WASHINGTON — NASA’s notional plan to send astronauts to an asteroid will leverage earlier probes launched or planned by space agencies around the globe, but additional robotic precursors will be necessary to reduce the risk of crewed missions, experts here agreed.
The challenge is funding a dedicated risk-reduction campaign in a budget environment that looks to be tight for the foreseeable future, one NASA official said.
“It comes down to funding,” Gentry Lee, chief engineer for solar system exploration at NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said by phone during a Jan. 14 meeting of the NASA-chartered Small Bodies Assessment Group.
The only funded asteroid mission in NASA’s portfolio now is the $800 million Osiris-Rex probe, which is slated to launch in 2016 and return a sample of asteroid 1999 RQ36 to Earth in 2023.
Within NASA’s Planetary Science Division, currently funded at an annual rate of $1.19 billion by a six-month temporary spending bill, “funding lines for flight missions are either all competitive or they’re with the Mars program,” Lee said. “We don’t have a funding line where we can just pick the money to go do what would be considered a directed space mission” to an asteroid.
U.S. President Barack Obama has a stated goal of sending astronauts to an asteroid around 2025. But representatives from various government space agencies in attendance at the meeting said too little is known about asteroids to safely carry out such a mission.
“A survey mission is a prerequisite for human exploration,” said Stefan Ulamec of the German Aerospace Research Center (DLR), principal investigator for the Philae lander on the European Space Agency’s Rosetta comet-chaser mission. Rosetta launched in 2004 and is expected to descend to the surface of comet 67P Churyumov-Gerasimenko in November 2014.
Ulamec said that despite some recent close encounters with asteroids — Japan returned an asteroid sample to Earth in 2010; NASA in 2011 put a probe called Dawn into orbit around one of the biggest asteroids in the solar system; Rosetta has done asteroid flybys — “we are not particularly rich in possible targets that would be applicable for human [asteroid] missions.”
The Canadian Space Agency, whose 2012 budget of about 424 million Canadian dollars ($431 million) is expected to decline by 13 percent by 2015, thinks it can help. Canada’s Near-Earth Object Survey Satellite, a 65-kilogram observatory bound for an 800-kilometer polar Earth orbit, “is dedicated to finding near-Earth asteroids [and] is going to be launched exactly one month from now by India,” Denise Laurie, the agency’s senior program scientist for space astronomy, said here Jan. 14.
Victoria Hipkin, the Canadian Space Agency’s senior program scientist for planetary exploration, added that Canada might be interested in providing some of its “signature technologies,” such as the lidar — or light detection and ranging — sensor the agency is developing for Osiris-Rex, for a future crewed asteroid sortie.
Junichiro Kawaguchi, manager of the Japan Aerospace Exploration Agency’s Hayabusa asteroid sample-return mission, said that in addition to finding more suitable targets, NASA must quickly decide “how many [robotic] landings are required” before human landings can be safely attempted.
“We want multiple robotic missions to be performed before humans visit,” said Kawaguchi, who led the first, and so far only, mission to return an asteroid sample to Earth. Japan’s space agency recovered Hayabusa’s capsule full of asteroid dust in 2010 and is now planning to launch an encore mission, Hayabusa 2, in 2014.
Kawaguchi said he favored a near-Earth asteroid as an early destination for long-duration crewed spaceflights, in part because such a mission would avoid the “huge and expensive” outlay required for a crewed Moon or Mars-system landing.
As in the United States, economic conditions in Japan are putting downward pressure on space spending, Kawaguchi said. This is despite expectations that the Liberal Democratic government Japanese voters returned to power in December will give “a slight plus” to the space agency’s budget, he said.
In its 2012 fiscal year, which ends March 31, the Japanese space agency had a budget of about $2.15 billion, according to a document posted on its website.
NASA, meanwhile, is trying to lay the foundation for a space-based asteroid survey network that does not break the bank.
“We want to have full-up survey capability in the near future, because that’s something that’s foundational,” said Paul Abell, lead for planetary small bodies within the Astromaterials Research and Exploration Science Directorate at NASA’s Johnson Space Center in Houston. “We do have some money that is being leveraged for technology development.”
One potential project, procurement for which could begin this year, according to a notice NASA posted online in August, is a $50 million asteroid tracking sensor small enough to ride to space as a hosted payload. In an August request for information, which has since closed, NASA said the instrument would have to last five years on orbit; be able to detect objects as small as 30 meters in diameter from distances as far as 75 million kilometers; weigh no more than 75 kilograms; be no larger than 0.5 cubic meters in volume; and draw no more than 500 watts of power.
NASA also has a Space Act Agreement with the B612 Foundation, a Mountain View, Calif., nonprofit led by former astronaut Ed Lu that plans to launch an asteroid-tracking telescope called Sentinel in 2017 or 2018 into a solar orbit near Venus. Under the agreement, NASA scientists and engineers would participate in Sentinel mission reviews.
NASA already has some idea about what sort of asteroid to look for once some kind of survey network is in place. Abell said the right asteroid must be larger than 30 meters in diameter, have a rotation period greater than “a couple of hours” and be fairly well understood in terms of its material and structural composition. The asteroid also must be in an orbit that provides a launch window of several weeks, is relatively easy to reach from low Earth orbit and would require a year or less to explore, from launch to return, he said.
The heavy-lift Space Launch System and Orion Multi-Purpose Crew Vehicle NASA, which is being developed for about $3 billion a year, can haul astronauts to an asteroid, but other hardware needed for such a mission, such as a habitat module and new space suits, have yet to receive significant funding.