747SP SOFIA de la NASA

[Vous devez être inscrit et connecté pour voir ce lien] reports positive results from initial open-door testing of its Stratospheric Observatory for Infrared Astronomy (Sofia), a research platform that includes a 19t telescope mounted on a [Vous devez être inscrit et connecté pour voir ce lien] 747SP (N747NA).
A 4.6m (15ft)-high by 4.3m-wide door on the aft left side of the aircraft that opens in flight to expose the telescope a clear view of the sky between 23° and 58° of elevation had been a key concern among engineers.
The result of two decades of engineering at a cost of more than $500 million in modifications, the 747 includes "ramps" and fairings designed to isolate the telescope from atmospheric buffeting as the former Pan Am and [Vous devez être inscrit et connecté pour voir ce lien] aircraft flies at M0.85 and 45,000ft during observations.
Open door tests on two of the four flights made since 9 December however have proven "nominal" from the buffet isolation standpoint, says Sofia programme manager Bob Meyer. During a 14 December test, Meyer says the crew opened the door to 10% of its fully open position, followed by an 18 December flight in which the door was opened to its 10%, 40%, 70% and 100% open positions, albeit only for 2min as per the flight test plan.
Tests were conducted at 15,000ft altitude and a speed of 225kt (415km/h) with the telescope turned off and locked in position, says Meyer. The fourth flight was cut short with no door opening due to a telemetry system problem.
"Everything looked nominal," says Meyer. "Pilots reported no change in handling qualities and sound pressure levels were as we predicted." In 2010, NASA plans to open the operational envelope for the aircraft, including tests with the telescope's pointing control system activated and "first light" operations of the telescope itself. First science flights are planned for autumn 2010.
A crucial test of how the aircraft handles with its door stuck in the fully open position is scheduled for early this year, says Meyer. The system was designed to handle 20min of worst case resonance with a factor of four safety factor, enough to allow the pilots to descend and land safely if the door fails in the open position.

A quelques semaines de ses premiers vols scientifiques dans la stratosphère, SOFIA (acronyme anglais de l'Observatoire Stratosphérique d'Astronomie Infrarouge) attend patiemment dans un immense hangar, sur une base de la Nasa à Palmdale, dans le désert de Mojave, à 60 km au nord de Los Angeles.

Développé conjointement par la Nasa et l'Agence spatiale allemande (DLR), SOFIA est l'héritier du Kuiper Airborne Observatory (KAO), dont les travaux, entre 1974 et 1995, avaient notamment permis à la Nasa de découvrir les anneaux de la planète Uranus ou de percer certains mystères de la Voie Lactée.....

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"Les infrarouges sont difficiles à observer depuis la Terre, car ils sont bloqués par la vapeur d'eau présente dans l'atmosphère", explique M. Meyer. "SOFIA est capable de voler au-dessus de la quasi-totalité de la vapeur".

Autre qualité de l'observation embarquée: elle peut se faire depuis n'importe quel point du globe, et permettre ainsi de chasser les éclipses de planètes, dont les ombres sont riches en enseignements scientifiques.

Hubble, sans doute le télescope le plus connu du grand public, est peu ou prou de la même taille que SOFIA, mais il ne
peut pas voir les même choses. "Hubble ne peut observer que ce qui est visible naturellement, ainsi que les ultraviolets. Mais sa capacité en infrarouges est limitée", précise M. Young.

Boeing 747-mounted telescope takes first pictures of space

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The [Vous devez être inscrit et connecté pour voir ce lien] made its first in-flight night observations Wednesday, NASA announced Friday.
"With this flight, SOFIA begins a 20-year journey that will enable a wide variety of astronomical science observations not possible from other Earth and space-borne observatories," Jon Morse, Astrophysics Division director in NASA's Science Mission Directorate, said in a news release. "It clearly sets expectations that SOFIA will provide us with 'Great Observatory'-class astronomical science."
SOFIA, a joint program by NASA and the German Aerospace Center, is a Boeing 747SP jetliner fitted with a 100-inch diameter reflecting telescope and a really big door that opens in flight (see video above). Wednesday's flight lasted six hours, reaching 35,000 feet.
"The crowning accomplishment of the night came when scientists on board SOFIA recorded images of Jupiter," Universities Space Research Association SOFIA senior science adviser Eric Becklin said. "The composite image from SOFIA shows heat, trapped since the formation of the planet, pouring out of Jupiter's interior through holes in its clouds."
The first look at performance data shows images will be sharp enough for front-line astronomical research, SOFIA project scientist Pam Marcum, of NASA's Ames Research Center in Moffett Field, Calif., said in the release. The release added that the stability and precise pointing of the telescope met or exceeded the expectations.
SOFIA's Faint Object infraRed CAmera captures in minutes images that would require many hour-long exposures by ground-based observatories. That's because SOFIA operates at an altitude above more than 99 percent of water vapor that blocks a clear infrared view on the ground