Chapter 4:
Distortion Correction and Drizzling of ACS Images
4.1 ACS Geometric Distortions
4.1.1 On-orbit Calibration Program
4.1.2 Distortion Model
4.1.3 Analysis
4.1.4 Results
4.1.5 Distortion Table (IDCTAB)
4.2 Combination of Dithered Data
4.2.1 Introduction to Dithering
4.2.2 Introduction to Drizzling
4.2.3 Overview of Drizzling Software Tools
4.3 PyDrizzle
4.3.1 Application by the Pipeline
4.3.2 Association Tables
4.3.3 PyDrizzle Data Products
4.4 Reprocessing with PyDrizzle
4.4.1 Specifying the 'Bits' Parameter
4.4.2 Creating Custom Association Tables
4.4.3 Applying User-defined Shifts
4.4.4 PyDrizzle Examples
4.5 MultiDrizzle
4.5.1 Reprocessing with MultiDrizzle
4.5.2 Tasks Performed by MultiDrizzle
4.5.3 Specifying Shifts Between Images
4.6 MultiDrizzle Example
4.6.1 Detailed Processing Steps & Parameters
This chapter describes the geometric distortion of the ACS and presents the available tools and methods for removing the distortion and combining dithered datasets into clean, undistorted, and photometrically faithful output products.
The first section describes how the distortion has been quantified and how this information is held in reference files which are used by the calibration pipeline. Plots of the distortion field are given for the three ACS detectors.
The remaining sections give an overview of the drizzle method and discuss the higher level PyDrizzle and MultiDrizzle software tools available for distortion correction and image combination.
