Spacecraft Enters Orbit of Mars After 10-Month Trip
After a 10-month voyage halfway around the solar system, a NASA spacecraft caught up with Mars late Thursday and began orbiting the Red Planet for a pioneering two-year survey of its alien landscape.
Rocketing over the martian north pole, the $250-million Mars Global Surveyor successfully fired its main engine to slow itself enough to be captured by the planet’s gravity and enter an arrival orbit Thursday evening. Had the thruster misfired, the spacecraft would have sped past Mars to join eight of its predecessors--like the $980-million Mars Observer that vanished in 1993--in interplanetary oblivion.
Hidden behind the bulk of the planet for much of the critical 22-minute maneuver, the robot probe safely re-emerged into radio contact with Earth about 7 p.m. as cheering project scientists at the Jet Propulsion Laboratory in Pasadena and flight engineers at Lockheed Martin Astronautics in Denver donned special red Mars mission caps and ear-to-ear grins.
“We have a healthy spacecraft in Mars orbit, and we are go,” JPL flight operations manager Joseph G. Beerer reported as the antennas of the Deep Space Network in Goldstone and Canberra, Australia, reestablished contact with the Global Surveyor.
“We are at Mars to stay,” said Wesley T. Huntress Jr., NASA associate administrator for space science, celebrating the second successful flight to Mars since July.
Preliminary engineering reports showed that the spacecraft and its engines performed almost perfectly in slowing the probe’s speed by almost 2,000 mph in order to enter orbit around Mars.
“Navigating to Mars is truly a remarkable achievement,” said project manager Glenn E. Cunningham at JPL. “We are really threading the needle. This is much like taking a baseball and throwing it from here . . . and hitting a specific window in the Empire State Building in New York.”
In the months to come, the probe is scheduled to conduct the most systematic survey ever attempted of Mars. It will help pave the way for a decade of sustained exploration of the solar system’s fourth planet by a series of robotic rovers, orbiting surveyor craft and eventually, National Aeronautics and Space Administration officials hope, human astronauts.
NASA scientists expect to turn on the Global Surveyor’s scientific instruments Saturday evening, and on Monday receive the craft’s first research data, which it is hoped will settle long-standing questions about the planet’s magnetic field.
In all, the probe carries six major sensors designed to, among other things, analyze the planet’s exotic terrain by using visible and infrared radiation to determine its mineral composition. The sensors also will monitor the planet’s weather, measure its magnetic field and precisely size up its remarkable hills and valleys.
The entire martian globe will be photographed in five times greater detail--sharp enough to reveal small surface features such as boulders and sand dunes--than obtained by the Viking orbiters, which studied the planet for several years in the late 1970s.
The Global Surveyor may even be able to photograph the Mars Pathfinder lander, which is still sending information from the planet’s surface. The surveyor “will rewrite the reference books on Mars,” Cunningham said.
Project scientists will be especially alert for any indication of water on the martian landscape, such as ancient drainage ways or sedimentary deposits, as an indirect indicator of the possibility of life.
“We have no instruments that would actually detect life,” said project scientist Arden L. Albee at Caltech. “But we will be looking for evidence of the kind of conditions that might be conducive for life.”
During the next four months, the spacecraft will use the drag of the martian atmosphere to slow itself down and ease itself into a more circular orbit, in a fuel-saving technique called aerobraking. From then until March it will position itself for the start of its two-year mapping survey.
Throughout the craft’s orbital maneuvers, project officials will be keeping a careful watch on seasonal dust storms that could kick potentially hazardous grit into the upper fringes of the martian atmosphere, where it could jeopardize the spacecraft. They are prepared to order the surveyor to a higher altitude at the first sign of danger.
Although its immediate predecessor--the Mars Observer--vanished as it prepared to enter the planet’s orbit, the Global Surveyor survived its long voyage in good condition. The only problem it has encountered is a solar panel being jammed by a piece of broken metal shortly after its launch in November.
Flight controllers had the craft shake gently during its cruise in an unsuccessful attempt to free the trapped debris. The panel still is tilted about 19 degrees from its fully deployed position, JPL project officials said. They believe the bent solar panel poses no danger, but they have reconfigured the spacecraft to ensure that it does not fold up on itself during the aerobraking.
“The mission has been completely redesigned to accommodate that condition,” said Claude W. McAnally III, the Lockheed program manager for the project. “There is a possibility with the forces on [the panel] during aerobraking, it could latch” into its proper position, he said. “If it moves at all, it will latch and remain latched for the duration of the mission.”
