• Eli is a contributing correspondent for Science magazine.

'Colorblind' NASA Satellite May Yet See Green Seas

13 August 2010 3:59 pm

There's rare good news for the beleaguered U.S. environmental satellite fleet.

Two years ago, officials with NASA and the National Oceanic and Atmospheric Administration said that a key weather and climate satellite called NPP scheduled for launch next year would be, as we put it then, "essentially colorblind, at least as far as the oceans are concerned." That was because the main sensor on that spacecraft, VIIRS, was providing good data on factors such as clouds, weather, and sea temperatures but lacked the capability to measure ocean color and aerosols, data used widely by marine biologists, oceanographers, and climate scientists. NASA repeated that prognosis this January.

With orbiting satellites that measure ocean color all beyond their shelf life, glum ocean scientists were left to hope that VIIRS could be fixed by 2013, in time for the launch of the next craft in the multi-satellite NPOESS series. (Since then, it's been split into two parts, which includes the JPSS program.)

Now, ScienceInsider has learned, recent tests by government experts suggest that VIIRS may yet collect high-quality data on ocean color. Scientists with the National Institute of Standards and Technology conducted a full examination of the sensor in June and found the "crosstalk"—interference on the sensor's different parts—less of a problem than NASA officials had been led to believe. "There's a fighting chance to get ocean color on NPP," says a newly optimistic David Siegel, an oceanographer at the University of California, Santa Barbara.

"It's nowhere as bad as what the original test data was telling us," he says.

Siegel believes the problem was that testing done in 2008 and earlier suggested that VIIRS, considered the Achilles' heel of the entire NPOESS program was performing more poorly than it actually was. "Contractors did not do an adequate job of building test equipment," he said.

Siegel says that ocean color, which indicates the presence of ocean life near the surface, was once thought to be too subtle a phenomenon to measure with the flawed sensor. Now, because those measurements appear to be within reach, he says, the challenge will be to design new data-filtering algorithms to tease out those subtle differences from light collected by the satellite. "It's not like measuring clouds—you need a much more sensitive approach," he says. Government scientists are also trying to get the bureaucracy to approve a monthly procedure to flip the satellite on its back. That will allow scientists to calibrate its sensor with the moon, a necessary step for the delicate ocean color readings.

Science Insider has asked Raytheon, the company that built VIIRS, for comment.

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