The British Broadcasting Corporation writes to say

The European Space Agency (Esa) says the latest two satellites for Europe's version of the American GPS satellite navigation system have not gone into the correct orbit.

The same article elaborates as follows

"Observations taken after the separation of the satellites from the Soyuz VS09 (rocket) for the Galileo Mission show a gap between the orbit achieved and that which was planned," said launch service provider Arianespace, in a statement.

The article is open on in-flight corrective measures

Arianespace declined to comment on whether their trajectories could be corrected, the AFP news agency reports.

This remark may qualify as hear-say (because it is!). A space-craft is tracked from launch through orbit by highly qualified personnel using high-end instruments & techniques. In the present instance the satellites were launched into the wrong orbit. The team at launch may have determined the discrepancy, and outcome thereof, from the flight-profile of the launch vehicle.

Can a launch-provider determine from the flight-profile whether the payload will enter the wrong orbit?

  • $\begingroup$ They should be able to, if nothing is broken. $\endgroup$
    – PearsonArtPhoto
    Commented Aug 24, 2014 at 19:38

3 Answers 3


It's important to keep in mind two very important concepts:

  • Launch and orbit insertion are typically two distinct phases of flight.
  • Ground controllers have very limited options during both phases.

Once the launch starts, about the only thing the mission control team can do is make the vehicle blow up. Most of those fantastic explosions you see of launch vehicles blowing up are because the mission control team made that happen. It's better to have a blown-up ex-rocket than a fully function but out of control rocket that hits some city. That didn't happen in this case. The launch appears to have been nominal. The problem instead apparently occurred during orbit insertion.

ESA issued a very short press release on August 22 that merely stated the vehicles were in the wrong orbit. They issued a much longer press release the following day that stated what that meant.

From that latter press release, the satellites were supposed to have been placed in a circular orbit with a semi-major axis of 29,900 kilometers and an inclination of 55 degrees. They are instead in an elliptical orbit with an eccentricity of 0.23, a semi-major axis of 26,200 km, and an inclination of 49.8 degrees. There's not much that can be done to fix the problem. What little fuel was left in the upper stage has been purged.

My guess is that everything went more or less okay during the launch and during the first transfer burn. The problem arose during the final orbit insertion. Those numbers suggest a significant underburn at orbit insertion. Minor underburns (this was not a minor underburn) can be caused by a number of things such as navigation errors and erroneous sensors. Significant underburns such as this are more often a result of bigger problems such as engine failure or running out of fuel.

So why didn't they see this on the ground? They did see this on the ground, but it took the mission control team a couple of hours to realize that the vehicles were in the wrong orbit. GPS doesn't work at that altitude. The only way to determine what orbit a high altitude vehicle is in is to make multiple range/range-rate measurements from the ground, spread out over time. Orbit determination isn't something that can be done by one single observation.


I didn't keep track of this answer. Today is October 27th, but the root cause was discovered over two weeks ago. The root cause was loss of attitude control due to frozen fuel lines on the Fregat upper stage. Hydrazine fuel lines that fed attitude control thrusters were routed too close to liquid helium lines that supplied helium used to pressurize the fuel tanks. Per the article A Simple Plumbing Problem Sent Galileo Satellites Into Wrong Orbits at IEEE Spectrum,

The fuel — hydrazine — didn’t reach the thrusters because it froze in its feed line, which was too close to another feed line carrying liquid helium. Both lines were mounted on a same support structure that, unfortunately, functioned as a thermal bridge cooling the hydrazine. The fault has also been discovered in other Fregat stages that are now under construction in Russia, and was apparently caused by ambiguities in the design documents of Fregat.

  • $\begingroup$ why would they purge extra fuel? seems unnecessary $\endgroup$
    – Stu
    Commented Aug 26, 2014 at 4:57
  • $\begingroup$ @Stu - Standard Operating Procedure. The fuel that was purged was whatever was left in the upper stage. This was done after the payload satellites had separated from the upper stage. Even if they didn't purge that fuel, what could they do with it? The upper stage and satellites can't dock or berth once separation has occurred. That extra fuel is just a bomb just waiting to go off if they leave it in the upper stage. Venting that fuel removes a hazard. $\endgroup$ Commented Aug 26, 2014 at 5:30
  • $\begingroup$ ah i get it now. i misread what you wrote! $\endgroup$
    – Stu
    Commented Aug 26, 2014 at 5:46

The simple answer is yes. Arianespace was asked to deliver the satellites to a given separation orbit. They track the rocket, so have data that tells what orbit was achieved. They provide the separation orbit elements to the customer about 30 minutes after separation, then a more accurate set later. In this case the discrepancy is large enough to be easy to see in the first set of elements. Once the satellites are separated, Arianespace cannot do anything to correct the orbit. Arianespace does not officially know whether the satellites can fix the problem themselves, hence the last statement. Arianespace may in fact know, but it is not their place to make that announcement.


There seem to be a number of directions to take with this question. This response tries to address the final part of the question "Can a launch-provider determine.."

There are two approaches that will occur in parallel during a launch:

  • position and velocity measurement, by what ever method

  • telemetry regarding the physical health and operation of the vehicle

Position and velocity. You can get a very clear idea of the difficulties of ranging by considering that the orbital period of Galileo is 14 hours. I don't know what the transfer orbit would be but I suspect a substantial fraction. This means that at 30 minutes, just to use the example in Ross Millikan's answer, the satellite would only have done a small fraction of an orbit.

Ask a friend to start drawing a circle and see if you can guess "exactly" how big it will be after they have only drawn ten percent of the way around. You might get it roughly right, but the difference between the first orbit estimate and one done later, after perhaps a half orbit, clearly in this case has been significant.

Telemetry. In principal this should provide a good idea of whether the mission is broadly going to plan. The apparent outcome is that the real failure, as described by David Hammen's answer was either not spotted (telemetry not observing that area) or that the information wasn't passed on to be made public until much later. I've not seen any discussion of the latter though its plausible given human nature.

Points for the future: Take a glance through these press releases from Arianespace:



the next day

I think this is simply the normal human-organisational difficulty. The "Success" is released prematurely in this case, but perhaps this was done on the basis of very early ranging. The latter two show progressive awareness developing and in this case, measurement by the customer, ESA, and CNES rather than the launch service provider, Arianespace.


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