Kepler Mission Options

[JRehling]

nprev, Kepler has certainly filled out our knowledge of intrinsic planetary frequency, or ƒ, but there are a lot of crucially interesting blanks:

1) ƒ as a function of stellar class and metallicity (and planet radius, which is known to be inter-related).
2) ƒ for earth-sized planets at any orbital period beyond ~100 days. This was a primary goal and pending further analysis, is unmet.

Much more to say about (2):

We know the distribution of Super Earths, within some bounds, into the habitable zone, and further analysis will certainly improve that information. Then it's a reasonable hypothesis that the distribution of Earths as a function of increasing orbital period might follow the same trend as Super Earths, but until we have data, that's only a hypothesis.

My belief is that further analysis will almost definitely give us information on ƒ[Super Earth] to periods of 300-500 days, which will help set expectations of ƒ[Earth] for those periods, but not provide any hard evidence.

If, as is likely, analysis of past observations can cover periods of 300-500 days, then even the non-detection of any Earths will provide an upper bound on ƒ[Earth] for those periods, which would still be useful (in a pessimistic sense).

[Fressin et al, 2013] showed that there is a significant rate of false positives wherein a larger body transits a background star (or dimmer binary companion), so their method is to estimate the rate of true positives in each size category, from largest to smallest. This provides estimated rates of false positives, but doesn't identify which candidates are false positives, so if the number of detected Earths in the 300-500 day range is, as is extremely likely, a small integer (possibly zero), it will not be easy to tell if one or all of those are false positives. But we'll probably end up either with zero detections (and this an upper bound on ƒ[Earth]) or a very small number of systems for detailed follow-up observations, which would have a good chance of distinguishing between actual Earths and false positives.

[monty python]

I'm sorry. I was just whimsically wondering that if we had, say a month of off and on third reaction wheel use (I'm no expert on this), what would be the best use of fine pointing. Since the data seems to just be getting to confirming earth type planets I was looking for a way to maximise their confirmation.

[JRehling]

Before each quarter of Kepler data is collected, there's a phase of getting the craft pointed correctly for that quarter. The time between quarterly science operations can be as short as about 20 hours, which includes data downlink, but it's not as straightforward as, say, getting one image of Dione from Cassini, where the pointing is tolerant by many pixels.

Given any highly interesting systems, earth-based observation is merited in any case. The Kepler field is going to garner a lot of observation time in the years to come, not because it's intrinsically unique, but because of Kepler having given us indications of which stars might have transiting planets.