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PS1 took approximately 370,000 exposures from 2010 to 2015. These exposures are detrended, astrometrically calibrated, resampled (warped) onto a standard sky coordinate grid, stacked, and differenced. The different types of images are described below. More details about image filenames and data formats are included in the description of the PS1 Image Cutout Service. |
The following information is taken from Waters et al., which should be cited appropriately.
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Raw Images
After an exposure is taken at the telescope, the raw image files of the 60 OTA CCDs (see PS1 GPC1 camera) are corrected for persistence issues and then handed over to the PS1 IPP pipeline for further analysis. The STScI PS1 Archive does not provide these images.
Camera Images
The camera images are created by applying PS1 Exposure detrending to the raw images (i.e., masking, bias subtraction, flat fielding), and determining the astrometric and photometric calibration. The STScI PS1 Archive does not provide these images.
PS1 Image artifacts and anomalies
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PS1 Warp images (available in DR2)
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PS1 Stack images (DR1)
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Difference Images (planned to be available in
DR3future)
Difference images are created by subtracting a warp from another image, in general the stack, after matching the PSFs and normalization using a spatially varying kernel. All static objects such as galaxies and constant stars are subtracted out, and only the excess flux from the different epochs is left. Even though the differences images are not stored on disk, they can be created, and it is planned to make them accessible through the STScI PS1 interface in a later release.
PS1 Mask image
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PS1 Weight image
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