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Artemis is a geostationary earth orbit satellite (GEOS) for telecommunications, built for 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.〔(【引用サイトリンク】 Japanese H2 may be used as Artemis launcher for Europe )〕 Launched by an Ariane 5 rocket on 12 July 2001, it originally reached an orbit much lower than planned (590 km x 17487 km) due to a malfunction in the launch vehicle's upper stage.〔(【引用サイトリンク】title=Ariane Launch Report: Ariane 5 failure investigation focuses on upper stage )〕 It was remotely reconfigured to reach its intended station by means of a novel procedure.〔(【引用サイトリンク】 Artemis Telecommunications Satellite, Europe )〕 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, 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.〔(【引用サイトリンク】 Artemis finally reaches operational orbit )〕 On January 1, 2014 Avanti, a London-based company, took the ownership of the satellite.〔(【引用サイトリンク】title=Contract win for satellite from European Space Agency ("ESA") )〕 ==Payload== The Artemis satellite has several payloads 〔(【引用サイトリンク】 NASA/NSF Panel on SATELLITE COMMUNICATIONS SYSTEMS AND TECHNOLOGY (1993 study) ARTEMIS section )〕 * 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.〔(【引用サイトリンク】 Another world first for ARTEMIS: a laser link with an aircraft )〕 It uses a 60 mW AlGaAs laser diode as the transmitter and a photodiode detector, with a 25 cm telescope aperture, and a data rate of 50Mbit/s; it weighs about 160 kg and uses 150 watts of power.〔(【引用サイトリンク】 Optical Communications in Space )〕 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 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Artemis (satellite)」の詳細全文を読む スポンサード リンク
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