Rosetta blog: CometWatch from Gaia

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This blog post is formed on an picture recover published on a ESA Space Science portal .

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Gaia picture of Comet 67P/C-G on 14 Sep 2015. Credit: ESA/Gaia/DPAC. Acknowledgement: Francois Mignard and Paolo Tanga, Observatoire de la Côte d’Azur, France.

On 14 Sep 2015, Comet 67P/Churyumov Gerasimenko was imaged by Gaia, ESA’s billion star surveyor.

Located during a Lagrange indicate L2, 1.5 million km divided from Earth in a conflicting instruction from a Sun, Gaia scans a whole sky about each 3 months to map a positions and motions of a billion stars in a Galaxy. In a process, a satellite also picks adult objects most closer to home, such as asteroids and comets in a solar system, entertainment information that will be used to establish their orbits to rare accuracy.

Gaia is optimised to detect stars, that seem as indicate sources in a camera, and magnitude their properties, though it does not customarily lapse images of astronomical objects. To acquire an picture of a sold object, a special pretence can be used. This is what Gaia astronomers did to safeguard that, when a satellite scanned a patch of a sky including Rosetta’s comet, a star-mapper camera would constraint an picture of this iconic object.

“Comet 67P/C-G had usually upheld a perihelion on 13 August, and calculations likely that a patch of a sky containing a comet and Rosetta would be scanned by Gaia on 14 September,” comments Fred Jansen, Gaia goal manager and former Rosetta goal manager.

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Artist’s sense of a Gaia spacecraft, with a Milky Way in a background. Cretids: ESA/ATG medialab; credentials image: ESO/S. Brunier

“It was a conspicuous occasion: Gaia and Rosetta, dual ESA scholarship missions distant by over 260 million kilometres, one looking during a other and a intent of study.”

For this special occasion, a astronomers done certain that Gaia’s star-mapper camera would cover that patch of a sky regulating a special mode in that a full picture is available and transmitted to a belligerent instead of indicate sources only, as in Gaia’s normal scholarship mode.

“This mystic picture has a special value for me: it’s my benefaction looking during my past,” adds Jansen.

Pictured in a picture are a comet’s coma and tail, while a iota and Rosetta, that was some 300 km from a aspect during a time, are both dark in a innermost pixel. A series of credentials stars are also sprinkled around a image, that measures about 4.5 arc mins across.

Comet 67P/C-G prisoner by a 2 m Liverpool Telescope during around 05:30 UT on 8 Oct 2015. The picture is a multiple of 9 x 15 second exposures, and shows a tail fluctuating 400,000 km from a comet. On 8 Oct a comet was was roughly 270 million km from a Earth and 212 million km from a Sun. This picture shows a full margin of perspective of a IO:O camera on a Liverpool Telescope, 10.4 arcminutes on a side, or approximately 640,000 km during a stretch of a comet. Credit: Colin Snodgrass / Liverpool Telescope

Comet 67P/C-G prisoner by a 2 m Liverpool Telescope during around 05:30 UT on 8 Oct 2015. Credit: Colin Snodgrass / Liverpool Telescope

The picture scale, 0.35 arc seconds per pixel, is roughly identical to that of an picture of a ground-based picture of 67P/C-G that was recently performed with a 2-m Liverpool Telescope during La Palma, in a Canary Islands.

Besides a special watching mode that was used to obtain a image, a comet was also held by a on-board showing program as a ‘suspected relocating object’. Over a three-second regard time, it seemed to pierce by some 100 km with honour to a credentials stars, as seen from a stretch of about 260 million kilometres.

Over a five-year prolonged mission, Gaia will observe hundreds of comets and regularly magnitude their position to rare accuracy. These information will concede scientists to urge a circuit integrity of many comets good over a pointing that can be achieved with ground-based observations alone; in addition, they will also use Gaia’s photometric observations of these comets to examine their combination and aspect properties.

“This is a latest in a period of Rosetta combinations with information from other ESA missions, including Cluster, Mars Express and also a Earth Observation satellite ENVISAT,” says Matt Taylor, ESA Rosetta plan scientist.

Source: Rosetta blog