Mars Odyssey today is a step closer toward its mission to map the Red Planet. Odyssey is carrying the Gamma Ray Spectrometer (GRS), built under the direction of Professor William V. Boynton at the University of Arizona Lunar and Planetary Laboratory.

The GRS is a suite of three instruments: the Gamma Subsystem, built by the UA; the Neutron Spectrometer, built by Los Alamos National Laboratory; and the High Energy Neutron Detector, built by the Space Research Institute, Moscow.

All three GRS component instruments operated as expected during the 11-month cruise to Mars.

The UA's Gamma Subsystem has been in a stowed, door-closed configuration during the flight to Mars. The stowed, door-closed configuration allowed the UA team to maintain warm temperatures required to protect the gamma subsystem.

The UA researchers successfully opened the door at 11 p.m. yesterday to allow the detector to cool to its very cold operational temperature of minus 138 degrees Celsius (minus 216 degrees Fahrenheit). The detector will begin collecting gamma rays at this temperature.