NASA’s SMAP mission, launched in January to map global soil moisture and detect whether soils are frozen or thawed, continues to produce high-quality science measurements with one of its two instruments.
Credits: NASA
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Mission managers
for NASA's Soil Moisture Active Passive (SMAP) observatory have
determined that its radar, one of the satellite’s two science
instruments, can no longer return data. However, the mission, which was
launched in January to map global soil moisture and detect whether soils
are frozen or thawed, continues to produce high-quality science
measurements supporting SMAP’s objectives with its radiometer
instrument.
The SMAP mission is designed to help scientists understand the links
between Earth's water, energy and carbon cycles and enhance our ability
to monitor and predict natural hazards like floods and droughts. SMAP
remains an important data source to aid Earth system modeling and
studies. SMAP data have additional practical applications, including
improved weather forecasting and crop yield predictions.
The SMAP spacecraft continues normal operations and the first data
release of soil moisture products is expected in late September.
"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," said Dara
Entekhabi, SMAP Science Team lead at the Massachusetts Institute of
Technology in Cambridge.
Photo: NASA |
On
July 7,
SMAP’s radar stopped transmitting due to an anomaly involving the
radar's high-power amplifier (HPA). The HPA is designed to boost the
power level of the radar's pulse to more than 500 watts, ensuring the
energy scattered from Earth's surface can be accurately measured.
The SMAP project at NASA's Jet Propulsion Laboratory (JPL) in
Pasadena, California, formed an anomaly team to investigate the HPA
issue and determine whether normal operation could be recovered. A
series of diagnostic tests and procedures was performed on both the
spacecraft and on the ground using flight spare parts.
Following an unsuccessful attempt on Aug. 24 to power up the radar
unit, the project had exhausted all identified possible options for
recovering nominal operation of the HPA and concluded the radar is
likely not recoverable.
NASA has appointed a mishap investigation board to conduct a
comprehensive review of the circumstances that led to the HPA anomaly in
order to determine how the anomaly occurred and how such events can be
prevented on future missions. JPL also will convene a separate failure
review board that will work with the NASA investigation.
SMAP was launched
Jan. 31 and began its science mission in April, releasing its first global maps of soil moisture on
April 21.
To date, the mission has collected more than four months of science
data, almost three months with the radar operating. SMAP scientists plan
to release beta-quality soil moisture data products at the end of
September, with validated data planned for release in April 2016.
SMAP's radar allowed the mission's soil moisture and freeze-thaw
measurements to be resolved to smaller regions of Earth – about 5.6
miles (9 kilometers) for soil moisture and 1.9 miles (3 kilometers) for
freeze-thaw. Without the radar, the mission's resolving power will be
limited to regions of almost 25 miles (40 kilometers) for soil moisture
and freeze-thaw. The mission will continue to meet its requirements for
soil moisture accuracy and will produce global soil moisture maps every
two to three days.
SMAP’s active radar and passive radiometer instruments are designed
to complement each other and mitigate the limitations of each
measurement alone. The radar enabled high-resolution measurements of up
to 1.9 miles, but with lower accuracy for sensing surface soil moisture.
In contrast, the microwave radiometer is more accurate in its
measurements but has lower resolution of about 25 miles. By combining
the active and passive measurements, SMAP was designed to estimate soil
moisture at a resolution of 5.6 miles.
The nearly three months of coincident measurements by the two
instruments are a first of their kind. The combined data set allows
scientists to assess the benefit of this type of combined measurement
approach for future missions. Scientists now are developing algorithms
to produce a freeze-thaw data product at 25-mile resolution from the
radiometer data. They also are evaluating whether the 25-mile radiometer
soil moisture resolution can be improved.
Based on the available SMAP mission data, scientists have identified
other useful science measurements that can be derived from the
radiometer data, such as sea surface salinity and high winds over the
ocean surface. Over the next several months, the SMAP project and NASA
will work to determine how to implement these new measurements into the
project's data products.
SMAP is managed for NASA's Science Mission Directorate in Washington
by JPL, with instrument hardware and science contributions made by
NASA's Goddard Space Flight Center in Greenbelt, Maryland. JPL built the
spacecraft and is responsible for project management, system
engineering, radar instrumentation, mission operations and the ground
data system. Goddard is responsible for the radiometer instrument and
science data products.
More information on the SMAP mission is available at:
http://www.nasa.gov/smap