Orion ready for lunar maneuver

WASHINGTON — NASA has approved plans to move forward with the next critical milestone in the Artemis 1 mission, a maneuver of the unmanned Orion spacecraft as it flies past the moon on Nov. 21.

NASA announced late Nov. 19 that the Artemis 1 mission management team approved the outbound powered flyby (OPF) maneuver, a burn of Orion’s main engine as the spacecraft passes about 80 miles (130 km) above the Moon’s surface. The maneuver will send Orion into a distant retrograde orbit around the moon.

The burn, scheduled to last two and a half minutes, is scheduled for 7:44 a.m. east of November 21. The maneuver will take place while the spacecraft is behind the moon, during a 34-minute blackout period between 7:25 A.M. 7:59 am east when the spacecraft is not in communication with Earth.

“This is absolutely a critical burn. It’s something that Orion needs to perform,” said Jim Geffre, manager of Orion vehicle integration at NASA’s Johnson Space Center, during a Nov. 18 briefing. The burn can be done by the main engine or multiple auxiliary thrusters if there is a problem with the main engine. “We call it critical, and that’s why we’ve configured the software to make sure the burn-in happens.”

A second maneuver, scheduled for November 25, will put Orion into a distant retrograde orbit, reaching up to 432,000 kilometers from Earth. It will remain in this orbit for six days before performing two more maneuvers to de-orbit and fly past the moon again, returning to Earth.

At the briefing, agency officials said Orion had been performing well since the Nov. 16 launch on the test flight. “Overall, the mission, in just three short days, is progressing and exceeding expectations,” said Mike Sarafin, Artemis 1 mission manager, in the Nov. 18 update.

However, the mission was not without problems. He said they looked at 13 anomalies, most of which he said were “relatively benign,” and learned about the system’s performance. One issue, with the spacecraft’s star trackers, did require the convening of an anomaly resolution team that completed its work by the November 18 update.

Sarafin said the problem with star trackers was “dazzling” for imagers of propellant plumes. “The thrusters were lifting off the star tracker because it was pushing above the star tracker’s field of view, by design,” he said. “The light was hitting the plume and collecting it,” confusing the software.

“The star detector itself is performing perfectly,” Geffre said, noting that the problem came from a combination of factors that could not be fully simulated on the ground. He said he expects to see the issue “periodically” for the rest of the mission, but the team is now ready to handle it.

The problem never violated flight rules, said Jeff Radigan, flight director. “It was really a case of seeing something we didn’t understand,” he said. “At all times they provided us with metrics that could allow the mission to move forward.”

Sarafin said the agency is still evaluating the performance of the Space Launch System rocket that launched Orion. “All indications were that the system was performing on the spot,” he said, noting that the main stage and boosters placed Orion and its ICPS upper stage very close to the planned altitude and that the ICPS burn that sent Orion to the moon “was exactly where we intended”.

The launch also caused some damage to ground systems, such as the mobile launch platform, creating hazards on the pad that delayed photographers taking remote cameras for two days. That included nitrogen and helium gas leaks, as well as elevator launch doors that blew off, putting the mobile launcher elevator out of service, according to Sarafin.

“We predicted some damage and they find some damage,” he said. “The mobile launcher itself performed well. We just have to work through some of the damage estimates.”

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