Orion ready for lunar flight maneuver

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

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

The burn, which is expected to last two and a half minutes, is scheduled for 7:44 a.m. Eastern Nov. 7:59 a.m. Eastern when the spacecraft has no connection to Earth.

“This is definitely a critical burn. It’s one that Orion needs to run,” said Jim Geffre, Orion vehicle integration manager at NASA’s Johnson Space Center, at a Nov. 18 briefing. The combustion can be done by the main engine or several auxiliary thrusters if there is a problem with the main engine. “We classify it as critical, so we’ve configured the software to make sure burning happens.”

A second maneuver, scheduled for Nov. 25, will put Orion into the distant retrograde orbit, as far as 432,000 kilometers from Earth. It will remain in that orbit for six days before making two more maneuvers to de-orbit and fly past the Moon again and return to Earth.

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

However, the mission did not go smoothly. He said they assessed 13 anomalies, most of which he said were “relatively benign” and learned about system performance. One problem, with the spacecraft’s star trackers, required the convening of an anomaly resolution team that completed its work at the Nov. 18 briefing.

Sarafin said the problem with the star trackers was the “blinding” of the imagers by thruster plumes. “The thrusters were picked up by the star-tracker because it was purposely pushing over the star-tracker’s field of view,” he said. “The light hit the plume and it picked it up,” confusing the software.

“The star tracker itself performs perfectly,” Geffre said, noting that the problem resulted from a combination of factors that could not be fully simulated on the ground. He said he expects the issue to occur “intermittently” for the remainder of the mission, but the team is now ready to address it.

The problem never violated flight rules, said Jeff Radigan, a flight director. “It was really a case of seeing something that we didn’t understand,” he said. “They provided us with measurements at all times that allowed the mission to proceed.”

Sarafin said the agency was also still assessing the performance of the Space Launch System rocket that launched Orion. “Everything indicated that the system was performing perfectly,” he said, noting that the core 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 what we intended it for.”

The launch also caused some damage to ground systems such as the mobile launch pad, creating hazards on the pad that prevented photographers from picking up remote cameras for two days. That included nitrogen and helium gas leaks, as well as elevator blast doors blown off, putting the mobile launch elevator out of service, Sarafin said.

“We expected some damage and they are finding some damage,” he said. “The mobile launcher itself performed well. We just have to work our way through some of the damage assessments.

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