Artemis (satellite)

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Artemis
[[File: Artemismodrp.jpg |]]
Model of Artemis
Start date July 12, 2001, 23:58 UTC
Launcher Ariane 5G V142
Launch site ELA-3 , Center Spatial Guyanais
COSPAR-ID : 2001-029A
Takeoff mass 3100 kg, of which 40 kg xenon, 1500 kg fuel and oxidizer
Empty mass 1560 kg, including 550 kg payload
Span in orbit 25 m
lifespan 10 years (nominal)
Stabilization Inertia wheel
operator European space agencyESA ESA , Avanti
Others
Electrical power 2.8 kW
Power storage NiH2, 60 Ah, 42.5 V.
Ground stations Redu Space Services
position
First position 21.5 ° East, 123 ° East
Actual position Cemetery orbit
drive Chemical thrusters and two different ion thrusters
List of geostationary satellites

Artemis is a European-Japanese geostationary communications satellite operated by the European Space Agency (ESA). Artemis stands for A dvanced R elay and TE chnology MIS sion (about: sophisticated Relay and Technology Mission). Special features were experimental optical data links ( Laser Communication Terminal ), two types of novel ion thrusters and flexible operating software. Artemis and the French reconnaissance satellite Spot -4 regularly set up a laser data link ( SILEX ). The tests with the Japanese research satellite Kirari were also successful. Optical data transmission to aircraft ( LOLA ), drones and ground stations were tested. His operational tasks include communication with Envisat and supply vehicles such as the ATV-4 as well as broadcasting the GPS correction signals from EGNOS .

The satellite had a launch weight of 3,100 kilograms. Its useful electrical output is 2.8 kilowatts. It was launched on July 12, 2001 together with the Japanese communications satellite BSAT 2b on board an Ariane 5 G.

Rescue with ion engines

The launcher was supposed to bring the satellites into a geostationary transfer orbit, but did not achieve full power , so the apogee was only 17,000 instead of 36,000 km. BSAT 2b was lost, but Artemis could be saved. The satellite's apogee motor was actually intended to raise the perigee to 36,000 km. For this and for the use of the attitude control Artemis had 1500 kg of fuel and oxidizer on board, 95% of which were now used to reach at least one circular orbit at a height of 31,000 km. In this park orbit, outside the dangerous Van Allen Belt , Artemis' attitude control was reprogrammed so that a pair of ion thrusters could bring the satellite into geostationary orbit. The spiral ascent of around 20 km per day lasted from February to November 2002. Artemis reached its final position at 21.5 ° East in March 2003.

Ion thrusters

Artemis was to test two new ion thrusters: A German development of an electrodeless radio frequency discharge excited by applied coils with 15 mN thrust, as well as an English product with electro-bombardment ( Kaufmann ?) Source and 18 mN thrust. For comparison: Artemis has 16 chemical attitude control thrusters with 10 N thrust each. Two types of ion thruster each were used, mounted in mixed pairs on the north and south sides of the satellite. Your task should be to correct orbital disturbances in geostationary orbit ( inclination only ). The electrical power consumption of a pair is 600 W. Xenon is used as a supporting mass. The common supply was only 40 kg. In order for this amount to be sufficient for the rescue of the satellite and its imminent transfer to the cemetery orbit , the engines were operated with maximum acceleration voltage: exit speed 40 km / s instead of the nominal 30 km / s.

[[File: Artemisanalemmarp.jpg | mini | Nadir von Artemis]] In order to save xenon, the north-south drift was not compensated. The geographical longitude of 21.5 ° East was approximately maintained by means of chemical control nozzles. The inclination was approx. 10 °, so that the satellite was not stationary above the equator, but rather traced a narrow analemma trajectory curve in the sky (see adjacent figure).

payload

Artemis communicates on the following bands:

  • L-band (1.6 GHz send to / receive from ground station)
    • Send: 15 channels
    • Receiving: 6 channels
    • A total of 400 voice channels with 4.8 kbits / sec each
  • S-band (2 GHz / 2.2 GHz send to / receive from ground station)
    • Send: 3 Mbps
    • Receiving: 1 Mbps
  • S-band (2 GHz / 2.2 GHz send to / receive from satellites)
    • Send: 1 Mbps
    • Receiving: 3 Mbps
  • Ka-band (26 GHz / 23 GHz send to / receive from ground station)
    • Send: up to 150 Mbps
    • Receiving: 10 Mbps
  • Ka-band (23 GHz / 26 GHz send to / receive from satellites)
    • Send: 10 Mbps
    • Receiving: up to 3 × 150 Mbps
  • In the optical range (820 nm / 848 nm send to / receive from satellites)
    • Send: 2 Mbps
    • Receiving: 50 Mbps

This enables the following data rate from a satellite via Artemis to a ground station:

Satellite → (optical, 50 Mbps; Ka, 150 Mbps; S, 3 Mps) → Artemis → (Ka, 150 Mps) ground station

The satellite was operated by ESA until 2014 and should be switched off in 2014. In 2013 the satellite and the right to use the position 21.5 ° East were sold to the British company Avanti Communications. In 2015, the satellite was moved to the position 123 ° East to secure the L-band rights for Indonesia and to replace Garuda 1 . After Indonesia failed to meet its payment obligations, Artemis was placed in cemetery orbit and deactivated in November 2017.

Individual evidence

  1. ↑ Chris Peat: ARTEMIS - Orbit. In: Heavens Above. August 13, 2012, accessed August 17, 2012 .
  2. ^ Artemis. Retrieved May 29, 2020 .

Web links