OBSERVING MODES

The majority of image data from the full focal plane are not saved due to constraints imposed by onboard storage and communications. Instead, data for specific targets are saved and transmitted as brightness-dependent subimages, with an average area of 32 pixels for a typical stellar target. This buffer size can be varied to accommodate extended or very bright objects.

All observations are taken at one of two temporal resolution settings: long (30-min) or short (1-min) cadence. A fixed number of targets have been reserved for GO observations and are available to successful proposers of Kepler solicitations: 3000 long cadence and 25 short cadence targets, assuming the average 32-pixel target size. There is a finite GO pixel budget and extended or bright objects requiring larger aperture sizes can decrease the total number of targets available to the GO program. These observations must be justified carefully.

Both long and short cadence target list uploads to the spacecraft will happen on a quarterly basis. Long cadence targets may be changed on a quarterly basis, while short cadence targets can be changed on a monthly basis. The ability to swap targets after some integral numbers of days provides the ability for observation of a larger number of total targets per year than the “slots” allocated to the GO program per quarter. Specification of target swapping during the course of the year and other details regarding planned observing modes needs to be included in the proposal using a target table, an example of which is given below. All GO observations terminate one year after the Cycle begins. Observers whose science objectives require observing timelines longer than one year may submit proposals to future cycles justifying the need for continuation of observations.

A judicious use of the short cadence targets is essential, given the small number of short cadences allocated to the GO program (25 targets per month). In other words, do not observe at 1- minute cadence on one particular object for an entire year if only one month of such data will be sufficient to achieve your science objective. Allow the fast cadence slot in those other months to be used for other targets (either yours or other observers) in order to maximize scientific return.

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