The European Space Agency is gearing up to launch an automated cargo freighter Tuesday for the International Space Station, continuing a wave of resupply missions to the orbiting lab from three continents.

The Ariane 5 rocket rolled to the launch pad Monday. Credit: Stephane Corvaja/ESA

The Automated Transfer Vehicle, Europe's second such spacecraft, is due for liftoff at 2213:27 GMT (5:13:27 p.m. EST) aboard an Ariane 5 rocket launched from the Guiana Space Center, a French-run spaceport on the northeast coast of South America.

The mission has just an instant to get off the ground, a requirement set by the geometry of the space station's orbit and the ATV's ability to reach the outpost.

The 165-foot-tall rocket rolled from the space center's assembly building to the ELA-3 launching zone Monday.

The Ariane 5 rocket will fly northeast from the Guiana Space Center, jettisoning its powerful solid rocket boosters and accelerating on the thrust of a hydrogen-fueled Vulcain main engine. The rocket's second stage, powered by storable hydrazine fuel, will fire twice to propel the 44,225-pound payload into a circular orbit 161 miles high with an inclination of 51.6 degrees.

It will be the 200th flight of an Ariane rocket, Europe's workhorse launcher for communications satellites and large government payloads. It is the second mission of an ATV, an unmanned resupply vehicle the size of a double-decker bus.

Named for Johannes Kepler, the famous German astronomer and mathematician, the spacecraft carries 5,929 pounds of dry cargo in its pressurized cabin. The ship will also deliver 220 pounds of breathing oxygen and 1,875 pounds of rocket propellant for the space station's Zvezda service module.

Technicians also loaded 14,474 pounds of propellant into the ATV's fuel tanks to guide the 33-foot-long to the space station, then raise the lab's orbit by nearly 25 miles this spring as the outpost prepares for life without the space shuttle.

The ATV's cargo load includes gear for NASA. The European Space Agency developed the resupply freighter to help pay for the agency's share of the station's operating costs.

Photo of the ATV spacecraft being prepared for launch in Kourou, French Guiana. Credit: ESA/CNES/Arianespace - Photo Optique Vidéo du CSG, L.Mira, 2010

The ATV will gradually adjust its orbit over the next eight days before its scheduled arrival at the space station Feb. 23.

Navigating with GPS satellite data and a futuristic optical laser sensor system, the ship will dock with the station's aft port at 1520 GMT (10:20 a.m. EST) next Thursday. Astronauts and cosmonauts aboard the complex will open its hatch and start unloading crew provisions, supplies and other equipment by hand. The ATV's fuel and oxygen will be transferred through internal plumbing.

Plans call for the ATV to remain at the station until about June 4, but the schedule could change. The ATV is certified to stay at the space station for more than six months in a dormant configuration.

The ATV mission is occurring amid a flurry of visiting spacecraft at the international outpost. Japan's H-2 Transfer Vehicle, similar in size to the ATV, arrived at the space station Jan. 27. A smaller Russian Progress freighter also docked at the complex last month.

The shuttle Discovery will launch Feb. 24, one day after the ATV's docking, to deliver an Italian-built stowage module with more fresh supplies.

Once Discovery arrives at the station, all of the program's existing servicing vehicles will be present at the complex. It will be the first and only time a space shuttle will be docked to the station along with Russian, European and Japanese spacecraft.

During the ATV's eight-day approach profile, the space station crew plans to unlimber the lab's robot arm and move Japan's HTV craft from the Earth-facing port of the Harmony connecting node to the module's upper berthing location.

The move will make room for Discovery, which docks to the forward port of Harmony.