NASA’s earth science division should create a new, medium-size $350 million mission line that is open to competition, according to a new report out today from the National Academies of Sciences, Engineering, and Medicine (NASEM) that lays out the agency’s earth science priorities in a so-called decadal survey, a consensus wish list for U.S. earth scientists. In addition to the call for the new mission line, the report recommends that five larger flagship missions be launched in the coming decade.
Over the past decade, thanks to an infusion of climate-focused spending from the administration of former President Barack Obama, NASA’s budget for satellite-based observation of Earth grew to $1.9 billion last year, the largest of NASA’s four science divisions. "We’re not at the bottom of some pit like we were before," says Bill Gail, chief technology officer at the Global Weather Corporation in Boulder, Colorado, and co-chair of the committee that wrote the report, titled Thriving on Our Changing Planet.
But assuming the earth science budget now remains flat—far from a sure bet with the administration of President Donald Trump, which has been leery of climate research—NASA will have tough choices to make on future missions. "The simple fact is there’s not enough money to do what we want to do," says Waleed Abdalati, director of the Cooperative Institute for Research in Environmental Sciences at University of Colorado in Boulder, and co-chair of the committee. Abdalati hopes that the new competitive mission line, along with a slim list of five flagship missions, will keep the earth science division within reasonable budgetary bounds.
In 2007, when NASEM released its first earth science decadal survey, it prioritized 15 explicitly defined missions, many already tied to NASA centers. The new report recommends different types of observations without naming particular missions—although the correspondence to specific mission plans is clear in some cases. The recommendations take into account existing and planned satellites, such as a new line of Sentinel satellites from the European Space Agency. The survey aims to provide continuity on some valued measurements, and plot where the United States can fill potential gaps.
The first priority observation recommended for flight, with a cost cap of $650 million, would target changes on Earth's surface, likely with imagery across a wide range of wavelengths. The technique, called hyperspectral imagery, would advance on pioneering observations from Hyperion, a satellite instrument that was decommissioned last year. The recommendation is likely a shot in the arm for the Hyperspectral Infrared Imager (HyspIRI), a mission from NASA's Jet Propulsion Lab in Pasadena, California, that was an uncompleted mission recommended by the last decadal.
The other two largest investments, each cost capped at $800 million, would target clouds and atmospheric particles called aerosols. Aerosols and clouds are the two biggest drivers of uncertainty when it comes to the speed of human-driven global warming. The missions could end up being successors to the CloudSat and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellites. Like the existing pair, the panel envisions the missions launched in close succession to take advantage of overlapped observations. The recommendation for two separate missions could complicate the future of an expensive proposed mission, called Aerosol/Clouds/Ecosystems, out of NASA's Goddard Space Flight Center in Greenbelt, Maryland, that would have combined these instruments on the same satellite.
The final two priority observations are a $300 million successor to the recently ended Gravity Recovery and Climate Experiment (GRACE) and its successor satellite, expected to be launched early this year, and a $500 million satellite that would target tiny movements in the surface of Earth using radar techniques.
Beyond these top priorities, the report names seven observations that should compete against one another in a new line of missions, called Earth System Explorer. NASA’s earth science has featured little competition in recent years, unlike the agency’s other science divisions. Within planetary science, for instance, NASA has two competitive lines, called Discovery and New Frontiers. With each mission capped at $350 million, the panel envisions explorer projects taking less than 4 years to develop, with the agency selecting three missions from among the seven candidates for flight this next decade.
The potential observations for the explorer line are: atmospheric winds; greenhouse gases, providing potential continuity with the Orbiting Carbon Observatories; ice elevation, which would continue measurements of the ice sheets from IceSat-2, launching late this year; ocean surface winds; ozone and trace gases; snow depth and amount; and land ecosystems. The report is not prescriptive in how these measurements should be made, Abdalati adds. These observations could come from single satellites or constellations of smaller satellites—whatever combines the best mix of science and cost.
The panel hopes that competition, and withholding specific mission recommendations, could help cure some of the cost inflation that came after the last survey, when missions were assigned to NASA centers and quickly saw their costs double in development. It was one of the mistakes of the last decadal, says Berrien Moore, the vice president of weather and climate programs at the University of Oklahoma in Norman and co-lead of the 2007 decadal. "The assignment of missions didn't have the rigor that a competitive environment enforces," he says.
Earth science in space involves a constant tension between exploring new scientific terrain and continuing existing observations, which sometimes need to last for decades to provide useful information about climate change. To help address this problem, the panel recommends another new competitive line, called Venture-Continuity, which would allow scientists to propose ways of continuing observations at lower cost. The panel foresees selecting two such missions next decade, each capped at $150 million.
Although the panel does not sound alarms like it did a decade ago, all of its recommendations are contingent on budgets rising with inflation. In its budget proposal last year, the Trump administration sought to boost planetary science and cut earth science. In particular, it plotted to kill four missions: the Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) satellite; the Orbiting Carbon Observatory-3 and the Climate Absolute Radiance and Refractivity Observatory Pathfinder, both set to be mounted on the space station; and an Earth-facing camera on the Deep Space Climate Observatory. It remains to be seen whether those cuts can make it through Congress. Moore hopes Senate opposition makes the cuts unlikely, and thinks that both planetary and earth science will thrive. "I wouldn't be surprised to see both boats rise," he says.
Of course, the report's influence depends on NASA's response. The Obama administration pushed for a climate-focused architecture that did not hew precisely to the 2007 decadal, and the George W. Bush administration's last NASA administrator, Mike Griffin, was hostile to their findings, Moore says. Trump’s nominee, Representative Jim Bridenstine (R–OK), has publically pledged to follow the decadal, however. He will likely face questioning on the decadal from the Senate—assuming he is renominated for the post and confirmed.