SAN FRANCISCO — Although NASA’s Soil Moisture Active Passive (SMAP) satellite has been in orbit just over seven weeks, mission officials are delighted by the results of early testing.
SMAP program officials at the Jet Propulsion Laboratory in Pasadena, California, and Goddard Space Flight Center in Greenbelt, Maryland, conducted initial tests Feb. 27 and 28 of SMAP’s L-band radiometer and L-band nonimaging synthetic aperture radar with the spacecraft’s 6-meter conically scanning deployable mesh reflector antenna, which was unfurled Feb. 18 on its 5-meter carbon composite boom. “Both radar and radiometer behaved very well,” said Simon Yueh, SMAP project scientist at JPL.
NASA published SMAP’s first images March 9, showing the ability of the onboard instruments to identify variations in moisture levels among different regions. SMAP mission officials plan to continue to verify the performance of the instruments and begin spinning SMAP’s signature feature, the largest rotating mesh antenna ever sent into orbit, built by Northrop Grumman’s Astro Aerospace unit of Carpinteria, California. The antenna is scheduled to reach a speed of 14.6 revolutions per minute on March 26, which will enable the instruments to gather data on a 1,000-kilometer-wide swath of Earth’s surface and create global maps every three days showing moisture in the top 5 centimeters of soil and whether that soil is frozen or thawed, Yueh said March 10 by email.
SMAP is the most recent of five NASA Earth Science missions launched successfully between February 2014 and January 2015. On Jan. 31, SMAP flew on a United Launch Alliance Delta 2 rocket from California’s Vandenberg Air Force Base. NASA also launched in February 2014 the Global Precipitation Measurement (GPM) Core Observatory, a joint NASA-Japan Aerospace Exploration Agency mission, on a Japanese H-2A rocket from Tanegashima Island, and the Orbiting Carbon Observatory (OCO)-2 in July 2014 on a Delta 2 rocket from Vandenberg.
SpaceX’s Dragon capsule carried two additional Earth Science instruments to their new home onboard the International Space Station. RapidScat, an ocean wind scatterometer, traveled to the station in September 2014, followed in January 2015 by the Cloud-Aerosol Transport System (CATS) instrument to observe the location and composition of clouds and tiny airborne particles.
After launch failures that destroyed two high-profile NASA Earth Science missions, the Orbiting Carbon Observatory in 2009 and the Glory climate monitoring spacecraft in 2010, NASA officials are thrilled that all five missions are safely in orbit with instruments that appear to function well.
“The highly accurate measurements from these new missions will help scientists around the world tackle some of the biggest questions about how our planet is changing,” Peg Luce, NASA Earth Science Division deputy director, said Feb. 26 in a press briefing.
The oldest of the five missions, GPM, is unifying data drawn from an international constellation of satellites to give researchers the most comprehensive information ever published on global rain and snowfall, Gail Skofronick-Jackson, GPM deputy project scientist at NASA Goddard, said during the briefing. With GPM data, NASA is publishing maps showing rain and snow falling every 30 minutes with a resolution of 8 kilometers. In addition, the GPM core observatory’s Microwave Imager built by Ball Aerospace and Technologies Corp. of Boulder, Colo., and the Dual-Frequency Precipitation Radar built by JAXA and Japan’s National Institute of Information and Communications Technology are enabling researchers to clearly identify the internal characteristics of clouds and precipitation, which is helping to improve weather forecasting and climate change models, Skofronick-Jackson said.
OCO-2 also is showing early promise, said Ralph Basilio, JPL’s OCO-2 project manager. OCO-2’s mission team has completed preliminary calibration and validation of the satellite’s three-channel grating spectrometer built by JPL. On March 30, the OCO-2 team plans to begin releasing its first two data products, estimates of atmospheric carbon dioxide and data on solar-induced fluorescence, the light emitted by plants at near-infrared wavelengths during photosynthesis, Basilio said March 9 by email.
Six months into its mission, RapidScat is providing the U.S. Navy and National Oceanic and Atmospheric Administration with ocean wind observations used in weather forecasts and climate models, said Bryan Stiles, RapidScat science processing lead. Prior to RapidScat, most ocean wind speed and direction data came from the European Space Agency’s Advanced Scatterometer, which provided coverage for all areas outside Earth’s polar regions every 48 hours. By combining Advanced Scatterometer and RapidScat data, researchers can obtain wind speed and direction every 24 hours, Stiles said during the briefing.
The second space station instrument, CATS, a technology demonstration designed to use lidar to observe clouds and aerosols in Earth’s atmosphere, was installed Jan. 22 on the outside of the Japanese Kibo module. Space station officials used two robotic arms to remove CATS from Dragon’s trunk and install it on the outside of the module in a process that took approximately seven hours, Matthew McGill, CATS principal investigator at Goddard, said during the briefing.
CATS began collecting scientific data Feb. 10 with its laser operating in two of its three possible wavelengths. With its first observations over Africa, CATS identified clouds, dust from the Sahara desert and smoke from biomass burning.
The CATS mission also is designed to test the utility of using a third laser wavelength. CATS currently is sending out rapid laser pulses of 1,064 and 532 nanometers, the same wavelengths used on NASA’s Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations mission launched in 2006.
CATS also will test how the addition of a 355-nanometer wavelength coupled with receivers designed to count individual photons reflected by atmospheric particles can help researchers determine the size and location of airborne particles.