Dr. William J. Glaccum Profile

Dr. William J. Glaccum

at Caltech

SPIE Involvement:

Author

Publications (26)

Proceedings Article | 24 July 2018 Paper

Spitzer/IRAC precision photometry: a machine learning approach

James Ingalls, Jessica Krick, Sean Carey, Patrick Lowrance, Carl Grillmair, William Glaccum, Seppo Laine, Jonathan Fraine

Proceedings Volume 10698, 106985E (2018) https://doi.org/10.1117/12.2313640

KEYWORDS: Calibration, Machine learning, Data modeling, Photometry, Instrument modeling, Exoplanets, Statistical analysis, Stars, Space telescopes, Statistical modeling

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The largest source of noise in exoplanet and brown dwarf photometric time series made with Spitzer/IRAC is the coupling between intra-pixel gain variations and spacecraft pointing fluctuations. Observers typically correct for this systematic in science data by deriving an instrumental noise model simultaneously with the astrophysical light curve and removing the noise model. Such techniques for self-calibrating Spitzer photometric datasets have been extremely successful, and in many cases enabled near-photon-limited precision on exoplanet transit and eclipse depths. Self-calibration, however, can suffer from certain limitations: (1) temporal astrophysical signals can become aliased as part of the instrument model; (2) for some techniques adequate model estimation often requires a high degree of intra-pixel positional redundancy (multiple samples with nearby centroids) over long time spans; (3) many techniques do not account for sporadic high frequency telescope vibrations that smear out the point spread function. We have begun to build independent general-purpose intra-pixel systematics removal algorithms using three machine learning techniques: K-Nearest Neighbors (with kernel regression), Random Decision Forests, and Artificial Neural Networks. These methods remove many of the limitations of self-calibration: (1) they operate on a dedicated calibration database of approximately one million measurements per IRAC waveband (3.6 and 4.5 microns) of non-variable stars, and thus are independent of the time series science data to be corrected; (2) the database covers a large area of the "Sweet Spot, so the methods do not require positional redundancy in the science data; (3) machine learning techniques in general allow for flexibility in training with multiple, sometimes unorthodox, variables, including those that trace PSF smear. We focus in this report on the K-Nearest Neighbors with Kernel Regression technique. (Additional communications are in preparation describing Decision Forests and Neural Networks.)

Proceedings Article | 10 July 2018 Presentation + Paper

Patrick Lowrance, Jessica Krick, Jim Ingalls, Seppo Laine, Sean Carey, William Glaccum, Joseph Hora, Carl Grillmair

Proceedings Volume 10704, 1070427 (2018) https://doi.org/10.1117/12.2313953

KEYWORDS: Calibration, Space operations, Astronomy, Space telescopes, Solar processes, Photometry, Telescopes, Infrared radiation

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Proceedings Article | 6 July 2018 Paper

Correcting distortions in the infrared array camera during the cryogenic mission of the Spitzer Space Telescope

Carl Grillmair, Patrick Lowrance, Sean Carey, John Stauffer, James Ingalls, Jessica Krick, William Glaccum, Seppo Laine, Roberta Paladini, David Shupe, Schuyler Van Dyk

Proceedings Volume 10698, 106985D (2018) https://doi.org/10.1117/12.2313706

KEYWORDS: Infrared telescopes, Infrared cameras, Space telescopes, Cameras, Infrared imaging

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Proceedings Article | 6 July 2018 Paper

Using the Spitzer IRAC science archive for instrument trending

Jessica Krick, Jim Ingalls, Patrick Lowrance, Sean Carey, Jessie Christiansen, William Glaccum, Carl Grillmair, Seppo Laine

Proceedings Volume 10698, 106985Y (2018) https://doi.org/10.1117/12.2310185

KEYWORDS: Exoplanets, Telescopes, Databases, Clouds, Stars, Photometry, Atmospheric sciences, Space telescopes, Calibration, Data archive systems

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Proceedings Article | 29 July 2016 Paper

Spitzer Infrared Array Camera (IRAC) Pipeline: final modifications and lessons learned

Patrick Lowrance, Sean Carey, Jason Surace, James Ingalls, William Glaccum, Jessica Krick, John Stauffer

Proceedings Volume 9904, 99045Z (2016) https://doi.org/10.1117/12.2233804

KEYWORDS: Infrared telescopes, Space telescopes, Infrared radiation, Infrared cameras, Infrared imaging, Infrared telescopes, Calibration, Distortion, Stars, Cryogenics, Cameras

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