This new map from COWVR shows Earth’s microwave emissions at 34 gigahertz at all latitudes visible from the space station (52 degrees north to 52 degrees south). This particular microwave frequency provides meteorologists with information about the strength of winds over the ocean surface, the amount of water in clouds, and the amount of water vapor in the atmosphere.
Green and white on the map indicate higher water vapor and clouds, while dark blue over the ocean indicates drier air and clear skies. The image captures typical weather patterns, such as tropical humidity and rain (the green band extending down the center of the map) and mid-latitude storms moving across the ocean.
“We’re off to a great start,” said Shannon Brown, the JPL technologist who designed the COWVR instrument. “Seeing this quality of data so early in the mission sets the stage for some very exciting things to come.”
COWVR is a complete overhaul of a classic instrument design, while TEMPEST is the product of a long push towards miniaturization of instrument components. If they continue to be successful, they will open the door to a new era where lower cost satellites will complement the existing fleet of weather satellites.
How Instruments Work
Radiometers need a rotating antenna so they can observe a wide swath of the Earth’s surface instead of just a narrow line. In all other spaceborne microwave radiometers, not only the antenna, but also the radiometer itself and the associated electronics rotate about 30 times per minute. There are good scientific and technical reasons for a design with so many rotating parts, but it’s a challenge to keep a spacecraft stable when there’s so much moving mass. Additionally, the mechanism that transmits power and data between the rotating side and the stationary side of the instrument proved to be time-consuming and difficult to construct.
Weighing about 130 pounds (57.8 kilograms), the COWVR has less than one-fifth the mass of the microwave radiometer used by the US military to measure ocean winds. Less than a third of its mass rotates. To avoid the need for a separate mechanism that transfers power and data from the spin to the stable parts, Brown mounted everything that needed to spin on a turntable.
He and his team enabled further design innovations by increasing the complexity of the data processing required – in other words, by finding software solutions to hardware challenges. For example, the team replaced a part of the instrument called the “hot target”, used to calibrate the radiometer’s polarization measurements, with a noise source that generates known polarized signals. When the calibration is complete, these known signals can be removed like any other noise in a data transmission.
COWVR’s companion instrument, TEMPEST, is the product of NASA’s decades of investment in technology to make space electronics more compact. In the mid-2010s, JPL engineer Sharmila Padmanabhan wondered what scientific goals could be achieved by packing a compact sensor into a CubeSat – a type of very small satellite often used to test new design concepts at low cost. costs. “We said, ‘Hey, if we can actually get a sensor compactly integrated into a CubeSat, we can get measurements of clouds, convection, and precipitation over time,'” Padmanabhan recalls. more information on storm growth.
Padmanabhan’s design was first tested in space from 2018 to last June. This CubeSat, known as TEMPEST-D (“D” for “demonstration”), measured water vapor in the atmosphere and captured images of many major hurricanes and storms. The newly deployed TEMPEST is about the size of a large cereal box and weighs less than 3 pounds (1.3 kilograms), with an antenna about 6 inches (15 centimeters) in diameter.
The size of the antenna dictates that TEMPEST can better observe only the shortest microwave wavelengths sensitive to water vapor – about 10 times shorter than those detected by COWVR. A smaller antenna “matches” the short wavelengths better, in the same way that the short column of air in a flute matches the short wavelengths of sound (high notes), while the long column of The tune of a tuba is best suited for the long wavelengths of low notes. .
The combined data from COWVR and TEMPEST provides most of the same measurements available from large microwave radiometers used for weather observations. The instruments have been funded by the US Space Force and the Navy, but users from other agencies, universities and branches of the military are also interested. These scientists are already working on mission concepts that would take advantage of new low-cost microwave sensor technologies to study long-standing questions such as how ocean heat feeds global weather patterns.