Galileo 5,6 launch and orbit update

The satellites are operational as described in today’s ESA press release it indicates that the satellite finally opened their solar panels (there had also been a problem with that!)

I have created 3D images on an excellent iPad application called ‘Orbit Architect’ which I can recommend to everyone as a great tool and wonderful to explain things to children!

OrbitArchitect-Galileo 5 OrbitArchitect-E11

The differences in the orbits is very dramatic as the new satellites (on the left) travel away and towards from the Earth now more than expected. This will affected the received signal power on the ground, initial thoughts are that a 4dB signal strength difference which can mean that the signal may be too weak when at apogee and too strong when at perigee … but it is not too bad, and the signal strength can be adjusted on-board the satellite but surely not continuously so a reasonable level will have to be found.

Therefore to summarise what we have so far;

    • The new orbit ground track is not terrible but optimising the ‘navigation service’ will not be easy as the expected slot in the orbit plane will be empty and providing consistent and correct worldwide coverage will not be possible.
  • Operations will be very complicated so the satellites may never go into operations since the control segment cannot easily adjust to the completely different orbits from other Galileo satellites.
  • Navigation messages and Almanac messages which are essential to use a Navigation service will be more difficult to maintain correct and may not even be able to accommodate the current orbits. These satellite position messages are essential for the receivers to know when to expect the satellite’s signals overhead.
  • The satellites are now generating power from its solar panels and so the navigation payload checkout can be done, since these are the first two satellites from the new OHB contractor they have to be fully tested to validate the new production lines.
  • Overall I am very hopeful that satellites 5 and 6 can be fully tested and that they will be turned ON and be available at least for scientific use, even if normal navigation users will have some issue using these satellites.

    Finally the EC and ESA have established an Inquiry Commission to fully investigate the actual problem with the rocket’s third stage. Lets hope that the problem is not very significant, and I do not expect it to be, since Fregat has been used successfully in the past and the flexibility that it offers is very good for orbit transfers. Being able to turn on and off the thrusting of the Fregat is a great feature which has been validated many times already, but unfortunately some of the recent upgrades have clearly not worked as intended in the launch of Aug 22. I am sure that European space industry will learn from this problem and continue to move forward to deploy Galileo as planned.

    Happy positioning!

    Nacho

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