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Definitive Ephemeris

Definitive Ephemeris is used for geometrically correcting Landsat data and provides improved accuracy over predicted ephemeris. Definitive Ephemeris files are available two days after acquisition.

Return to Landsat Calibration/Validation Overview
 

An ephemeris is a set of data that provides the assigned places of a celestial body (including a manmade satellite) for regular intervals. Definitive Ephemeris shows the position and velocity of the spacecraft at the time imagery is collected, and shows the position and velocity of the satellites in one-minute intervals.
 

Landsat 7

Landsat 7 scenes were initially processed with predicted ephemeris shortly after acquisition, and were then reprocessed with definitive ephemeris one to two days later. Section 5 of the Landsat 7 Data Users Handbook provides more technical information about Definitive Ephemeris and how it was used in Landsat 7 product generation.  

Search for Landsat 7 definitive ephemeris files: Landsat 7 Definitive Ephemeris Search. Landsat 5 definitive ephemeris files are also available from this page. 
 

Landsat 8

Landsat 8 DE files are available as of January 1, 2024 and can be downloaded from https://landsat.usgs.gov/landsat8-de. DE files become available two days after acquisition.

In late 2023, the satellite experienced GPS faults that caused the spacecraft  position and velocity to drift from the actual location. This in turn affected the quality of the data acquired by the Operational Land Imager and Thermal Infrared Sensor. The L8 DE files are useful by providing additional ephemeris information.  

Telemetry information for Landsat 8 DE files in the form of Two-Line Element (TLE) Set — which lists the orbital elements that describe the state (position and velocity) of each of the Landsat spacecrafts- is provided on Landsat 8: https://www.n2yo.com/satellite/?s=39084
 

Landsat 9

Landsat 9 does not require definitive ephemeris, since the Payload Correction Data (PCD) for the satellites is very accurate. The TLE information can be found at https://www.n2yo.com/satellite/?s=49260.

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