Artemis orbit evolution
communicationg with SPOT 4 (artists impression)
Thanks to ion propulsion, the Artemis mission is turning near-defeat into a success story. Nominal operations could start this summer, with ESA’s satellite, manufactured by Alenia Spazio as prime contractor (I), playing a significant role in the pursuit of high technology and advanced telecommunications.
On 12 July 2001, 30 minutes after lift-off from Europe’s spaceport in Kourou, French Guiana, it became apparent that the Ariane 5 launcher had propelled the Artemis satellite into a transfer orbit that was lower than expected, with the apogee (the most distant point from Earth) at only 17 000 km rather than the nominal 36 000 km.
Under normal circumstances a conventional satellite does not carry enough fuel to compensate for a shortfall in launcher performance of this magnitude. But with an innovative application of ion propulsion (*), a system 10 times more efficient than conventional chemical propulsion, recovery appeared possible. Embedded in a novel and remarkably flexible system design, used with outstanding ingenuity, team spirit and operational skills, Artemis’ propulsion capabilities proved to be the key to the rescue of an otherwise lost mission.
In January 2002 all new software modules were completed and fully tested by Alenia Spazio and Astrium . Today, Artemis starts spiralling out of its safe parking orbit to bridge the gap of some 5000 km at a rate of roughly 1 km per hour.
Whereas the initial part of the orbit-raising process, using chemical thrusters, was completed within a few days, the remaining part is expected to last more than 200 days, requiring two ion engines to fire almost continuously. That is because the thrust of these engines is very weak indeed (15 millinewtons). Their task can be compared to driving an ocean liner with an outboard motor. Artemis is expected to arrive this summer at its nominal altitude of 36 000 km.
In parallel with orbit-raising preparations, in-orbit verification of the communication payloads was performed. The most spectacular events were communication tests with the CNES (French Space Agency) SPOT-4 Earth observation satellite (see ESA press release 75/2001), during which image data from SPOT 4 were transmitted by laser light to Artemis and from there by radio waves to the Spot Image processing centre in Toulouse. All tests confirmed that Artemis’ payloads are healthy and ready to support the technological and operational communication programme.
Now the spacecraft is on course for its nominal slot in geostationary orbit. An all but lost mission is on its way to full recovery since Artemis will eventually be able to serve its users from its geostationary position for at least 5 years of nominal operation.
(*) The principle of any kind of thruster in space is to accelerate molecules and expel them from the satellite at the highest possible speed. Conventional thrusters use a chemical reaction between fuel and oxidiser to heat a gas and eject the molecules at a speed of typically 1 km/sec. Electrical propellant systems first ionise (i.e. electrically charge) the molecules of a gas (xenon, for instance). The ionised gas is then accelerated by electrical fields and ejected from the satellite at a speed of typically 10 m/sec.
Gotthard Oppenhauser | ESA
Spintronics: Researchers show how to make non-magnetic materials magnetic
06.08.2020 | Martin-Luther-Universität Halle-Wittenberg
Manifestation of quantum distance in flat band materials
05.08.2020 | Institute for Basic Science
Scientists at the Fraunhofer Institute for Laser Technology ILT have come up with a striking new addition to contact stamping technologies in the ERDF research project ScanCut. In collaboration with industry partners from North Rhine-Westphalia, the Aachen-based team of researchers developed a hybrid manufacturing process for the laser cutting of thin-walled metal strips. This new process makes it possible to fabricate even the tiniest details of contact parts in an eco-friendly, high-precision and efficient manner.
Plug connectors are tiny and, at first glance, unremarkable – yet modern vehicles would be unable to function without them. Several thousand plug connectors...
An international research team has found a new approach that may be able to reduce bone loss in osteoporosis and maintain bone health.
Osteoporosis is the most common age-related bone disease which affects hundreds of millions of individuals worldwide. It is estimated that one in three women...
Traditional single-cell sequencing methods help to reveal insights about cellular differences and functions - but they do this with static snapshots only...
“Core-shell” clusters pave the way for new efficient nanomaterials that make catalysts, magnetic and laser sensors or measuring devices for detecting electromagnetic radiation more efficient.
Whether in innovative high-tech materials, more powerful computer chips, pharmaceuticals or in the field of renewable energies, nanoparticles – smallest...
An international research team with Prof. Cornelia Denz from the Institute of Applied Physics at the University of Münster develop for the first time light fields using caustics that do not change during propagation. With the new method, the physicists cleverly exploit light structures that can be seen in rainbows or when light is transmitted through drinking glasses.
Modern applications as high resolution microsopy or micro- or nanoscale material processing require customized laser beams that do not change during...
23.07.2020 | Event News
21.07.2020 | Event News
07.07.2020 | Event News
06.08.2020 | Earth Sciences
06.08.2020 | Power and Electrical Engineering
06.08.2020 | Life Sciences