ITHACA, N.Y. -- Culminating a six-year development and building process led by Cornell University's Steven Squyres, the second of two Mars-bound clusters of scientific instruments, called the Athena payload, arrived March 11 at the Kennedy Space Center, Cape Canaveral, Fla.

The instruments will ride aboard NASA's twin Mars Exploration Rovers, scheduled for separate launches beginning May 30 and June 25.

"I've poured my heart and soul into this project, and the instruments feel almost like children to me. Starting in two weeks or so, the rovers will each be put onto their respective landers, the petals surrounding them will be closed and we'll never see them again," says Squyres, Cornell professor of astronomy and the principal investigator for the Athena science payload. "It's going to feel strange to say goodbye."

Carried as the science payload on each of the rovers, the Athena instruments promise to provide the most vivid images and to conduct the most comprehensive geologic examination yet of the Martian surface. The mission seeks to determine the history of the planet's climate while looking for sites that provide evidence of whether water once flowed and whether life once might have been possible.

"This will be a whole new experience for Martians like us," says James Bell, Cornell assistant professor of astronomy and payload element lead for the panoramic cameras, known as Pancams, carried by both rovers as part of the Athena packages. The cameras will provide high-resolution, 20/20 images, Bell says. "With this camera, we'll be able to capture the planet's sweeping landscapes and beautiful vistas. We don't know exactly what it will look like where we land, so we'll need the Pancam to help decide which way to go."

The airbag-enclosed, pyramid-shaped landers carrying the rovers will bounce onto the Martian surface three weeks apart next January. After that, the rovers will explore the surface through the winter and spring of 2004, each lasting 90 Martian days, or "sols" (a Martian sol is slightly longer than an Earth day). The rovers might be capable of traveling up to 100 yards per sol under ideal conditions, which is as far as NASA's Sojourner rover traveled during its entire mission in 1997.

In addition to the Pancam, the Athena instruments include a microscopic imager, three spectrometers (Mössbauer, alpha particle X-ray and infrared) and a rock abrasion tool, or RAT, to scrape away the outer layers of Martian rock. Other institutions that have helped build the payload include NASA's Jet Propulsion Laboratory (JPL), the U.S. Geological Survey, Arizona State University, Honeybee Robotics, the University of Mainz in Germany, the Max Planck Institut für Chemie in Mainz and the University of Copenhagen. JPL, in Pasadena, Calif., manages the Mars Exploration Rover mission.

Squyres and his research team have collaborated with engineers from JPL to integrate the Athena payloads with the rovers and to verify that the instruments can withstand the airbag landing, patterned on the Mars Pathfinder mission six years ago.

Additionally, the Athena team of more than 120 scientists from the United States, Germany, Denmark and other nations needed to prove that the instruments will work at frigid temperatures in the planet's meager atmosphere. It is common for Martian nights to dip to minus 90 degrees Centigrade (minus130 degrees Fahrenheit). "On the Martian surface there's a huge change in temperature from day to night. The instruments will expand and contract, so we put a lot of effort into thermal testing," says Squyres. Final testing of the Athena instruments will take place over the coming weeks at Cape Canaveral.

A full-scale rover model is on display at the Sciencenter, a science museum in Ithaca. In May, the model will move to its permanent home at the Smithsonian Institution's National Air and Space Museum in Washington, D.C.

On a bulletin board outside Squyres' Cornell office is a countdown to the first launch. With the instruments safely at Cape Canaveral, Squyres is relieved. "We've got a date with a rocket in May and June," he says. "The planets are lining up, and it's time to head for Mars."