InSight approaching Mars
NASA's InSight spacecraft will perform a final trajectory correction maneuver less than a day before landing on Mars to slightly adjust the location of its landing site. Credit: NASA/JPL-Caltech

PASADENA, Calif. — NASA’s InSight spacecraft will perform a final maneuver less than 24 hours before its scheduled landing to slightly adjust the location of its landing site.

During a briefing at the Jet Propulsion Laboratory here Nov. 25, project leaders said they decided to carry out a sixth and final trajectory correction maneuver (TCM) that is part of the cruise phase of the mission. Managers had suggested at a briefing Nov. 21 that, based on the accuracy of the trajectory at that time, they might skip that final maneuver.

Tom Hoffman, project manager for InSight, said at the briefing that after the fifth TCM Nov. 18, the center of the landing ellipse, representing the region on the planet the spacecraft would land in, was off its target by about 18 kilometers. That difference was enough for him and other mission officials, at a meeting a few hours before the briefing, to decide to carry out the final maneuver.

“We want to avoid the area up here,” he said, referring to a region with rougher terrain near the edge of the current landing ellipse. “That’s not a great area to land.”

That maneuver, known as TCM-6 and taking place about 22 hours before the 2:54 p.m. Eastern Nov. 26 landing, will change the spacecraft’s velocity by just a few centimeters per second. “Hopefully within a few hours after that we’re going to know exactly where we’re landing,” he said. “Things should be in good shape.”

The maneuver, he said, is intended to move the center of the landing ellipse back to the target, marked on images with a red X, and avoid the undesirable terrain, a decision that came after what Hoffman called a “very exciting” meeting earlier in the day.

“We listened to all the different inputs and the final decision was to go ahead and do the TCM and move ourselves back to that red X,” he said, “and be exactly where we really want to land from both a safety standpoint as well as making sure we have the right location for our science instruments.”

Officials said that, other than the decision to perform the final maneuver, there are no issues with the spacecraft, formally known as Interior Exploration using Seismic Investigations, Geodesy and Heat Transport. The mission, with a total cost including international contributions of nearly $1 billion, is designed to study the composition and structure of the interior of Mars using a seismometer and heat flow probe.

Once on the surface, InSight will deploy those two instruments over the next few months, collecting data on a prime mission scheduled to last two years. “It feels like a climax,” said Bruce Banerdt, principal investigator of InSight at JPL, of the landing, “but it’s actually the beginning.”

He and others involved with the mission expressed a mix of confidence that the spacecraft, based on the Phoenix Mars Lander that successfully landed on Mars a decade ago, would make to the surface, as well as nervousness as the landing approaches. “I’m actually really confident, personally, that we’re going to land safely tomorrow,” Banerdt said. “It doesn’t mean I’m not nervous.”

“We recognize that we never take Mars for granted,” said Thomas Zurbuchen, NASA associate administrator for science. “Mars is hard.”

Hoffman noted he spent the Thanksgiving holiday with family, including three young grandsons who, when excited, run around and yell. “Inside of me right now I’m just about the same,” he said. As soon as he receives word of a successful landing, he said, “I’m going to unleash my inner four-year-old.”

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...