NASA To Test New Atomic Clock

Were you a Payload Officer at 2 SOPS? And, are you referring to the Space or Ground segment? If you mean the backup clocks in the Mod, then that's slightly outside my knowledge. As far as the Space Segment, they've been reliably using Cesium and Rubium (atomic) clocks for over 3 decades. They don't want to change because it's known, reliable, etc. I was curious to note the newest generation of satellites dropped the 4th clock, and now launch with only 3. Since each clock is only usable a number of years (varies too much for me to generalize), I'd have thought they kept all four just in case the electrical system outlives normal design life, and you end up needing to go with a 4th clock when the 3rd one becomes too "deviant".

I think the GPS relevence is buried at the bottom of the article. Cesium and Rubidium clocks are both accurate to the nanosecond. That's just about as accurate as can be practical. The new atomic clock, however, they're saying is accurate LONGER. On GPS Satellites, the original satellites (Block I, II, IIA, IIR) launched with Cesium and Rubidium, 2 each. Usually you have one operational, sometimes one on "ready standby", and the other two off. As each atomic clock reaches the end of its mission-usable life, it's turned off. It become's "mission-unusable" (not a real term, I just made that up) when it's signal varies outside a normal window of acceptable predictability in terms of its output signal. There are design differences, such as Rubidium clocks have to stay within a tenth of a degree (F) in temperature stability (if memory serves correct). So, if they can create a clock that's more stable, for a longer period of time, this has huge potential for future GPS satellites. However, since we just awarded contract to Boeing the contract for IIF birds, with only 2 of 12 launched, it's going to be a very long time (decade at best) before you'd see this in a GPS satellite. Design life has also expanded from 7 to 12 years for each satellite (for point of reference Block I only had a design life of 3 years since they were R&D), so this pushes any usage even farther out since we're going to go longer before replacements need to be launched.

Source: http://rss.slashdot.org/~r/Slashdot/slashdotScience/~3/j14-05S4B5o/nasa-to-test-new-atomic-clock

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