JJ Hermes edited Observations, Extractions and Detrending.tex  about 10 years ago

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The unconstrained spacecraft roll is an unstable equilibrium, and the pointing needs to be corrected every $3-6$\,hr by firing the thrusters. No data is lost during a thruster firing (known as a reset), but the change in attitude causes a strong jump in the measured flux from the star. The spacecraft rolls by no more than 25 arcsec between resets, which corresponds to motion of a star at the extreme edge of the field of view by no more than 1 pixel. {\em K2} can point a single field for up to 80 days, before the angle of the sun with respect to the solar panels exceeds allowed limits. \citet{Putnam14} provides further details of the capabilities and limitations two wheel operation.  %Resats -- I don't think I need We collected data on GD\,1212 from 2014\,Jan\,17  to talk about these  %Each one loses 1 LC 2014\,Feb\,13 in short-cadence mode (SC), where each exposure is 58.8\,s. After the first 2.6 days, the observations were interrupted for 15.1\,days by a safe-mode event  and 27 SC. subsequent engineering fault analysis. The final 9.0-day light curve can be found in Figure~\ref{fig:GD1212lc}. We have removed all points falling more than 4$\sigma$ from the light curve mean, resulting in 2.6- and 9.0-day observations with a duty cycle of more than 98.2\% and 98.9\%, respectively.  We collected data on GD\,1212 from 2014\,Jan\,17 In contrast  to 2014\,Feb\,13 in short-cadence mode (SC), the primary mission,  where only small masks were placed around  each exposure is 58.8\,s. After star,  the first 2.6 days, our observing data on GD\,1212  were interrupted for 15.1\,days by collected using  a safe-mode event and subsequent engineering fault analysis. $50 \times 50$ pixel ``super aperture.'' We expect the aperture size used in two-wheel mode will decrease as confidence in the spacecraft pointing ability increases.  The final 9.0-day observed pixels were processed through the CAL module of the {\em Kepler} pipeline \citep{2010SPIE.7740E..64Q} to produce target pixel files (TPFs);  light curve can be found in Figure\,\ref{fig:GD1212lc}. We have removed files were not produced for this commissioning data. TPF data for  all points falling more than 4$\sigma$ from stars observed during this engineering run are available at  the light curve mean, resulting in 2.6- and 9.0-day observations with a duty cycle of more than 98.2\% and 98.9\%, respectively. MAST Kepler archive\footnote{\url{http://archive.stsci.edu/kepler}}.  In contrast to the primary mission where only small masks were placed around each star, the data on GD\,1212 were collected using a $50 \times 50$ pixel ``super aperture.'' We expect the aperture size used in two-wheel mode will decrease as confidence in the spacecraft pointing ability increases. The observed pixels were processed through the CAL module of the {\em Kepler} pipeline \citep{Quintana10} to produce target pixel files (TPFs); light curve files were not produced for this commissioning data. TPF data for all stars observed during this engineering run are available at the MAST Kepler archive\footnote{\url{http://archive.stsci.edu/kepler}}. Our final 9.0-day dataset is nearly continuous and has a formal frequency resolution of 1.29 \muhz. The median noise level in the Fourier transform (FT) near 500 and 1500 \muhz\ for this 9.0-day run is roughly 0.0036\% (36 ppm). For the entire 26.7-day (42.8\% duty cycle) data set, set on the $K_p=13.3$ mag GD\,1212,  the median noise level is roughly 0.0028\% (28 ppm).