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Primary Atomic Reference Clock In SpaceThe Primary Atomic Reference Clock in Space or PARCS is an atomic-clock mission scheduled to fly on the International Space Station (ISS) in 2008. The mission, funded by NASA, involves a laser-cooled caesium atomic clock, and a time-transfer system using Global Positioning System (GPS) satellites. PARCS will fly concurrently with the Superconducting Microwave Oscillator (SUMO) a different sort of clock that will be compared against the PARCS clock to test certain theory. The objectives of the mission are to: Experiment Location The proposed ISS location for the experiment is on the External Facility of the Japanese Experimental Module (JEM). This location affords good views of the GPS constellation of satellites, needed for comparing space and ground clocks. In addition, the volume, available power, and coolant system are well matched to the mission requirements. Goals The microgravity environment of space allows slowing of atoms to speeds well below those used in terrestrial atomic clocks, providing for substantial improvement in clock accuracy. This very accurate space clock will be compared continuously to the SUMO oscillator, and these two clocks (being fundamentally different) will provide a test of "local position invariance." Comparisons between the space and earth clocks will yield a related, but important measurement of the gravitational frequency shift. Finally, the signals conveyed to the ground through the GPS time-transfer system will serve as a truly international time standard available to anyone on earth. Institutions and People PARCS is a cooperative effort between the following organizations: Staff Bill Klipstein of JPL is the Project Scientist, and Dave Seidel of JPL is the Project Manager. The Co-Principal Investigators are Don Sullivan and Bill Phillips of NIST, and Neil Ashby of the University of Colorado. John Lipa of Stanford University is the Principal Investigator for SUMO and John Dick of JPL serves as the Project Scientist for that program. Reference
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