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Primary Atomic Reference Clock in Space

 

 
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Primary Atomic Reference Clock in Space
 
 
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The Primary Atomic Reference Clock in Space or PARCS is an atomic-clock
Atomic clock

An atomic clock is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. They are the most accurate time and frequency standards known, and are used as primary standards for international Time dissemination, and to control the frequency of television broadcasts and GPS satellite signals....
 mission once scheduled to fly on the International Space Station
International Space Station

The International Space Station is a research facility Assembly of the International Space Station in outer space. On-orbit construction of the station began in 1998, and is scheduled to be complete by 2011, with operations continuing until around 2015....
 (ISS) in 2008, but cancelled to make way for the Bush Mars initiative
Vision for Space Exploration

The Vision for Space Exploration is the U.S. National Space Policy announced on January 14, 2004 by U.S. President George W. Bush. It is seen as a response to the Space Shuttle Columbia disaster, the state of human spaceflight at NASA, and a way to regain public enthusiasm for space exploration....
. The mission, to have been funded by NASA
NASA

The National Aeronautics and Space Administration is an agency of the Federal government of the United States, responsible for the nation's public list of space agencies....
, involved a laser-cooled caesium
Caesium

Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only liquid metal that are liquid at or near room temperature....
 atomic clock, and a time-transfer system using Global Positioning System
Global Positioning System

The Global Positioning System is a global navigation satellite system developed by the United States Department of Defense and managed by the United States Air Force 50th Space Wing....
 (GPS) satellites. PARCS was to 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.






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The Primary Atomic Reference Clock in Space or PARCS is an atomic-clock
Atomic clock

An atomic clock is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. They are the most accurate time and frequency standards known, and are used as primary standards for international Time dissemination, and to control the frequency of television broadcasts and GPS satellite signals....
 mission once scheduled to fly on the International Space Station
International Space Station

The International Space Station is a research facility Assembly of the International Space Station in outer space. On-orbit construction of the station began in 1998, and is scheduled to be complete by 2011, with operations continuing until around 2015....
 (ISS) in 2008, but cancelled to make way for the Bush Mars initiative
Vision for Space Exploration

The Vision for Space Exploration is the U.S. National Space Policy announced on January 14, 2004 by U.S. President George W. Bush. It is seen as a response to the Space Shuttle Columbia disaster, the state of human spaceflight at NASA, and a way to regain public enthusiasm for space exploration....
. The mission, to have been funded by NASA
NASA

The National Aeronautics and Space Administration is an agency of the Federal government of the United States, responsible for the nation's public list of space agencies....
, involved a laser-cooled caesium
Caesium

Caesium or cesium is the chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-gold alkali metal with a melting point of , which makes it one of only liquid metal that are liquid at or near room temperature....
 atomic clock, and a time-transfer system using Global Positioning System
Global Positioning System

The Global Positioning System is a global navigation satellite system developed by the United States Department of Defense and managed by the United States Air Force 50th Space Wing....
 (GPS) satellites. PARCS was to 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 were to have been:

  • Test gravitational theory
  • Study laser-cooled atom
    Atom

    |-! bgcolor=gray | Properties|-||}The atom is a basic unit of matter consisting of a dense, central atomic nucleus surrounded by a electron cloud of electric charge electrons....
    s in microgravity
  • Improve the accuracy of time
    Time

    Time is a component of the measurement used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects....
    keeping on earth


Experiment location

The proposed ISS location for the experiment was on the External Facility of the Japanese Experimental Module (JEM). This location afforded good views of the GPS constellation of satellite
Satellite

In the context of spaceflight, a satellite is an Physical body which has been placed into orbit by human endeavor. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....
s, needed for comparing space and ground clocks. In addition, the volume, available power, and coolant system were 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
    Jet Propulsion Laboratory

    Jet Propulsion Laboratory is a List of federally funded research and development centers and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, California, United States....
     (JPL), which contributed Flight Hardware Development
  • National Institute of Standards and Technology
    National Institute of Standards and Technology

    The National Institute of Standards and Technology , known between 1901 and 1988 as the National Bureau of Standards , is a measurement standards laboratory which is a non-regulatory agency of the United States Department of Commerce....
     (NIST), which contributed Concept/Development Testing
  • University of Colorado
    University of Colorado at Boulder

    The University of Colorado at Boulder is a public research university located in Boulder, Colorado. Considered a Public Ivy, it is the flagship university of the University of Colorado system and was founded five months before Colorado was admitted to the union in 1876....
    , which contributed Gravitational Testing


Staff

Bill Klipstein of JPL was the Project Scientist, and Dave Seidel of JPL was the Project Manager. The Co-Principal Investigators were Don Sullivan and Bill Phillips of NIST, and Neil Ashby of the University of Colorado. John Lipa of Stanford University was the Principal Investigator for SUMO and John Dick of JPL serves was the Project Scientist for that program.

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