PASADENA, Calif. -- NASA will launch a $135 million satellite to Mars on April 7, 2001, marking the U.S. space agencys return to the Red Planet after the recent failure of two other martian probes.

"All the pieces are in place, all the contractors are working toward that date," said Project Manager George Pace at NASAs Jet Propulsion Laboratory (JPL).

The spacecraft should arrive at Mars, and go into orbit on October 20, 2001. It will then take 76 days to gradually edge closer to the planets surface. By the first week of January 2002 the satellite will be whipping around Mars once every two hours.

The satellite will be the first NASA spacecraft to arrive at Mars since the losses of the $125 million Mars Climate Orbiter in September 1999 and the $165 million Mars Polar Lander three months later.

NASA originally planned to launch an orbiter and lander to Mars in 2001. In the wake of the loss of Polar Lander, NASA has delayed sending another lander to Mars until 2003 at the earliest.

Had the two 2001 missions proceeded as planned, NASA would have launched the lander from Cape Canaveral Air Force Station, Florida, and the orbiter from Vandenberg Air Force Base, California, both within days of each other. The orbiter launch would have been the first send-off of a planetary spacecraft from the West Coast.

Since the lander has been delayed, NASA has since moved the launch of the orbiter to Cape Canaveral, Pace said. A Boeing Delta 7925 rocket -- a Delta 2 with nine strap-ons -- will carry the orbiter into space.

The orbiter will carry three scientific instruments to probe the planet.

The instruments are:

• Gamma Ray Spectrometer: This instrument, a copy of one lost on the failed Mars Observer spacecraft in 1993, will measure the abundance of hydrogen (and thus water) in the upper 3 feet (1 meter) of the soil across the whole of Mars. The measurements will allow scientists to gauge the amount of water on Mars, including that frozen in the planets polar ice caps.
• Thermal Emissions Imaging System: This instrument will identify rock and mineral types on the martian surface, search for traces of hydrothermal activity and help pick out suitable landing areas for future missions. It will also image the surface of the planet at a 66-foot (20-meter) resolution.
• Mars Radiation Environment Experiment: This instrument will gather data on martian radiation, which could pose significant risks to astronauts on future human missions to Mars.

The satellite also will act as a high-speed data relay for future missions that will land on Mars, be they large spacecraft, like the 2003 lander, or even tiny rovers, airplanes or balloons. Over time, NASA hopes to boost the rate at which data can be sent to and from Mars by building what it calls an "interplanetary internet."

"This is the first internet node at Mars," Pace said of the 1,668-pound (758-kilogram) orbiter, designed to last at least four years, but which will probably last at least seven or eight.

For the time being, NASA calls the spacecraft the "Mars Surveyor 2001 Orbiter." However, at some point during the year NASA Headquarters will choose a snappier moniker for the probe.

Pace said the suggestions are already pouring in, including one that tips its hat to one of late director Stanley Kubricks best-known films.

"A lot of people want to call it 2001: A Mars Odyssey," Pace said.