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NASA Space

Instrument and Sensing Technology

Space Clocks and Frequency Control Technology

On this page:

• General Background
• Cesium Atomic Fountain Frequency Standards
• Hydrogen Maser Clock Information
• Stable Local Oscillator (LO) Information
• Surface Acoustic Wave (SAW) Information
• Trapped Ion Frequency Standards
• Using Pulsars as Frequency Standards
• Return to:

General Background

Clocks and Frequency Control Devices play important roles in space communication, navigation, sensing, and science. High-stability oscillators have enabled systems such as the GPS. They support astronomy such as very long baseline interferometry (VLBI), and could be used in space for space-based VLBI and gravity wave detection. Stable oscillators are also used for sensitive in situ sensors.

Because of the many civil and military applications of these devices, the NASA/DOD Advisory Group on Electron Devices (AGED) Working Group on Microwave Devices held a Special Technology Area Review (STAR) on Frequency Control Devices in March of 1995.

I have begun collecting on this page information on the NASA technology efforts in space clocks and frequency control devices, along with related background information. These are in roughly alphabetical order...

Cesium Atomic Fountain Frequency Standards

• Cesium Atomic Fountain Frequency Standards from the Clock Development Division at the United States Naval Observatory (USNO)

Hydrogen Maser Clock Information

• HMC (Hydrogen Maser Clock) We recently had to make the unfortunate but necessary decision to cancel plans for the Hydrogen Maser Clock flight experiment. The Smithsonian Astrophysical Observatory was under contract to the NASA Marshall Space Flight Center to develop the Hydrogen Maser Clock (HMC). HMC was scheduled to be transported to the Russian Space Station, Mir, on STS-86 (September 1997) to be be attached to the Mir Docking Module via astronaut EVA. A click here for a description of the HMC from the The Crustal Dynamics Data Information System at GSFC.
• Information on the Sigma Tau hydrogen maser clock used by the Time Service Department at the U.S. Naval Observatory, Washington, DC.
• The IEEE paper Time Synchronization in Orbiting VLBI by Larry R. D'Addario provides background on why a stable time source like the hydrogen maser clock is needed for space-based very long baseline interferometry (VLBI) radio astronomy. This paper discusses operational workarounds because " at present it is not feasible for orbiting radio telescopes to include sufficiently stable on-board oscillators (e.g., H masers) to permit time synchronization to be achieved in the same way as in ground-based VLBI."

Stable Local Oscillator (LO) Information

NASA is developing stable local oscillators (LO) for heterodyne remote sensing at submillimeter wavelengths. See the Submillimeter Sensors Program page for more information.

Surface Acoustic Wave (SAW) Information

• NASA is developing a Micro Weather Station For Earth and Mars use. We recently flight-tested (on a DC-8) a surface acoustic wave (SAW)-based micro-hygrometer for dew-point/humidity measurements. This work is being done at the Center for Space Microelectronics Technology (CSMT) at JPL.
• Development of a Real-Time Nonvolatile Residue Monitor for Use in Cleanrooms (based on a SAW sensor) from the NASA KSC TechTracS Forum, part of the NASA Commercial Technology Network. This is just one of many Surface Accoustic Wave sensors. Try searching on Surface, Accoustic, Wave, SAW from the NCTN Search the Network page. There are now too many listings for me to recreate here!

Trapped Ion Frequency Standards

• Mercury-based Trapped Ion Frequency Standards from the Clock Development Division at the United States Naval Observatory (USNO)
• Trapped Ion Frequency Standard from the JPL RESEARCH AND TECHNOLOGY 1994 ANNUAL REPORT. The task objective is for the Jet Propulsion Laboratory (JPL) to develop a mercury trapped ion frequency standard (atomic clock) for the United States Naval Observatory (USNO) with long term frequency stability better than 1x10-16/day.

Using Pulsars as Frequency Standards

• The USNO Pulsar Data Archive from the Clock Development Division at the United States Naval Observatory (USNO)

Return to:

• Instrument and Sensing Technology Page
• Advanced Technology and Mission Studies Division Page
• Office of Space Science
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The world wide web uniform resource locator (URL) for this page is:

http://ranier.hq.nasa.gov/Sensors_page/Background/HMC.html