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Hubble Space Telescope
Software Tools

This page contains links to various software tools having applications to WFC3 data.

Tools for planning WFC3 observations


The Exposure Time Calculators (ETCs) are on-line tools useful for predicting the signal-to-noise for various observing modes, once the characteristics of the source are known.


The Astronomer's Proposal Tool (APT) is the general proposal planning tool for all HST instruments.


The ST-ECF has extended John Krist's Tiny Tim Hubble PSF simulator to allow modelling of WFC3 point-spread-functions.


The dithering handbook explains the concept of dithering your observations and how to reduce the data using the three flavors of Drizzle software below.

aXeSIM Grism Simulator

ST-ECF have developed aXeSIM, a dedicated PyRAF/IRAF package to simulate 2-dimensional WFC3 slitless spectroscopic images. aXeSIM also can optionally produce a matching direct image (through a user-selected filter) for each slitless image.

In addition, aXeSIM for WFC3 is available via a Web application. Without any registration the user can select a WFC3 slitless mode, adjust additional parameters and start the simulation. Once ready, the simulation images and data can then be downloaded from the web. The web interface targets new, less experienced or occasional users and offers a subset of all options existing in aXeSIM.

Software for analyzing WFC3 data


the IRAF package containing CALWF3, which is used to process WFC3 data. STSDAS Help Pages.


PyRAF package that performs automated image registration, cosmic-ray rejection and final combination with AstroDrizzle, with a large number of optionally user-adjustable parameters.


"On the fly reprocessing". Requests for WFC3 data from the HST Archive always return data reprocessed with the current version of CALWF3 and the best available reference files. In most cases it is easier to let the OTFR pipeline reprocess data for you. If standard pipeline processing is inadequate, however, CALWF3 may be downloaded and run locally.

CTE Tools

Alpha-version of the pixel-based CTE correction for UVIS.

Crosstalk Tools

Tool for correcting crosstalk in the UVIS detector, and information on mitigating IR crosstalk.