Scientists at NASA’s Langley Research Center in Hampton, Virginia, have set out to transform the way the agency measures Earth’s energy budget — a key gauge of climate health.
The energy budget — or radiation budget — is the balance between the radiant energy that reaches Earth from the Sun and the energy that flows from Earth back out to space. When the balance tips toward more energy coming in than flowing out, warming occurs.
Using spare parts from a program called the Clouds and the Earth’s Radiant Energy System (CERES), Langley scientists recently completed work on an instrument called Athena. The first CERES instrument launched aboard the Tropical Rainfall Measuring Mission in 1997 (but decommissioned in 2015) and the most recent, CERES FM6, aboard the National Oceanic and Atmospheric Administration’s NOAA-20 satellite in 2017. All together there have been five CERES instruments operating, including TRMM, Terra (launched in 1999), Aqua (launched in 2002), Suomi-NPP (launched in 2011) and NOAA-20.
If spare parts from the CERES program don’t exactly bring to mind groundbreaking technological advances, don’t worry. There’s more.
Athena isn’t expected to gather much more than some basic top of atmosphere (TOA) energy budget measurements. But the real transformation here isn’t just in the measurements themselves — it’s in proving that Athena can make those measurements on a new type of satellite host.
“We’re trying to demonstrate the critical science measurement, but also an architecture that is adaptable and more cost-effective for the taxpayer and the government,” said Kory Priestley, principal investigator for Athena at Langley.
Earlier this month, Athena was shipped to a California company called NovaWurks, which has developed a type of satellite called a Hyper-Integrated Satlet, or HISat. Taking cues from human biology, specifically the structure and interactions of cells, HISats are engineered to aggregate, share resources, and conform to different sizes and shapes.
“We’re really merging the capabilities of the HISats and the payload,” said Priestley. “So our payload doesn’t need to bring as many resources to the overall effort.”
To be more specific, the capability of the HISat architecture to move easily in space and the fact that it has a built-in orientation system make it unnecessary for the Athena payload to carry its own orientation gimbal. The HISat also does much of the computer processing necessary to make a payload operate properly on orbit, which saves Athena having to carry its own system for doing so.
Another advantage of the platform is that it’s much smaller than a traditional satellite. Satellites such as Terra and Aqua were as big as school buses. A traditional CubeSat would’ve forced engineers to significantly shrink a CERES-like instrument. Not so with the HiSat. Priestley says the complete Athena HISat platform will be about as big as the electric toy car his granddaughter drives around in — bigger than a CubeSat, but about the same size as a CERES instrument alone, and with no requirement to shrink components because the spacecraft provides services the instrument used to provide itself.
Of course, in order to make complete measurements, CERES-type observations of incoming and outgoing TOA radiation must be coupled with simultaneous or near-simultaneous cloud property observations from instruments such as the Moderate Resolution Imaging Spectroradiometer (MODIS), which is on both the Terra and Aqua satellites, and Visible Infrared Imaging Radiometer Suite (VIIRS), which is on Suomi-NPP and NOAA-20. That’s not a problem when the instruments are located together on a large satellite. It’s still an issue scientists will need to address, though, in order to make reconfigurable sensorcraft such as NovaWorks’ HISats a viable option for a full-on radiation budget mission.
“What I want to do is evolve this into a small Earth radiation budget sensorcraft that makes the broadband measurements that CERES does as well as the narrow spectral- and spatial-resolution measurements of MODIS or VIIRS,” said Priestley.
Following satellite integration and pre-flight testing, Athena is currently scheduled to launch no earlier than December 2022.
Joe Atkinson
NASA’s Langley Research Center