Earth Orientation Parameters Data Documentation

Data used:
1. Files:
  Contains: NGA coefficients for the upcoming week (see Documentation)
  
  Updated: Weekly (Thursday)
  Each week a file of the form EOPPyddd.TXT is produced where y is the last digit of the year and ddd is the day of the year.
2. Files:
  Contains: Observed data (x, y, UT1-UTC, LOD, δΔψ, δΔε), (δX, δY)
  
  Updated: Daily
3. Files:
  Contains: Predicted data (to +90 days) from Bulletin A
  (x, y, UT1-UTC, LOD, δΔψ, δΔε), (δX, δY)
  
  Updated: Daily
4. Files:
  Contains: Predicted Data (to +1 year) from Bulletin A
  
  Updated: Weekly
5. Files:
  Contains: TAI-UTC data
  
  Updated: With new leap seconds
Data documentation can be found at:
- Earth Orientation Parameter Prediction Description (NGA Coefficients)
- EOP C04 Series
- Explanatory Supplement to IERS Bulletins A and B
- Bulletins A and B Data Formats
Process:
1. NGA coefficients for the coming week are obtained from Source 1.
2. Observed data is produced using Source 2.
3. Predicted data is obtained from Source 3 for the first 90 days from the current date and then Source 4 is used for the remainder of the upcoming year. The first week of data from Source 4 is blended using the offset between Source 3 and Source 4 at Day 90 to minimize discontinuities between the two forecasts.
4. Leap second (TAI-UTC) data is obtained from Source 5.
Keywords:
- VERSION major.minor
  Provides major and minor version of current data format.
- UPDATED yyyy Mon dd hh:mm:ss UTC
  Provides UTC date and time of current update.
- BEGIN NGA_COEFFICIENTS
  END NGA_COEFFICIENTS
  Marks beginning and end of NGA coefficients.
- NUM_OBSERVED_POINTS number
  Indicates number of records of data in the Observed Data section.
- BEGIN OBSERVED
  END OBSERVED
  Marks beginning and end of the Observed Data section.
- NUM_PREDICTED_POINTS number
  Indicates number of records of data in the Predicted Data section.
- BEGIN PREDICTED
  END PREDICTED
  Marks beginning and end of the Predicted Data section.

Observed and Predicted Data Format:

------------------------------------------------------------------------------------------------------
FORMAT(I4,I3,I3,I6,2F10.6,2F11.7,4F10.6,I4)
------------------------------------------------------------------------------------------------------
Column
000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000111
000000000111111111122222222223333333333444444444455555555556666666666777777777788888888889999999999000
123456789012345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012
------------------------------------------------------------------------------------------------------
yyyy dd mm MJD      x         y        UT1-UTC     LOD        dPsi    dEpsilon    dX        dY     DAT
------------------------------------------------------------------------------------------------------
yyyy dd mm nnnnn +n.nnnnnn +n.nnnnnn +n.nnnnnnn +n.nnnnnnn +n.nnnnnn +n.nnnnnn +n.nnnnnn +n.nnnnnn nnn
------------------------------------------------------------------------------------------------------
2000 01 01 51544  0.043251  0.377681  0.3555151  0.0009068 -0.050825 -0.002257 -0.000222  0.000124  32
------------------------------------------------------------------------------------------------------

Columns	Description
001-004	Year
006-007	Month (01-12)
009-010	Day
012-016	Modified Julian Date (Julian Date at 0h UT minus 2,400,000.5)
018-026	x (arc seconds)
028-036	y (arc seconds)
038-047	UT1-UTC (seconds)
049-058	Length of Day (seconds)
060-068	δΔψ (arc seconds)
070-078	δΔε (arc seconds)
080-088	δX (arc seconds)
090-098	δY (arc seconds)
100-102	Delta Atomic Time, TAI-UTC (seconds)

	TLE Data	Space Data
	Current Archives Documentation	GPS EOP Space Weather
	SATCAT	Columns
	Boxscore	Software
	SOCRATES

Dr. T.S. Kelso [TS.Kelso@celestrak.com]
Last updated: 2007 October 16 23:28:39 UTC
Accessed 20,542 times since 2000 December 16
Current system time: 2008 November 20 20:44:58 UTC