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.

"I am really excited about finally getting to see real Mars data," Boynton said this morning. "I started this project in 1985, and now we are down to just hours before we see the results. I can imagine it must be like giving birth, except here we have a 17-year gestation period."

Bill Feldman of Los Alamos National Lab, head of the Neutron Spectrometer experiment, said, "I am so excited, I can hardly restrain myself!"

Missions operations team members Michael Ward and Kris Kerry said they are "exhausted, optimistic, and very excited."

The GRS gamma sensor head will remain in this stowed, door-open configuration for several months, measuring the background gamma rays emitted by the Mars Odyssey spacecraft itself. At the end of this calibration period, researchers will deploy the sensor head on a 6-meter boom. Once the GRS is in its deployed, open-door configuration, the team will begin collecting science data for mapping the elemental composition of Mars.

Boynton and other Mars Odyssey scientists will detail their science objectives Friday, March 1, at news conference to be telecast from the NASA Jet Propulsion Laboratory in Pasadena, Calif. For more about the news conference, contact Mary Hardin of JPL Media Relations at 818-354-5011, mary.a.hardin@jpl.nasa.gov