Eutelsat W1

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W1 Satellite

 

W1 - Bringing Low-Cost Satellite Internet in Europe

Eutelsat W1 is located at the 10 degrees East position. The satellite serves a full range of applications that include business communications, Internet-based services and television transmission. It has 28 channels, 20 of which provide coverage of Europe, North Africa, the Middle East and central Asia via a fixed wide beam, with the remaining eight connected to a steerable spot beam, to address new markets in geographical areas outside the wide beam coverage area (notably southern Africa). Services can be simultaneously provided within both coverage.

W1 is designed to provide 28 operational transponders at saturation for a minimum satellite lifetime of 12 years in geostationary orbit.
The frequency plan is shown in Figure 1. It comprises six "B" channels, eight "D" channels, eight "DS" channels and six "F" channels. The frequency bands utilized by each of the channel groups are as follows:

B 14.25 - 14.50 GHz 10.95 - 11.20 GHz

D, DS 13.75 - 14.00 GHz 11.45 - 11.70 GHz

F 14.00 - 14.25 GHz 12.50 - 12.75 GHz

The usable bandwidth of each communications channel is as follows:

- 72 MHz for the B and F channels

- 62 MHz for Channels D3, D4, D3S and D4S

- 54 MHz for Channels D5 to D8 and D5S to D8S

- 40 MHz for Channels D1, D2, D1S and D2S

There are ten channel frequencies on both the uplink and the downlink, each of which is re-used within the fixed coverage by means of linear orthogonal polarization. Thus there are twenty channels connected to the fixed coverage on both the uplink and the downlink (the B, D and F channels). Figures 2 and 3 show the fixed receive and transmit coverages, respectively, from 10º East Additionally, eight channels (four channel frequencies) are re-used by employing spatial isolation between the steerable coverage and the fixed coverage. Thus there are eight channels (the DS channels) connected to the steerable coverage on both the uplink and the downlink.

The centre of the steerable beam can be moved to any point on the visible earth. Also, the orientation of the elliptical beam can be rotated by up to ± 90º. Figure 4 and 5 show the actual receive and transmit coverage, respectively, of the W1 single steerable beam.

Flexible cross-connection between the fixed and steerable coverages is provided for Channels D1, D3, D5, D7 and D1S, D3S, D5S, D7S as follows:• 

Channels D1, D3, D1S and D3S can each receive from either the fixed coverage or the steerable coverage, the choice of uplink coverage being made on a channel-by-channel basis.

•A signal received from any given coverage can be simultaneously transmitted to both coverages. For example, the channel pair D1 and D1S could be used to "broadcast" the same signal received from the steerable coverage to both the fixed and steerable coverages.

In addition, Channels D5, D7, D5S and D7S each provide the possibility to receive signals from both coverages and to transmit them to a single coverage or to both coverage. In this case, performance in terms of G/T takes into account the wider uplink coverage and discrimination between uplink carriers must be ensured through FDMA (i.e. the spectra of the carriers must not overlap). For example, the lower half of the 54 MHz bandwidth occupied by the channel pair D5/D5S could be used to receive traffic from the fixed coverage whilst the upper half could be used to receive traffic from the steerable coverage. The combined traffic could then be transmitted to the fixed coverage via Channel D5 and simultaneously to the steerable coverage via Channel D5S. This type of networking between two different coverages can offer attractive mission features for certain types of services.