1 / 16

Coordinated Universal Time (UTC)

Coordinated Universal Time (UTC). Judah Levine JILA –- Time and Frequency Div. NIST and Univ. of Colorado Boulder, Colorado 80309 Jlevine@boulder.nist.gov. Outline of the talk. Definition of atomic time and UTC BIPM computation of UTC, TAI, … Realization of UTC(lab) at timing laboratory

danil
Télécharger la présentation

Coordinated Universal Time (UTC)

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Coordinated Universal Time (UTC) Judah Levine JILA –- Time and Frequency Div. NIST and Univ. of Colorado Boulder, Colorado 80309 Jlevine@boulder.nist.gov

  2. Outline of the talk • Definition of atomic time and UTC • BIPM computation of UTC, TAI, … • Realization of UTC(lab) at timing laboratory • Time transfer from a timing lab • What should a user do with calibration data?

  3. Definition of civil time scale Length of day Atomic clocks Civil Time

  4. Post-1972 definition of UTC • Duration of second defined by unperturbed cesium hyperfine transition on the rotating geoid: 9,192,631,770 cycles  1 second • Atomic-time day is 246060= 86400 s • Astronomical day defined by UT1 • “Leap Seconds” added to UTC to keep UT1- UTC < 0.9 s • The times they are a-changing

  5. Not confusing enough yet? • Resolution S2 (1996) of the Consultative Committee for the Definition of the Second (CCDS): • Apply black-body correction to primary frequency standards. • Correction for a room-temperature standard is about 210-14 or about 0.6 s/yr

  6. A clock ensemble – NIST style Clk 1 Clk 2 Clk 3 Clk 4 Clk n Weighted Average (AT1 scale) Phase Stepper Clock data to BIPM Steering based on BIPM data (Circular T) UTC(NIST) To services

  7. The role of the BIPM Lab 1 Lab 2 Lab 3 Lab 4 Lab n EAL: Weighted average of 250 clocks Stability => Add fountain data: TAI Accuracy => Add UT1 data: UTC Astronomy => Circular T (monthly) gives UTC-UTC(lab) for every lab

  8. The questions … • How well do TAI and UTC realize the definition of the SI second? • The BIPM has no clocks • TAI and UTC are post-processed paper scales • TTBIPM is post-post-processed TAI scale • Realization of UTC is only via UTC(lab) • How well does UTC(lab) track UTC?

  9. Comparison of Primary Standards ^ Feb. 1997 Dec. 2001^

  10. (MJD = Modified Julian Date)

  11. 2.510-14 (Gerard Petit, PTTI, 2003)

  12. 10-14 (Gerard Petit, PTTI, 2003)

  13. 10-15

  14. The common-view method GPS satellite => Transmitter Receiver Receiver Measure time differences and subtract, attenuates common-mode errors (SV clock, ionosphere, radial position, …

  15. Dec,2002 Dec,2003

  16. 2.310-14 July, 2005 Jan, 2004

More Related