We comment on the potential for continuing asteroseismology of solar-type and
red-giant stars in a 2-wheel Kepler Mission. Our main conclusion is that by
targeting stars in the ecliptic it should be possible to perform high-quality
asteroseismology, as long as favorable scenarios for 2-wheel pointing
performance are met. Targeting the ecliptic would potentially facilitate unique
science that was not possible in the nominal Mission, notably from the study of
clusters that are significantly brighter than those in the Kepler field. Our
conclusions are based on predictions of 2-wheel observations made by a space
photometry simulator, with information provided by the Kepler Project used as
input to describe the degraded pointing scenarios. We find that elevated levels
of frequency-dependent noise, consistent with the above scenarios, would have a
significant negative impact on our ability to continue asteroseismic studies of
solar-like oscillators in the Kepler field. However, the situation may be much
more optimistic for observations in the ecliptic, provided that pointing resets
of the spacecraft during regular desaturations of the two functioning reaction
wheels are accurate at the < 1 arcsec level. This would make it possible to
apply a post-hoc analysis that would recover most of the lost photometric
precision. Without this post-hoc correction---and the accurate re-pointing it
requires---the performance would probably be as poor as in the Kepler-field
case. Critical to our conclusions for both fields is the assumed level of
pointing noise (in the short-term jitter and the longer-term drift). We suggest
that further tests will be needed to clarify our results once more detail and
data on the expected pointing performance becomes available, and we offer our
assistance in this work.Comment: NASA Kepler Mission White Paper; 10 pages, 2 figure
