MARECS ( Maritime European Communication Satellite ) is a series of geostationary satellites that were developed by ESA as maritime communications satellites and were used within the international Inmarsat system. The program started in 1973 with the Maritime Orbital Test Satellite (MAROTS). The three-axis stabilized satellites were based on the communications satellite ECS from British Aerospace (prime contractor) and Marconi Space Systems (payload). They served the data and information exchange (more than 35 telephone calls simultaneously) between ships and the mainland, with which they C-band - and L-band - repeaters were equipped.
MARECS A was launched on December 19, 1981 with an Ariane 1 rocket and positioned at 26 ° west with the help of a solid kick stage . After MARECS B was lost in a false start of Ariane 1 on September 9, 1982, the replacement satellite MARECS B2 was launched with an Ariane 3 rocket on November 10, 1984 and positioned on 177.5 ° West. MARECS A was used by Inmarsat until mid-1991. Then relocated to a 22.5 ° East orbit due to the aging solar cell surfaces, still used by ESA for experiments until August 1996, then moved into a cemetery orbit and finally switched off. MARECS B2 was used by Inmarsat until the end of 1996, and from 1997 to 2000 by the Italian company Nuovo Telespazio at position 26 ° West. At the beginning of 2002 it was placed in a cemetery orbit 300 km higher and finally switched off.
96 kg of the launch mass of around 1050 kg belong to the communication payload. This consisted of six (plus four reserve) L-band SSPS with a total of 75 watts of output power ( EIRP 33.1 dBW) for communication with ships and a C-band TWTA with 1 watt of output for communication with the ground station. The transmission frequencies were 6420.25 to 6425 MHz (ground satellite), 1537.75 to 1542.5 MHz (satellite - ship), 1638.6 to 1644.5 MHz (ship satellite) and 4144.6 to 4200.5 MHz (satellite-ground). More than 35 calls on the 1.54 GHz frequency and more than 50 calls on 1.64 GHz could be received and forwarded. The energy supply was provided by two three-part solar cell booms, each 1.3 × 5.2 m in size and two nickel-cadmium batteries with 21 Ah each, with 425 watts of the 955 watts supplied to operate the payload. The position control of the three-axis stabilized satellites was carried out with momentum wheels and redundant 0.5 N and 2 N hydrazine engines with 90 kg of fuel in four tanks. To control were earth and sun sensors used.
|Surname||MARECS A||MARECS B|
|size||2.3 × 3.1 × 1.8 m (at the start)||2 × 2.5 m|
|span||13.8 m (across the 2 solar panels )|
|power supply||two solar panels and two nickel-cadmium batteries|
|Electrical power||955 watts|
|Antennas||1 * 2m + 2 horn antennas (1 reception, 1 transmission)|
|Takeoff mass||1060 kg||1050 kg|
|Circulating mass||562 kg (BOL)||497 kg|
|fuel||Hydrazine (for attitude control system)|
|planned service life||7 years|
- ESA: The Third Phase of the Telecommunications Program. ECS, Marecs and Olympus (English; PDF; 8.5 MB)
- ESA: Cemetery orbit for MARECS B2 - Review of the decommissioning of the last MARECS satellite
- Gunter's Space Page: MARECS A, B, B2 (English)
- MARECS in the Encyclopedia Astronautica (English)