35-Year-Old Seasat Images Now Available From The Alaska Satellite Facility
Lee Rannals for redOrbit.com – Your Universe Online
The Alaska Satellite Facility (ASF) Distributed Active Archive Center (DAAC) has released newly processed digital images from NASA’s Seasat satellite that were taken 35 years ago.
The Seasat satellite was the first mission dedicated to oceanographic research. The satellite supported the first nonmilitary orbital synthetic aperture radar ever deployed. The newly released imagery commemorated the satellite’s 35th launch anniversary on June 27 this year.
“For the past 20 years, I’ve had scientists calling me and emailing me from many places in the world asking me when Seasat data might be available,” said Ben Holt, a senior research scientist at NASA’s Jet Propulsion Laboratory. “It still has unexamined value; it represents a now climatically relevant data set that has not been digitally processed to completion and so not fully analyzed.”
The imagery is derived from synthetic aperture radar (SAR), which works by bouncing a microwave radar signal off the surface of Earth to detect physical properties like surface roughness. SAR can see through darkness, clouds and rain, unlike optical sensor technology such as NASA’s Landsat mission.
Seasat suffered a catastrophic power failure during its fourth month after only operating for 106 days in orbit. However, the satellite was able to collect more information about the ocean surface than what had been acquired in the previous 100 years of shipboard research.
ASF said researchers may be able to use the new suite of Seasat images to study the rates of change in North America and Pacific Rim volcano faults known to be active at the time. Researchers could also use the 1978 data set to to establish an older baseline than what is currently available from other sensors. Examples might include observations of glaciers, sea ice, forest land cover and cities. This research could help establish an older baseline than what is currently available from other sensors.
Seasat SAR data had originally been archived on magnetic tapes, and images processed from the tapes were available only as optical images of film strips or scanned digital images.
“For software engineers, the most interesting thing about processing SAR images of 1978 are the challenges of resurrecting data that sat dormant on magnetic tapes for 35 years,” said ASF senior software engineer Tom Logan. “Basically we’ve been processing the newest SAR products from the oldest SAR data around. Images of Earth from 1978 have been gradually revealed as we’ve cleaned everything from ‘bit rot’ to time records.”
ASF said its interest in revitalizing the Seasat data came about through a combination of advances in processing technology and ongoing interest from scientists in tracking changes of the Earth’s surface over time.