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EOP Commands

The eop command group provides access to Earth Orientation Parameters (EOP) data from IERS (International Earth Rotation and Reference Systems Service). EOP data is required for accurate transformations between ECI and ECEF reference frames.

Commands

download

Download EOP data from IERS and save to file.

Syntax: 

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brahe eop download <FILEPATH> --product <PRODUCT>

Arguments: - FILEPATH - Output file path for EOP data

Options: - --product [standard|c04] - Data product type (required) - standard - Standard rapid EOP data (daily updates, ~1 year of predictions) - c04 - EOP 14 C04 long-term series (high accuracy, historical)

Examples:

Download standard EOP data: 

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brahe eop download ~/.cache/brahe/eop/iau2000_standard.txt --product standard

Download C04 long-term series: 

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brahe eop download ~/.cache/brahe/eop/iau2000_c04_20.txt --product c04

Update local EOP file: 

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brahe eop download /path/to/eop_data.txt --product standard

Tip

It's usually not necessary to manually download EOP data. If you are using a caching file provider, the package data will automatically download and cache EOP data as needed.

get-utc-ut1

Get the UTC-UT1 offset (ΔUT1) at a specific epoch.

Syntax: 

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brahe eop get-utc-ut1 <EPOCH> [OPTIONS]

Arguments: - EPOCH - Epoch to query (ISO-8601 format)

Options: - --product [standard|c04] - EOP data product (default: standard) - --source [default|file] - EOP data source (default: default) - --filepath <path> - Custom EOP file path (if --source file)

Examples:

Get ΔUT1 for a specific date: 

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brahe eop get-utc-ut1 "2024-01-01T00:00:00Z"
# 0.0087837

Use custom EOP file: 

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brahe eop get-utc-ut1 "2024-01-01T00:00:00Z" --source file --filepath /path/to/eop.txt

Use C04 product: 

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brahe eop get-utc-ut1 "2024-01-01T00:00:00Z" --product c04
# 0.0087572

get-polar-motion

Get polar motion parameters (x_p, y_p) at a specific epoch.

Syntax: 

1
brahe eop get-polar-motion <EPOCH> [OPTIONS]

Arguments: - EPOCH - Epoch to query (ISO-8601 format)

Options: - --product [standard|c04] - EOP data product (default: standard) - --source [default|file] - EOP data source (default: default) - --filepath <path> - Custom EOP file path (if --source file)

Examples:

Get polar motion parameters: 

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brahe eop get-polar-motion "2024-01-01T00:00:00Z"
# 6.63768107080688e-07, 9.802447818353709e-07

get-cip-offset

Get Celestial Intermediate Pole (CIP) offset (dX, dY) at a specific epoch.

Syntax: 

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brahe eop get-cip-offset <EPOCH> [OPTIONS]

Arguments: - EPOCH - Epoch to query (ISO-8601 format)

Options: - --product [standard|c04] - EOP data product (default: standard) - --source [default|file] - EOP data source (default: default) - --filepath <path> - Custom EOP file path (if --source file)

Examples:

Get CIP offset: 

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brahe eop get-cip-offset "2024-01-01T00:00:00Z"
# 1.4302003592731312e-09, -4.6057299705405924e-10

get-lod

Get Length of Day (LOD) variation at a specific epoch.

Syntax: 

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brahe eop get-lod <EPOCH> [OPTIONS]

Arguments: - EPOCH - Epoch to query (ISO-8601 format)

Options: - --product [standard|c04] - EOP data product (default: standard) - --source [default|file] - EOP data source (default: default) - --filepath <path> - Custom EOP file path (if --source file)

Examples:

Get LOD variation: 

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brahe eop get-lod "2024-01-01T00:00:00Z"
# 0.00023750000000000003

See Also