Station-bound freighter poised for critical practices
BY STEPHEN CLARK
Posted: March 27, 2008
Europe's Jules Verne space transporter fired its engines early Thursday to leave a parking orbit and begin moving toward the complex, setting up for the first of two rendezvous dress rehearsals this weekend.
The series of three burns was completed about an hour-and-a-half later, putting the bus-sized spacecraft on track to begin the first day of demonstrations Saturday morning.
Jules Verne, which began its mission with a rain-soaked nighttime launch March 9, completed early testing and reached the parking orbit last Wednesday. The station partners agreed to flight rules prohibiting other vehicles from docking while the space shuttle is present.
The craft is the first Automated Transfer Vehicle fielded by the European Space Agency. Measuring 34 feet long and up to 15 feet wide, the ATV is carrying more than 2,500 pounds of dry cargo, 1,900 pounds of refueling propellant, nearly 600 pounds of water and 46 pounds of oxygen for the station.
After coasting toward the station for nearly two days, Jules Verne will conduct more maneuvers Friday night to guide the ship to an "interface point" 24 miles behind and three miles below the station Saturday morning.
Saturday's round of tests is the first of two "demo days" scheduled in advance to showcase the craft's ability to autonomously fly in close proximity to the outpost.
"In each of those, we demonstrate various aspects of the ATV and prove that those features are working properly to ensure the safety of the vehicle and the station," said Bob Chesson, head of ESA's human spaceflight and exploration operations.
With ground controllers looking over the shoulder of Jules Verne's futuristic autopilot system, the ship will automatically fly toward the station through waypoints at various distances from the complex.
See our preliminary rendezvous timeline here.
The ship's computers will process data derived from the ATV's relative GPS navigation system, which generates precise position data from antennas on both Jules Verne and the space station during the early portion of the rendezvous sequence. The computer automatically compares the positions and uses them to plot a course toward the next waypoint.
Jules Verne will pass through a point 9.6 miles behind and three miles below the station at 1505 GMT (11:05 a.m. EDT), where it will begin raising its altitude to match the outpost's orbit.
At approximately 1551 GMT (11:51 a.m. EDT) Saturday, Jules Verne will arrive at a site 2.2 miles behind the station, a hold point where the craft will turn on its external tracking lights and activate the Russian-built Kurs rendezvous radar. The venerable Kurs system will provide supplemental data during the ATV's approach to the station.
The station's crew will send several test commands to Jules Verne as it is parked off the stern of the complex to demonstrate the crew's ability to intervene if the ship's control system experiences problems.
Russian cosmonaut Yuri Malenchenko, the station's flight engineer, will serve as the primary crew member responsible for overseeing Jules Verne's rendezvous. Stationed at a control station in the Zvezda service module, Malenchenko will be able to send emergency commands for the craft to quickly fly away from the station.
Malenchenko's control panel also includes hold, retreat and resume options to correct smaller errors.
"We've already had training on this, and we're going to have a few days more preparation for this, but as I said, we're expecting it's going to be successful on the automatic mode," Malenchenko said during an in-flight news conference Sunday.
Station commander Peggy Whitson will follow along in a backup role.
Yuri and I are going to watch this vehicle rendezvous," Whitson said. "We'll do two practice days. It's got a different rendezvous system, so we obviously want to keep close tabs on it as it approaches."
After more than 90 minutes of tests, the ATV control center in Toulouse, France, will order Jules Verne to escape the station's vicinity at 1729 GMT (1:29 p.m. EDT). Up to a dozen more thruster firings will put the ship on track for an ambitious second day of demonstrations Monday that will bring the ATV within 36 feet of the Zvezda docking port.
"This will be a very exciting time, but we've really got to make sure that the vehicle is behaving exactly as we want," said John Ellwood, ATV project manager.
Demo day two will focus on checking out Jules Verne's high-tech optical guidance sensors attached to the forward end of the ship. Two videometers and two telegoniometers will fire laser light toward reflectors near Zvezda's aft docking port. The reflected light will be analyzed by the ship's cameras, allowing the ATV to autonomously determine its orientation, closing rate and range to the space station.
If everything behaves as expected Monday, officials will approve the preliminary plan to attempt docking next Thursday. Docking is scheduled for 1438 GMT (10:38 a.m. EDT) April 3.
"It will do two approaches to different distances from the station, and then on the third day it will approach and dock," Whitson said. "We did some training on this and are looking forward to actually getting yet another module on-board the station with the ATV, and I think Yuri's looking forward to the challenge of it as well."