New year in space; NASA zeros in on planet earth - National Aeronautics and Space Administration 1994 mission schedule

Science News, Jan 15, 1994 by Ron Cowen

From ultraviolet imaging of the heavens to a long-awaited exploration of the sun's polar regions, an assortment of projects forms the lineup of NASA's 1994 mission schedule. But the majority of flights this year - running the gamut from ozone measurements to radar imaging of ocean and land features -- zero in on planet Earth. And with a little bit of luck, a spacecraft will take the first closeup portrait of a near-Earth asteroid.

As usual, mechanical and operational delays will likely alter the flight schedule over the year. But the following calendar gives the space agency's best estimate for research flights throughout 1994.

January: On Jan. 25, an unusual mission kicks off the year in space science. The satellite Clementine, sponsored by the Pentagons former "Star Wars" office, will test an armada of high-tech detectors by orbiting and observing the moon. Many of the detectors on board, though not ideal for high-resolution science studies, will provide new observations of the moon in visible, ultraviolet, and infrared light.

If all goes well, Clementine will fly by the near-Earth asteroid Geographos on Aug. 31, just before the end of the mission. This would be the first time a spacecraft has encountered an asteroid that lies so close to our planet. But astronomers caution that because Clementine - in contrast to the typical research mission -- doesn't have redundant hardware in case of equipment failure, the craft may not last long enough to meet the asteroid. Indeed, says Richard P. Binzel of the Massachusetts Institute of Technology, given all the maneuvers the craft must perform before meeting the asteroid, the craft may only have about a 50 percent chance of surviving until the encounter.

March: A space shuttle will host the second flight of the U.S. Microgravity Payload. These missions, which NASA hopes to continue about once a year, investigate the effects of the space environment on a variety of materials. Mounted on carriers open to space instead of housed in a pressurized space laboratory, experiments are limited to those that shuttle crew members can conduct using remote commands.

Also this month, one of NASA's frequent fliers - the Shuttle Solar Backscatter Ultraviolet (SSBUV) experiment-will hitch a ride on a shuttle orbiter for the sixth time. During its eight-day sojourn, SSBUV will once again measure concentrations of ozone, the fragile blanket of gas that protects life on Earth by absorb- ing much of the sun's harmful ultraviolet radiation. The satellite accomplishes this task by comparing the amount of solar ultraviolet radiation striking Earth with the amount scattered back into space by our planet's atmosphere. The greater the amount of light scattered, the lower the concentration of ozone.

The instrument will allow scientists to compare ozone measurements and calibrate ozone detectors on such long-duration craft as the NOAA-9 and NOAA-11 weather satellites and NASA's Upper Atmosphere Research Satellite (UARS). Simultaneous measurements made by the various SSBUV missions and the UARS will allow researchers to assess long-term changes in the ozone concentration in the stratosphere.

April: NASA plans three launches in the fourth month of 1994.

Mounted in the shuttle's cargo bay, the Space Radar Laboratory, making the first of two 1994 flights, will study Earth's surface and atmosphere using two instruments. Shuttle Imaging Radar, built in collaboration with the German and Italian space programs, will use a 12-meter radio antenna to take radar images of land, ocean, snow, and ice cover at three radio wavelengths.

A second instrument, Measurement of Air Pollution from Space (MAPS), will map the distribution of carbon monoxide in the atmosphere, a chemical implicated in the buildup of greenhouse gases.

Using an Atlas rocket, NASA also plans to send aloft another weather satellite in the Geostationary Operational Environmental Satellite series. Known as GOES-I, the craft will snap pictures of the atmosphere, measure variations in atmospheric temperature and humidity, and monitor wind velocity and the development of storms over Earth's western hemisphere.

Also in April, a craft called Wind will join the ranks of an international group of instruments designed to study the sun's influence on Earth. In particular, this satellite will study the impact of the solar wind -- the stream of charged particles that continuously blows out from the sun. The stream exits the sun through regions of exceptionally low atmospheric density and temperature known as coronal holes. Wind will act, in part, as an early warning system, detecting global magnetic storms, auroras, and other disturbances triggered by the solar wind.

During the first part of its mission, the craft will take readings in the turbulent region where the solar wind bounces back from a shock wave that forms when the wind rams into Earth's magnetic field.

To reach its final flight path, Wind will swing by the moon for a gravitational kick that will hurl it into its new orbit, some 1.4 million kilometers from Earth.