LA CAÑADA FLINTRIDGE >> Half of the two, large science instruments in a breakthrough Jet Propulsion Laboratory-led satellite project broke about seven months after the mission began, NASA announced this week.
The Soil Moisture Active Passive spacecraft’s two scientific tools are an active radar and a passive radiometer. They make up for the other’s limitations. Together the scientific tools were supposed to estimate soil moisture at a resolution of about 5.6 miles.
The radar was the only tool responsible for collecting freeze-thaw information, so NASA and JPL are working on algorithms to extract freeze-thaw information from the partner radiometer instrument, said Kent Kellogg, SMAP’s JPL-based project manager.
“We do a lot of testing on the ground to make sure the designs will be built properly and will last in the environment,” Kellogg said. “But space is a very unforgiving place, and we can have these kinds of problems where despite our best efforts with design and vigorous testing, something surprises us. It’s very uncommon, but these things can happen occasionally.”
NASA budgeted $914.5 million for the mission to help scientists better understand how Earth’s water, energy and carbon cycles are linked. One of the goals is to enhance humanity’s ability to monitor and predict natural hazards such as floods and droughts. SMAP data also improves weather forecasting and crop yield predictions.
Launched on Jan. 31, the SMAP satellite is the first mission where scientists have attempted to collect high-resolution, high-accuracy soil moisture data, Kellogg said.
The broken radar collected soil moisture and freeze-thaw measurements at a higher resolution of up to 1.9 miles. The still functioning radiometer generates more accurate soil moisture measurements but resolution is lower at about 25 miles.
Although SMAP’s radar can no longer return data, the earth sciences satellite continues to produce high-quality measurements, NASA reported.
“Although some of the planned applications of SMAP data will be impacted by the loss of the radar, the SMAP mission will continue to produce valuable science for important Earth system studies,” Dara Entekhabi, SMAP science team lead at the Massachusetts Institute of Technology, said in a statement.
SMAP’s primary mission is expected to conclude in April 2018 unless NASA decides to extend the mission, Kellogg said.
Recently, NASA has produced a greater number of highly targeted missions with fewer instruments that are larger in size, Kellogg said.
“It’s not unusual that earth missions in particular have instruments that are very focused on specific science objectives,” he said. “We know a lot about Earth and we’re trying to refine that knowledge, so the instruments tend to be more sophisticated, and they tend to be larger. And for that reason, they tend to be more like us — more interdependent.”
What went wrong and the investigation
Without any signs of impending trouble, SMAP’s radar ceased transmitting on July 7, Kellogg said. There was an anomaly with the radar’s high-power amplifier, which is designed to increase its power supply to more than 500 watts.
Following an unsuccessful power up attempt on Aug. 24, a JPL team determined “it had exhausted all identified possible options for recovering nominal operation of the (high-power amplifier),” JPL said. The device is probably not recoverable.
NASA has organized a mishap investigation board to try to understand what led to the device malfunction and to figure out how these events could be prevented in future missions. JPL will assemble a separate failure review board to collaborate with NASA’s probe. The two are expected to release more in-depth analysis of the malfunction by the end of the year, Kellogg said.
What happens now
In the meantime, scientists are working on algorithms to improve SMAP’s resolution to about 12 miles, Kellogg said. NASA may be able to figure out techniques using other satellites to get 6-mile resolutions, but that’s mere speculation at this point, Kellogg said.
The satellite, whose science mission began in April, continues normal operations. It released initial global soil moisture maps on April 21. Thus far, the mission has gathered more than four months of science data, nearly three of which included a functioning radar instrument.
SMAP scientists are expected to release beta-quality soil moisture data at the end of September, and validated data is scheduled to be released in April 2016.
