An Orbital ATK Antares rocket is set to launch Cygnus supply ship on Monday to deliver tons of cargo to the International Space Station (ISS), NASA said in a statement. The spacecraft will lift of at 4:39 a.m. EDT on the company's CRS-9 cargo resupply mission, from Virginia Space's Mid-Atlantic Regional Spaceport Pad 0A at NASA's Wallops Flight Facility on Virginia's Eastern Shore. The Cygnus spacecraft is scheduled to arrive at the ISS on the morning of May 24. "Weather is going to potentially affect visibility" of the launch in the region, although cloud cover can occasionally enhance views when the rocket illuminates them during flight, said Doug Voss, deputy chief of the Range and Mission Management Office at NASA Wallops. The Antares will launch with the Cygnus spacecraft filled with 7,400 pounds of cargo for ISS, including science experiments, crew supplies and vehicle hardware. The mission is Orbital ATK's ninth contracted cargo delivery flight to ISS for NASA. Weather remains at 65 per cent favourable for the May 21 launch window. The current forecast for a one-day slip in the launch has 55 per cent favourable weather and 75 per cent favourable for a two-day slip, the report said.