Archive for 2014

Galileo 5,6 launch and orbit update

Thursday, August 28th, 2014

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!


    Galileo bad orbit insertion

    Sunday, August 24th, 2014

    Unfortunately the launch of the two latest Galileo satellites has left a very bad taste in our mouth.

    The entire GNSS Community was looking forward to the next step in the Galileo constellation deployment. The launch went well from French Guyana aboard the Soyuz rocket, but apparently something went wrong at the orbit insertion point and the Fregat transfer stage did not insert into the correct orbit. Fortunately the separation of the satellites was correct and the new satellites are both under control of the ESA/ESOC center.

    Looking at the TLE’s (orbit two line elements) from, Thank guys! I have plotted using the Mac application SatTrackerBasic (from and for comparison included one of the currently active Galileo satellites (E11), the three newly launched elements are 2 Galileo satellites and one Fregat module and they are all still flying close together as expected, their TLEs are only referred to as 14050A, 14050B, 14050C it is not clear to me which are the satellites and which Fregat, so I have selected 14050A as an example. In the ground track plot below showing two full orbits you can clearly see the effect of the large eccentricity (0.23) in that the 14050A ground track is ’tilted’ over the earth’s map. Whereas the E11 has a very low eccentricity and thus its distance to the surface of the earth is constant in each revolution around the planet at around 23200 Km, the new satellites have a point of closest approach to the earth’s surface of 13800 Km and a farthest point of 25900 Km (both are preliminary values!).

    Screen Shot 2014-08-24 at 16.01.11

    Finally the orbit inclination is also wrong, you can see this as the point furthest south and north of the orbit track over the Earth’s map. A normal Galileo orbit (such as E11 shown in the plot) should reach to +/- 55 deg in latitude, but in the new orbits you can clearly see that they only have a 49 deg inclination.

    The initial report from arianespace confirms all these findings: Arianespace initial report Galileo FOC M1 launch

    I am sure that my excellent Flight Dynamics colleagues at ESOC will do their best to make the satellites useful for the final Galileo constellation. Considering that the satellites are apparently in good working order they could still provide their navigation signal as expected and be useful over their lifetime for position, navigation and scientific investigations.

    The big initial concern as remarked by my colleague Dr. Tim Springer in the last entry of his blog (Groundtrack of the Galileo Satellites) is that the two new satellites will be crossing the orbital planes of other Navigation satellite constellations such as GPS and GLONASS which is indeed scary in terms of possible collision warnings, etc, since it could affect the operations of all the GNSS constellations and cause possible reduction of those other satellite’s lifetimes as on-board station-keeping fuel would be consumed faster than planned if collision avoidance manoeuvres should ever be needed. In-space collisions remain very unlikely in any case but with these orbits there is a remote chance they could happen.

    Let us hope for the best and that the satellites 5 and 6 of Galileo can still be positive for our growing GNSS family!

    Happy positioning!


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