Orbital ATK's Cygnus Resupply Mission Launches May 21, With A 24-Hour Delay

The Cygnus spacecraft set to deliver more than three tons of goods and science gear to the International Space Station (ISS) will be blasting off into space a day later than expected.

Initially scheduled for tomorrow (May 20), the launch of NASA's next resupply mission — dubbed OA-9, or CRS-9, because it represents Orbital ATK's ninth commercial resupply service performed for the space agency — was postponed for 24 hours due to a worrisome weather forecast, Space.com reported.

Under the circumstances, NASA and the Virginia-based private space company decided to push back the launch until weather conditions improve and use the extra time to conduct additional inspections of the Antares rocket that will shoot the Cygnus spacecraft into space.

NASA and Orbital ATK are now targeting a launch date of May 21. The company's Antares rocket will be lifting off from the Mid-Atlantic Regional Spaceport at NASA's Wallops Flight Facility in Virginia at 4:39 a.m. EDT (08:39 GMT).

Orbital ATK's rocket and resupply vehicle have arrived at their Wallops launch pad late Thursday (May 17). The video below, released by the company a day after, details the pre-launch preparations that led up to this moment. According to a Twitter update from NASA, the Antares rocket is already poised for Monday's launch.

The Range Control Center (RCC) at Wallops has forecast a 70 percent chance of favorable weather on May 21, NASA announced.

"The main weather concern for Monday's launch attempt is sky screen (essentially local visibility conditions)," the space agency stated in a news release.

The RCC estimates that Monday's sky will feature "increased cloud cover and a slight chance for an isolated shower leading up to the projected launch." Even so, spectators along the U.S. East Coast may still get a chance to see the Antares take off, Space.com notes in a separate article.

The May 21 launch may be visible to viewers "from Massachusetts all the way down to South Carolina, and almost as far west as Pittsburgh," reports the media outlet.

In case you don't live in the visibility region outlined above, you can still catch the launch of the OA-9/CRS-9 mission on NASA Live. The coverage of the May 21 event starts as early as 4 a.m. EDT.

The unmanned Cygnus spacecraft will be delivering 7,385 pounds (3,350 kilograms) of science experiments, food, and other supplies to the Expedition 55 crew currently on board the ISS.

Once the resupply vehicle reaches the orbiting space station, it will be grappled by NASA astronauts Scott Tingle and Ricky Arnold, while Andrew Feustel will be in charge of monitoring the spacecraft's systems during its approach to the ISS. The three flight engineers of Expedition 55 will be using the station's robotic Canadarm2 to pick up the Cygnus capsule, which will be installed on the ISS's Unity module.

Orbital ATK's resupply vehicle will remain in orbit until July 15. Unlike SpaceX's Dragon capsule, the Cygnus cargo hauler is not designed to return to Earth intact. Instead, the spacecraft will burn up in our planet's atmosphere after the Expedition 55 crew loads it up with trash or other unneeded items, NASA points out.