On 17 October 2014 Gaia was observed by the Bologna Faint Object Spectrograph and Camera (BFOSC) at Loiano Observatory, Italy. The 1.52m G.D. Cassini telescope provided a plate scale of 0.58 arcsec/pixel.

The animation above is a collection of twelve single frames, mainly taken in white-light and in the Johnson-Cousins V, R and Gunn z-bands. The sequence is a timelapse taken between 20:08 and 21:42 UTC, and covers a small region (3x3 arcmin across).

A differential telescope tracking on the satellite was switched on in most of the frames, giving the characteristic "trailing-star" pattern. This greatly enhanced the extremely faint signal of Gaia (magnitude R=21.0), allowing the observers to pick up the satellite while heading North-East at 1.39 million km from Earth, around the Sun-Earth L2 Lagrangian point. Like past space observatories (WMAP, Planck, Herschel) and forthcoming missions (JWST, Euclid, Athena), Gaia operates in a complex Lissajous orbit around L2, where the combined gravitational forces from the Sun and the Earth are balanced by the centrifugal force. Measurements such as these aid the reconstruction of the position and velocity vector of the satellite in the Solar system at a level required to fully exploit Gaia's unprecedented astrometric capabilities.

Night observers were A. Buzzoni, I. Foppiani and R. Gualandi of INAF, Bologna Astronomical Observatory.

Image credit and copyright: G. Altavilla, A. Buzzoni

[Published: 01/12/2014]