Final ATV on track to arrive at space station Tuesday
BY STEPHEN CLARK
Posted: August 11, 2014
A massive European supply ship is approaching the International Space Station for an automated linkup Tuesday with food, experiments and fuel.
A suite of telegoniometers and videometers will guide the supply ship to docking with the space station with help from a GPS navigation system for long-range tracking.
The optical guidance system will fire lasers on final approach to the space station, bouncing the light off of specially-located reflectors mounted on the aft end of the outpost's Zvezda service module.
The 20-ton ATV will approach the complex from behind, with the space station crew on standby to issue retreat, abort, or escape commands to the cargo craft if there is a problem.
"It's one million lines of code, just to give you idea, because it's very complex to have an automatic docking," said Eric Beranger, head of space programs at Airbus Defence and Space, lead contractor for the cargo spacecraft. "You need to anticipate all possible mishaps using sensors, and yet be able not to lose track of your target and be able to dock. This software onboard ATV is able to dock with a precision within 6 centimeters (2.4 inches)."
The spaceship took a longer route than normal after its July 29 launch aboard an Ariane 5 rocket to try out next-generation rendezvous sensors that could be used to help clean up space junk or approach objects like asteroids.
The Laser Infrared Imaging Sensors, or LIRIS, carried on the ATV do not require the retro-reflectors, enabling future missions to rendezvous with nearly any object in orbit.
ESA's ATV contractor Airbus Defence and Space, along with Sodern and Jena-Optronik, proposed flying the new laser and infrared sensors on the ATV 5 mission. The infrared camera was provided by French company Sodern, with German-based Jena-Optronik supplying the laser lidar, according to ESA.
"The purpose is to validate, in a real operational environment, these partially new technologies that might be used in the future," said Massimo Cislaghi, ESA's ATV 5 mission manager, before the launch. "We don't have a real application yet, but they might be used in the future for rendezvous and docking with non-cooperative targets. It's a little bit like science fiction, but the typical example is the retrieval of a spacecraft out of control before it becomes a danger for re-entry or debris."
The "fly-under" maneuver to test the infrared camera occurred Friday, when the ATV passed less than 4 miles below the space station, then ahead and above the outpost to line up for another rendezvous Tuesday. The laser lidar sensor will be tested during the ATV's final approach Tuesday.
About 14,500 pounds of cargo and fuel will be delivered with the ATV's docking Tuesday.
The cargo complement includes 1,896 pounds of propellant to be pumped inside the Russian Zvezda service module, 1,858 of fresh water, 220 pounds of air and pure oxygen, and about 5,941 pounds of dry cargo.
Cargo items include coffee, soy sauce and supplies for a Japanese experiment on fish.
The largest piece of hardware aboard ATV 5 is an electromagnetic levitator for ESA's Material Science Laboratory inside the Columbus module. The device will melt down metallic samples for research in material thermodynamics, according to ESA.
The first ATV took off for the space station in 2008 with more launches in 2011, 2012, 2013 and last month.
"Georges Lemaitre is the last ATV, six years after the launch of the first, which was in March 2008," said Jean-Jacques Dordain, ESA's director general. "Six years have gone by in the meantime, but the ATV is, and will remain for a long time to come, a unique space vehicle. It's the most complex vehicle that ESA and European industry have ever developed and produced. It's both a launcher and a satellite. It's both automatic and man-rated. It's capable of unparalleled accuracy and controlled atmospheric re-entry."
ESA is retiring the ATV in favor of a new program to design and build the service module for an unmanned test flight of NASA's Orion multipurpose crew vehicle set for launch at the end of 2017.
"To say it very bluntly, if Europe had not done ATV, the service module for [Orion] MPCV would have been a no go," said Bart Reijnen, head of orbital systems and space exploration at Airbus Defence and Space.
Officials said they wished to put engineers to work on developing a new spacecraft instead of building more ATVs. Cargo deliveries to the space station will continue with a fleet of supply vehicles from the United States, Russia and Japan.
The U.S. Dragon and Cygnus cargo craft, along with Japan's H-2 Transfer Vehicle, can carry up larger experiments than the ATV, which attaches to the Russian segment of the space station with a smaller passageway than NASA's modules.
Russia's Progress spacecraft delivers propellant, but in smaller quantities than the ATV.
But the ATV is the only cargo craft to do it all.
With the arrival of the Georges Lemaitre spacecraft, Europe's five ATVs will have delivered 31,446 kilograms, or 69,327 pounds, of cargo, fuel, water and air to the space station, according to Thomas Reiter, head of ESA's human exploration and operations directorate.
The ATV missions were part of a barter agreement between ESA and NASA. The resupply capabilities offered by the ATV paid Europe's share of the space station's operating costs through 2017.
ESA's payment for the station's operating expenses from 2017 through 2020 will be paid with the provision of the Orion spacecraft's service module, which is valued at approximately 450 million euros, or about $600 million.
At the end of the ATV 5 mission, currently scheduled for January or February, the ATV will undock from the space station's Zvezda service module with trash and waste. Like the previous European cargo ships, the ATV 5 mission will plunge back into the atmosphere, destroying itself and the garbage inside, clearing precious room on the space station for fresh experiments and cargo.
But NASA and ESA officials have devised a plan to change the re-entry trajectory to collect data on how the ATV responds when it falls into the atmosphere, helping engineers validate computer models to predict how the space station will re-enter at the end of its mission as a crewed orbiting research laboratory.
Pending final approval from safety officials, the shallow re-entry profile would occur over the uninhabited South Pacific Ocean.
The ATV also carries an internal camera to record and transmit imagery of the re-entry from inside the spaceship's pressurized module.
Follow Stephen Clark on Twitter: @StephenClark1.