NASA Instrument To Measure Soil Moisture On Earth
WASHINGTON: NASA is launching a new remote sensing instrument in space that will measure the moisture lodged in Earth’s soils with unprecedented accuracy and resolution.
The Soil Moisture Active Passive (SMAP) instrument scheduled for launch on January 29, 2015, has three main parts — a radar, a radiometer and the largest rotating mesh antenna ever deployed in space.
Remote sensing instruments are called “active” when they emit their own signals and “passive” when they record signals that already exist.
The mission’s science instrument ropes together a sensor of each type to corral the highest-resolution, most accurate measurements ever made of soil moisture — a tiny fraction of Earth’s water that has a disproportionately large effect on weather and agriculture.
To enable the mission to meet its accuracy needs while covering the globe every three days or less, SMAP engineers at NASA’s Jet Propulsion Laboratory in Pasadena, California, designed and built the largest rotating antenna that could be stowed into a space of only one foot by four feet for launch.
The dish is 19.7 feet in diameter.
“We call it the spinning lasso,” said Wendy Edelstein of JPL, the SMAP instrument manager.
The antenna is attached on one side to an arm with a crook in its elbow. It spins around the arm at about 14 revolutions per minute (one complete rotation every four seconds).