Europe's last cargo freighter set for launch Tuesday
BY STEPHEN CLARK
Posted: July 29, 2014
KOUROU, French Guiana -- After more than two decades of design, development and flights of Europe's biggest-ever spacecraft, the last Automated Transfer Vehicle is ready for takeoff Tuesday to haul more than 7 tons of fuel, food and supplies to the International Space Station.
Liftoff is scheduled for 2347:38 GMT (7:47:38 p.m. EDT) Tuesday during an instantaneous launch opportunity when the space station's orbital path passes over the tropical spaceport.
After a series of orbital maneuvers and tests, the ATV will approach the space station Aug. 12 for an automatic, laser-guided docking to the Russian Zvezda service module.
It is the fifth ATV mission since 2008, and the spacecraft weighs in at more than 20 tons, making it the largest in the fleet of international resupply vehicles servicing the space station.
But Tuesday's launch will mark the last flight of the ATV, which is being phased out in favor of U.S.-built commercial cargo craft and Japan's resupply freighter -- called the H-2 Transfer Vehicle.
The U.S. and Japanese vehicles 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.
While the space station's other resupply freighters can deliver large experiments, fuel and basic supplies, the ATV does it all.
"The first studies started in the 1980s, so we are 25-to-30 years down the road, and there is a lot of energy, motivation, and competencies in ATV," said Bart Reijnen, head of orbital systems and space exploration at Airbus Defence and Space, lead contractor for the cargo spacecraft. "For all the teams that have been working over such a long time period, it's not easy to say farewell to ATV. You can be sure about that."
Technicians packed approximately 14,500 pounds of cargo inside the fifth ATV, which is named Georges Lemaitre after the Belgian priest and physicist behind the Big Bang theory.
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 5,900 pounds of dry cargo.
Cargo items include coffee, soy sauce and supplies for a Japanese experiment on fish.
"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. "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). It gives you an idea at 28,000 kilometers per hour (17,400 mph). On top of that, this ATV will be the heaviest ever launched -- more than 20 [metric] tons."
The fluids and air will be transferred into tanks on the space station's Russian segment, while astronauts and cosmonauts aboard the research lab will unpack the dry cargo, which includes experimental hardware for European, Japanese and U.S. investigations ongoing inside the outpost.
The European cargo craft can also boost the space station's orbit and maneuver the huge complex out of the way of space junk during its mission.
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.
Officials decided to stop building ATVs, opting to focus on a new development using the spacecraft's technologies to keep European engineering teams sharp.
After considering a cargo return vehicle and an orbital cleanup spaceship to clear space debris from orbit, ESA member states agreed in November 2012 to build a service module for NASA's Orion crew capsule, a U.S.-led program to send astronauts on missions to deep space destinations, such as asteroids, the moon and Mars.
The agreement covers the construction of a service module for an unmanned test flight of the Orion spacecraft around the moon set for launch no earlier than late 2017. Based on technologies and components developed for the ATV, the service module supplies propulsion and power for the Orion capsule.
"I think in this way we can nicely demonstrate that all the effort we have taken to build such a fantastic vehicle to do this fantastic cargo transfer and automated docking ... is not lost, but it's built upon for future activities," said Thomas Reiter, a former astronaut and director of ESA's space exploration programs.
Negotiations have not started for European construction of service modules for later Orion missions, including crewed flights.
Beranger called the final ATV mission "both an au revoir and the beginning of a new adventure."
The ATV's primary rendezvous sensors, a suite of telegoniometers and videometers, have guided the supply ships to four dockings with the space station with help from a GPS navigation system for long-range tracking.
The optical guidance system fires 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 Laser Infrared Imaging Sensors, or LIRIS, carried on the ATV do not require the 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. "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 is set for Aug. 8, and the laser lidar sensor will be tested during the ATV's final approach on docking day.
At the end of the 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.
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