And new: An experimental German companion to the CM.
Update # 155 of November 2nd, 1999, at 13:45 UTC
MPL performs trajectory adjustmentThe Mars Polar Lander spacecraft successfully fired its thrusters for 12 seconds Oct. 30th to fine-tune its flight path for arrival at the Martian south pole on December 3. Flight controllers said the spacecraft performed as planned and that preliminary data show the desired trajectory change was achieved. Previous thruster firings were accomplished on January 21, March 15, and September 1. The next thruster firing is scheduled for November 30. The landing site is located at 76 degrees south latitude and 195 degrees west longitude, near the northern edge of the layered terrain in the vicinity of the Martian south pole. The lander is now about 14 million km from Mars, traveling at a speed of 4.8 km/s relative to Mars. |
Status Report of Oct. 30 and coverage from Fla. Today (before the burn), Space.com, CNN, MSNBC, SpaceViews (afterwards). In other Mars news: Yet another story on the MPL Mars microphone (the most popular payload...) from CNN. Phobos' shadow on Mars has been captured by the MGS: MSSS Page. A detailled infrared spectrum of Mars with many water vapor absorption lines has been obtained by the ISO satellite in 1997: ISO Info. |
A meteor shower from comet C/1999J3 (LINEAR)?Since the middle of October meteor-related mailing lists are buzzing with speculations about the possibility of a meteor shower on (or near) November 11th that the recently discovered comet C/1999J3 (LINEAR) might be causing. The comet is expected to pass fairly close to Earth's orbit, at 0.0115 AU outside of the Earth's orbit, and at a location that we will pass on November 11.82 UT. But there is a problem, as outlined (not only) by NASA's meteor man Peter Jenniskens: "This is a long-period comet, with a period of some 63,000 years long. This type of comets cause 'far-comet' type outbursts, i.e. outbursts that do not correlate with the return of the comet to perihelion."Instead, the planets cause a dust trail in the comet orbit to move in the Earth's path once in a while. Typically once or twice every sixty years. The showers are brief (less than 1-2 hours) and they occur close to the node of the comet orbit. The reason why the showers do not correlate with the return of the comet is because the long period orbit causes large differences in orbital period for individual grains that are ejected with a range of ejection velocities. Hence, the dust spreads rapidly along the comet orbit during even a single orbit, and quickly dillutes so much as to be hardly detectable. "A shower from this comet may have occurred in the past, which should have been much at the same solar longitude as the decending node of the comet orbit. The maximum effect of planetary perturbations is needed to move the trail by 0.0115 AU. Hence, the years when the planets Jupiter and Saturn lined up in the right direction will have had best chance. Hence, it is unlikely that there will be activity from comet C/1999J3 this year, unless the planets happen to favor a position of the dust trail that is right in Earth's path. That is unlikely. Nevertheless, keep an eye out for the unexpected! Also, this type of 'far-comet' outbursts must occur relatively frequently all throughout the year, many showers of which remain to be discovered." (Posting on meteor.obs on Oct. 31, 1999) |
More information on the "LINEARids" possibility can be found in special pages from Sky & Telescope (by J. Rao) and the Dutch Meteor Society (by R. Bouma) as well as in an article from Space.com. The prospects for the Leonidsone week later were already discussed in Update # 153 (story 2) - here are more links: CSIRO (more dusty models - and visibility maps!), NASA Science News (stresses uncertainties), JPL NEO News, Starfire Optical Range Page, Space Daily (all on LIDAR studies of meteor trains), Space.com (on satellite fears), ESO, Dutch Meteor Society, ASTRONET.Meet a - possible - Leonid particle in person: During a stratospheric ballon flight close to last year's Leonids maximum (see Update # 111) several particles were captured, and one of them is probably coming from interplanetary space, a detailled analysis has now shown. The chemistry looks o.k., but there is no way directly link the particle with the Leonid meteoroids: Preprint by Noever et al. NASA plans another Leonids balloon launch and more experiments this year: NASA Science News, Space.com. Information about advanced meteor observing methods can be found e.g. on radio detection and photography ( another site) while the basics of video astronomy are explained here (with more video astronomy stuff here). |
Another successful detection of ripples in the Cosmic Microwave BackgroundThis time the measurements come from the South Pole where the Viper telescope has been scanning the faint radio noise from the Big Bang at a frequence of 40 GHz: There is anisotropy (i.e. spatial structure) in this radiation on all size scales that were checked. It cannot yet be excluded completely that an unknown population of strange celestial objects with far-IR emission is partly responsible for the structure seen, but at the moment there is no reason not to attribute the ripples in the radiation to the Cosmic Microwave Background. The Viper telescope is one of few that can look for these ripples at different size scales at the same time and thus produce an anisotropy power spectrum. Viper's spectrum, as crude as it is, shows a marked peak at a scale where many inflation models predict one - and the overall spectrum matches well the currently popular world model with a large cosmological constant (see Update # 148 sidebar of story 4) while contradicting the old favorite with critical density. (Peterson & al., Preprint) |
Viper Homepage. Preprint von Peterson & al.. List & Links of many other CMB experiments. Just weird: Creationists want to ban teaching of the Big Bang and invent crazy "physics": New York Times. |
Hubble views of Planetary Nebulae drive theorists towards more complex modelsDozens of spectacular images of planetary and protoplanetary nebulae provided by the HST have revealed morphological aspects completely unexpected before, and the "newly found complexity represents a challenge for researchers trying to understand the mechanisms of stellar death," says Cornell professor Yervant Terzian. "The general stages of the late stellar evolution are reasonably well understood, but the mechanism by which these old stars eject their envelopes remain mysterious, and we have been unable to understand what factors contribute to creating a particular nebular morphology."Not one of HST's images "shows a simple expanding bubble," marvels Terzian: "Most objects have complex bipolar structures with central torii, multipolar bubbles, jetlike filaments, and globules. Some objects even show sets of circular rings," and often there are detailled point and mirror symmetries. While simulations of single stars at the end of their lives have been able to match some of the observations, both strong magnetic fields and a fast rotation of the stars are often needed while their origin is not well understood. (Science of Oct. 15, 1999, p. 425-6) |
A truly spectacular Hubble Planetary Nebula Gallery. A basic introduction to planetary nebulae and the fate of our Sun. Another Planetary Nebula gallery, this time ground-based images (not bad either). |
4 meter Liquid Mirror Telescope to scan the sky over ChileAn International Liquid Mirror Telescope (ILMT) mit a 4 meter mirror made out of spinning mercury is being built in the North of Chile in the Atacama desert by an international consortium and will become operational two years from now. The instrument will be fully dedicated to a zenithal direct imaging survey in two broad spectral bands, B and R. Because a liquid telescope cannot be tilted, it will use a drift-scan CCD and should be able to reach 23rd magnitude stars: With a field of view of 30 arc minutes it will observe, night after night, all objecrs in a fixed declination strip of approx. 140 square degrees - and all kinds of gravitational lensing studies can be performed. |
A very detailled report about the ILMT. A short paper by Jean & al. on the telescope and the lensing experiments planned. Related: A nice primer about gravitational lensing. |
First Proton fragments foundAround 30 fragments of the ill-fated Russian Proton booster rocket and its Express-A1 satellite have been recovered in a 15-20 km area near the village of Atasu: Space.com. Baikonur launch ban continues: Fla. Today, SpaceViews.More Shuttle delays - a shuttle mission to the ISS once planned for December has now been delayed to at least mid March, but the Hubble mission seems to remain set for Dec. 2nd: Space.com, SpaceViews. No Shuttle will be in space at the onset of Y2K as NASA isn't completely sure the machine is Y2K compliant (therefore the HST mission cannot launch past Dec. 14): Space.com. Ongoing volcanism on Neptune's moon Tritonis indicated by the small number of craters in some areas that, together with new models for the influx of impactors from the Kuiper belt, give ages of only 10 to 100 millions years. Apparently the lingering radioactive decay in Triton's interior is still making enough heat to melt its exotic ices. (Science of Oct. 15, 1999, p. 383-5)Ground-based pictures of Mercury taken with the 0.5 meter Swedish Vacuum Solar Telescope (SVST) at La Palma show some details: Special Page. Two new ESA Earth missions close to approvalFrom four proposals for Earth Explorer Core Missions two have now been selected for Phase B study and subsequent implementation: In order of priority this are the Gravity and Steady State Ocean Circulation Earth Explorer (GOCE) and the Atmospheric Dynamics Earth Explorer (ADM). It is likely that both will be approved by the ESA Science Programme Committee this month. The conference where the selection was made and the ESA Earth Explorer Missions Homepage.ISS to be used extensively for Earth observation - a special window designed to constantly face the Earth will enable a wealth of research projects: Space.com |
Japanese Lunar Exploration: Robots Now, People LaterAt the 2nd Canadian Space Workshop Koichiro Tsuruda from the Japanese Ministry of Education's Institute for Space and Astronautics (ISAS) spoke most enthusiastically about Japan's upcoming missions to the moon: SpaceRef.Understanding what a comet nucleus looks like to a passing spacecraft is essential for coming encounters, e.g. by Deep Space 1 and Deep Impact: Space.com. Orbiting filling station to keep spy satellites aloftA robot that can refuel and service U.S. spy satellites in orbit is being developed by Department of Defense researchers. The new system could extend a satellite's life many times over: New Scientist, Space Daily, SpaceViews.Auction of Challenger heat tile stoppedAn alleged thermal tile from the space shuttle Challenger has been offered at an online auction site as the "ultimate christmas gift", although federal law prohibits possession of debris from the Challenger wreckage - but after the story broke on various online space news services, the item was quickly withdrawn: the initial CollectSpace story (now updated) and more early coverage from MSNBC. SpaceViews, Space.com and Discovery on the withdrawal. What you might get for stealing Challenger debris explains a Florida Today story from 1996.
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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 dfischer@astro.uni-bonn.de!), Skyweek