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:

>>> line1 = "1 25544U 98067A   21001.50000000  .00001764  00000-0  40967-4 0  9997"
>>> epoch = epoch_from_tle(line1)
>>> epoch.year()
2021

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.