Free Astronomy Magazine July-August 2014

INSTRUMENTS over 156,000 stars, Kepler was now out of use, unable to remain accurate- ly and for a long time pointed on the preset targets. However, since apart from the gy- roscopes the rest of the equipment was in perfect working order, the engineers of the NASA’s Ames Re- search Center start- ed to look at ways of solving, at least in part, the orientation problem, so as to use Kepler in fallback observations that did not require it to stay steadily and con- stant over time pointed at a target. Some- how there was the need to find a way that would allow the telescope to remain pas- sively aligned on one axis, while the re- maining gyroscopes and thrusters aboard the spacecraft would have taken care of aligning it on the other two axes. The near-terrestrial orbit of Kepler (with a period of 372 days) favoured a solution as simple as it is ingenious, already suggest- ed as far back as August of last year: ex- ploiting the solar radiation pressure to keep the instrument aligned along the di- rection of its propagation. By orienting the telescope in preferably, but not neces- sarily, opposite di- rections to that of the Sun, and by of- fering to the ra- diation pressure of this the least possi- ble surface area on which to act (con- sistently with the need to collect energy through solar panels), it would have been possible to control the instrument also on the axis not managed by gyroscopes. Obviously it is not the same as having three working gyroscopes, but it can nonetheless be a satisfactory solution for conducting re- searches specifically planned for an instru- ment with that kind of drawback. The Kepler’s team decided therefore to ask the astronomical community to pro- pose research programs that could exploit the present conditions of the telescope, which is now pointed towards targets near the ecliptic. (The ecliptic is the projec- tion on the celestial sphere of the Earth's orbital plane, which is almost coincident with the projection of the telescope’s or- bital plane.) Between September 2013 and February 2014, the Ames Research Center’s engineers T his page: two different re- presentations of the 9 regions of the sky where the Kepler’s K2 mis- sion will be con- ducted. Above we can see them po- sitioned on the ecliptic and in re- spect to the Milky Way plane; below instead, are listed some identifying details related to these regions. [ESO/S. Brunier/NASA Ke- pler Mission] Steve B. Howell et al.