NASA Kepler's Second Light
This image from NASA's Kepler spacecraft shows the telescope's field of view taken in a new demonstration mode in late October. A new mission concept, dubbed K2, would continue Kepler's search for other worlds, and introduce new opportunities to observe star clusters, young and old stars, active galaxies and supernovae.
Photons of starlight from a distant star field were collected over a 30-minute period and produced an image quality within five percent of Kepler's original mission image quality, which used four reaction wheels to control pointing stability. The full frame image shows part of the constellation Sagittarius located in the southern celestial hemisphere.
Kepler lost the second of four gyroscope-like reaction wheels in May, ending new data collection for the original mission. Using the sun and the two remaining working wheels, engineers have devised an innovative technique to stabilize and control the spacecraft in all three directions of motion. This technique of using the sun as the 'third wheel' to control pointing is currently being tested on the spacecraft.
The grid lines across the picture show how the focal plane is laid out on Kepler's camera -- the largest ever launched in space at 95 megapixels. 40 of the 42 charge-coupled devices (CCDs), paired into square-shaped modules, whose outline can be seen in the image, remain operational. A thin black line in each module shows adjacent pairs of CCDs. The thicker black lines that cross through the image are from structures holding the modules together.
The four black corners of the image show where the fine-guidance sensors reside on the focal plane. These sensors were used during the original mission to hold the telescope's gaze steady. However, for this image the lower-resolution star trackers were used to measure the spacecraft's position on the sky and feed the information to the onboard attitude control system, which resulted in the five percent larger blur of the image. Tests are underway to determine if the fine-guidance sensors can be used during K2 in order to restore the exquisite pointing stability of the main mission.
The K2 mission concept has been presented to NASA Headquarters. A decision to proceed to the 2014 Senior Review – a biannual assessment of operating missions – and propose for budget to fly K2 is expected by the end of 2013.