U.S. Naval Observatory Earth Orientation Department


International Earth Rotation and Reference Systems Service
Service International de la Rotation de la Terre et des Systemes de Reference


IERS Rapid Service/Prediction Center

for Earth Orientation Parameters

IERS The IERS Rapid Service/Prediction Center is the product center of the International Earth Rotation and Reference Systems Service responsible for providing Earth orientation parameters (EOPs) on a rapid turnaround basis. This service is primarily intended for real-time users and others needing the highest quality EOP information sooner than is available in the IERS final series (Bulletin B) published by the IERS Earth Orientation Center, which is based at the Observatoire de Paris.
USNO EO Dept This Center is an activity of the Earth Orientation (EO) Department at the U.S. Naval Observatory (USNO). The mission of the USNO includes determining the positions and motions of celestial bodies, measuring the Earth's rotation and orientation, maintaining the master clock for the U.S., and disseminating precise time (atomic and astronomical). The EO Dept. contributes to this mission by collecting suitable observations and performing data analyses to determine and predict the time-varying orientation of the terrestrial reference frame within the quasi-inertial celestial reference frame. The key parameters determined and disseminated are polar motion coordinates, Universal Time (UT1), precession, and nutation. The user community is very broadly based, the main applications involving principally high-accuracy navigation and positioning, particularly in real-time and near real-time modes.

Contact Information: 202-762-1518 (primary); 202-550-6407 (alternate); 202-762-1444 (alternate)


Please note that daily and Bulletin A EOP data can be obtained from the primary Earth Orientation (EO) servers at:
* http://maia.usno.navy.mil;     ftp://maia.usno.navy.mil
and from the backup EO server at:
* http://toshi.nofs.navy.mil;     ftp://toshi.nofs.navy.mil

An additional backup mirror of the daily and Bulletin A EOP data
is now hosted by NASA's Archive of Space Geodesy Data server at:
* ftp://cddis.gsfc.nasa.gov/pub/products/iers
Daily EOP data will be uploaded here daily at 18:00 UTC, and
Bulletin A EOP data should by available by 20:00 UTC each Thursday.

 2017 IERS Bulletin A Vol. XXX Website  

General Information about Earth Orientation

IERS Bulletin A -- Rapid Service/Prediction of Earth Orientation

  Additional information concerning IERS Bulletin A:

  Publications about IERS Bulletin A:

  Standard data files available by anonymous ftp -- now updated weekly (Thursday), prior to 1 July 2002 (Tuesday and Thursday):

  Daily data files available by anonymous ftp -- updated daily (normally about 17:05 UTC), for highest accuracy real-time applications

  Delta T values

NEW! (as of 2/18/2011)
The Linux k-shell script, getusnoeop.ksh, is provided as a convenience to users of our USNO EOP data products.
The intent is to check our primary server and our back-up server in Flagstaff, Arizona for new data. Details on the use of this script are available here.

Earth Orientation Matrix Calculator (Earth orientation matrix (based on Tech Note (TN) 32 -- equinox-based) at user-specified epochs.)

NEW! (as of June 2011)
Earth Orientation Matrix Calculator update (Earth orientation matrix (based on TN 36 -- equinox-based) at user-specified epochs.)
    Validation of the calculator results are on-going.

NEW! (as of September 2011)
"finals.daily" solution re-computed at 03:10 UTC A second RS/PC EOP solution, computed just after 03:10 UTC, is available at http://maia.usno.navy.mil/2xdaily. Normally, the integrated IGS Length-of-day (LOD) inputs produced from "18-hour" and "0-hour" IGS Ultra-Rapid orbit solutions (IGS Ultras) -- which contain the results reported for 06:00 and 12:00 UTC, respectively -- are the only additional inputs beyond those inputs used in the 17:00 daily UTC run; however, when VLBI intensives processing is occasionally late, and misses the 17:00 UTC daily solution it will be added to the next 03:10 UTC solution. Also, RS/PC personnel do not as closely monitor this solution as the 17:00 UTC daily solution. Users who notice problems with the solution may contact the RS/PC at ser7 at maia.usno.navy.mil.

  Discontinued data files -- no longer available:

IERS Bulletin B ("Final" EOP values)

IERS Bulletin C (Leap Second Announcements)

IERS Bulletin D (Announcements of DUT1)

General Publications

This is an official U.S. Navy web site.

Send comments to ser7 at maia.usno.navy.mil or
U.S. Naval Observtory, EO Dept. Attn: ser7
3450 Massachusetts Avenue NW
Washington, DC 20392-5420 last updated 09 Jan 2017