SGP Propagator¶

The SGP4/SDP4 propagator for satellite orbit propagation using Two-Line Element (TLE) data. The SGP (Simplified General Perturbations) propagator implements the SGP4/SDP4 models for propagating satellites using TLE orbital data. This is the standard model used for tracking objects in Earth orbit and is maintained by NORAD/Space Force.

Key Features: - Industry-standard orbit propagation - Atmospheric drag modeling - Automatic selection between SGP4 (near-Earth) and SDP4 (deep-space) models - Compatible with standard TLE format

Module: brahe.orbits

Example Usage¶

import brahe as bh

# ISS TLE data (example)
line1 = "1 25544U 98067A   24001.50000000  .00016717  00000-0  30000-3 0  9005"
line2 = "2 25544  51.6400 150.0000 0003000 100.0000 260.0000 15.50000000300000"

# Create propagator from TLE
prop = bh.SGPPropagator.from_tle(line1, line2)

# Get current epoch
epoch = prop.epoch()

# Propagate to a specific time
future_epoch = epoch + 3600.0  # 1 hour later
state = prop.propagate(future_epoch)  # Returns [x, y, z, vx, vy, vz] in TEME frame

# Propagate to multiple times
import numpy as np
times = np.linspace(0, 86400, 100)  # 1 day in 100 steps
epochs = [epoch + dt for dt in times]
states = prop.propagate_multiple(epochs)  # Returns array of states

Class Reference¶

SGPPropagator ¶

SGPPropagator()

SGP4/SDP4 satellite propagator using TLE data.

The SGP (Simplified General Perturbations) propagator implements the SGP4/SDP4 models for propagating satellites using Two-Line Element (TLE) orbital data. This is the standard model used for tracking objects in Earth orbit.

Note

This class is created via class methods, not direct instantiation. Use SGPPropagator.from_tle() or SGPPropagator.from_elements().

Attributes:

Name	Type	Description
`current_epoch`	`Epoch`	Current propagation time
`initial_epoch`	`Epoch`	TLE epoch
`step_size`	`float`	Current step size in seconds
`norad_id`	`int`	NORAD catalog ID
`satellite_name`	`str or None`	Satellite name if available
`trajectory`	`OrbitTrajectory`	Accumulated trajectory states

Example

import brahe as bh

# ISS TLE data (example)
line1 = "1 25544U 98067A   24001.50000000  .00016717  00000-0  30000-3 0  9005"
line2 = "2 25544  51.6400 150.0000 0003000 100.0000 260.0000 15.50000000300000"

# Create propagator
prop = bh.SGPPropagator.from_tle(line1, line2, step_size=60.0)

# Propagate to a specific epoch
epc = bh.Epoch.from_datetime(2024, 1, 2, 12, 0, 0.0, 0.0, bh.TimeSystem.UTC)
state_eci = prop.state(epc)
print(f"Position: {state_eci[:3]}")
print(f"Velocity: {state_eci[3:]}")

# Propagate multiple epochs
epochs = [epc + i*60.0 for i in range(10)]  # 10 minutes
states = prop.states(epochs)

Initialize instance.

arg_perigee `property` ¶

arg_perigee: float

Get argument of periapsis at TLE epoch.

Returns:

Name	Type	Description
`float`	`float`	Argument of periapsis in degrees.

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

argp = prop.arg_perigee
print(f"Argument of periapsis: {argp:.4f} deg")

current_epoch `property` ¶

current_epoch: Epoch

Get current epoch.

Returns:

Name	Type	Description
`Epoch`	`Epoch`	Current propagator epoch.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
propagator = bh.SGPPropagator.from_tle(line1, line2)
propagator.step()
print(f"Current epoch: {propagator.current_epoch}")

eccentricity `property` ¶

eccentricity: float

Get eccentricity at TLE epoch.

Returns:

Name	Type	Description
`float`	`float`	Eccentricity (dimensionless).

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

ecc = prop.eccentricity
print(f"Eccentricity: {ecc:.6f}")

ephemeris_age `property` ¶

ephemeris_age: float

Get age of ephemeris data (time since TLE epoch).

Returns:

Name	Type	Description
`float`	`float`	Time since TLE epoch in seconds.

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

age = prop.ephemeris_age
print(f"Ephemeris age: {age:.1f} s")

epoch `property` ¶

epoch: Epoch

Get TLE epoch.

Returns:

Name	Type	Description
`Epoch`	`Epoch`	Epoch of the TLE data.

inclination `property` ¶

inclination: float

Get inclination at TLE epoch.

Returns:

Name	Type	Description
`float`	`float`	Inclination in degrees.

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

inc = prop.inclination
print(f"Inclination: {inc:.4f} deg")

line1 `property` ¶

line1: str

Get TLE line 1.

Returns:

Name	Type	Description
`str`	`str`	First line of the TLE.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
propagator = bh.SGPPropagator.from_tle(line1, line2)
print(propagator.line1)

line2 `property` ¶

line2: str

Get TLE line 2.

Returns:

Name	Type	Description
`str`	`str`	Second line of the TLE.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
propagator = bh.SGPPropagator.from_tle(line1, line2)
print(propagator.line2)

mean_anomaly `property` ¶

mean_anomaly: float

Get mean anomaly at TLE epoch.

Returns:

Name	Type	Description
`float`	`float`	Mean anomaly in degrees.

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

ma = prop.mean_anomaly
print(f"Mean anomaly: {ma:.4f} deg")

norad_id `property` ¶

norad_id: int

Get NORAD ID.

Returns:

Name	Type	Description
`int`	`int`	NORAD catalog ID.

right_ascension `property` ¶

right_ascension: float

Get right ascension of ascending node at TLE epoch.

Returns:

Name	Type	Description
`float`	`float`	Right ascension of ascending node (RAAN) in degrees.

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

raan = prop.right_ascension
print(f"RAAN: {raan:.4f} deg")

satellite_name `property` ¶

satellite_name: str

Get satellite name (if available).

Returns:

Type	Description
`str`	str or None: Satellite name if provided.

Example

import brahe as bh

name = "ISS (ZARYA)"
line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
propagator = bh.SGPPropagator.from_3le(name, line1, line2)
print(f"Satellite: {propagator.satellite_name}")

semi_major_axis `property` ¶

semi_major_axis: float

Get semi-major axis at TLE epoch.

Returns:

Name	Type	Description
`float`	`float`	Semi-major axis in meters.

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

sma = prop.semi_major_axis
print(f"Semi-major axis: {sma:.3f} m")

step_size `property` ¶

step_size: float

Get step size in seconds.

Returns:

Name	Type	Description
`float`	`float`	Step size in seconds.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
propagator = bh.SGPPropagator.from_tle(line1, line2)
print(f"Step size: {propagator.step_size} seconds")

terminated `property` ¶

terminated: bool

Check if propagation was terminated by an event.

Returns:

Name	Type	Description
`bool`	`bool`	True if propagation was stopped by a terminal event.

trajectory `property` ¶

trajectory: SOrbitTrajectory

Get accumulated trajectory.

Returns:

Name	Type	Description
`OrbitalTrajectory`	`SOrbitTrajectory`	The accumulated trajectory.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
prop.propagate_steps(100)
traj = prop.trajectory
print(f"Trajectory has {traj.len()} states")

add_event_detector `method descriptor` ¶

add_event_detector(event: TimeEvent | AscendingNodeEvent | DescendingNodeEvent | AltitudeEvent | AOIEntryEvent | AOIExitEvent) -> Any

Add an event detector to the propagator.

Supported event types: - TimeEvent: Triggers at a specific epoch - AscendingNodeEvent: Triggers at ascending node crossings - DescendingNodeEvent: Triggers at descending node crossings - AltitudeEvent: Triggers at altitude crossings - And other orbital element events (SemiMajorAxis, Eccentricity, etc.)

Note

Custom ValueEvent and BinaryEvent with Python callbacks are not supported for SGPPropagator. Use NumericalOrbitPropagator for custom event functions.

Parameters:

Name	Type	Description	Default
`event`	`TimeEvent \| AscendingNodeEvent \| DescendingNodeEvent \| AltitudeEvent \| AOIEntryEvent \| AOIExitEvent`	Event detector to add	required

Example

import brahe as bh

prop = bh.SGPPropagator.from_tle(line1, line2)

# Add time event
epoch = prop.epoch
event = bh.TimeEvent(epoch + 1800.0, "30 Min Mark")
prop.add_event_detector(event)

# Add node crossing event
asc_node = bh.AscendingNodeEvent("Ascending Node")
prop.add_event_detector(asc_node)

# Propagate and check events
prop.propagate_to(epoch + 6000.0)
for e in prop.event_log():
    print(f"{e.name}: {e.window_open}")

clear_events `method descriptor` ¶

clear_events() -> Any

Clear all events from the event log.

current_state `method descriptor` ¶

current_state() -> ndarray

Get current state vector.

Returns:

Type	Description
`ndarray`	numpy.ndarray: Current state vector in the propagator's output format.

event_log `method descriptor` ¶

event_log() -> list[DetectedEvent]

Get all detected events from the event log.

Returns:

Type	Description
`list[DetectedEvent]`	list[DetectedEvent]: List of all detected events.

Example

import brahe as bh

prop = bh.SGPPropagator.from_tle(line1, line2)
event = bh.AscendingNodeEvent("Asc Node")
prop.add_event_detector(event)

prop.propagate_to(prop.epoch + 6000.0)

for e in prop.event_log():
    print(f"{e.name} at {e.window_open}")

events_by_name `method descriptor` ¶

events_by_name(name: str) -> list[DetectedEvent]

Get events filtered by name.

Parameters:

Name	Type	Description	Default
`name`	`str`	Exact event name to match.	required

Returns:

Type	Description
`list[DetectedEvent]`	list[DetectedEvent]: Events matching the name.

events_in_range `method descriptor` ¶

events_in_range(start: Epoch, end: Epoch) -> list[DetectedEvent]

Get events within a time range.

Parameters:

Name	Type	Description	Default
`start`	`Epoch`	Start of time range.	required
`end`	`Epoch`	End of time range.	required

Returns:

Type	Description
`list[DetectedEvent]`	list[DetectedEvent]: Events within the range.

from_3le `builtin` ¶

from_3le(name: str, line1: str, line2: str, step_size: float = 60.0) -> SGPPropagator

Create a new SGP propagator from 3-line TLE format (with satellite name).

Parameters:

Name	Type	Description	Default
`name`	`str`	Satellite name (line 0).	required
`line1`	`str`	First line of TLE data.	required
`line2`	`str`	Second line of TLE data.	required
`step_size`	`float`	Step size in seconds for propagation. Defaults to 60.0.	`60.0`

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	New SGP propagator instance.

from_omm_elements `builtin` ¶

from_omm_elements(epoch: str, mean_motion: float, eccentricity: float, inclination: float, raan: float, arg_of_pericenter: float, mean_anomaly: float, norad_id: int, step_size: float = 60.0, object_name: Union[str, None] = None, object_id: Union[str, None] = None, classification: Union[str, None] = None, bstar: Union[float, None] = None, mean_motion_dot: Union[float, None] = None, mean_motion_ddot: Union[float, None] = None, ephemeris_type: Union[int, None] = None, element_set_no: Union[int, None] = None, rev_at_epoch: Union[int, None] = None) -> SGPPropagator

Create a new SGP propagator from CCSDS OMM (Orbit Mean-elements Message) fields.

This method directly constructs an SGP4 propagator from OMM orbital elements, bypassing TLE parsing. It creates synthetic TLE lines for API consistency.

Parameters:

Name	Type	Description	Default
`epoch`	`str`	ISO 8601 datetime string (e.g., "2025-11-29T20:01:44.058144").	required
`mean_motion`	`float`	Mean motion in revolutions per day.	required
`eccentricity`	`float`	Orbital eccentricity (dimensionless).	required
`inclination`	`float`	Orbital inclination in degrees.	required
`raan`	`float`	Right ascension of ascending node in degrees.	required
`arg_of_pericenter`	`float`	Argument of pericenter in degrees.	required
`mean_anomaly`	`float`	Mean anomaly in degrees.	required
`norad_id`	`int`	NORAD catalog ID.	required
`step_size`	`float`	Step size in seconds for propagation. Defaults to 60.0.	`60.0`
`object_name`	`str or None`	Satellite name (OBJECT_NAME). Defaults to None.	`None`
`object_id`	`str or None`	International designator (OBJECT_ID). Defaults to None.	`None`
`classification`	`str or None`	Classification character ('U', 'C', or 'S'). Defaults to 'U'.	`None`
`bstar`	`float or None`	B* drag term. Defaults to 0.0.	`None`
`mean_motion_dot`	`float or None`	First derivative of mean motion / 2. Defaults to 0.0.	`None`
`mean_motion_ddot`	`float or None`	Second derivative of mean motion / 6. Defaults to 0.0.	`None`
`ephemeris_type`	`int or None`	Ephemeris type (usually 0). Defaults to 0.	`None`
`element_set_no`	`int or None`	Element set number. Defaults to 999.	`None`
`rev_at_epoch`	`int or None`	Revolution number at epoch. Defaults to 0.	`None`

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	New SGP propagator instance.

Example

import brahe as bh

# ISS OMM data
prop = bh.SGPPropagator.from_omm_elements(
    epoch="2025-11-29T20:01:44.058144",
    mean_motion=15.49193835,
    eccentricity=0.0003723,
    inclination=51.6312,
    raan=206.3646,
    arg_of_pericenter=184.1118,
    mean_anomaly=175.9840,
    norad_id=25544,
    object_name="ISS (ZARYA)",
    object_id="1998-067A",
    bstar=0.15237e-3,
    mean_motion_dot=0.801e-4,
    rev_at_epoch=54085,
)
state = prop.state(prop.epoch)
print(f"Position: {state[:3]}")

from_tle `builtin` ¶

from_tle(line1: str, line2: str, step_size: float = 60.0) -> SGPPropagator

Create a new SGP propagator from TLE lines.

Parameters:

Name	Type	Description	Default
`line1`	`str`	First line of TLE data.	required
`line2`	`str`	Second line of TLE data.	required
`step_size`	`float`	Step size in seconds for propagation. Defaults to 60.0.	`60.0`

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	New SGP propagator instance.

generate_uuid `method descriptor` ¶

generate_uuid() -> Any

Generate a new UUID and set it in-place (mutating).

get_elements `method descriptor` ¶

get_elements(angle_format: AngleFormat) -> ndarray

Get Keplerian orbital elements from TLE data.

Extracts the Keplerian elements directly from the TLE lines used to initialize this propagator.

Parameters:

Name	Type	Description	Default
`angle_format`	`AngleFormat`	Format for angular elements (DEGREES or RADIANS).	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: Keplerian elements [a, e, i, Ω, ω, M] where: - a: semi-major axis [m] - e: eccentricity [dimensionless] - i: inclination [rad or deg] - Ω: right ascension of ascending node [rad or deg] - ω: argument of periapsis [rad or deg] - M: mean anomaly [rad or deg]

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

# Get elements in degrees
oe_deg = prop.get_elements(bh.AngleFormat.DEGREES)
print(f"Inclination: {oe_deg[2]:.4f} degrees")

# Get elements in radians
oe_rad = prop.get_elements(bh.AngleFormat.RADIANS)
print(f"Inclination: {oe_rad[2]:.4f} radians")

get_id `method descriptor` ¶

get_id() -> int

Get the current numeric ID.

Returns:

Type	Description
`int`	int or None: The numeric ID, or None if not set.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2).with_id(25544)
print(f"ID: {prop.get_id()}")

get_name `method descriptor` ¶

get_name() -> str

Get the current name.

Returns:

Type	Description
`str`	str or None: The name, or None if not set.

Example

import brahe as bh

name = "ISS (ZARYA)"
line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_3le(name, line1, line2)
print(f"Name: {prop.get_name()}")

get_uuid `method descriptor` ¶

get_uuid() -> str

Get the current UUID.

Returns:

Type	Description
`str`	str or None: The UUID as a string, or None if not set.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2).with_new_uuid()
print(f"UUID: {prop.get_uuid()}")

initial_state `method descriptor` ¶

initial_state() -> ndarray

Get initial state vector.

Returns:

Type	Description
`ndarray`	numpy.ndarray: Initial state vector in the propagator's output format.

latest_event `method descriptor` ¶

latest_event() -> DetectedEvent

Get the most recent detected event.

Returns:

Type	Description
`DetectedEvent`	DetectedEvent or None: Most recent event, or None if no events.

propagate_steps `method descriptor` ¶

propagate_steps(num_steps: int) -> Any

Propagate forward by specified number of steps.

Parameters:

Name	Type	Description	Default
`num_steps`	`int`	Number of steps to take.	required

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2, step_size=60.0)
prop.propagate_steps(10)  # Advance by 10 steps (600 seconds)
print(f"After 10 steps: {prop.current_epoch}")

propagate_to `method descriptor` ¶

propagate_to(target_epoch: Epoch) -> Any

Propagate to a specific target epoch.

Parameters:

Name	Type	Description	Default
`target_epoch`	`Epoch`	The epoch to propagate to.	required

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
target = prop.epoch + 7200.0  # 2 hours later
prop.propagate_to(target)
print(f"Propagated to: {prop.current_epoch}")

reset `method descriptor` ¶

reset() -> Any

Reset propagator to initial conditions.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
initial_epoch = prop.epoch
prop.propagate_steps(100)
prop.reset()
print(f"Reset to: {prop.current_epoch == initial_epoch}")

reset_termination `method descriptor` ¶

reset_termination() -> Any

Reset the termination flag.

Call this to allow propagation to continue after a terminal event.

set_eviction_policy_max_age `method descriptor` ¶

set_eviction_policy_max_age(max_age: float) -> Any

Set trajectory eviction policy based on maximum age.

Parameters:

Name	Type	Description	Default
`max_age`	`float`	Maximum age in seconds to keep states in trajectory.	required

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
prop.set_eviction_policy_max_age(86400.0)  # Keep 1 day of history
print("Trajectory limited to 24 hours of states")

set_eviction_policy_max_size `method descriptor` ¶

set_eviction_policy_max_size(max_size: int) -> Any

Set trajectory eviction policy based on maximum size.

Parameters:

Name	Type	Description	Default
`max_size`	`int`	Maximum number of states to keep in trajectory.	required

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
prop.set_eviction_policy_max_size(1000)
print("Trajectory limited to 1000 states")

set_id `method descriptor` ¶

set_id(id: Union[int, None]) -> Any

Set the numeric ID in-place (mutating).

Parameters:

Name	Type	Description	Default
`id`	`int or None`	Numeric ID to assign, or None to clear.	required

set_identity `method descriptor` ¶

set_identity(name: Union[str, None], uuid_str: Union[str, None], id: Union[int, None]) -> Any

Set all identity fields in-place (mutating).

Parameters:

Name	Type	Description	Default
`name`	`str or None`	Optional name to assign.	required
`uuid_str`	`str or None`	Optional UUID string to assign.	required
`id`	`int or None`	Optional numeric ID to assign.	required

set_name `method descriptor` ¶

set_name(name: Union[str, None]) -> Any

Set the name in-place (mutating).

Parameters:

Name	Type	Description	Default
`name`	`str or None`	Name to assign, or None to clear.	required

set_output_format `method descriptor` ¶

set_output_format(frame: OrbitFrame, representation: OrbitRepresentation, angle_format: Union[AngleFormat, None]) -> Any

Set output format (frame, representation, and angle format).

Parameters:

Name	Type	Description	Default
`frame`	`OrbitFrame`	Output frame (ECI or ECEF).	required
`representation`	`OrbitRepresentation`	Output representation (Cartesian or Keplerian).	required
`angle_format`	`AngleFormat or None`	Angle format for Keplerian (None for Cartesian).	required

set_step_size `method descriptor` ¶

set_step_size(new_step_size: float) -> Any

Set step size in seconds (explicit method).

Parameters:

Name	Type	Description	Default
`new_step_size`	`float`	New step size in seconds.	required

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
propagator = bh.SGPPropagator.from_tle(line1, line2)
propagator.set_step_size(120.0)  # Can use explicit method
# or propagator.step_size = 120.0  # Can use property

state `method descriptor` ¶

state(epoch: Epoch) -> ndarray

Compute state at a specific epoch.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: State vector in the propagator's current output format.

state_ecef `method descriptor` ¶

state_ecef(epoch: Epoch) -> ndarray

Compute state at a specific epoch in ECEF coordinates.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: State vector [x, y, z, vx, vy, vz] in ECEF frame.

state_eci `method descriptor` ¶

state_eci(epoch: Epoch) -> ndarray

Compute state at a specific epoch in ECI coordinates.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: State vector [x, y, z, vx, vy, vz] in ECI frame.

state_eme2000 `method descriptor` ¶

state_eme2000(epoch: Epoch) -> ndarray

Compute state at a specific epoch in EME2000 coordinates.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: State vector [x, y, z, vx, vy, vz] in EME2000 frame (meters, m/s).

state_gcrf `method descriptor` ¶

state_gcrf(epoch: Epoch) -> ndarray

Compute state at a specific epoch in GCRF coordinates.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: State vector [x, y, z, vx, vy, vz] in GCRF frame (meters, m/s).

state_itrf `method descriptor` ¶

state_itrf(epoch: Epoch) -> ndarray

Compute state at a specific epoch in ITRF coordinates.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: State vector [x, y, z, vx, vy, vz] in ITRF frame (meters, m/s).

state_koe_mean `method descriptor` ¶

state_koe_mean(epoch: Epoch, angle_format: AngleFormat) -> ndarray

Compute state as mean Keplerian elements at the given epoch.

Mean elements are orbit-averaged elements that remove short-period and long-period J2 perturbations using first-order Brouwer-Lyddane theory.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Epoch for state computation.	required
`angle_format`	`AngleFormat`	If AngleFormat.DEGREES, angular elements are returned in degrees, otherwise in radians.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: Mean Keplerian elements [a, e, i, raan, argp, mean_anomaly].

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

# Get mean elements at initial epoch
epoch = prop.epoch
mean_deg = prop.state_koe_mean(epoch, bh.AngleFormat.DEGREES)
osc_deg = prop.state_koe_osc(epoch, bh.AngleFormat.DEGREES)
print(f"Mean semi-major axis: {mean_deg[0]/1000:.3f} km")
print(f"Osc semi-major axis: {osc_deg[0]/1000:.3f} km")

state_koe_osc `method descriptor` ¶

state_koe_osc(epoch: Epoch, angle_format: AngleFormat) -> ndarray

Compute state as osculating elements at a specific epoch.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required
`angle_format`	`AngleFormat`	If AngleFormat.DEGREES, angular elements are returned in degrees, otherwise in radians.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: Osculating elements [a, e, i, raan, argp, mean_anomaly].

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

# Get osculating elements at initial epoch
epoch = prop.epoch
elements_deg = prop.state_koe_osc(epoch, bh.AngleFormat.DEGREES)
print(f"Semi-major axis: {elements_deg[0]/1000:.3f} km")
print(f"Inclination: {elements_deg[2]:.4f} degrees")

# Get elements in radians
elements_rad = prop.state_koe_osc(epoch, bh.AngleFormat.RADIANS)
print(f"Inclination: {elements_rad[2]:.4f} radians")

state_pef `method descriptor` ¶

state_pef(epoch: Epoch) -> ndarray

Compute state at a specific epoch in PEF coordinates.

Parameters:

Name	Type	Description	Default
`epoch`	`Epoch`	Target epoch for state computation.	required

Returns:

Type	Description
`ndarray`	numpy.ndarray: State vector [x, y, z, vx, vy, vz] in PEF frame.

states `method descriptor` ¶

states(epochs: list[Epoch]) -> List

Compute states at multiple epochs.

Parameters:

Name	Type	Description	Default
`epochs`	`list[Epoch]`	List of epochs for state computation.	required

Returns:

Type	Description
`List`	list[numpy.ndarray]: List of state vectors in the propagator's current output format.

states_eci `method descriptor` ¶

states_eci(epochs: list[Epoch]) -> List

Compute states at multiple epochs in ECI coordinates.

Parameters:

Name	Type	Description	Default
`epochs`	`list[Epoch]`	List of epochs for state computation.	required

Returns:

Type	Description
`List`	list[numpy.ndarray]: List of ECI state vectors.

states_gcrf `method descriptor` ¶

states_gcrf(epochs: list[Epoch]) -> List

Compute states at multiple epochs in GCRF coordinates.

Parameters:

Name	Type	Description	Default
`epochs`	`list[Epoch]`	List of epochs for state computation.	required

Returns:

Type	Description
`List`	list[numpy.ndarray]: List of GCRF state vectors.

states_itrf `method descriptor` ¶

states_itrf(epochs: list[Epoch]) -> List

Compute states at multiple epochs in ITRF coordinates.

Parameters:

Name	Type	Description	Default
`epochs`	`list[Epoch]`	List of epochs for state computation.	required

Returns:

Type	Description
`List`	list[numpy.ndarray]: List of ITRF state vectors.

states_koe_mean `method descriptor` ¶

states_koe_mean(epochs: list[Epoch], angle_format: AngleFormat) -> List

Compute states as mean Keplerian elements at multiple epochs.

Mean elements are orbit-averaged elements that remove short-period and long-period J2 perturbations using first-order Brouwer-Lyddane theory.

Parameters:

Name	Type	Description	Default
`epochs`	`list[Epoch]`	List of epochs for state computation.	required
`angle_format`	`AngleFormat`	If AngleFormat.DEGREES, angular elements are returned in degrees, otherwise in radians.	required

Returns:

Type	Description
`List`	list[numpy.ndarray]: List of mean Keplerian element vectors [a, e, i, raan, argp, mean_anomaly].

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

# Get mean elements at multiple epochs
epoch0 = prop.epoch
epochs = [epoch0 + i*3600.0 for i in range(10)]  # Every hour for 10 hours
mean_list = prop.states_koe_mean(epochs, bh.AngleFormat.DEGREES)

for i, elements in enumerate(mean_list):
    print(f"Hour {i}: mean a={elements[0]/1000:.3f} km")

states_koe_osc `method descriptor` ¶

states_koe_osc(epochs: list[Epoch], angle_format: AngleFormat) -> List

Compute states as osculating elements at multiple epochs.

Parameters:

Name	Type	Description	Default
`epochs`	`list[Epoch]`	List of epochs for state computation.	required
`angle_format`	`AngleFormat`	If AngleFormat.DEGREES, angular elements are returned in degrees, otherwise in radians.	required

Returns:

Type	Description
`List`	list[numpy.ndarray]: List of osculating element vectors [a, e, i, raan, argp, mean_anomaly].

Example

import brahe as bh

line1 = "1 25544U 98067A   08264.51782528 -.00002182  00000-0 -11606-4 0  2927"
line2 = "2 25544  51.6416 247.4627 0006703 130.5360 325.0288 15.72125391563537"
prop = bh.SGPPropagator.from_tle(line1, line2)

# Get elements at multiple epochs
epoch0 = prop.epoch
epochs = [epoch0 + i*3600.0 for i in range(10)]  # Every hour for 10 hours
elements_list = prop.states_koe_osc(epochs, bh.AngleFormat.DEGREES)

for i, elements in enumerate(elements_list):
    print(f"Hour {i}: a={elements[0]/1000:.3f} km, e={elements[1]:.6f}")

step `method descriptor` ¶

step() -> Any

Step forward by the default step size.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
prop.step()  # Advance by default step_size
print(f"Advanced to: {prop.current_epoch}")

step_by `method descriptor` ¶

step_by(step_size: float) -> Any

Step forward by a specified time duration.

Parameters:

Name	Type	Description	Default
`step_size`	`float`	Time step in seconds.	required

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
prop.step_by(120.0)  # Advance by 2 minutes
print(f"Advanced to: {prop.current_epoch}")

step_past `method descriptor` ¶

step_past(target_epoch: Epoch) -> Any

Step past a specified target epoch.

Parameters:

Name	Type	Description	Default
`target_epoch`	`Epoch`	The epoch to step past.	required

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2)
target = prop.epoch + 3600.0  # 1 hour later
prop.step_past(target)
print(f"Stepped past target")

with_id `method descriptor` ¶

with_id(id: int) -> SGPPropagator

Set the numeric ID and return self (consuming constructor pattern).

Parameters:

Name	Type	Description	Default
`id`	`int`	Numeric ID to assign to this propagator.	required

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	Self with ID set.

with_identity `method descriptor` ¶

with_identity(name: Union[str, None], uuid_str: Union[str, None], id: Union[int, None]) -> SGPPropagator

Set all identity fields at once and return self (consuming constructor pattern).

Parameters:

Name	Type	Description	Default
`name`	`str or None`	Optional name to assign.	required
`uuid_str`	`str or None`	Optional UUID string to assign.	required
`id`	`int or None`	Optional numeric ID to assign.	required

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	Self with identity set.

Example

import brahe as bh
import uuid

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
my_uuid = str(uuid.uuid4())
prop = bh.SGPPropagator.from_tle(line1, line2).with_identity("ISS", my_uuid, 25544)
print(f"Name: {prop.name}, ID: {prop.id}, UUID: {prop.uuid}")

with_name `method descriptor` ¶

with_name(name: str) -> SGPPropagator

Set the name and return self (consuming constructor pattern).

Parameters:

Name	Type	Description	Default
`name`	`str`	Name to assign to this propagator.	required

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	Self with name set.

Example

import brahe as bh

line1 = "1 25544U 98067A   21027.77992426  .00003336  00000-0  68893-4 0  9990"
line2 = "2 25544  51.6461 339.8014 0002571  24.9690  60.4407 15.48919393267689"
prop = bh.SGPPropagator.from_tle(line1, line2).with_name("My Satellite")
print(f"Name: {prop.name}")

with_new_uuid `method descriptor` ¶

with_new_uuid() -> SGPPropagator

Generate a new UUID, set it, and return self (consuming constructor pattern).

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	Self with new UUID set.

with_uuid `method descriptor` ¶

with_uuid(uuid_str: str) -> SGPPropagator

Set the UUID and return self (consuming constructor pattern).

Parameters:

Name	Type	Description	Default
`uuid_str`	`str`	UUID string to assign to this propagator.	required

Returns:

Name	Type	Description
`SGPPropagator`	`SGPPropagator`	Self with UUID set.

SGP Propagator¶

Example Usage¶

Class Reference¶

SGPPropagator ¶

arg_perigee property ¶

current_epoch property ¶

eccentricity property ¶

ephemeris_age property ¶

epoch property ¶

inclination property ¶

line1 property ¶

line2 property ¶

mean_anomaly property ¶

norad_id property ¶

right_ascension property ¶

satellite_name property ¶

semi_major_axis property ¶

step_size property ¶

terminated property ¶

trajectory property ¶

add_event_detector method descriptor ¶

clear_events method descriptor ¶

current_state method descriptor ¶

event_log method descriptor ¶

events_by_name method descriptor ¶

events_in_range method descriptor ¶

from_3le builtin ¶

from_omm_elements builtin ¶

from_tle builtin ¶

generate_uuid method descriptor ¶

get_elements method descriptor ¶

get_id method descriptor ¶

get_name method descriptor ¶

get_uuid method descriptor ¶

initial_state method descriptor ¶

latest_event method descriptor ¶

propagate_steps method descriptor ¶

propagate_to method descriptor ¶

reset method descriptor ¶

reset_termination method descriptor ¶

set_eviction_policy_max_age method descriptor ¶

set_eviction_policy_max_size method descriptor ¶

set_id method descriptor ¶

set_identity method descriptor ¶

set_name method descriptor ¶

set_output_format method descriptor ¶

set_step_size method descriptor ¶

state method descriptor ¶

state_ecef method descriptor ¶

state_eci method descriptor ¶

state_eme2000 method descriptor ¶

state_gcrf method descriptor ¶

state_itrf method descriptor ¶

state_koe_mean method descriptor ¶

state_koe_osc method descriptor ¶

state_pef method descriptor ¶

states method descriptor ¶

states_eci method descriptor ¶

states_gcrf method descriptor ¶

states_itrf method descriptor ¶

states_koe_mean method descriptor ¶

states_koe_osc method descriptor ¶

step method descriptor ¶

step_by method descriptor ¶

step_past method descriptor ¶

with_id method descriptor ¶

with_identity method descriptor ¶

with_name method descriptor ¶

with_new_uuid method descriptor ¶

with_uuid method descriptor ¶

See Also¶

arg_perigee `property` ¶

current_epoch `property` ¶

eccentricity `property` ¶

ephemeris_age `property` ¶

epoch `property` ¶

inclination `property` ¶

line1 `property` ¶

line2 `property` ¶

mean_anomaly `property` ¶

norad_id `property` ¶

right_ascension `property` ¶

satellite_name `property` ¶

semi_major_axis `property` ¶

step_size `property` ¶

terminated `property` ¶

trajectory `property` ¶

add_event_detector `method descriptor` ¶

clear_events `method descriptor` ¶

current_state `method descriptor` ¶

event_log `method descriptor` ¶

events_by_name `method descriptor` ¶

events_in_range `method descriptor` ¶

from_3le `builtin` ¶

from_omm_elements `builtin` ¶

from_tle `builtin` ¶

generate_uuid `method descriptor` ¶

get_elements `method descriptor` ¶

get_id `method descriptor` ¶

get_name `method descriptor` ¶

get_uuid `method descriptor` ¶

initial_state `method descriptor` ¶

latest_event `method descriptor` ¶

propagate_steps `method descriptor` ¶

propagate_to `method descriptor` ¶

reset `method descriptor` ¶

reset_termination `method descriptor` ¶

set_eviction_policy_max_age `method descriptor` ¶

set_eviction_policy_max_size `method descriptor` ¶

set_id `method descriptor` ¶

set_identity `method descriptor` ¶

set_name `method descriptor` ¶

set_output_format `method descriptor` ¶

set_step_size `method descriptor` ¶

state `method descriptor` ¶

state_ecef `method descriptor` ¶

state_eci `method descriptor` ¶

state_eme2000 `method descriptor` ¶

state_gcrf `method descriptor` ¶

state_itrf `method descriptor` ¶

state_koe_mean `method descriptor` ¶

state_koe_osc `method descriptor` ¶

state_pef `method descriptor` ¶

states `method descriptor` ¶

states_eci `method descriptor` ¶

states_gcrf `method descriptor` ¶

states_itrf `method descriptor` ¶

states_koe_mean `method descriptor` ¶

states_koe_osc `method descriptor` ¶

step `method descriptor` ¶

step_by `method descriptor` ¶

step_past `method descriptor` ¶

with_id `method descriptor` ¶

with_identity `method descriptor` ¶

with_name `method descriptor` ¶

with_new_uuid `method descriptor` ¶

with_uuid `method descriptor` ¶