Managers of Europe’s Automated Transfer Vehicle (ATV), an unmanned cargo-carrying spacecraft,
said they are almost certain to launch the 19,100-kilogram vehicle between Feb. 22 and March 9 regardless of what the traffic flow is at the international space station.
If necessary, they said, the long-delayed ATV will be placed into a parking orbit for several weeks to wait for a docking opportunity at the station, which in February is being prepared for the arrival of two U.S. space shuttle missions and one Russian unmanned Progress cargo carrier.
Current plans call for ATV to be launched between Feb. 22 and March 9 aboard a specially designed European Ariane 5 rocket from Europe’s Guiana Space Center spaceport. Rendezvous and docking with the station could occur between March 15 and March 19, or between March 30 and April 5, program managers said at a press briefing here Jan. 29.
John Ellwood, ATV program manager at the European Space Agency (ESA), said the vehicle would use about 20 kilograms of fuel per day while stationed in orbit waiting for the go-ahead to dock with the station.
For ESA and for the Arianespace commercial-launch consortium, clearing ATV from the launch manifest as early as possible – and moving its 500,000 kilograms of supplies out of the principal satellite-preparation facility at the spaceport – is a high priority.
Arianespace has scheduled seven or eight Ariane 5 launches in 2008 including the first ATV in what would be a record launch pace. The quicker ATV is on its way, the more likely it is that this launch rate can be achieved.
ATV has been at the Guiana Space Center since August. In recent weeks it has completed most of its pre-launch tests, including reviews by NASA, as space station contractor, and by the Russian space agency, Roskosmos, whose Service Module is where ATV will dock.
The ATV is designed to carry food, water, fuel and other supplies to the space station once every 18 months or so. It
also will re-boost the station into its preferred operating orbit. Flying at altitudes between 350 and 430 kilometers above the Earth’s surface,
the station gradually loses altitude because of the force of the Earth’s gravity and because of atmospheric drag at that altitude.
The ATV has three times the cargo capacity of Russia’s Progress vehicle and is being developed by ESA as part of a barter arrangement with NASA. Instead of paying cash for its share of the station’s common operating costs, and also to secure additional astronaut access, ESA is providing ATV and other gear.
So far, ESA member nations have spent some 1.3 billion euros ($1.9 billion) on developing the ATV, a figure that includes the cost of the first launch. The agency currently plans to build four other ATVs, with the second due for launch in 2010 –
�assuming the first flight occurs without a hitch.
For this first ATV, called Jules Verne, ESA, NASA and Roskosmos have agreed on a go-slow approach as ATV, which will be operating automatically, nears the station and docks to it.
To be sure the vehicle responds to commands, it will be ordered to stop at various distances from the station, then withdraw and wait for further instructions.
Program managers estimate that following ATV’s launch aboard a specially designed European Ariane 5 rocket, it will take about 10 days for the vehicle to climb to the station’s orbiting altitude.
Depending on the traffic at the station, ATV may be sent into a parking orbit to wait for the U.S. space shuttle, or a Russian Progress vehicle, or a Russian Soyuz manned capsule to complete its mission at the station and depart.
Ellwood said ATV operations require the use of NASA’s Tracking and Data Relay Satellite System, TDRSS, whose capacity will be fully used fully during shuttle launches. The next shuttle launch, of Europe’s Columbus space station laboratory,
currently is scheduled for Feb. 7.
ATV’s need for TDRSS is minimal if the vehicle is parked at a safe distance from the station while waiting for a docking opportunity, Ellwood said, meaning that the launch date is not directly dependent on whether the Feb. 7 shuttle launch is further delayed.
In addition to needing to steer clear of other traffic to and from the station, ATV’s rendezvous and docking schedule is governed by the position of the sun relative to both ATV and the station, Ellwood said.
ATV’s final approach to the station is guided by lasers. Ellwood said mission managers want to avoid having direct sunlight in front of the vehicle as it chases the station to avoid confusing the laser guidance.
The station’s astronauts will be monitoring the approach of ATV using a small camera mounted on board the station. To maintain a clear view, the maneuver must occur when the sun is not shining directly into the camera, Ellwood said.