Two small NASA satellites measure soil moisture, volcanic gases

Two NASA probes were recently deployed into low-Earth orbit, where they are demonstrating new technologies for observing atmospheric gases, measuring freshwater and detecting signs of volcanic eruptions.

The Low-Noise Radio Receiver of Opportunity B-Band Investigation Signals (SNoOPI) is testing a new technique for measuring root-zone soil moisture using radio signals produced by commercial satellites—a major undertaking for the 6U CubeSat. Shoe box.

Separately, the Hyperspectral Thermal Imager (HyTI) measures trace gases linked to volcanic eruptions. HyTI, a 6U CubeSat, will pave the way for future missions dedicated to detecting volcanic eruptions weeks or months in advance.

Both instruments were launched March 21 from NASA's Cape Canaveral Space Force Station to the International Space Station aboard SpaceX's Dragon cargo shuttle as part of the company's 30th commercial resupply mission. On April 21, the instruments were launched from the station into orbit.

'Flying ace' for finding fresh water in soil and snow

As a measurement technique, „signals of opportunity try to reuse what's already there,” said James Garrison, a professor of aeronautics and space at Purdue University and principal investigator of SNoOPI.

Garrison and his team will collect B-band radio signals produced by several commercial telecommunications satellites and try to reproduce them for scientific applications. The instrument enhances the value of space-based assets already in orbit, turning existing radio signals into research instruments.

„By looking at what happens when satellite signals are reflected off the Earth's surface and comparing it to a non-reflective signal, we can extract important characteristics about the surface where the signal is reflected,” Garrison said.

B-band radio signals are powerful and penetrate the Earth's surface to a depth of about one foot (30 cm). This makes them ideal for studying root-zone soil moisture and snow water equivalents.

„By monitoring the amount of water in the soil, we get a better understanding of crop growth and can intelligently monitor irrigation,” Garrison said. „Similarly, snow is very important because it also stores water. It's difficult to measure accurately on a global scale with remote sensing.”

More time for HDI and high-resolution thermal imaging

„I study volcanoes from space, when they start and stop erupting,” said Robert Wright, director of the Hawaii Institute of Geophysics and Planetology, director of the University of Hawaii at Hawaii University, and HIDI's principal investigator.

Hyperspectral imagers such as HDI measure a broad spectrum of thermal radiation signatures and are particularly useful for characterizing gases at low concentrations. Wright and his team hope that HDI can help calculate concentrations of sulfur dioxide in the atmosphere around volcanoes.

Volcanoes release large amounts of sulfur dioxide and other trace gases weeks or months before they erupt. Measuring those gases can signal an impending eruption, and HyTI's sensitivity to thermal radiation is also useful for observing water vapor and convection.

„HyTI has two scientific objectives. We want to try to improve how we can predict when a volcano will erupt and when an eruption will end,” Wright said. „And we're going to measure soil moisture depending on drought.”

Through its Earth Science Technology Office (ESTO), NASA worked closely with both Garrison and Wright to help turn their research into fully functional, space-ready prototypes.

„The ESTO program allows scientists to have interesting ideas and actually turn them into reality,” Wright said. Garrison agreed. „ESTO is a great partner.”