hostile' nations, however, this signal had been scrambled with SA most of the time: The positional accuracy was degraded to 100 meters 95% of the time. With SA turned off, the accuracy should jump to 12 meters 95% of the time and even 6 meters half the time. The national security arguments that had led to SA's implementation had faded over the years. First, the military difference between 100 and 12 meters accuracy turned out to be smaller than thought - and second, the civilian user community had found a clever way around SA with Differential GPS (where a fixed antenna delivers correction signals). So SA had become a considerable nuisance for the civilian user while it didn't make much defense sense - since 1995 the National Research Council had called for an immediate end to SA. Clinton's quick decision now was a surprise nonetheless. (With AW&ST of April 17, 2000, p. 44) |
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50 km: Burn puts NEAR Shoemaker in ideal science observation orbitOn April 30 at 16:15 UTC the NEAR Shoemaker spacecraft successfully completed one of its largest orbit correction maneuvers to date: The hydrazine engine burn lasted approximately 2 minutes and 20 seconds and moved the spacecraft from a 100 x 50 km orbit to a 50 kilometer circular orbit over Eros' north and south poles. This is the sixth time the spacecraft's thrusters have been fired to adjust its position since it began orbiting Eros on February 14, 2000. The burn also successfully reduced spacecraft momentum buildup by slowing the four momentum wheels that spin faster and faster as the spacecraft works to stay sun pointing.For the next two months the spacecraft will remain in the new orbit, giving the imager its closest view yet of the slowly tumbling asteroid and the Laser Rangefinder and X-Ray Gamma Ray Spectrometer instruments a chance to begin collecting data from a distance optimum for their design. All instruments are operational at this time. The April 30 burn left NEAR Shoemaker travelling at 11 km/h - a reduction of 5 km/h from its previous speed. Although gravity is so slight that a baseball tossed from the surface of Eros would easily leave the asteroid's gravitational confines, there is still enough of a pull to influence the spacecraft's flight. The next orbit correction maneuver is expected to take place July 7. |
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Case for "flatness" of Universe strengthened by Balloon-borne CMB detectorEven before the next generation of cosmology satellites is up, a mm wave telescope studying the Cosmic Microwave Background (CMB) from a balloon over Antarctica seems has already provided the strongest evidence to date that the geometry of the Cosmos as a whole is flat - and this result, combined with the low density of matter in it (see Updates # 68 and 115), all but proves that the Cosmological Constant is positive (and not zero) and that the Universe, in all likelyhood, will expand forever and even accelerate.There had been a number of CMB observations recently that hinted at a flat Universe (see e.g. Updates # 148 story 4 sidebar or 155 story 3), but the new images from the BOOMERANG instrument (already mentioned in Update # 168 story 1 sidebar) are being widely hailed as the most convincing ever. BOOMERANG (Balloon Observations of Millimetric Extragalactic Radiation and Geophysics) had circumnavigated the Antarctic in late 1998, suspended from a balloon which had carried the telescope at an altitude of 37 to 39 kilometers for 10 1/2 days. The result: the first images of resolved structure in the microwave background anisotropies over a significant part (2.5 %) of the sky, with 35 times higher angular resolution than the COBE satellite a decade earlier. Maps at four frequencies between 90 and 400 GHz help to clearly distinguish the microwave background from Galactic foreground emission. The BOOMERANG images are the first to bring the CMB into really sharp focus: They reveal hundreds of complex regions that are visible as tiny variations - typically only one ten-thousandth of a Kelvin - in the temperature of the CMB. The complex patterns visible in the images confirm predictions of the patterns that would result from sound waves racing through the early universe, creating the structures that by now have evolved into giant clusters and super-clusters of galaxies. And it is the mathematical analysis of the size of the structures in the CMB that is delivering the most precise measurements to date of the geometry of space-time, strongly indicating that the geometry of the universe is flat, not curved. The angular spectrum of the CMB computed from the maps shows a peak at Legendre multipole l(peak) = (197+/-6), i.e. most structure has a scale of about 1 degree of arc, with an amplitude of about 70 Mikrokelvin in the CMB temperature. "This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe," the BOOMERANG researchers conclude, "as favoured by standard inflationary models."
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STS-101 now set for May 18thAfter the third scrub in as many days (this time because of bad weather at all TAL emergency landing sites) the launch of Atlantis to the ISS (mission goals described in the last Update story 3) had to be delayed until May 18th because many other launches at the Cape are also in line: Mission Status Center, news about the new launch date from KSC, SpaceViews, Space.com, Spaceflight Now, Fla. Today, earlier post-scrub coverage by Fla. Today, AP, SPIEGEL, AFP, RP, BBC, Discovery, CNN, Spaceflight Now, Space.com, SpaceViews.Zarya can wait, Khrunichev says: Interfax. Progress reaches Mir without problems: MirCorp Press Release, BBC, Space.com, AFP, SPIEGEL, SpaceViews. Survival of Mir beyond summer still not guaranteed - if MirCorp is unable to raise more money, the station could the deorbited in October: Discovery, AFP. MirCorp sees bright future for Mir: Press Release. Latest U.S. weather satellite launched just in caseThe United States launched its newest weather-watching satellite early on May 3rd to ensure forecasters have accurate information during this summer's predicted active hurricane season. GOES-L, to be renamed GOES-11 once it reaches the operational orbit, becomes a critical backup satellite that will ultimately replace one of the two GOES spacecraft currently operating: GOES Homepage, SpaceViews, AP, Discovery, Space.com, CNN, RP, Spaceflight Now.Debris from 1996 Delta rocket falls on S Africa as a pair of "flaming balls": BBC (before the mystery was solved), SpaceViews, RP, AP, BBC. Russian and Kazakhstan eye joint rocket planRussia and Kazakhstan may work together on a project to create the Yamal space rocket because the Sodruzhestvo project to design a new launch vehicle based on the Zenit has yet to take shape - neither Kazakhstan, Russia nor Ukraine possess the sort of finances needed to deliver the Sodruzhestvo project, which is aimed at creating a heavy-duty rocket: Interfax.Iridium still hoping for buyer - Iridium has not yet destroyed its $6b satellite network, and there could now be a bidder after all: BBC. High Dollar space rocks inspire wonder, devoted collectorsMeteorites are coveted by collectors and by scientists alike: several stories in a Space.com Special.'Custody battle' over NY meteorite in the Hayden planetarium continues: Archaeology.org. |
Spiral structure found in dwarf galaxyAn entirely unexpected, well developed spiral structure has been found within an otherwise seemingly normal dwarf elliptical galaxy, IC 3328 in the Virgo Cluster of Galaxies: A preprint and an ESO Press Release.Measuring cosmic distances with X-ray halosBy exploiting the scattering properties of interstellar dust, Chandra observations were used to measure the distance to the periodically varying source Cyg X-3: MSFC Press Release, NASA Science News, Discovery, Space.com, RP stories.A supernova remnant seen in many 'colors' at the same time, that highlight different physical processes: MSFC Photo, Spacefl. Now, CNN, Space.com, SPIEGEL. XMM enters, exits safemode in early April: ESA Science News. First XMM science meeting: ESA Science News. XMM photographed over Europe: ESA Science News. Integral launch in 2002 confirmed - a Russian Proton rocket will put the gamma-ray satellite into orbit on 22 April 2002: ESA Science News. Role of amateur astronomers in high-energy astrophysics emphasized at Pro-Am conference; GRB afterglows most important topic: SpaceScience (preview). Delays for the Outer Planet missions?Instead of launching to Pluto in 2003 (see last Update small items) budget contraints could force NASA to stretch the whole Outer Planets program: Space.com.Many plans for commercial Moon missions - but not one of the 7 or so candidates has a firm launch date: Space.com. "Area 51" images with 2 and 1 meter resolutiontaken by commercial Russian and U.S. satellites, resp., have been published in April - and, egad, no parked Flying Saucers can be spotted on the secret U.S. base: TerraServer page, ABC, EXN, Fox, Fla. Today ( earlier), Discovery, Space.com (earlier) stories, Area 51 resources. 'Spysat' image business booms: Space.com.
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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
since it was issued (the German site has no counter).
Compiled and written by Daniel Fischer
(send me a mail to [email protected]!), Skyweek
