WASHINGTON — NASA Mars czar Jim Watzin on March 30 defended the agency’s plans to follow up the Mars 2020 sample-collecting rover with a telecommunications orbiter that would launch in 2022 and possibly serve as a testbed for technologies applicable to future sample-return and even human spaceflight missions.

Watzin made his case for the orbiter to the NASA Advisory Council’s (NAC) planetary science subcommittee at NASA Headquarters here. Some NAC members wondered why, in Watzin’s words, an orbiter is the “next logical step” in the Mars sample-return campaign anointed as the top U.S. planetary science priority in a 10-year science roadmap, or decadal survey, published by the National Research Council in 2011.

The White House has been reluctant to commit to a multimission sample-return program because of the substantial investment required. However, it did allow NASA to start work in 2013 on a Mars 2020 sample-digging rover leveraging designs and hardware recycled from the Mars Science Laboratory mission, which landed the nuclear-powered Curiosity rover on the red planet in 2012.

When the Mars 2020 rover arrives in 2020, it will dig up samples and leave them on the ground to be collected and returned to Earth by a future mission or missions.

Yet the logical follow-on to Mars 2020, Watzin said, is not a collect-and-return craft, but a new orbiter. The probe might even feature the same sort of solar-electric propulsion system NASA’s Human Exploration and Operations Mission Directorate says it needs to haul cargo to Mars in advance of a crewed landing, Watzin said. It could also carry an optical communications payload to transmit more data more quickly between Earth and Mars.

The need to refurbish NASA’s Mars telecommunications infrastructure is “very real,” Watzin said, because the agency currently relies on the 13 year-old Mars Odyssey rover to relay data from its surface-crawling rovers to Earth.

Solar-electric propulsion is likewise beneficial, possibly even necessary, since an eventual Mars sample-return spacecraft might need to arrive at Mars in a certain orbit and then transfer to another to rendezvous with whatever Mars ascent vehicle is built to tote Mars 2020 samples up from the surface. Propellant-thrifty electric propulsion not only allows NASA mission planners the flexibility to change orbits, but also reduces the total mass of the sample-return spacecraft, Watzin noted.

“There’s a lot of baby steps, if you will, toward the capabilities that we want in the science program as well as what the [human exploration] guys are looking at … that could be accomplished in an orbiter,” Watzin said in his first NAC presentation since he returned to the agency in December to become director of NASA’s Mars Exploration Program.

Watzin unveiled the Mars 2022 orbiter concept during an address at the Feb. 24 meeting of the Mars Exploration Program Analysis Group in Pasadena, California. During the presentation he repeatedly extolled the virtues of more closely aligning the objectives of NASA’s robotic Mars exploration and human spaceflight programs.

Whatever cross-agency benefits may exist, the Mars 2022 orbiter is not yet even a notional part of NASA’s budget and will not be until the White House submits its 2017 budget request early next year, Watzin said.

So while the proposed Mars 2022 orbiter deserves “serious study,” Watzin said, “I’m not saying ‘we’re going to go do this.’”

Watzin also said the Human Exploration and Operations Mission Directorate — a roughly $8 billion enterprise that includes both deep-space development efforts such as the Space Launch System and the near-Earth International Space Station — will not get a free ride on the back of NASA’s $1.4 billion planetary science division.

“If it’s a joint effort, there’s going to have to be a joint contribution to the funding activity,” Watzin said.