Rubidium Frequency Standard, Model FRK
name: label: maker
content: Efratom
notes: label: Description
content: This object, marked “F. Nr. E250/116,” is an unflown back-up for two rubidium frequency standards installed on NTS-1, the first of the Navigation Technology Satellites (NTS) launched to validate the key concepts and hardware for the Global Positioning System (GPS). NTS-1 (originally named Timation III) was built at the Naval Research Laboratory (NRL), Washington, D.C. It was launched in July 1974 and carried the first atomic clocks into space.
label: Description
content: The compact rubidium frequency standard for NTS-1 is the Model FRK made by Efratom Elektronik, Munich, Germany. Gerhard Hübner and Ernst Jechart established the firm in 1971 and a year later supplied examples of the clock to NRL. Researchers had constructed relatively large laboratory rubidium frequency standards in the 1950s, and portable commercial versions were available by the mid1960s. But the FRK—weighing roughly three pounds and measuring about four inches on a side—was the smallest frequency standard of any type available in the early 1970s and attractive for space applications. NRL modified the commercial model for use in space, specifically to permit controlling its rate and frequency output from the ground.
label: Description
content: Efratom established a branch in Irvine, California, in 1973 and manufactured compact rubidium frequency standards there for a variety of customers. The firm became a division of Ball Aerospace in 1982 and then part of Datum in 1995. Symmetricom acquired Datum in 2002.
label: Description
content: Reference:
label: Description
content: 1. Carroll O. Alley et al., “Performance of the New Efratom Optically Pumped Rubidium Frequency Standards and Their Possible Application in Space Relativity Experiments,” <i>Proc. of the 4th Ann. Precise Time and Time Interval (PTTI) Appl. and Planning Meeting</i>, 1972, 29-40.
label: Description
content: 2. Stephen A. Nichols, Joseph D. White and Danzy, Frederick. <i>Design and Ground Test of the NTS-1 Frequency Standard System</i>. Naval Research Laboratory Report 7904. Washington, D.C., September 5, 1975.
label: Description
content: Brief description of an atomic clock
label: Description
content: Electromagnetic waves of very specific and consistent frequencies can induce atoms to fluctuate between two energy states, and by measuring that frequency we can determine the “tick” of an atomic clock. A second in a cesium clock, for example, is defined as 9,192,631,770.0 cycles of the frequency that causes the cesium atom to jump between those states. Different atoms “tick” at different rates – strontium atoms tick about 10,000 times faster than cesium atoms – but all atoms of a given element tick at the same rate, making atomic clocks much more consistent than clocks based on macroscopic objects such as pendulums or quartz crystals.
label: Description
content: Steven Jefferts, physicist, National Institute of Standards and Technology.
label: Description
content: For additional background information go to:
label: Description
content: http://www.nist.gov/pml/div688/timekeeping.cfm
label: Location
content: Currently not on view
place: label: place made
content: West Germany
topic: label: general subject association
content: Modern Physics
label: general subject association
content: Science & Scientific Instruments
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content: Medicine and Science: Modern Physics
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content: Time and Navigation
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content: Science & Mathematics
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content: Measuring & Mapping
creditLine: label: Credit Line
content: Naval Research Laboratory
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1982.0634.01
label: catalog number
content: 1982.0634.01
label: accession number
content: 1982.0634
objectType: label: Object Name
content: Efratom rubidium-vapor frequency standard
physicalDescription: label: Physical Description
content: steel (overall material)
label: Physical Description
content: glass (overall material)
label: Measurements
content: overall: 3 7/8 in x 3 7/8 in x 5 5/8 in; 9.8425 cm x 9.8425 cm x 14.2875 cm