The Primary Atomic Reference Clock in Space or PARCS was an
atomic-clock mission scheduled to fly on the
International Space Station
The International Space Station (ISS) is the largest modular space station currently in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA (United States), Roscosmos (Russia), JAXA ...
(ISS) in 2008, but cancelled to make way for the
Vision for Space Exploration
Vision, Visions, or The Vision may refer to:
Perception Optical perception
* Visual perception, the sense of sight
* Visual system, the physical mechanism of eyesight
* Computer vision, a field dealing with how computers can be made to gain und ...
.
The mission, to have been funded by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeeding t ...
, involved a laser-cooled
caesium
Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...
atomic clock, and a time-transfer system using
Global Positioning System
The Global Positioning System (GPS), originally Navstar GPS, is a satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of the global navigation satellite sy ...
(GPS) satellites. PARCS was to fly concurrently with the
Superconducting Microwave Oscillator (SUMO)
[http://www.ips.gov.au/IPSHosted/NCRS/wars/wars2002/proceedings/invited/print/tobar.pdf ] a different type of clock that was to be compared against the PARCS clock to test certain theories. The objectives of the mission were to have been:
*Test
gravitational theory
In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong ...
*Study laser-cooled
atom
Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons.
Every solid, liquid, gas, and ...
s in
microgravity
The term micro-g environment (also μg, often referred to by the term microgravity) is more or less synonymous with the terms ''weightlessness'' and ''zero-g'', but emphasising that g-forces are never exactly zero—just very small (on the I ...
*Improve the accuracy of
time
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...
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
A satellite or artificial satellite is an object intentionally placed into orbit in outer space. Except for passive satellites, most satellites have an electricity generation system for equipment on board, such as solar panels or radioisotope ...
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
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States.
Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...
(JPL), which contributed Flight Hardware Development
*
National Institute of Standards and Technology
The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical sci ...
(NIST), which contributed Concept/Development Testing
*
University of Colorado
The University of Colorado (CU) is a system of public universities in Colorado. It consists of four institutions: University of Colorado Boulder, University of Colorado Colorado Springs, University of Colorado Denver, and the University of Co ...
, 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 was the Project Scientist for that program.
References
{{reflist
External links
National Institute of Standards and Technology
Atomic clocks