Updated 8:35 p.m. Eastern with new launch date.

WALLOPS ISLAND, Va. — A technical issue scrubbed a scheduled Feb. 9 launch a Cygnus cargo mission to the International Space Station as NASA is considering changes to the schedule of future cargo missions and science activities on the station given uncertainties about the size of the station’s crew.

A Northrop Grumman Antares rocket was scheduled to lift off from Pad 0-A the Mid-Atlantic Regional Spaceport at 5:39 p.m. Eastern Feb. 9, carrying a Cygnus spacecraft on a mission designated NG-13. However, the launch was first pushed to the end of its five-minute window, and then scrubbed a few minutes before the revised launch time.

NASA and Northrop Grumman said about three hours after the scrub that the launch was postponed because of “off-nominal readings from a ground support sensor.” The launch has been rescheduled for Feb. 13 at 4:06 p.m. Eastern because of both time to correct the issue and poor weather in the forecast.

The Cygnus is carrying 3,633 kilograms of cargo, including about 1,600 kilograms of vehicle hardware and nearly 1,000 kilograms of science payloads. Crew supplies and other equipment constitute the rest of the cargo on the spacecraft.

As NASA reschedules this cargo mission, the agency may be shifting future missions around as well to reflect the status of the station’s crew. By April, the station will have only a three-person crew, including a single NASA astronaut, Chris Cassidy, for potentially several months. Uncertainty about when commercial crew vehicles will fly, and the duration of their missions, has created challenges for planning the resources needed for the station and the science that can be performed there.

“We are discussing the best cadence on which to launch the cargo missions, and one factor is when we’ll have crewmembers on board,” said Ven Feng, manager of NASA’s ISS Transportation Integration Office. The schedule of commercial crew vehicles as well as plans to complete science investigations on the station are key factors in that planning.

“We’re trying to position ourselves to have the most flexibility possible to get the most and highest quality science done as we hope to see our commercial crew vehicle arrive some time this year,” he said.

Feng said that Northrop has done a “tremendous” job demonstrating its ability to fly earlier than planned for the NG-13 mission. “We may pull on that again in the near future,” he said. Northrop officials at Wallops said the next Cygnus mission, NG-14, is tentatively scheduled for October but could be moved up to August.

SpaceX’s next cargo Dragon mission, CRS-20, is scheduled for launch March 2, and will be the last of that version of the spacecraft. The company will start using a version of its Crew Dragon spacecraft for future cargo missions under its new Commercial Resupply Services 2 contract with the CRS-21 mission no earlier than August.

The reduced crew size will also affect science on the station. A Nov. 14 report by NASA’s Office of Inspector General concluded that with only one NASA astronaut on board, the amount of science done on the station would drop from an average of about 35 hours a week to just 5.5 hours.

“We’re taking that into account,” said Heidi Parris, assistant program scientist for the ISS program at NASA. “We’re talking with our researchers, we’re talking with the different funding sponsors, and making sure that everybody understands the situation.”

Parris said that some experiments on the station don’t require crew time. “Those are certainly helpful in a time like this when we’re not going to have a lot of crew time available,” she said. There’s also “reserve science” that astronauts can do when they’re able to free up time in their schedules.

“We’re doing everything that we can to keep doing as much science as possible during this deficit in crew time,” she said.