Lucy and Psyche
NASA's Lucy mission (left) will visit a series of Trojan asteroids while Psyche (right) will visit a metallic asteroid of the same name. Credit: SwRI and SSL/Peter Rubin

GRAPEVINE, Texas — NASA has selected two missions to asteroids in the latest round of its Discovery planetary science program, a move that NASA says puts the program back on track after a recent drought of missions.

NASA announced Jan. 4 that it has selected Lucy and Psyche for launch in the early 2020s. Each mission has a cost cap of $450 million, although NASA did not disclose the estimated costs of the individual missions.

“These small body missions complement NASA’s exploration and are crucial parts of learning about our solar system and crucial parts of our programs going forward,” said Thomas Zurbuchen, NASA associate administrator for science, in a media teleconference about the missions.

Lucy, led by Harold Levison of the Southwest Research Institute, will launch first, in 2021. It will visit a main belt asteroid in 2025 before reaching its final destination, two groups of asteroids known as Trojans in the same orbit around the sun as Jupiter. The spacecraft will visit six Trojan asteroids from 2027 to 2033.

Those Trojan asteroids, Levison noted, are believed to be largely unaltered remnants of the formation of the solar system. “One of the really surprising aspects about this population is its diversity,” he said. “We believe that’s telling us something about how the solar system formed and evolved. These small bodies really are the fossils of planet formation.”

Psyche, led by Lindy Elkins-Tanton of Arizona State University, will launch in 2023 and make flybys of the Earth and Mars in 2024 and 2025, respectively, before arriving in 2030 at the main belt asteroid Psyche, thought to be the remnant of a core of a small planet destroyed in the early history of the solar system.

“We have never seen a metal world,” Elkins-Tanton said. “By visiting Psyche, we can literally visit a planetary core, the only way that humankind ever can.” The studies of Psyche, she added, could also support future asteroid mining ventures by providing insights into the conditions of metallic asteroids.

NASA selected Lucy and Psyche over three other finalists. Two were missions to Venus: an orbiter called Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy (VERTIAS) and an atmospheric probe called Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI). The other was Near Earth Object Camera (NEOCam), a space telescope designed to look for near Earth asteroids.

NASA didn’t go into details about why Lucy and Psyche fared better in the evaluation than the Venus missions or NeoCAM. “The Discovery program is a competition,” said Jim Green, director of NASA’s planetary science division. “In that competition, we’re looking for top science, top scientific implementation, minimizing our technical risk.”

The decision is a letdown for scientists who study Venus, who were optimistic NASA would select the agency’s first mission to the planet since the Magellan radar mapper, launched in 1989. “Unfortunately, these missions did not receive the level of evaluation that the top two missions that we selected,” Green said. He added, though, that the call for proposals released in December for the New Frontiers program does include a Venus mission as one of six options.

NEOCam, on the other hand, will get something of a reprieve. NASA announced it will provide an additional year of funding, known as an extended Phase A study, of the NEOCam concept to further its development, although its future after that study remains unclear.

“It is really an acknowledgement that even though it was not selected for a full, complete implementation, we want them to address issues that were identified in the Discovery evaluation process,” Green said of DAVINCI and VERITAS. The exact value of the study will be negotiated with the NEOCam team, he said.

The selection of two missions, which Green and other NASA officials had hinted as being a possibility for months, is intended to get the Discovery program back on track after a long gap. The last Discovery selection, of the Insight Mars lander, was in August 2012. That mission was to launch in 2016, but was postponed to May 2018 because of problems with one of the spacecraft’s key instruments, a seismometer.

Work on getting Insight ready for that 2018 launch is going well. “Everything looks great. It’s on track,” Green said. The French space agency CNES, which developed the seismometer, is completing the redesign of the instrument. “Right now we’re on schedule and everything’s looking fine.”

With two missions now on the books after Insight, Green said he plans to select future missions roughly every three years. That is a frequency along the lines of recommendations made in the 2011 planetary science decadal survey but which NASA found difficult to implement because of budget cuts.

“We’re going to try and get the program back into a cadence that’s much like what was recommended in the planetary decadal. We’re probably on the order of a 32 to 36 months cadence,” he said.

The long durations of the missions, extending into the 2030s, are factored into NASA’s long-term budgeting, Green said. Both have options for extended missions, which could perhaps bring the two together at some point in the future. Levison said that an extended mission for Lucy could include additional flybys of Trojan and main belt asteroids, one of which, he said, is the asteroid Psyche.

“We should be able to do more at the end of the mission,” he said, “if NASA agrees.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...