Solar Sensor Dropped From First Environmental Satellite in Troubled Program

Eli is a contributing correspondent for Science magazine.

The Obama Administration has decided to leave a critical sunlight sensor off the first of a series of environmental satellites that have been plagued with technical problems, cost overruns, and poor management.

The $14 billion program formerly known as NPOESS has been split into two new programs. Responsibility for its myriad climate sensors now falls to the Joint Polar Satellite System, to be run jointly by NOAA and NASA. (The other program, run by the Pentagon and focused entirely on weather, is called DMSP.) But the Total Solar Irradiance Sensor (TSIS) appears to have lost out in the reorganization. NOAA official Mary Kicza told reporters yesterday that the JPSS-1 satellite, set to launch in 2014, will not include TSIS. She said the decision was an attempt "to reduce risk."

At stake is a data record measuring the total amount of radiation striking Earth from the sun that goes back to 1978. That record, maintained by a series of satellites, is crucial to making accurate planetary energy budgets and measuring global warming as the intensity of sunlight fluctuates. Gaps in the record could be devastating to climate science because researchers require overlapping missions so as to calibrate each sensor to one another.

The previous versions of the solar sensor currently in orbit have an expected life of 30 months, and four satellites that have TSIS-like sensors that measure total solar radiation aboard are well beyond their design life. Virgo, for example, was launched in 1995, and SORCE was put into orbit in 2003.

There is a TSIS sensor scheduled to fly on NASA's Glory, which is set to launch in September. It is expected to temporarily fill the gap, provided that the launch goes smoothly.

Climate scientists have long relied on such short-life, experimental crafts for their satellite data. The goal of the failed NPOESS program was to "operationalize" measurements by flying satellites designed to pump out data for 7 years or longer. The idea was to combine NASA's focus on experimental missions with NOAA's expertise in providing continuous weather data, translated into payloads to monitor climate. "We're still quite concerned about finding [another] ride for TSIS," says NOAA solar physicist Rodney Viereck.

In 2005, plans to fly the TSIS on NPOESS were dropped as part of a major realignment of the program prompted by skyrocketing costs. Two years later, climate scientists were thrilled when the Bush Administration reinstated the sensor on NPOESS. There is a TSIS sensor built and ready for launch, but JPSS-1's main body, known as the satellite bus, will be too small to accommodate it.

Now they're back to square one. NOAA's Kicza says the agency "is working closely with NASA to explore options for flying TSIS." Viereck says that could mean launching it on a commercial rocket or adding it to an existing NOAA or NASA payload.

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