NASA announced the impossibility to reactivate the radar of its SMAP (Soil Moisture Active Passive) satellite. The instrument ceased to function on July 7 and NASA engineers had been trying to reactivate it for weeks but without success. SMAP is an observatory designed to monitor the moisture present in the top 5 centimeters (2 inches) of soil and now will continue its mission in a limited way.
The SMAP satellite was launched on January 31, 2015 and, after having reached its orbit, its rotating mesh reflector with a diameter of 6 meters (about 20 feet) was deployed successfully. That seemed the most critical phase of the mission and during the first months SMAP regularly sent data from its radar and its other instrument, a radiometer.
The measurement of soil moisture is part of other missions such as that of ESA’s SMOS (Soil Moisture and Ocean Salinity) satellite, also using a radiometer called MIRAS (Microwave Imaging Radiometer using Aperture Synthesis). The importance of the SMAP mission was given by the fact that the combination of radar and radiometer was used to obtain accurate measurements of small areas of soil.
After the period of instrument calibration, SMAP worked regularly until July 7, so much that in April a first global map of soil moisture was released. When the radar stopped working, NASA engineers started working immediately to understand the origin of the problem and to try to make it work again.
The analysis of the situation went on for a few weeks and at the end the team charged with the task determined that the fault is in a high power amplifier (HPA). It’s designed to boost the radar’s pulse power levels to over 500 watts to allow the energy coming from the Earth’s surface to be measured accurately.
Unfortunately there’s no backup system for the failed amplifier. After attempting to reactivate the radar on August 24, the team ran out of possibilities and in the following days announced that it was impossible to recover the instrument. A commission was appointed to try to understand why the amplifier failed to try to avoid similar problems in the future.
Now at NASA they’re trying to determine the best way to use the SMAP satellite with the radiometer only. The development of software algorithms can help to partly compensate for the lack of radar data but there will be limitations to the mission. It’s really a shame because the SMAP mission was really ambitious and useful in various ways. We can only hope that it’s not limited too much by the radar’s failure.
