Velocity

2013

NovAtel's Annual Journal of GNSS Technology Solutions and Innovation

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ACES/geophones ments, including a test of the theory of relativity. Back on Earth, an innovative dual-antenna design is making it possible to map subterranean formations thousands of metres below the surface without ripping up the surface ecosystems. Keeping Up with Einstein E=MC2 ? ACES will use two atomic clocks—PHARAO, a cesium cold-atom clock developed and provided by CNES, the French space agency, and a space hydrogen maser (SHM), which is being contributed by the Swiss. The time kept by the clocks whirling by in orbit will be compared with that maintained by laboratory clocks on the ground to try and detect any differences. The idea is to test the relativity theories of noted physicist Albert Einstein, says Dr. Achim Helm, the project integration manager of the project for Germany's Astrium Space Transportation, which is building ACES for the European Space Agency (ESA). "Time is one element that you can measure with very, very high precision, and now the clocks are in a range where we can really see and check whether Einstein is right," says Helm. "We (also) want to look to see if some physical constants really are not constants. If we can prove this, then physics has to be rewritten." "These clocks are so sensitive that they can determine their position in space-time," explains Robert Tjoelker, supervisor of the Frequency More than Timing: ACES Clocks May Aid Satellite Navigation Clock technology being developed "PHARAO is the frst (space) fight room temperature-based mercury for the European Space Agency's of a cold atom clock. There are a ions. … We also have space fight ACES project may lead to improved number of other clock technologies programs for that technology clocks on navigation satellites. as well. This clock is too big to and we've actually done some fy on a GPS satellite, but preliminary development for the other variations of cold atom GPS program of that reference clocks may not be," said technology. I don't know that the Robert Tjoelker, supervisor cold atom clock will necessarily be of the Frequency and Timing the next-generation GPS clock. It's Advanced Instrument very possible that the ultra-stable Development Group at NASA's mercury ion clock will be the next- Jet Propulsion Laboratory. His generation GPS clock." group is developing one of the ground reference clocks for the ACES mission. Schematic drawing of ACES GNSS antenna (lower righthand corner of purple panel) with boresight pointing +50° off ISS fight direction and tilted 30° toward zenith direction. Astrium illustration. 10 velocity 2013 Tjoelker said NASA is developing a shoebox-size version of the mercury ion clock that would be "The ground clock that we suitable for space fight as part of it are developing here is based Deep Space Atomic Clock or DSAC on a different technology— program. For more Solutions visit http:/ /www.novatel.com

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