IPP Analysis Programs
The primary IPP tasks are performed by a handful of programs.
- ppImage This program is the work-horse of the IPP. It is responsible for performing the detrend analysis on the individual images. It also handles the transformation of mosaic CCD camera images from one representation (eg, separate data arrays per cell) into other representations (eg, single data arrays for each chip). It also calls the photometry and astrometry modules psphot and psastro. All of the features of ppImage may be optionally selected by the user or based on the 'recipe' which defines the way the analysis is performed for a given circumstance and camera.
- psphot This program performs the complete object analysis for images in the IPP. It determines the PSF for the image using any of a wide variety of analytical models (and eventually pixel-based models as well). It then identifies objects which are PSF-like and measures their photometry. It also applies any of several extended-source models to the non-PSF-like sources and determines their parameters. Objects which it detects are subtracted from the images so that fainter sources can be detected and crowded objects can be measured accurately. psphot is available as a stand-along program, and it is available as a library module for integration with other analysis programs. It is an optional portion of ppImage.
- psastro This program accepts a collection of sources detected on an image and performs astrometric calibration. It has three major stages of operation, each optionally selectable depending on the quality of the input data and calibration goals. In the first stage, an initial astrometric calibration is determined based on the supplied image parameters, assuming the image is poorly calibrated. Either a triangle or a grid search is used to get a rough initial match between the image and reference objects. In the second stage, a complete linear or higher-order astrometric calibration is performed with iterative clipping to improve the match between image and reference. In the third stage, a collection of objects from different chips in a mosaic image are calibrated as an ensemble, with a single optical distortion model and individual models for each chip of the camera. Chips whose initial guess position fall outside the expected range of the chips locations are reset to be in their correct locations given the solution from the bulk of the mosaic chip positions. psastro is available as a stand-along program, and it is available as a library module for integration with other analysis programs. It is an optional portion of ppImage.
- stac this program performs the geometric warping and robust combination of a stack of science images observed at the same location.
- poisub this program performs the PSF-matching and image difference analysis.
- ppMerge this program performs robust stacking of images without geometric warping, allowing for manipulation of the pixel values as a function of image. This program is the core of the detrend creation stages.