Feature Story

Spotlight on GALEX Guest Investigator Projects

Written by Linda Vu (Spitzer Science Center)
March 22, 2006

Don't let size fool you. Weighing in at 500 pounds, the Galaxy Evolution Explorer (GALEX) may be classified as one of NASA's Small Explorers, but it has enormous scientific capabilities.

Launched in April 2003, the telescope was built to answer one big question: how do galaxies grow and change over 10 billion years of cosmic history? By surveying millions of galaxies at ultraviolet wavelengths, scientists can determine how fast they are forming stars, and in what locations within galaxies the stars are forming-- all stepping stones to answering the larger question.

As keepers of one of the most sensitive ultraviolet telescope ever unleashed into space, members of the GALEX Principle Investigator team, led by Dr. Christopher Martin of Caltech, also know that the telescope has the potential to contribute great insights into astronomical topics beyond the scope of this main question. Thus, early on, it was decided to establish a Guest Investigator (GI) program, which allows astronomers from all over the world to use the telescope for observations that may be unrelated to galaxy evolution.

"GALEX is an extremely capable little telescope that can be used for lots of experiments for which it was not designed," says GALEX Mission Scientist, Dr. Susan Neff of the Goddard Space Flight Center.

According to Neff, GI programs are usually focused on very specific questions and need not be confined to galaxy studies.

"One person may wish to understand star formation in a particular unusual galaxy, and another may wish to characterize the gas associated with a dying star," she adds. "GI observations are driven by the individual investigators in the community, not by a focused science team."

The GI program classifies proposed observations into one of two categories: Standard and Legacy. Similar to the difference between an individual conducting a survey and a census survey, the data gathered from standard observations, like an individual's survey, are analyzed solely by the guest scientist. Meanwhile data from legacy observations, like the census, are made public and can be simultaneously analyzed by the guest scientist and the rest of the astronomical community. Guest Investigators may also carry out research using the extensive GALEX data archive, where the PI team observations are made publicly available to the scientific community.

As a tribute to telescope's great scientific capabilities, the GALEX Science Operations Center will post a series of spotlight articles featuring various Guest Investigator projects.