Primary Atomic Reference Clock in Space

The 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 cesium atomic clock, and a time-transfer system using Global Positioning System (GPS) satellites. PARCS will fly concurrently with theSuperconducting 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:

• Test gravitational theory
• Study laser-cooled atoms in microgravity
• Improve the accuracy of timekeeping on earth

Table of contents

1 Experiment Location 2 Goals 3 Institutions and People 4 Staff 5 Source

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:

Jet Propulsion Laboratory (JPL), which contributed Flight Hardware Development

National Institute of Standards and Technology (NIST), which contributed Concept/Development Testing

University of Colorado, which contributed Gravitational Testing

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.

Source

National Institute of Standards and Technology