Two small NASA satellites will measure soil moisture and volcanic gases

Two NASA pathfinding missions recently deployed to low Earth orbit, demonstrating new technologies for observing atmospheric gases, measuring freshwater and even detecting signs of possible volcanic eruptions.

The Signals of Opportunity P-Band Investigation (SNoOPI), a low-noise radio receiver, is testing a new technique for measuring root zone soil moisture using radio signals produced by commercial satellites – a big job for a 6U CubeSat the size of a shoebox.

In addition, the Hyperspectral Thermal Imager (HyTI) measures trace gases associated with volcanic eruptions. HyTI, also a 6U CubeSat, could pave the way for future missions aimed at detecting volcanic eruptions weeks or months in advance.

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

‘Flying bait’ for finding fresh water in ground and snow

As a measurement technique, “signals of opportunity try to reuse what already exists,” says James Garrison, professor of aeronautics and astronautics at Purdue University and principal investigator for SNoOPI.

Garrison and his team will attempt to collect the P-band radio signals produced by many commercial telecommunications satellites and reuse them for scientific applications. The instrument maximizes the value of space-based assets already in orbit, transforming existing radio signals into research instruments.

“By looking at what happens when satellite signals reflect off the Earth’s surface and comparing that to the signal that is not reflected, we can extract important properties about the surface where the signal reflects,” Garrison said.

P-band radio signals are powerful and penetrate the Earth’s surface to a depth of about 30 cm. This makes them ideal for studying soil moisture and snow water equivalent in the root zone.

“By monitoring the amount of water in the soil, we get a good insight into crop growth. We can also monitor irrigation more intelligently,” says Garrison. “Similarly, snow is very important because it is also a place where water is stored. It has been difficult to measure accurately on a global scale with remote sensing.”

High time for HyTI and high-resolution thermal imaging

“I study volcanoes from space to try to figure out when they start and stop erupting,” says Robert Wright, director of the Hawaii Institute of Geophysics and Planetology at the University of Hawai’i at Mānoa and HyTI’s principal investigator.

Hyperspectral imaging sensors such as HyTI measure a broad spectrum of thermal radiation signatures and are especially useful for characterizing gases in low concentrations. Wright and his team hope that HyTI will help them quantify the concentrations of sulfur dioxide in the atmosphere around volcanoes.

Weeks or even months before they erupt, volcanoes often emit larger amounts of sulfur dioxide and other trace gases. Measuring these gases could indicate an impending eruption. HyTI’s sensitivity to thermal radiation will also be useful for observing water vapor and convection.

“There are two scientific objectives for HyTI. We want to try to improve how we can predict when a volcano will erupt and when a volcanic eruption will end,” Wright said. “And we will also measure the soil moisture content in connection with drought.”

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

“The ESTO program allows scientists to have interesting ideas and actually put them into practice,” said Wright. Garrison agreed. “ESTO has been a great partner.”