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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.'"
To make sure there is no concurrence from another global measuring system. CT ? Possibly. But is that far fetched ?
Europeans are the big boys in satellites.
No, no they don't
Nothing improves ductility and wetting like lead and to knock tin scavenging on the head you need to do more than dope it with .5% copper or bismuth or whatever. Considering our current propensity for shoving high-pin count BGA packages on top of each other and then sticking them into hot little boxes and then shoving them in our pockets we couldn't have chosen a worse time to drop lead, the rate at which devices are failing due to thermal stress induced cracking is embarrassing.
and it just so happens that lead doesn't leech out of landfill, so it's almost as if the whole exercise was pointless.
You are wrong. Please refrain from commenting on things you have no clue about.
And don't get "electrical engineering and physics" clocks (jargon for "frequency reference") with layman and computer science clocks (devices that output a time coordinate relative to some frame of reference). Atomic clocks are *always* clocks only in the electrical engineering/physics jargon sense. They are pure frequency references *only*.
Also, "atomic clocks" are always disciplined. Active Hydrogen Masers (in the ground) are primary references, but you always use several of them together to reduce *jitter* (it is not to "majority vote"). Anything else is disciplined by such masers long-term, and often output far more precise short term frequency references (rubidium oscillators, for example) e.g. due to better phase error measurement characteristics, etc.
In the case of a Galileo satellite down to one clock, it will have somewhat reduced performance, and it *will* still be disciplined by the ground telemetry signal.
NASA had a similar problem years ago. They were testing the component by exposing it to voltage spikes. Passing the test also damaged the component.
Actually, surprisingly enough. RoHS does not apply to things manufactured within the EU, just items imported into the EU.
It is more a protectionist regulation than an environmental one.
The Chinese now have a much more restrictive RoHS policy than the EU does on paper