Europe's next Automated Transfer Vehicle, set for launch in June to the International Space Station, was hoisted atop an Ariane 5 launcher in French Guiana on Friday.

Photo of the Automated Transfer Vehicle being prepared to move to the Ariane 5 final assembly building last week. Credit: ESA/CNES/Arianespace/Photo Optique video du CSG/P Baudon

The robotic spacecraft's tanks are filled with propellant, water, air and pure oxygen. Technicians will load the ATV's cargo module with fresh food and other last-minute items over the next week before the Ariane 5's 17.7-foot-diameter payload fairing is added to enshroud the resupply freighter.

Christened Albert Einstein, the cargo craft is Europe's fourth Automated Transfer Vehicle. When it blasts off June 5, the freighter will be the heaviest spacecraft ever launched by Europe - weighing in at an estimated 44,610 pounds, according to the European Space Agency.

It is also the largest vehicle to visit the space station since the retirement of the space shuttle. The ATV measures 32 feet long and 15 feet wide, and its four solar panels, arranged in a distinctive X-shaped patten, stretch out 73 feet tip-to-tip when extended in space.

Each ATV can haul three times more cargo than Russian Progress resupply spacecraft, and twice as much mass as SpaceX's Dragon cargo ship.

The massive spacecraft does not return cargo. At the end of each mission, it falls back into the atmosphere and burns up, disposing of trash in a safety zone over the Pacific Ocean.

The Albert Einstein spacecraft arrived last year at the European-run spaceport in Kourou, French Guiana.

Timed to the second in order to reach the space station, the launch is set for June 5 at 2136:59 GMT (5:36:59 p.m. EDT; 6:36:59 p.m. Kourou time). The launch time could change slightly based on further tracking of the space station's orbit, according to Alberto Novelli, ESA's ATV 4 mission manager.

The Ariane 5 ES rocket, missing its payload, rolled to the final assembly building in Kourou in March. Credit: ESA/CNES/Arianespace/Photo Optique video du CSG/S Martin

Docking with the space station's Zvezda service module is scheduled for June 15.

Managers decided on May 8 to continue preparations for launch June 5, but engineers are analyzing a potential problem with a navigation aid attached to the space station's docking port.

Officials are concerned a stuck antenna on a Russian Progress resupply craft may have damaged a laser reflector mounted on the aft end of the Zvezda module. Reflectors are used in concert with the ATV's laser-guided navigation system to feed range, orientation and closing rate information to the ATV's computers, which control the spacecraft's automatic approach to the space station.

An array of 26 reflectors is positioned on the back end of the Zvezda module, beaming laser light back to sensors on the ATV, creating unique light patterns captured and recognized by the spacecraft's cameras.

The ATV carries a backup system using telegoniometers, similar to police radar guns, to emit laser light at a different wavelength up to 10,000 times per second.

Cosmonauts Pavel Vinogradov and Roman Romanenko replaced one of the laser reflectors on a spacewalk April 19. Engineers suspected contamination may have damaged the old reflector.

Novelli said the reflector suspected of damage from the Progress docking is in a different location and has a different use than the unit replaced during the April 19 spacewalk.

Until the Progress leaves the space station, there is no way to inspect the reflector without another spacewalk.

File photo of an ATV in orbit. Credit: NASA

The only firm plan now is to use a camera on the Progress cargo vessel to inspect the reflectors when it undocks June 11, according to Kelly Humphries, a spokesperson at NASA's Johnson Space Center in Houston.

While engineers develop backup plans in case there is damage to the reflector, workers in French Guiana were directed to press on with launch preparations.

Technicians loaded the first cache of cargo into the ATV's pressurized cabin earlier this year.

Officials planned to launch the Albert Einstein mission in April, but ESA decided to swap out a failed avionics component, requiring the spaceship to be disassembled and retested, setting back the launch nearly two months.

Filling of the spacecraft's tanks with fuel, water and gas began in early April.

Technicians completed the month-long procedure in phases, first with water, oxygen and air, then with 12,500 pounds of propellant to power the ATV's engines, raise the space station's orbit, and refuel the Russian segment's propulsion tanks.

The Albert Einstein mission is the fourth of five ATVs built by Astrium Space Transportation. Its cargo carriers are built by Thales Alenia Space in Italy, and the pressurized section meets the ATV service module at an Astrium plant in Bremen, Germany.

The fifth ATV mission is set for launch in April 2014. Astrium and ESA are developing a modified ATV service module for NASA's Orion crew module. The European service module and Orion will make an unmanned test flight together in 2017.

Each ATV mission costs about 450 million euros, or nearly $600 million, according to ESA.

Logo for the Albert Einstein mission. Credit: ESA

The fourth ATV will haul more cargo than its three predecessors, thanks to upgrades in both the spacecraft and a performance improvement on its Ariane 5 ES launcher. The rocket upgrade adds about 100 kilograms, or 220 pounds, of lift capacity, Novelli said.

"ATVs are never carbon copies," Novelli said in an interview with Spaceflight Now. "Either we have anomalies we have to correct from one ATV to the next, or we have to implement an improvement. Therefore, every time we launch an ATV, it is slightly different, both on the cargo side and the ATV side."

During its four-month mission, the ATV will transfer about 1,900 pounds of propellant into the space station's fuel tanks. The rest of the ATV's fluid complement includes 1,256 pounds of water and 220 pounds of air and pure oxygen.

Another new feature for the Albert Einstein mission is the ability for workers to enter the spacecraft while it is mounted vertically on the rocket inside the final assembly building.

Officials have selected about 40 cargo bags, including fresh food, for installation into the ATV's Integrated Cargo Carrier beginning as soon as this week.

"We produced a new device that allows one person to go inside the ICC by opening the hatch," Novelli said. "Now we have a new kind of device that allows us to bring inside much heavier and bigger cargo to go into all the possible positions inside the ICC. We have improved our capability to respond to late requests for new cargo. We're doing both."

Workers will seal the ATV's hatch after the final cargo loading. The Ariane 5's payload fairing will be lowered over the spacecraft in the last week of May, and the launcher's upper stage will be filled with storable hydrazine and nitrogen tetroxide propellants.

Rollout of the 166-foot-tall rocket to the launch pad is set for June 4.