Galaxy Evolution Explorer GALEX Release 1 (GR1) Documentation

1.   Data Release Status

GR1 data have been released to the public in stages at MAST, the Multi-mission Archive at Space Telescope. The GR1 release is now complete.

GR1a) Released 30 Nov 2004, MIS (Medium Imaging Survey) and NGS (Nearby Galaxy Survey)

GR1b) Released 06 Dec 2004, AIS (All-sky Imaging Survey)

GR1c) Released 04 Jan 2005, DIS (Deep Imaging Survey)

GR1d) Released 24 May 2005, WSS (Wide Spectroscopic Survey) and MSS (Medium Spectroscopic Survey)

            See the GALEX spectroscopy primer for an introduction to GALEX Spectroscopic data.

Note that the actual exposure times accumulated in the data released in GR1 can vary widely from the nominal values (Survey summary), which are for long range planning only.  


The GALEX Early Release Observations, the previous public data release, was released Mar 11, 2004 by MAST. That release is now superseded by GR1, but is still available at .


Observations continue on the surveys. The NGS is largely complete. In spectroscopic observations, we are concentrating on MSS and DSS (Deep Spectroscopic Survey) before deciding whether to continue with WSS, which has lower S/N.


Guest Investigator Program cycle 1 observations began Oct 2004. For cycle 2 see . Dates are as follows:



11 March 2005

GALEX GI Cycle 2: Notice of Intent deadline

8 April 2005

GALEX GI Cycle 2: Proposal submission deadline

~1 October 2005

GALEX GI Cycle 2 observations begin

After 1 Nov 2005

GALEX Data Release 2 (GR2)


MAST will release guest investigator survey data to the public six months after releasing it to the guest investigator.

NASA has extended the GALEX baseline mission through September 2006, with an extended mission recommended through September 2008.

1.1.          Documentation Status

The GR1 documentation is being updated. Check back for changes and additions.


For questions about the use and interpretation of GALEX data, email . Answers will be emailed and/or posted to FAQ (see below). Please be patient.


For questions about using the MAST archive or database see .

2.   Documentation

In the PDF versions of HTML pages below, the links are not live, in spite of their look.

2.1.          GR1 Caveats [ PDF Version ]

Included here are various caveats that the user should be aware of to insure that the data is understood and used appropriately. In addition there are some idiosyncrasies that it may be helpful for the user to be aware of.

2.2.          Summary Information

2.2.1.                  Instrument/performance summary  [ PDF Version ]

Summary of the instrument and it’s performance.

2.2.2.                  Survey summary  [ PDF Version ]

Summary of the baseline GALEX survey plan.

2.3.          General information about the Mission

2.3.1.                  Mission & instrument overview  [ PDF Version ]

An overview of the mission written for astronomers planning to examine GR1 data or considering Guest Investigations. In any instances where this older document has not yet been updated and conflicts with other GR1 documentation,
the other documents take precedence.

2.3.2.                  Martin ApJL (PDF only)

“THE GALAXY EVOLUTION EXPLORER A SPACE ULTRAVIOLET SURVEY MISSION,” lead article in the Astrophysical Journal Letters dedicated GALEX issue, due out Feb. 2005.

2.4.          GR1 Data description

2.4.1.                  Basic data description   [ PDF Version ]

Description of GR1 emphasizing basic data products.

2.4.2.                  Observers guide  [ PDF Version ]

Guide for planning or interpreting GALEX observations.

2.4.3.                  Pipeline and advanced data description  [ PDF Version ]

GALEX Data pipeline overview with information about advanced data products.

2.4.4.                  Background determination & source extraction for GALEX data    (PDF only)

Detailed explanation of background determination and subtraction, image processing, and source extraction in the GALEX data pipeline.

2.4.5.                     Column descriptions for -xg-gsp.fits  [ PDF Version ]

Description of parameters provided in the band-combined spectroscopic files, -xg-gsp.fits.

2.4.6.                     GALEX spectroscopy primer   [ PDF Version ]

Description of GALEX spectroscopy including an explanation of slitless grism spectroscopy data and source overlaps, sensitivity, data products, quality assessment, a gallery of GALEX spectra, and an IDL tool for examining GALEX spectra efficiently.

2.4.7.                     GALEX spectroscopy artifacts   [ No PDF Version ]

Description of artifacts in GALEX spectroscopy including those caused by masking of nearby sources.

2.4.8.                     GALEX spectroscopy tool   [ No PDF Version ]

Description of an IDL tool for examining GALEX spectra efficiently.

2.5.          Calibration

2.5.1.                  Calibration ApJL (PDF only)

“THE ON-ORBIT PERFORMANCE OF THE GALAXY EVOLUTION EXPLORER,” the calibration article from the Astrophysical Journal Letters dedicated GALEX issue, due out Feb. 2005.

2.5.2.                  Calibration Nov 2004 update (PDF only)

A presentation that updates the earlier analysis contained in “THE ON-ORBIT PERFORMANCE OF THE GALAXY EVOLUTION EXPLORER,” especially in the areas of astrometry and photometry.

2.6.          Useful Information

2.6.1.                   FAQ

2.6.2.                  Glossary  [ PDF Version ]

2.7.          Technical background information

2.7.1.                  Detector guide (PDF only)

A detailed guide to operating the GALEX detectors.