SIRIUS 4

SES SIRIUS has awarded a contract to US company Lockheed Martin for delivery of a new satellite, SIRIUS 4, which should be ready for launch in 2007. SIRIUS 4 will be SES SIRIUS biggest satellite and a welcome addition to the satellite fleet. SIRIUS 4 is intended to meet todays growing demands and tomorrows new challenges.

Latest news about SIRIUS 4

SIRIUS 4 is at present at Lockheed Martins facilities in Sunnyvale, California for integration and final tests.

The satellite is tested during conditions that will occur during the launch and operation in the geostationary orbit. This means that it is exposed to vibrations that will match the worst conditions during the launch (with a margin). It is also tested in a vaccum chamber with temperature variations up and down corresponding to the temperatures it will have in orbit, when exposed to sunlight and shadow.

100_4802_72_utsnitt

Photo courtesy: Lockheed Martin Commercial Space Systems

Temperature variations are very big for the external part of the satellite, which are exposed for direct sunlight and shadow, i.e. solar panels and antennas. The solar panels are exposed to variations between -170 C and + 133 C and the antennas from -165 C to +100 C. In order to have a margin, the satellite is tested for the intervals -180 C to +143 C resp. -175 C to +110 C, e.g. 10 degrees margin both ways.

The payload, i.e. the part that receives, treats and sends out the signals that come from the ground (receivers, channel filters, amplifiers, frequency converters etc) is mounted inside the satellite body and is more protected against the temperature variations with help from heaters etc. These parts are tested in the interval 0 C till +75 C.

The tests of the payload are now finalized. As usual during this kind of tests, a few problems are discovered. In our case there are two frequency converters for the Ka-band (19-30 GHz) and a satellite gyro that showed certain problems. These units are examined at present and it cannot yet be determined which impact this will have on the delivery of the satellite, if any.

Later in February the antenna systems will be tested in order to verify that they still meet the specifications for antenna ranging, so called ranging tests. If everything goes according to the time schedule the satellite will be ready for shipping to the launch site in Baikonur, Kazakstan some time in June/July. The preparations in Baikonur will take around 1 month. The predicted time for launch is at present beginning of August.