PARIS—The failure of the radar instrument on NASA’s Soil Moisture Active Passive (SMAP) satellite will have no effect on the European Space Agency’s purchase of U.S. technology similar to what is flying on SMAP, ESA Earth Observation Director Volker Liebig said Sept. 4.
In an interview, Liebig said ESA is moving forward with the selection this autumn of a prime contractor for the $500 million Biomass mission, to launch in 2020. The competing industrial teams submitted their bids this summer and a decision is expected in the coming weeks from ESA’s Tender Evaluation Board.
ESA and NASA’s Jet Propulsion Laboratory have agreed to a Technical Assistance Agreement that allows JPL to discuss deployable-antenna designs with the Europeans. JPL built the SMAP spacecraft and is responsible for mission operations, while Northrop Grumman Astro Aerospace provided the unfurlable antenna.
With no European manufacturer able to produce the hardware, ESA plans to purchase a 12-meter-diameter unfurlable antenna from either Northrop Grumman Astro Aerospace of Carpenteria, California, or the only other U.S. company that builds such systems, Harris Corp. of Melbourne, Florida.
Deployment of SMAP’s 6-meter-diameter antenna earlier this year was closely watched by ESA and went smoothly.
Liebig noted that SMAP instrument’s failure is in the power amplifier, not the antenna, and as such has no bearing on Biomass. “For us it’s only the structure we are buying, and that worked perfectly,” Liebig said. “The loss of the high-resolution imagery from SMAP is very sad for the global Earth observation community, not just NASA. I am not aware of any similar instrument being built anywhere else. It’s a real loss.”
SMAP’s JPL-built radar broke down July 7 because of a still-undiagnosed problem with the low-voltage power supply on its high-power amplifier. The amplifier boosts the power of the radar, which bounces radio signals off the surface of Earth to derive information including moisture levels in the soil.
The SMAP radar was built on a novel design that had not been tested in space before, a JPL official said.
“This specific radar instrument and design has not flown before, but its assemblies, including the high power amplifier and it’s power supply, leverage portions of past designs that JPL has flown,” Kent Kellogg, SMAP project manager at JPL, wrote in a Sept. 4 email.
After JPL tried and failed to restart the radar in a last-ditch effort Aug. 24, NASA headquarters appointed a mishap investigation board to look into the cause of failure. A separate JPL-led board will also investigate, NASA said in a statement.
Losing the radar means SMAP cannot fulfill the Level 1 science objectives, or minimum success criteria, NASA set in approving the mission. However, the spacecraft remains healthy and can continue creating global soil-moisture maps every three days, albeit at a lower resolution than intended.
SMAP will accomplish that with its second instrument: A passive radiometer built by NASA’s Goddard Space Flight Center. With the radiometer, SMAP can produce maps at a 40-kilometer spatial resolution, meaning a single pixel on a SMAP map equates to that many square kilometers. If the radar worked, the soil-moisture maps would have a resolution of roughly 9 kilometers.
Meanwhile, scientists will develop new algorithms to cope with SMAP’s limited resolution. NASA is also assessing whether it is possible to improve the radiometer’s resolution, according to the press release.
SMAP was one of the Earth Science community’s top priorities in the decadal survey published by the National Academies in 2007 — and according to NASA’s top Earth Science official, even the degraded mission satisfies the objectives scientists set out in that document.
“The decadal survey called for a mission that would make frequent global measurements of soil moisture and the freeze-thaw cycle with as high a resolution as possible,” NASA Earth Science Director Michael Freilich wrote in a Sept. 4 email. “Measurements from the radiometer-only SMAP mission will advance that science and form the basis for a host of applications consistent with recommendations in the decadal survey.”
The radiometer-only results are expected to be good enough, Freilich said, that even though SMAP’s radar failed, “NASA does not intend to pursue a replacement mission at this time.”
