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Two-Line Element (TLE)

Functions for parsing, validating, and converting Two-Line Element sets.

For propagating orbits from TLE data, use the SGPPropagator class.

TLE Utility Functions

epoch_from_tle builtin 

epoch_from_tle(line1: str) -> Epoch

Extract Epoch from TLE line 1

Extracts and parses the epoch timestamp from the first line of TLE data. The epoch is returned in UTC time system.

Parameters:

Name Type Description Default
line1 str

First line of TLE data

 required

Returns:

Name Type Description
Epoch Epoch

Extracted epoch in UTC time system

Examples:

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line1 = "1 25544U 98067A   21001.50000000  .00001764  00000-0  40967-4 0  9997"
epoch = epoch_from_tle(line1)
epoch.year()

keplerian_elements_from_tle builtin 

keplerian_elements_from_tle(line1: str, line2: str) -> Tuple

Extract Keplerian orbital elements from TLE lines.

Extracts the standard six Keplerian orbital elements from Two-Line Element (TLE) data. Returns elements in standard order: [a, e, i, raan, argp, M] where angles are in radians.

Parameters:

Name Type Description Default
line1 str

First line of TLE data.

 required
line2 str

Second line of TLE data.

 required

Returns:

Name Type Description
tuple Tuple

A tuple containing: - epoch (Epoch): Epoch of the TLE data. - elements (numpy.ndarray): Six Keplerian elements [a, e, i, raan, argp, M] where a is semi-major axis in meters, e is eccentricity (dimensionless), and i, raan, argp, M are in radians.

keplerian_elements_to_tle builtin 

keplerian_elements_to_tle(epoch: Epoch, elements: ndarray, norad_id: str) -> Tuple

Convert Keplerian elements to TLE lines.

Converts standard Keplerian orbital elements to Two-Line Element (TLE) format. Input angles should be in degrees for compatibility with TLE format.

Parameters:

Name Type Description Default
epoch Epoch

Epoch of the elements.

 required
elements ndarray

Keplerian elements [a (m), e, i (deg), raan (deg), argp (deg), M (deg)].

 required
norad_id str

NORAD catalog number (supports numeric and Alpha-5 format).

 required

Returns:

Name Type Description
tuple Tuple

A tuple containing (line1, line2) - the two TLE lines as strings.

create_tle_lines builtin 

create_tle_lines(epoch: Epoch, inclination: float, raan: float, eccentricity: float, arg_perigee: float, mean_anomaly: float, mean_motion: float, norad_id: str, ephemeris_type: int, element_set_number: int, revolution_number: int, classification: str = None, intl_designator: str = None, first_derivative: float = None, second_derivative: float = None, bstar: float = None) -> Tuple

Create complete TLE lines from all parameters.

Creates Two-Line Element (TLE) lines from complete set of orbital and administrative parameters. Provides full control over all TLE fields including derivatives and drag terms.

Parameters:

Name Type Description Default
epoch Epoch

Epoch of the elements.

 required
inclination float

Inclination in degrees.

 required
raan float

Right ascension of ascending node in degrees.

 required
eccentricity float

Eccentricity (dimensionless).

 required
arg_perigee float

Argument of periapsis in degrees.

 required
mean_anomaly float

Mean anomaly in degrees.

 required
mean_motion float

Mean motion in revolutions per day.

 required
norad_id str

NORAD catalog number (supports numeric and Alpha-5 format).

 required
ephemeris_type int

Ephemeris type (0-9).

 required
element_set_number int

Element set number.

 required
revolution_number int

Revolution number at epoch.

 required
classification str

Security classification. Defaults to ' '.

 None
intl_designator str

International designator. Defaults to ''.

 None
first_derivative float

First derivative of mean motion. Defaults to 0.0.

 None
second_derivative float

Second derivative of mean motion. Defaults to 0.0.

 None
bstar float

BSTAR drag term. Defaults to 0.0.

 None

Returns:

Name Type Description
tuple Tuple

A tuple containing (line1, line2) - the two TLE lines as strings.

validate_tle_line builtin 

validate_tle_line(line: str) -> bool

Validate single TLE line.

Parameters:

Name Type Description Default
line str

TLE line to validate.

 required

Returns:

Name Type Description
bool bool

True if the line is valid.

validate_tle_lines builtin 

validate_tle_lines(line1: str, line2: str) -> bool

Validate TLE lines.

Parameters:

Name Type Description Default
line1 str

First line of TLE data.

 required
line2 str

Second line of TLE data.

 required

Returns:

Name Type Description
bool bool

True if both lines are valid.

calculate_tle_line_checksum builtin 

calculate_tle_line_checksum(line: str) -> int

Calculate TLE line checksum.

Parameters:

Name Type Description Default
line str

TLE line.

 required

Returns:

Name Type Description
int int

Checksum value.

parse_norad_id builtin 

parse_norad_id(norad_str: str) -> int

Parse NORAD ID from string, handling both classic and Alpha-5 formats.

Parameters:

Name Type Description Default
norad_str str

NORAD ID string from TLE.

 required

Returns:

Name Type Description
int int

Parsed numeric NORAD ID.

norad_id_numeric_to_alpha5 builtin 

norad_id_numeric_to_alpha5(norad_id: int) -> str

Convert numeric NORAD ID to Alpha-5 format or pass through if in legacy range.

Parameters:

Name Type Description Default
norad_id int

Numeric NORAD ID (0-339999). IDs 0-99999 are passed through as numeric strings. IDs 100000-339999 are converted to Alpha-5 format.

 required

Returns:

Name Type Description
str str

For IDs 0-99999: numeric string (e.g., "42"). For IDs 100000-339999: Alpha-5 format ID (e.g., "A0001").

norad_id_alpha5_to_numeric builtin 

norad_id_alpha5_to_numeric(alpha5_id: str) -> int

Convert Alpha-5 NORAD ID to numeric format.

Parameters:

Name Type Description Default
alpha5_id str

Alpha-5 format ID (e.g., "A0001").

 required

Returns:

Name Type Description
int int

Numeric NORAD ID.