HST Moving Target Pipeline

Source Code Available Via GitHub Repository

Introduction

This archival collection of Hubble Space Telescope (HST) images of Solar System objects was specially prepared using a software package designed to handle images involving moving targets. This includes images of planets, natural satellites, asteroids, comets, etc, from several HST cameras (WFPC2, ACS, WFC3). HST moving target observations have typically made use of a header keyword (MTFLAG=YES), so many of the images were identified using this header keyword ¹. However, WFPC2 images were still carefully searched for and included in this collection manually as well, to catch any that did not use this keyword appropriately. A special search interface for these WFPC2 images was created, and will be updated to include later ACS and WFC3 imaging in the future. Until that time, we encourage users to make use of the Interactive Table at the bottom of this page, which includes the Version 1.0 files for all the instruments.

The standard HST pipeline was designed with fixed-targets in mind, and removes artifacts by aligning images based on their World Coordinate System and combining multiple images. But this doesn’t work for targets which are moving, rotating, or include secondary objects (e.g. satellites). So the images in this collection are always processed as single images, leaving any subsequent combinations to the user. The images are optimally resampled onto a common pixel scale, and are always oriented such that north is up for easy comparison between other images. The processing consists of three steps: artifact rejection (bad pixels, cosmic rays, star trails), image drizzling, and intensity scaling (for quick-look PNG images).

Cosmic ray (CR) rejection is performed using LA Cosmic, a Laplacian CR detection algorithm, implemented in the C programming language and freely available through a github repository. Full details of the algorithm can be found in van Dokkum, P.G. 2001, PASP, 13, 1420. Pixel resampling is accomplished using the AstroDrizzle tool within STScI's DrizzlePac software package. The drizzling is applied to both the CR-rejected and non-CR-rejected images. To ensure preview images (as PNG files) can be most useful for all types of observations, both a linear and log scaling version are created. This first release includes HST moving target observations from 1994 (after HST Servicing Mission 1) through August 2014.

Support for HST/AR program 12142 was provided by NASA through a grant from STScI, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Data Products

Each HST observation has the following data products created, with file names that follow the MAST HLSP standard rules:

Product Description	File Extension
CR-rejected, pixel resampled, intensity scaled image	_sci.fits
Non-CR-rejected, pixel resampled, intensity scaled image	_img.fits
AstroDrizzle weight maps (the same _wht applies to both the _sci and _img)	_wht.fits
CR-rejected, flat-fielded images ("acs" or "wfc3" only; applicable to _sci)	_flt.fits
calibrated image and data quality file, respectively ("wfpc2" only)	_c0m.fits, _c1m.fits
Preview image for _sci file with linear scaling applied	_sci-linscale.fits
Preview image for _sci file with log scaling applied	_sci-logscale.fits
Preview image for _img file with linear scaling applied	_img-linscale.fits
Preview image for _img file with log scaling applied	_img-logscale.fits

Data Access And Interactive Displays

You can search using the table below or each target's directory using the "Browse" link in the table. Table Instructions:

The first three columns are sortable by clicking on their headers.
You can search for a proposal ID or target description using the text boxes below the first two columns' headers. Wildcards are supported, .e.g, "*mars*"
You can select one of the instruments using the drop-down menu under the third column's header. Choose the top (blank) option to reset to all instruments.
Interactive Display links in the table allow you to see the processed images from all observations for a given program, and provides contrast control and zoom capabilities.
The tarball links allow you to download all the HLSP files from a given program.

Proposal ID
(sortable)

Target Description
(sortable)

Instrument Used

Linear Scale Previews

Log Scale Previews

Data Access

9059

mp762-pulcova

acs