An Automatic Image Reduction Pipeline for the Advanced Camera for Surveys

TL;DR

This paper presents Apsis, an automated, Python-based image processing pipeline for the ACS instrument that handles image alignment, cosmic ray removal, combination, object detection, and redshift estimation, streamlining data analysis.

Contribution

The paper introduces Apsis, a flexible, object-oriented pipeline that automates multiple processing steps for ACS images, including new modules for redshift estimation and XML data encapsulation.

Findings

Automates image alignment, cosmic ray rejection, and combination.

Supports multi-band photometry and redshift estimation.

Encapsulates products in XML for archive ingestion.

Abstract

We have written an automatic image processing pipeline for the Advanced Camera for Surveys (ACS) Guaranteed Time Observation (GTO) program. The pipeline, known as Apsis, supports the different cameras available on the ACS instrument and is written in Python with a flexible object-oriented design that simplifies the incorporation of new pipeline modules. The processing steps include empirical determination of image offsets and rotation, cosmic ray rejection, image combination using the drizzle routine called via the STScI Pyraf package, object detection and photometry using SExtractor, and photometric redshift estimation in the event of multiple bandpasses. The products are encapsulated in XML markup for automated ingestion into the ACS Team archive.