Galileo bad orbit insertion

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 celestrak.com, Thank guys! I have plotted using the Mac application SatTrackerBasic (from ClearandDark.com) 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!

Nacho

Additional news stories;

    Leave a Reply