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Hubble Space Telescope

DrizzlePac is new software package for aligning and combining HST images, which brings an array of new features and algorithmic improvements. It is recommended as the successor to the older, widely used MultiDrizzle software.

Starting in July 2012, all drizzled data products obtained from MAST are produced with AstroDrizzle. An abbreviation for Astrometric Drizzle, AstroDrizzle was designed from the ground-up to substantially improve the handling of distortion in the image header World Coordinate System.

AstroDrizzle removes geometric distortion, corrects for sky background variations, flags cosmic-rays, and combines images with optional subsampling. Drizzled data products from MAST are generated for single visit associations only.

To combine data from additional visits, TweakReg may be used to update the image WCS using matched source lists. Once the full set of images of a given target are properly aligned, they may be combined using AstroDrizzle.

The latest DrizzlePac release notes may be found on this page.


  • To obtain the latest version of DrizzlePac (v2.0 and higher), users are recommended to install the new AstroConda distribution. . This version is required to reprocess MAST data products retrieved after Feb 23, 2016.
  • DrizzlePac may still be obtained via Ureka, but only the SSBDEV distribution contains v2.0. Ureka has been deprecated, so users are strongly encouraged to switch to AstroConda.

SUPPORT FOR AUTOMATED MOSAIC BUILDING Align sets of images into a large mosaic in one step Read more
IMPROVED SKY MATCHING Produce seamless mosaics using new sky matching techniques. More details can be found in an example where these techniques are compared.
ACS TIME-DEPENDENT DISTORTION CORRECTION Supports the new ACS distortion calibration: Only DrizzlePac 2.0 is able to interpret and apply the latest ACS/WFC distortion reference files Read more
MITIGATION OF FALSE DETECTIONS Select point-source targets for alignment based on sharpness/roundness and use of DQ masks to limit inclusion of artifacts/cosmic-rays. Read more
ALIGN DIFFERENT HST CAMERAS Specify separate source finding parameters for input and reference images to optimize source detection from images taken with different HST cameras. Read more
ALIGN HST IMAGES TO NON-HST IMAGES Allows undistorted non-HST images to be used as references for aligning and drizzling HST data. Read more
NEW SUPPORT FOR EXCLUSION INCLUSION REGIONS Select specific areas of interest to use for alignment. We provide an example where these techniques are discussed.
FULL SET OF UPDATES Please see the DrizzlePac release notes



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