Los Angeles - Jan 21, 2003
Meanwhile aross the Atlantic, some press sources have gone into a panic over the likely effects of the fact that the European Space Agency's Rosetta mission to rendezvous with and actually land on a comet nucleus -- a billion-dollar mission which is extremely important scientifically -- must now miss its January launch window to reach its target of Comet Wirtanen.
Rosetta, which weighs 2900 kg, requires launch by Europe's powerful Ariane 5 booster, and then must make one gravity-assist flyby of Mars and two of Earth and also carry out deep-space rocket burns totaling fully 7900 km/hr in order to match orbits with Wirtanen in late 2011.
But the last Ariane 5 launch on Dec. 11 -- the first flight of the new, more powerful "ECA" version -- ended in disaster when the coolant system for the nozzle of its new Vulcain 2 first-stage engine failed, and the nozzle became so hot that it disintegrated, causing the rocket to veer off course and self-destruct before its equally new second stage even had a chance to fire.
Originally it was hoped that this would not force cancellation of Rosetta's launch on the original model of Ariane 5, which has an entirely different Vulcain 1 engine which has never failed (although three of the 13 flights of the original Ariane 5 have failed for other reasons).
However, after tentative initial approval of the launch, it became known that the final review board report on the failure was more damning than thought, revealing a whole series of as-yet undescribed problems in the design and testing procedures even of the regular Ariane 5 -- especially since the Rosetta launch requires an unprecedented long 2-hour stay in parking orbit for the second stage.
So the board of the Arianespace organization unanimously ended up recommending against risking the Rosetta launch until an extensive review has corrected these problems -- after all, four failures in 14 flights is a lousy track record.
According to the BBC, "Even though Arianespace and ESA officials knew that Rosetta was grounded on Jan. 12, scientists and public relations officials were not informed. Indeed, in several European countries press conferences were held on Jan. 13 where scientists told the media that all was OK." The next day, the total launch cancellation was announced.
The problem is that Rosetta is so heavy that -- even with multiple gravity-assist flybys -- there are some problems finding another short-period comet with which it can rendezvous.
Daniel Fischer of the "Cosmic Mirror" news site reports that the result has been "media stories, especially here in Germany, about a total disaster of the mission" due to inability to find any other opportunity to fly it to ANY comet in the reasonably near future.
But he points out that such stories are also "plain nonsense". There must be an extensive review to find the new best target for Rosetta and the best flight plan to reach that target -- a process that may in itself take several months. But there are several good possibilities, and its launch some time in the next 3 years (and maybe a lot sooner) is a virtual certainty.
Moreover, Rosetta Project Scientist Gerhard Schwehm tells "SpaceDaily" that there is no chance that some of Rosetta's science instrument payload (such as its separate 97-kg comet nucleus lander, "Roland") will have to be removed to enable such a launch -- largely because such a change in the spacecraft's configuration would produce so many new problems that the mission cost would probably actually be increased.
He also denies rumors that the decision might be made to have Rosetta make a gravity-assist flyby of Venus, for which its thermal control system would have to be completely redesigned (including a reflective sunshade). Any gravity-assist flybys it makes will be of Earth and/or Mars, as originally planned. This probably rules out any chance of launching it to Wirtanen later (a Venus flyby might have enabled it to be launched to Wirtanen this fall).
According to Schwehm, comets under serious consideration right now as its new target include "Tempel 2, Churyumov-Gerasimenko, duToit-Hartley, Howell, and Hartley 2."
This may not be a complete list -- as mentioned, the search for good possibilities has just begun -- but Schwehm did not confirm the reports of other news agencies that possible target comets may also include Schwassmann-Wachmann 2, Brooks 2, Finlay, Tau, and Wild 2 (which is also the target of NASA's "Stardust" flyby probe next year).
When the Rosetta mission was originally being planned back in 1992, its primary target was Schwassmann-Wachmann 3, to which it could be launched this July. However, Schwehm tells this reporter that this comet is now definitely OFF the list -- paradoxically, for the same reason it was one of the targets for America's failed 2002 CONTOUR multiple comet flyby.
The reason is that on its last close pass by the Sun in 1995, it ruptured into at least three pieces. By flying past one of these fragments in 2006, CONTOUR might have been able to get a cross-sectional view of the inside of a comet nucleus before its freshly exposed interior surface had been baked and modified by the Sun.
But Schwehm says that any of the fragments is simply too small to be a good final destination for a full-fledged comet rendezvous -- especially since there's a real chance that they may fragment into still smaller pieces later on. (By contrast, most of the potential new target comet nuclei are somewhat bigger than Wirtanen, and may actually end up being a little better scientifically.)
One of the best targets may be Churyumov-Gerasimenko, for which there is probably a usable launch window in February 2004. But a delay of the launch all the way into 2005 is a definite possibility.
This hardly compares to the staggering delay of almost eight years in the launch of America's "Galileo" Jupiter probe due to the Space Shuttle's parade of major problems in the Eighties, but the delay probably will add about $50-100 million to Rosetta's current $1.06 billion total cost -- at a time when the ESA's space science program is already stretching its budget to the limit.
However, ESA Science Director David Southwood assures SpaceDaily that there is no chance that the ESA will pay for the delay by canceling the 2005 Venus Express mission, which was finally approved by the skin of its teeth two months ago after being actually cancelled earlier last year.
According to Southwood, "the die is cast" and Venus Express (which cannot tolerate any launch delay without a sharp rise in its unusually low mission cost) will definitely fly.
This makes it likely that the ESA will pay for the Rosetta delay by delaying some of its other space science missions this decade, virtually all of which can tolerate delays much better than Venus Express.
At any rate, the last week has given us an unusually strong object lesson in the potential for major error in aerospace news reporting. It's a safe bet that we will continue to receive such lessons -- hopefully less frequently.
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Europe's Great Leap Upwards
Los Angeles - Jan 06, 2003
There have been several interesting developments in the past month where the space science programs of the European nations are concerned. They're a mixed bag -- although, on the whole, they're rather discouraging. Funding remains a serious problem for space science in virtually every country, given its very high cost relative to other forms of research.
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