Celestrak Earth Orientation Parameters File

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The Celestrak Earth Orientation Parameters (earth_orientation_parameters_celestrak.csv) file contains the parameters for polar motion and non-uniform Earth rotation (variation in sidereal time). The file contains correction angles for polar motion (also called polar motion) and values for UT1 and UTC time differences. The file contains both positive and negative leap second values (DAT: Delta Atomic Time). The data is based on definitive and predicted data as published on Celestrak.

This file is updated daily and hosted by Celestrak at: http://celestrak.org/SpaceData/.

Note: In addition to the CSV format, FreeFlyer also supports the legacy fixed-field format.

Celestrak Earth Orientation Parameters Format

The Celestrak Earth Orientation Parameters (CSV formatted) file contains the following data in columns from left to right:

Field	Description
DATE	UTC Year-Month-Day (ISO 8061)
MJD	Modified Julian Date (Julian Date at 0h UTC minus 2400000.5)
X	x (arc seconds)
Y	y (arc seconds)
UT1-UTC	UT1-UTC (seconds)
LOD	Length of Day (seconds)
DPSI	δΔψ (arc seconds)
DEPS	δΔε (arc seconds)
DX	δX (arc seconds)
DY	δY (arc seconds)
DAT	Delta Atomic Time, TAI-UTC (seconds)
DATA_TYPE	O = Observed, P = Predicted

An excerpt of the file is given below:

12/25/2023 60303 0.15506 0.201511 0.0081766 0.0000317 -0.112136 -0.005482 0.000189 -0.000138 37 O

12/26/2023 60304 0.151962 0.20183 0.0082315 -0.0001214 -0.111834 -0.005682 0.000196 -0.000137 37 O

12/27/2023 60305 0.148892 0.201572 0.0083827 -0.0001818 -0.111595 -0.005936 0.000204 -0.00014 37 O

12/28/2023 60306 0.146072 0.201391 0.0085784 -0.0002035 -0.111475 -0.006102 0.00021 -0.000146 37 O

12/29/2023 60307 0.143398 0.201376 0.0087799 -0.00017 -0.111372 -0.006094 0.000216 -0.000152 37 O

12/30/2023 60308 0.141083 0.201513 0.0088907 -0.0000427 -0.111171 -0.005959 0.000219 -0.000155 37 O

12/31/2023 60309 0.138974 0.201947 0.0088494 0.0001109 -0.110885 -0.005822 0.00022 -0.000156 37 O

1/1/2024 60310 0.136893 0.202227 0.0086824 0.0002271 -0.110618 -0.005744 0.000217 -0.000155 37 O

1/2/2024 60311 0.134898 0.202522 0.0084039 0.0003261 -0.110441 -0.005669 0.000212 -0.000155 37 O

1/3/2024 60312 0.133126 0.203145 0.0080429 0.0003908 -0.110393 -0.005526 0.000205 -0.000159 37 O

1/4/2024 60313 0.131368 0.203986 0.0076366 0.0004143 -0.110547 -0.005361 0.000197 -0.000165 37 O