“‘We want to be really sure it’s not coming from the star before we go tell the press and make a big stink about it,’” says Elisa Quintana, mission lead for Pandora at NASA. That’s just a summary of the problem that astronomers are trying to solve today: separating the dim, filtered light of a planet from its bright star.
The James Webb Space Telescope (JWST), however, has already given astronomers unparalleled insight into distant worlds that are literally hundreds of light-years away, from identifying carbon dioxide in the atmosphere of WASP-39 b to spotting promising signs of water vapor in rocky exoplanets such as GJ 486 b. However, these exciting discoveries are always tinged with a degree of doubt. It is possible that stars may generate spectroscopic patterns, including water vapor, that can either mimic or hide what researchers are trying to find in planetary atmospheres. “Stellar contamination” has proved one of the most intractable obstacles in trying to determine whether a planet could potentially support life.
Pandora, a refrigerator-size satellite launched from Vandenberg Space Force Base on a SpaceX Falcon 9 rocket, was built to solve this very issue. Orbiting in a polar Sun-synchronous “twilight” orbit 380 miles above the equator, Pandora will focus on 20 target exoplanet systems for 24 hours at a time during its one-year primary mission. By viewing both the star and the planet at the same time in visible and infrared wavelengths, Pandora will enable the measurement of starspots and flares and changes in starlight on long timescales. This will enable scientists to correct the spectra from Webb’s observations of the exoplanets with absolute certainty.
Of course, JWST could do this, but its schedule is already full of high-priority observations throughout the cosmos. “Big missions, such as the James Webb, don’t have the time for that, so they have to focus on one thing and then move on,” commented Trevor Foote, a mission manager who worked on the data analysis pipeline for the Pandora mission. “With a mission of this type, though, we have the luxury of staring at a system for 24 hours and understanding the whole picture of the surface of the star.”
The engineering design in Pandora is just as revolutionary as its scientific objectives. Pandora has been developed under NASA’s Astrophysics Pioneers program, which has a budget cap of $20 million for its missions. Pandora uses a commercial satellite platform developed by Blue Canyon Technologies, along with a half-meter CODA all-aluminum telescope developed at Lawrence Livermore National Laboratory. By utilizing designs that have already been proven successful in previous missions and making only necessary changes, the team managed to bring down the costs of its instruments to only 15% of NASA’s estimates for such a class of missions.
The Pandora mission also benefited from SpaceX’s ride-sharing service. In this manner, NASA will save tens of millions of dollars that it would have had to pay for a dedicated launch vehicle. The strategy of offering small satellite solutions and ride-sharing launches is transforming the landscape for science missions that aim to provide focused support to flagships rather than compete with them.
The implications are great. Worlds that orbit small and cool stars, and especially red dwarf stars, have turned up as some of the most promising candidates for discovering earth-like environments. The close proximity of these worlds makes it possible for transit observations of their atmospheres. These same stars, however, tend to be active and have light that is not constant. The findings of Pandora may have implications that reach far beyond its current targets of 20. As Quintana explained, “We have a well-corrected spectrum. We know there is water. We know there is nitrogen. We know there are Earths out there. We know they are numerous. We know they have atmospheres. But do we know if they have life?” Pandora won’t necessarily provide the answer to that final question. But by removing one of the biggest hurdles in exoplanet research, it leads scientists one day closer to getting that answer.”