04/11/94

Student Report One

April 10, 1994

Alicyn Campbell
Jonathan Woodring
Aaron Moshiashwili

In the summers of '92 and '93, through the combined efforts of the Johns Hopkins' Center for Talented Youth and Earthwatch's Challenge Awards program, eleven students from across the country worked at NASA's Jet Propulsion Laboratory assembling the crew notebook for shuttle mission STS-59, the Space Radar Laboratory.(SRL) This April, three of those students are following up on that, working at Johnson Space Center in Houston (Mission Control) as crew support during the actual mission.

This mission is the first in a series that will be wholly devoted to looking back at planet Earth, as opposed to looking outward at other planets and areas. The SRL is being carried by the Space Shuttle Endeavor and consists of three different instruments created to image and monitor the state of planet Earth -- MAPS, SIR-C and X-SAR. MAPS, or, Mapping Air Pollution from Space, was created by NASA at Langley Research Center in Langley, Virginia. It will be recording and gauging the global distribution of carbon monoxide in the earth's atmosphere.

Also on board is SIR-C/X-SAR, the first multi-frequency, multi-polarization radar ever to take images of earth from space. SIR-C, the first half of this dual unit, was created and assembled by the Jet Propulsion Laboratory in Pasadena, California. SIR stands for Shuttle Imaging Radar, and C designates it as the third such radar to have been sent into space. What distinguishes it from other such radars is that SIR-C utilizes two frequencies of radar, the L and C bands, and can collect the returns, or 'backscatter,' in up to four different ways, known as polarizations. Each different band and polarization will give dramatically different results and reveal different information about the area being scanned.

X-SAR, the X-Band Synthetic Aperture Radar, is the other half of this dual unit. Unlike SIR-C, X-SAR only operates on one frequency (X band) but X-SAR also has the ability to record multiple polarizations (editors note: X-SAR only collects V transmit, V Receive). X-SAR is attached to the SIR-C unit, but it was created by a coalition of the Italian space agency, ASI, and DARA, the German space agency.

The radar draws from the shuttle's power source and can see through the clouds, (and just about any other kind of weather disturbance) and can operate during day or night. Together they make a multifrequency radar capable of imaging the earth more precisely and effectively than ever before. In fact, the total amount of data to be recorded on this mission is estimated to be about 32 terabits, or a stack of encyclopediae twenty thousand volumes high.

As of today, the Shuttle mission seems to be going along quite smoothly. X- SAR had a few problems when it started up, but they were easily corrected and the radar is now working as expected. The first SIR-C images have been released and already are providing new insight into the state of the earth. For example, one of the images released, of Raco Michigan already displays differences from previous AIRSAR data.(AIRSAR is Airborne Synthetic Aperture Radar -- a less powerful unit built along the same lines and mounted on an aircraft used by NASA) The Raco images will be used not only for in-depth study of the area's ecology, but for the radar's calibration as well as to hopefully develop new algorithms to help us further understand the massive amounts of data the SRL is giving us.