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Galileo Satellites Are Experiencing Multiple Clock Failures (bbc.com)
elgatozorbas writes: According to a BBC article, the onboard atomic clocks that drive the satellite-navigation signals on Europe's Galileo network have been failing at an alarming rate. From the report: "Across the 18 satellites now in orbit, nine clocks have stopped operating. Three are traditional rubidium devices; six are the more precise hydrogen maser instruments that were designed to give Galileo superior performance to the American GPS network. Each Galileo satellite carries two rubidium and two hydrogen maser clocks. The multiple installation enables a satellite to keep working after an initial failure. All 18 spacecraft currently in space continue to operate, but one of them is now down to just two clocks. Most of the maser failures (5) have occurred on the satellites that were originally sent into orbit to validate the system, whereas all three rubidium stoppages are on the spacecraft that were subsequently launched to fill out the network. Esa staff at its technical centre, ESTEC, in the Netherlands are trying to isolate the cause the of failures - with the assistance of the clock (Spectratime of Switzerland) and satellite manufacturers (Airbus and Thales Alenia Space; OHB and SSTL). It is understood engineers have managed to restart another hydrogen clock that had stopped. It appears the rubidium failures 'all seem to have a consistent signature, linked to probable short circuits, and possibly a particular test procedure performed on the ground.'"
Why would RoHS directives apply to spaceflight? That would be silly.
Ezekiel 23:20
Since the Indians are not experiencing the same failure rate on identical hardware, it seems likely that it's something about the environment in the EU's satellites that is causing the problem. Maybe power supply issues, temperature control issues, or vibration issues.
As you say, lots of things (like test equipment and of course aerospace) are exempt from RoHS so it's unlikely to be that. They will have used the most suitable materials.
const int one = 65536; (Silvermoon, Texture.cs)
SJW, n: "Someone I don't like, and by the way I'm a fuckwit" - AC
"The only property we really wanted from the lead was the lower melting point"
and better wetting
and higher ductility so thermal cycling doesn't crack your joints
and suppression of tin scavenging so your solder bath doesn't strip the gold off your boards
and suppression of whisker growth
and the inhibition of tin pest
along with of course the lower process temperature
it's almost as if a eutectic lead-tin alloy was the ideal material for making solder joints.....
GLONASS and Beidou work fine.
I suspect that these would be the most likely targets should the CIA want to disable competing systems. Europe is supposedly an ally, Russia and China, not so much.
This is not true for frequency references, which are the function of the on-board clocks. And they are externally disciplined by the two ground stations, which have an array of Cesium and Active Hydrogen Maser clocks.
The Galileo satellites can operate with only a single atomic clock, at reduced performance. They can operate with two clocks of different types at full performance.