SIX happy astronauts are ready to return to Earth tomorrow with a spaceship full of scientific ``pay dirt.''
Reports from the Johnson Space Center in Houston say that the data coming in from the space shuttle Endeavour's German-Italian-American mapping radar and its air-pollution sensor are ``delighting scientists on the ground.'' Summing up this 10-day mission as it nears its end, National Aeronautics and Space Administration (NASA) scientist Vickie Connors told a press briefing that ``our science has been beyond our wildest dreams.''
That enthusiastic assessment is based on ``quick look'' data transmitted from Endeavour. Much of the detailed mapping data - which will cover about 50 million-square kilometers (18 million-square miles) - is stored on 180 high-density tape cartridges on board the orbiter. NASA estimates it will take five months to produce a complete set of images from these data.
Although the mission's main objective was to thoroughly test the Earth scanning instruments, the data gathered has practical scientific value. The radar images cover a wide variety of terrain and sea conditions. Often these give geologists, hydrologists, and oceanographers a detailed overview of areas that would otherwise be difficult to reach. The $366 million instrument has imaged the Gulf Stream to trace how its warm waters spread into the Atlantic Ocean. Radar images can also show such subtle features as the snow-melt line as spring advances into Canada.
Also the predesignated targets were expanded to cover areas of flooding in the American Midwest and eastern Germany. Project scientist Diane Evans from the Jet Propulsion Laboratory in Pasadena, Calif., explained that ``radar really is the ideal sensor'' for this purpose because it can see through the cloud cover. The overview this gives hydrologists will help them assess the future course of the flooding.
The radar-science team also is taking advantage of the new moisture the recent storms have brought to the Midwest to test radar's ability to sense soil moisture. Some of the ``quick look'' data have provided moving video images starting just north of the Oklahoma border in Kansas and ending just south of the Oklahoma River in Texas. Thomas Engman at NASA's Goddard Space Flight Center in Greenbelt, Md., will compare these data with on-the-spot soil moisture measurements.
If radar can give a reliable assessment of soil moisture, it could ultimately give agricultural planners and hydrologists an overview of moisture changes on a day-to-day and week-to-week basis. This would be a powerful aid both for economic forecasting and for flood- or drought-potential determination.
Meanwhile, scientists working with the Measurement of Air Pollution from Satellite (MAPS) experiment also mounted in Endeavour's cargo bay are surprised by the relatively high levels of carbon monoxide over the Northern Hemisphere. Previous space-based surveys had shown the highest concentrations over the Southern Hemisphere, possibly due to burning of grasslands and forests. MAPS principal investigator Henry Reichie Jr. from NASA's Langley Research Center in Hampton, Va., says the teams ``didn't expect [the North] to be as dirty as it appears to be.''
He speculated that the effect may be seasonal. Whatever the cause, this unexpected finding shows the importance of maintaining space surveillance to monitor global air-pollution changes.
Endeavour is scheduled to carry the Space Radar Laboratory and MAPS instrument back into orbit in August for a second nine-day surveillance mission.
Eventually, similar equipment may be placed permanently in space on unmanned satellites.