Free Astronomy Magazine July-August 2014

INSTRUMENTS Clearly, programs that will require a mini- mum deviation from the ecliptic are prefer- able, since, in addition to making pointing easier, they allow to save propellant and extend the operational life of the instru- ment. NASA engineers feel sure that the campaigns planned for the K2 mission will provide interesting results, since Kepler is still after all a telescope with a primary mirror of 1.4 metres in diameter, equipped with high-quality photometric devices and a 95 megapixel sensor covering a field of some 100 square degrees. Unlike Kepler Prime, which was managed by a single science team specializing in transits of extrasolar planets on stellar disks, K2 will instead have the cooperation of various specialists from various fields, who will take turns in controlling the in- strument. Although optimism seems to prevail among all those involved, K2 is not how- ever the solution to all problems. In fact, while the strategy of having Kepler oper- ate by mostly lying on its orbital plane has the advantage of taking it to spontane- ously frame an always different sky as it gradually moves along its orbit, this will though mean that planets and other bright objects will from time to time enter into its field of view, with the ensuing deg- radation of the acquired images which will be affected by glare and reflections. Similar problems can arise while framing particularly dense regions of stars and gas clouds. It is estimated that the noise of the photometric measurements will be on aver- age 1.5 to 2 times higher than that found during Kepler’s prime mission. In addition, the contingency ori- entation provided by the solar radiation pressure is only reli- able up to a point, such that to compen- sate the ascertained telescope’s tendency to drift, there is the actual need to brief- ly fire its thrusters every 6 hours. None- theless, it is always better than definite- ly losing such a high- quality instrument that has given an un- precedented boost to planetary science, regardless of what it will be able to ac- complish in the next two years. T he two illu- strations on this page show the positions of the main internal and external components of the Kepler space telescope. [NASA] n SUN SHADE SUN SHADE FOCAL PLANE ELECTRONICS FOCAL PLANE 42CCDs PHOTOMETER RADIATOR CCD ONBOARD COMPUTERS CONTROL THRUSTERS HIGH GAIN ANTENNA REACTION WHEEL #4 REACTION WHEEL #3 SOLAR PANELS PRIMARY MIRROR MOUNTING COLLET THERMAL RADIATOR SCHMIDT CORRECTOR