NASA aims satellite at asteroid


Soon after Valentine's Day in 1996, an asteroid named for the Greek god of love will become the target of a $125 million arrow shot into space by scientists at the Johns Hopkins University Applied Physics Laboratory in Laurel.

The interplanetary mission, dubbed Near Earth Asteroid Rendezvous (NEAR), will attempt to place a satellite into orbit around the asteroid Eros by December 1998. It is one of NASA's "Discovery" series of "quicker and cheaper" space science missions.

Eros is a chunk of rock about 22 miles long, circling the sun in a path that crosses the orbits of both Earth and Mars. It is the smallest celestial body that scientists have ever attempted to orbit with a spacecraft.

It's a tricky problem in orbital mechanics, said the APL's mission manager, Robert W. Farquhar, "but that's what makes it fun for a lot of people."

The mission is a welcome boost to the APL and its Space Department, which is facing severe post-Cold War cutbacks in Defense Department contracts.

In addition to designing and building the 1,700-pound spacecraft, APL scientists will control it from their facilities in Laurel -- another first. Previous planetary missions have been controlled from NASA's own centers, such as the Jet Propulsion Laboratory in California.

"There will be new jobs," said the space department's head, Stamatios M. Krimigis. "But most important will be the preservation of jobs, and of a [scientific] capability honed over a number of years."

In all, about 70 percent of the 400 jobs sustained by NEAR will be in Maryland, mostly at the APL, which currently employs 2,800.

Sen. Barbara A. Mikulski, a Maryland Democrat who supports the space program and chairs the Senate appropriations subcommittee that oversees NASA's budget, negotiated with the White House earlier this year to free $66 million for NEAR in this year's budget.

"I believe that science leads to technology, which leads to products, which leads to jobs," she told about 300 APL scientists and engineers yesterday. "If you can't look to the future . . . you will be shackled to the past and be left behind."

NEAR is the first of NASA's Discovery missions, a new breed of space project mandated by Congress to shrink the time and money needed to place satellites in space and produce scientific returns for researchers on the ground.

Giant projects such as the Hubble Space Telescope and the planned space station have fallen from political grace in recent years because they take decades and billion-dollar budgets to build and launch.

The APL's goal is to get NEAR into space in just 26 months, and for less than the $150 million ceiling set by NASA.

APL officials listed about a dozen recent satellites the laboratory has built for NASA and the Defense Department, in time frames of just one to three years, budgets of $18 million to $132 million and cost overruns averaging just 2 percent. "We feel we have the right combination of skills to do this job and do it well," Dr. Krimigis said.

Eros, chosen for its size and accessibility, is one of perhaps 1,000 "near-Earth" asteroids bigger than a kilometer (.62 miles) in diameter that cross paths with Earth. It caused a stir in 1975 when it passed within 14 million miles of Earth, a close encounter astronomical standards.

Occasionally, asteroids do collide with Earth. A small one is thought to have caused a huge explosion in Tunguska, Siberia, in 1908 that flattened a forested area bigger than Baltimore and its suburbs.

Astronomers believe asteroids are relics of the "nebula" of dust and gas that coalesced 4.5 billion years ago to form the early solar system. Because of their small size, they have been unaffected by the volcanism and weathering that have altered the compositions of planets such as Earth, Mars and Venus.

"They are frozen in place, if you like," said Dr. Krimigis. "So if you study an asteroid, you can learn about their composition and that of the planetary nebula."

Color cameras, X-ray and infrared spectrometers and other instruments aboard the NEAR probe will study the asteroid's size, shape, mass, gravity field and spin. NEAR is scheduled for launch in February 1996 from the Kennedy Space Center aboard an unmanned Delta II rocket. It's a date on which NEAR can be sent on its way to Eros with the least expenditure of energy, and therefore money, at launch. The first milestone in its journey will be an August 1996 flyby of another asteroid called Iliya, which lies in the "Main Belt" of asteroids between the orbits of Mars and Jupiter.

After a course change in January 1997, NEAR will circle back toward Earth, passing within 258 miles of its home planet in January 1998.

With a kick from Earth's gravitational force, NEAR will then shift into a new orbit that will deliver it to Eros in December 1998 -- by coincidence the 100th anniversary of its discovery.

Controllers at the APL will then maneuver the satellite into a once-daily orbit around the asteroid.

"We will start at a good distance away [around 62 miles] . . . and stay there for a while to get all the characteristics of the asteroid," said Dr. Farquhar.

The APL's orbital scientists need to study the asteroid's irregular shape, uncertain density and spin in order to fine-tune and maintain NEAR's orbit. Their job is complicated by the need to keep their spacecraft's solar panels aimed at the sun and its antenna toward Earth.

"Then we'll try to get in closer," he said, perhaps as close as 15 miles, where features as small as 3 feet across will become visible.

NEAR is expected to orbit Eros for about one year before exhausting its maneuvering fuel.

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