Artemis (satellite)
Encyclopedia
Artemis is a geostationary earth orbit satellite (GEOS) for telecommunications, built for and owned by ESA
. The Artemis satellite operates at the 21.5E orbital position.
The mission was planned for many years, with launch initially intended for 1995 and slipping; it was intended for launch on Ariane 5
but at one point there were suggestions that a Japanese H-II rocket
might be used.
Launched by an Ariane 5
rocket on 12 July 2001, it originally reached an orbit much lower than planned (590 km x 17487 km). It was remotely reconfigured to reach its intended station by means of a novel procedure . First, over the course of about a week, most of its chemical fuel was used to put it in a 31,000 km circular orbit (by raising first the apogee then the perigee, so going via a 590 km x 31000 km orbit). Then, its electric-ion motor
- originally intended for station keeping, and for firing a few minutes at a time, was instead kept running for most of 18 months, pushing the spacecraft into an outward spiral trajectory. It gained altitude at the rate of about 15 km per day, until it reached the intended geostationary orbit.
Images of the Artemis satellite are available at http://esapub.esrin.esa.it/br/br200/Artemis.pdf
is established daily . It can also be used on an emergency basis; for example, it was used to relay information from the automated transfer vehicle Jules Verne
while mission control at Houston was unavailable due to a hurricane.
It is now considered a precursor for the EDRS
programme.
European Space Agency
The European Space Agency , established in 1975, is an intergovernmental organisation dedicated to the exploration of space, currently with 18 member states...
. The Artemis satellite operates at the 21.5E orbital position.
The mission was planned for many years, with launch initially intended for 1995 and slipping; it was intended for launch on Ariane 5
Ariane 5
Ariane 5 is, as a part of Ariane rocket family, an expendable launch system used to deliver payloads into geostationary transfer orbit or low Earth orbit . Ariane 5 rockets are manufactured under the authority of the European Space Agency and the Centre National d'Etudes Spatiales...
but at one point there were suggestions that a Japanese H-II rocket
H-II
The H-II rocket was a Japanese satellite launch system, which flew seven times between 1994 and 1999, with five successes. It was developed by NASDA in order to give Japan a capability to launch larger satellites in the 1990s. It was the first two-stage liquid-fuelled rocket Japan made using only...
might be used.
Launched by an Ariane 5
Ariane 5
Ariane 5 is, as a part of Ariane rocket family, an expendable launch system used to deliver payloads into geostationary transfer orbit or low Earth orbit . Ariane 5 rockets are manufactured under the authority of the European Space Agency and the Centre National d'Etudes Spatiales...
rocket on 12 July 2001, it originally reached an orbit much lower than planned (590 km x 17487 km). It was remotely reconfigured to reach its intended station by means of a novel procedure . First, over the course of about a week, most of its chemical fuel was used to put it in a 31,000 km circular orbit (by raising first the apogee then the perigee, so going via a 590 km x 31000 km orbit). Then, its electric-ion motor
Ion thruster
An ion thruster is a form of electric propulsion used for spacecraft propulsion that creates thrust by accelerating ions. Ion thrusters are categorized by how they accelerate the ions, using either electrostatic or electromagnetic force. Electrostatic ion thrusters use the Coulomb force and...
- originally intended for station keeping, and for firing a few minutes at a time, was instead kept running for most of 18 months, pushing the spacecraft into an outward spiral trajectory. It gained altitude at the rate of about 15 km per day, until it reached the intended geostationary orbit.
Payload
The Artemis satellite has several payloads- SILEX (Semiconductor-laser Intersatellite Link Experiment) is a laser link, which has been used both to communicate with the SPOT-4 remote-sensing satellite and with a plane in flight . It uses a 60 mW GaAlAsAluminium gallium arsenideAluminium gallium arsenide is a semiconductor material with very nearly the same lattice constant as GaAs, but a larger bandgap. The x in the formula above is a number between 0 and 1 - this indicates an arbitrary alloy between GaAs and AlAs.The bandgap varies between 1.42 eV and 2.16 eV...
laser diode as the transmitter and a photodiode detector, with a 25 cm telescope aperture, and a data rate of 50Mbps; it weighs about 160 kg and uses 150 watts of power. The telescope is in a fork mounting. The system is designed and built by Astrium.
- SKDR (S/Ka band Data Relay), a system for relaying data from other satellites. This uses a 2.85-metre antenna.
- LLM (L-band Land Mobile), a system designed for satellite communication with fairly small vehicle-based terminals in Europe. This uses a second 2.85-metre antenna, providing four beams; one covers Europe from western Spain to eastern Turkey and from the southern point of Tunisia to the north of Norway, whilst three spot beams cover respectively France and Spain; central Europe and Italy; Turkey and south-East Europe.
- EGNOS navigation-signal transmitter
- An advanced ion propulsion system with 44 kg of xenon reaction mass.
Images of the Artemis satellite are available at http://esapub.esrin.esa.it/br/br200/Artemis.pdf
Operations
Artemis is used operationally for data relay from ESA's satellites in low Earth orbit; a SILEX link to SPOT-4SPOT (satellites)
SPOT is a high-resolution, optical imaging Earth observation satellite system operating from space. It is run by Spot Image based in Toulouse, France...
is established daily . It can also be used on an emergency basis; for example, it was used to relay information from the automated transfer vehicle Jules Verne
Jules Verne ATV
The Jules Verne ATV, or Automated Transfer Vehicle 001 , was an unmanned cargo resupply spacecraft launched by the European Space Agency . The ATV was named after the French science-fiction author Jules Verne...
while mission control at Houston was unavailable due to a hurricane.
It is now considered a precursor for the EDRS
European Data Relay Satellite
The European Data Relay Satellite system will be a constellation of GEO satellites intended to relay information between other satellites and ground stations, to allow full-time communications even with satellites in low-Earth orbit which are often not visible from any European-operated ground...
programme.
External links
- http://www.esa.int/artemislaunch/ Artemis news page at European Space Agency.