New Frontiers

Committee praises NASA’s planetary science program but raises some concerns

Europa lander

WASHINGTON — NASA has done a good job implementing the recommendations of its latest planetary science decadal survey despite past budget problems, but needs to improve some programs, a recent report concluded.

The midterm assessment of the 2011 planetary science decadal survey, prepared by a National Academies committee and published Aug. 7, found that NASA was able to make progress on both flagship and smaller missions recommended by the survey even with funding cuts in the early years of the decade.

“The committee concluded that despite significant cuts to the Planetary Science Division’s budget early in this decade, NASA has made impressive progress at meeting the decadal survey’s goals,” the committee noted in its final report, a reference to a nearly 20 percent cut in planetary science funding in 2013 to less than $1.3 billion. Its budget has subsequently risen significantly, to $2.2 billion in 2018.

The progress includes work on two flagship-class missions prioritized in the report, a Mars rover mission to cache samples for later return to Earth and a spacecraft to orbit Jupiter’s icy moon Europa. Those concepts have become the Mars 2020 and Europa Clipper missions, respectively, after undergoing redesigns to reduce their projected budgets from the decadal report.

The committee, though, did note concerns about the potential cost of Europa Clipper, a multi-billion-dollar mission. “NASA should continue to closely monitor the cost and schedule associated with the Europa Clipper to ensure that it remains executable” without affecting other missions, the committee recommended. “If the [lifecycle cost] exceeds this range, NASA should de-scope the mission.”

The committee was more skeptical about a third flagship-class mission in the early stages of development, a Europa lander mission. The mission has enjoyed funding well above any administration requests largely due to the advocacy of Rep. John Culberson (R-Texas), who chairs the House appropriations subcommittee that funds NASA and is the most prominent congressional supporter of the mission.

A Europa lander, the committee noted, was not prioritized in the latest decadal survey, which called it a “far term” mission that did not receive a detailed cost and technical assessment at the time. “The midterm committee, although it lacks an official cost estimate, believes the mission cost to be in the multiple billions of dollars range,” it concluded.

“Given its cost and its potential impact on the rest of the planetary science program, the committee concluded that the mission should be vetted within the decadal survey process,” the report stated.

The committee also raised concerns about the future of Mars exploration. NASA’s only Mars exploration under development is Mars 2020, although the agency has started studies of a so-called “lean” sample return architecture announced last August. That would require two more missions, one to collect the cached samples and launch them into Mars orbit, and another to collect the sample canister in Mars orbit and return it to Earth.

The committee concluded NASA should continue to study that Mars sample return architecture, but argued that with no other missions on the books, the sample return missions could be vulnerable to failures of existing Mars orbits that serve as communications relays. No other Mars science missions are under development as well.

“There is a risk that ongoing and soon-to-be landed assets on Mars will be left without telecommunications support because of the aging orbiters. The system is fragile and aging,” the committee stated. “There is currently no vision for a program beyond sample return, either for scientific investigation or to prepare for future human exploration.”

The committee recommended that NASA create a Mars Exploration Program (MEP) “architecture, strategic plan, management structure, partnerships (including commercial partnerships), and budget that address the science goals for Mars exploration” outlined in the decadal survey. “This approach of managing the MEP as a program, rather than just as a series of missions, enables science optimization at the architectural level.”

Another recommendation of the committee was to increase the cadence of the Discovery and New Frontiers programs of low- and medium-cost competitively selected planetary science missions. Budget cuts earlier in the decade affected the pace of competitions in both programs, and NASA has struggled to catch up even with increased funding in recent years.

The committee concluded that, to meet the mission cadence recommended in the decadal survey, NASA select three missions in upcoming competitions expected to take place in 2019 and 2021. NASA selected two missions, Lucy and Psyche, in its previous Discovery competition that concluded in January 2017.

The report also offered advice for the next decadal survey in the planetary sciences, which will likely begin by mid-2020 for publication in the spring of 2022. That survey will need to take into account both new science objectives, particularly in astrobiology, as well as new technologies and capabilities, such as smallsats.

The committee in particular recommended that NASA sponsor 8 to 10 concept studies of missions for potential consideration in the next decadal survey. That includes revisiting a previous study of an “ice giants” mission to Uranus and/or Neptune, citing different scientific objectives in a 2017 study versus those outlined in the decadal survey as well as concerns that “the scientific payload proposed in the study carries significant risk of failing to make the measurements” outlined in the decadal.

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NASA selects comet and Titan missions as New Frontiers finalists

Dragonfly, one of the two finalists for the next New Frontiers mission, would send a rotorcraft to Saturn’s moon Titan capable of exploring regions tens to hundreds of kilometers apart. Credit: NASA

DENVER — NASA has selected missions to return samples from a comet and to explore Titan with a drone as finalists for the next New Frontiers medium-class planetary science mission.

The two missions, selected from a pool of 12 proposals and announced by NASA Dec. 20, will receive funding for additional studies through 2018 before NASA picks one of them in the spring of 2019 for full development and launch in 2025.

One, called Comet Astrobiology Exploration SAmple Return, or CAESAR, would visit the comet 67P/Churyumov-Gerasimenko and collect a sample from its nucleus for return to Earth, the first such sample return mission. The mission would be managed by NASA’s Goddard Space Flight Center using a spacecraft built by Orbital ATK.

The other, Dragonfly, would send a spacecraft to land on Titan, Saturn’s largest moon and a world with a dense atmosphere. That spacecraft, similar to a quadcopter drone, would be able to fly to several locations on the surface, tens to hundreds of kilometers apart, to study its composition and habitability. The mission would be managed by the Applied Physics Laboratory (APL) of Johns Hopkins University, which would also build the spacecraft.

The announcement of two missions for further study surprised many in the planetary science community. NASA officials had previously suggested that the agency would select three, or possibly more, proposals for additional study.

Thomas Zurbuchen, NASA’s associate administrator for science, said at a media teleconference he had no set number of proposals in mind to select for further study. “I didn’t start with a number,” he said, focusing instead on the “outstanding and visionary science” the missions promised to carry out. “Basically, where I ended up with is the two that we’re currently talking about.”

Zurbuchen and others didn’t go into details about how CAESAR and Dragonfly beat out the other 10 proposals. “This is a very tough competition,” said Jim Green, director of NASA’s planetary science division. “The science in the two selected was just the top science.”

Both missions will go to objects already visited by earlier missions. In the case of CAESAR, comet 67P/Churyumov-Gerasimenko was studied by the European Space Agency’s Rosetta mission, which ended last year. That mission also deployed a lander, Philae, that operated briefly on the surface of the comet’s nucleus.

That previous mission will help the development of CAESAR. “The reason that we’re going back to Churyumov-Gerasimenko is that it provides us with an enormous amount of information about how to conduct our mission,” said Steve Squyres of Cornell University, the principal investigator of CAESAR. “We are able to design our mission, design our spacecraft, specifically for the conditions that we know to exist there.”

CAESAR is designed to collect both volatile ices and nonvolatile materials, which will be separated and placed in different containers in a return capsule. That return capsule will be provided by the Japanese space agency JAXA, based on its experience with the Hayabusa asteroid sample return missions.

CAESARComet Astrobiology Exploration SAmple Return, or CAESAR, one of two New Frontiers finalists, would collect samples from the nucleus of comet 67P/Churyumov-Gerasimenko for return to Earth. Credit: NASA

NASA’s Cassini spacecraft studied Titan extensively in a 13-year mission that ended in September, while ESA’s Huygens probe landed on Titan’s surface in early 2005. “That is exceedingly useful for being able to characterize potential landing site and know where on Titan the best places to land are,” said Elizabeth “Zibi” Turtle of APL, the principal investigator for Dragonfly.

“Those missions left us with a lot of fundamental unknowns,” she added, such as the basic composition of Titan’s surface. “Dragonfly is designed to go back and build on what we learned from Cassini/Huygens and answers the fundamental unknowns that remain about Titan.”

Losing out on the competition were proposals that ranged from Venus orbiters and landers and a lunar sample return mission to missions to Saturn and its icy moon Enceladus.

However, NASA said it would provide technology development funding for two of those concepts, Enceladus Life Signatures and Habitability (ELSAH) and Venus In situ Composition Investigations (VICI). The exact amount of funding, and the scope of work, will be negotiated with those proposal teams.

“What are the investments in technology that would not only help a specific mission but also help a field?” Zurbuchen said of the decision to support technology for those two mission concepts. These would include life-detection instrument technology in the case of Enceladus and, for Venus, instruments that can operate in the high temperatures found on the planet’s surface.

The winning mission, CAESAR or Dragonfly, will be the fourth in NASA’s New Frontiers program of missions larger than Discovery-class spacecraft but less expensive than flagship-class missions. The first three missions are New Horizons, which flew by Pluto in 2015 and will fly by the Kuiper Belt object 2014 MU69 in just over a year; Juno, currently orbiting Jupiter; and OSIRIS-REx, a mission en route to the asteroid Bennu to collect samples for return to Earth.

Either CAESAR or Dragonfly, if selected, will operate well into the 2030s. Dragonfly would land on Titan in 2034, Turtle said, and operate there for several years, powered by a radioisotope thermoelectric generator. CAESAR, Squyres said, would return its samples to Earth on Nov. 20, 2038.

Proior to working on CAESAR, Squyres had led the Mars Exploration Rovers program, which landed the rovers Spirit and Opportunity on Mars in early 2004. Opportunity continues to operate, nearly 14 years after landing. “Knowing when the thing is going to end,” he said of CAESAR, “is a virtue.”

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