PIPE (PSF Imagette Photometric Extraction) is a photometric extraction package for CHEOPS that is complementing the official Data Reduction Pipeline (DRP). While the DRP is using aperture photometry on the 200x200 pixel subarrays provided by CHEOPS, PIPE is using PSF photometry and can also extract photometry from the D=60 pixel imagettes sometimes provided for brighter stars. Imagettes have the advantage of shorter cadence than the subarrays, improving the time resolution.
Why should you care about PIPE when we already have the DRP? There are a couple of advantages in using PIPE:
- The shorter cadence of imagettes increases the time resolution of the photometry. This can be of a distinct advantage for some applications, e.g. when stellar activity such as flares need to be time resolved, or when ingress/egress is desired to be better resolved for timing purposes.
- PSF photometry is less influenced by background contaminant stars. PIPE can extract disentangled photometry from background stars (of separations greater than arcsec).
- For faint targets, PSF extraction makes better use of the signal by weighting it over the PSF, so that higher S/N photometry can be extracted.
- The shorter cadence of imagettes and producing an accurate PSF model make it easier to find and correct for cosmic rays.
- PSF photometry can properly deal with hot or bad pixels by either giving them a lower weight or masking them entirely in the fitting process. This becomes increasingly important as the detector ages in space.
The comprehensive PIPE manual includes instructions on how to install PIPE and how to download required calibration files (including a PSF library). The latest updated PIPE manual can be found at overleaf:
https://www.overleaf.com/read/ftwcbvsxdsyd#657246
Original author: Alexis Brandeker <[email protected]>, Stockholm University.
This project is Copyright (c) Alexis Brandeker and licensed under the terms of the GNU GPL v3+ license. This package is based upon the Openastronomy packaging guide which is licensed under the BSD 3-clause licence. See the licenses folder for more information.