Cygnus departs ISS after reboost test

WASHINGTON — A Cygnus cargo spacecraft departed the International Space Station June 28, three days after it demonstrated its ability to raise the station’s orbit.

The station’s Canadarm2 robotic arm unberthed the NG-17 Cygnus spacecraft and released it at 7:07 a.m. Eastern, after which it maneuvered away from the station. The spacecraft, loaded with garbage for disposal, is scheduled to reenter after a June 29 deorbit burn by the spacecraft.

The Cygnus left the station three days after the spacecraft used its main thruster to raise the station’s orbit. The spacecraft fired its engine for 301 seconds, raising the station’s perigee by about 0.8 kilometers and its apogee by nearly 0.2 kilometers. The test demonstrated the ability of Cygnus to raise the station’s orbit, although

“This reboost of the ISS using Cygnus adds a critical capability to help maintain and support the space station,” Steve Krein, vice president of civil and commercial space at Northrop Grumman, said in a company statement. Maintenance of the station’s orbit is usually handled by thrusters on the Russian segment of the station or Progress spacecraft docked to it.

The June 25 maneuver was the second attempt by Cygnus to raise the station’s orbit. A maneuver June 20 was aborted after just five seconds. NASA later said that “system parameters that differed from Cygnus flight operations” triggered the abort, but that engineers concluded that the parameters were acceptable.

A Northrop Grumman Antares rocket launched the Cygnus Feb. 19, which arrived at the station two days later. It delivered nearly 3,800 kilograms of cargo, including supplies, equipment and scientific payloads to the station.

The next Cygnus mission is scheduled for launch no earlier than August. The long-term future of Cygnus missions is uncertain, though, because the Antares rocket uses a Russian engine, the RD-181, in a first stage manufactured by Ukraine’s Yuzhnoye/Yuzhmash. The availability of both is uncertain after Russia’s invasion of Ukraine days after the Antares launch of the NG-17 Cygnus mission.

In a prelaunch briefing in February, Northrop executives said they had all the components needed for two more Antares launches, but did not discuss what would happen after those two launches. “We have a plan in place that we could use other sources if needed, beyond those two launches,” Kathy Warden, president and chief executive of Northrop Grumman, said in an earnings call in April. She did not disclose details of that plan.

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