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PS1 took approximately 370,000 exposures from 2010 to 2015, each exposure consisting of 60 CCD images. 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.
|Schematic of the images and analysis processing stage of the PS1 IPP Pipeline, described in Magnier et al.|
After an exposure is taken at the telescope, the raw image files of the 60 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.
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.
Image artifacts and anomalies
Warp images (available in DR2)
Stack images (DR1)
Difference images (planned to be available in future)
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 3-color image of NGC 894