WASHINGTON — A lunar sample-return mission that was among the three finalists in the 2011 NASA competition that punched Osiris-Rex’s ticket to an asteroid will make another bid for $1 billion in funding in the agency’s next New Frontiers competition, the mission’s principal investigator said.

“We are indeed planning to propose to the next New Frontiers opportunity,” Bradley Jolliff, professor of Earth and planetary sciences at Washington University in St. Louis and principal investigator for the Lunar South Pole-Aitken Basin Sample Return Mission, wrote in a June 24 email.

A call for proposals is expected sometime after Sept. 30, the start of the U.S. government’s 2016 budget year. The winning mission would launch in 2021, but exactly when NASA will formally start the race for funding remains a mystery, including to Jolliff.

“We hope to learn soon the time line for the next opportunity,” Jolliff wrote in his email. Pending more details from NASA about the timeline, he declined to discuss what he called “aspects of implementation,” such as who would build the spacecraft and its instruments.

However, the proposal Jolliff and his team submitted to NASA for the last New Frontiers competition shows the mission would pack a dedicated UHF relay satellite and a lander with a detachable ascent-and-return vehicle into a package small enough to fit inside the 5.4-meter fairing on a United Launch Alliance Atlas 5-531 rocket. Lockheed Martin Space Systems of Denver was the principal industry partner on the proposal last time around.

New Frontiers are competitively selected planetary science missions with development costs, excluding launch, capped at about $1 billion. Missions are managed by a principal investigator, who also acts as the top scientist.

The science case for exploring the moon’s enormous South Pole-Aitken basin has only become “more and more compelling” since Osiris-Rex clinched the last New Frontiers award in 2011, Jolliff said.

Robotic moon missions such as NASA’s Gravity Recovery and Interior Laboratory, which ran from 2011 to 2012, and the still-operating Lunar Reconnaissance Orbiter that launched in 2009 “all contribute context and compelling, testable hypotheses about the early Moon, its formation, and the early evolution of the Solar System,” Jolliff said.

The South Pole-Aitken basin is essentially an enormous impact crater, similar to those found all over Earth. However, the moon’s comparatively static environment and lack of biosphere mean the big crater still contains well-preserved traces of materials deposited there by the ancient impact that formed it.

Compelling science is essential for any mission trying win a NASA competition, but Jolliff is also counting on a boost from agency interest in the lunar sample-return mission’s engineering elements.

“This mission would represent a number of firsts: the first soft landing on the Moon’s far side; the first automated sample return from a body with substantial gravity for the U.S. and relevant to future Mars sample return missions; and the first sample return from the Moon’s far side,” Jolliff said.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.