KNOXVILLE, Tenn. — NASA expects to soon end efforts to contact the Opportunity Mars rover, silent for more than four months after a major dust storm, but will continue to listen for signals from the spacecraft for months to come.

Opportunity, which has been on Mars since January 2004, last contacted Earth June 10. A powerful globe-spanning dust storm blocked the sun and deprived the rover of solar power, putting it into a low-power mode.

On Sept. 11, NASA’s Jet Propulsion Laboratory said that the optical depth, a measure of the haziness of Martian skies, had dropped to a level low enough to allow enough sunlight to reach the rover for it to generate power. At that point, controllers started an effort known as “active listening” where they transmitted commands to the rover in the event it was unable to revive itself and listened for any transmissions by the rover in response.

After more than a month, Opportunity has not responded to those commands, and that active listening effort will soon end. “We intend to keep pinging Opportunity on a daily basis for at least another week or two,” said Lori Glaze, acting director of NASA’s planetary science division, during a presentation Oct. 22 at the annual meeting of the American Astronomical Society’s Division for Planetary Sciences here.

Glaze said that a factor in ending the active listening campaign is to prepare for the landing of the InSight spacecraft on Mars Nov. 26. “We want to wind that down before InSight gets to Mars and make sure all our orbital assets are focused on a successful landing of InSight,” she said.

That schedule is consistent with previous plans for attempting to restore contact with Opportunity. NASA said Aug. 30 that, once skies cleared sufficiently, it would attempt active listening for 45 days. “If we do not hear back after 45 days, the team will be forced to conclude that the sun-blocking dust and the Martian cold have conspired to cause some type of fault from which the rover will more than likely not recover,” John Callas, Opportunity project manager, said in a statement outlining those plans.

Some former rover controllers were critical about that plan, arguing that it wasn’t enough time to see if Opportunity could be revived, particularly if its solar panels were coated in dust. NASA countered that, once the active listening effort ends, it will continue to listen for any transmissions by Opportunity for months to come, but not transmit any commands to it.

That remains the case, Glaze said. “Just because we’re not actively pinging Opportunity, no one is giving up,” she said. “We’re going to keep listening for quite a while just to see if there’s a chance that the solar panels might get some dust blown off and it may be able to recharge the batteries.”

One challenge to those efforts is the health of those batteries. Glaze noted that, while the dust storm moderated temperatures, the return of clear skies means sharp drops in temperature each night. “The batteries may be getting too cold, and that may be too much for the little rover that could,” she said.

For now, the active listening effort continues, with rover controllers following a tradition similar to past NASA human spaceflight missions by playing a “wakeup song” each day. After playing a song by the classic rock band The Who one night, the band’s Twitter account responded, “Wake up, Mars! The Who are here.”

Wake up, Mars! The Who are here.

— The Who (@TheWho) October 22, 2018

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...