338 research outputs found
Kepler Presearch Data Conditioning I - Architecture and Algorithms for Error Correction in Kepler Light Curves
Kepler provides light curves of 156,000 stars with unprecedented precision.
However, the raw data as they come from the spacecraft contain significant
systematic and stochastic errors. These errors, which include discontinuities,
systematic trends, and outliers, obscure the astrophysical signals in the light
curves. To correct these errors is the task of the Presearch Data Conditioning
(PDC) module of the Kepler data analysis pipeline. The original version of PDC
in Kepler did not meet the extremely high performance requirements for the
detection of miniscule planet transits or highly accurate analysis of stellar
activity and rotation. One particular deficiency was that astrophysical
features were often removed as a side-effect to removal of errors. In this
paper we introduce the completely new and significantly improved version of PDC
which was implemented in Kepler SOC 8.0. This new PDC version, which utilizes a
Bayesian approach for removal of systematics, reliably corrects errors in the
light curves while at the same time preserving planet transits and other
astrophysically interesting signals. We describe the architecture and the
algorithms of this new PDC module, show typical errors encountered in Kepler
data, and illustrate the corrections using real light curve examples.Comment: Submitted to PASP. Also see companion paper "Kepler Presearch Data
Conditioning II - A Bayesian Approach to Systematic Error Correction" by Jeff
C. Smith et a
Initial Characteristics of Kepler Short Cadence Data
The Kepler Mission offers two options for observations -- either Long Cadence
(LC) used for the bulk of core mission science, or Short Cadence (SC) which is
used for applications such as asteroseismology of solar-like stars and transit
timing measurements of exoplanets where the 1-minute sampling is critical. We
discuss the characteristics of SC data obtained in the 33.5-day long Quarter 1
(Q1) observations with Kepler which completed on 15 June 2009. The truly
excellent time series precisions are nearly Poisson limited at 11th magnitude
providing per-point measurement errors of 200 parts-per-million per minute. For
extremely saturated stars near 7th magnitude precisions of 40 ppm are reached,
while for background limited measurements at 17th magnitude precisions of 7
mmag are maintained. We note the presence of two additive artifacts, one that
generates regularly spaced peaks in frequency, and one that involves additive
offsets in the time domain inversely proportional to stellar brightness. The
difference between LC and SC sampling is illustrated for transit observations
of TrES-2.Comment: 5 pages, 4 figures, ApJ Letters in pres
TESS Data Release Notes: Sector 18 DR25
This release note discusses the science data products produced by the Science Processing Operations Center at Ames Research Center from Sector 18 observations made with the TESS spacecraft and cameras as a means to document instrument performance and data characteristics
Measuring Transit Signal Recovery in the Kepler Pipeline II: Detection Efficiency as Calculated in One Year of Data
The Kepler planet sample can only be used to reconstruct the underlying
planet occurrence rate if the detection efficiency of the Kepler pipeline is
known, here we present the results of a second experiment aimed at
characterising this detection efficiency. We inject simulated transiting planet
signals into the pixel data of ~10,000 targets, spanning one year of
observations, and process the pixels as normal. We compare the set of
detections made by the pipeline with the expectation from the set of simulated
planets, and construct a sensitivity curve of signal recovery as a function of
the signal-to-noise of the simulated transit signal train. The sensitivity
curve does not meet the hypothetical maximum detection efficiency, however it
is not as pessimistic as some of the published estimates of the detection
efficiency. For the FGK stars in our sample, the sensitivity curve is well fit
by a gamma function with the coefficients a = 4.35 and b = 1.05. We also find
that the pipeline algorithms recover the depths and periods of the injected
signals with very high fidelity, especially for periods longer than 10 days. We
perform a simplified occurrence rate calculation using the measured detection
efficiency compared to previous assumptions of the detection efficiency found
in the literature to demonstrate the systematic error introduced into the
resulting occurrence rates. The discrepancies in the calculated occurrence
rates may go some way towards reconciling some of the inconsistencies found in
the literature.Comment: 13 pages, 7 figures, 1 electronic table, accepted by Ap
TESS Data Release Notes: Sector 17, DR24
This release note discusses the science data products produced by the Science Processing Operations Center at Ames Research Center from Sector 17 observations made with the TESS spacecraft and cameras as a means to document instrument performance and data characteristics
The K2 Mission: Characterization and Early results
The K2 mission will make use of the Kepler spacecraft and its assets to
expand upon Kepler's groundbreaking discoveries in the fields of exoplanets and
astrophysics through new and exciting observations. K2 will use an innovative
way of operating the spacecraft to observe target fields along the ecliptic for
the next 2-3 years. Early science commissioning observations have shown an
estimated photometric precision near 400 ppm in a single 30 minute observation,
and a 6-hour photometric precision of 80 ppm (both at V=12). The K2 mission
offers long-term, simultaneous optical observation of thousands of objects at a
precision far better than is achievable from ground-based telescopes. Ecliptic
fields will be observed for approximately 75-days enabling a unique exoplanet
survey which fills the gaps in duration and sensitivity between the Kepler and
TESS missions, and offers pre-launch exoplanet target identification for JWST
transit spectroscopy. Astrophysics observations with K2 will include studies of
young open clusters, bright stars, galaxies, supernovae, and asteroseismology.Comment: 25 pages, 11 figures, Accepted to PAS
TESS Data Release Notes: Sector 20, DR27
This release note discusses the science data products produced by the Science Processing Operations Center at Ames Research Center from Sector 20 observations made with the TESS spacecraft and cameras as a means to document instrument performance and data characteristics
TESS Data Release Notes: Sector 9 DR11
This release note discusses the science data products produced by the Science Processing Operations Center at Ames Research Center from Sector 9 observations made with the TESS spacecraft and cameras as a means to document instrument performance and data characteristics
TESS Data Release Notes: Sector 16, DR22
This release note discusses the science data products produced by the Science Processing Operations Center at Ames Research Center from Sector 16 observations made with the TESS spacecraft and cameras as a means to document instrument performance and data characteristics
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