1. MissionSequence#

class MissionSequence(name: str, propagator: Propagator)#

Bases: object

Represents a sequence of mission segments, including propagation legs and impulsive burns.

Manages the trajectory propagation structure, ensuring logical consistency between consecutive mission segments. Defines the order of events, maintains state vectors, handles epoch continuity, and enables dynamic modeling through an associated propagator.

Parameters:

  • name (str) – The name of the mission sequence.

  • propagator (Propagator) – The propagator responsible for simulating the spacecraft dynamics.

Notes

  • The first leg must define the complete initial state.

  • A leg cannot follow another leg without an intervening impulsive burn.

  • Estimated impulsive burns must be followed by a “dv_man” parameter in the next leg.

  • The mission sequence structure ensures strict consistency in epochs and state transitions.

Examples

# initial setup
import scarabaeus as scb

# Define propagator
prop = scb.Propagator(...)

# Initialize mission sequence
mission = scb.MissionSequence(name="EMA123", propagator=prop)

# Define initial leg
state_vec = scb.StateArray(...)  # Initial state vector
mission.addLeg(name="Outbound Leg", period=ArrayWUnits(86400, "s"),
            state_vector=state_vec, dt=ArrayWUnits(60, "s"))

# Define and add impulsive burn
dV = scb.ImpulsiveBurn(...)
mission.addBurn(name="Midcourse Correction", dV=dV)

# Define and add another leg
next_leg = scb.StateArray(...)  # State vector for second leg
mission.addLeg(name="Final Approach", period=ArrayWUnits(43200, "s"), state_vector=next_leg, dt=ArrayWUnits(60, "s"))

Attributes

dts

List of time step lengths used for integration in each segment.

epochs_vec

List of EpochArray objects defining the timestamps associated with each mission phase.

last_idx

Indices marking the last step of each segment within the overall timeline.

models

List of state models, representing either propagation states or impulsive maneuvers.

name

The name of the mission sequence.

names

List of names corresponding to each sequence segment.

num_steps

Number of integration steps per leg, or None for impulsive burns.

periods

List of time durations for each leg in the sequence, or None for impulsive burns.

propagator

The propagator associated with the mission sequence.

states_n

List of the number of states in each leg, or None for impulsive burns.

types

List of segment types, such as "Leg" (propagation phase) or "Impulsive Burn".

Methods

addBurn(name, dV)

Adds an impulsive burn to the mission sequence.

addLeg(name, period, state_vector[, dt, epochs])

Adds a propagation leg to the mission sequence.

check_sequence_consistency()

Checks the consistency of the mission sequence.

validate_impulsive_burn(name, dV)

Validates the parameters of an impulsive burn before adding it.

validate_leg(name, period, dt, state_vector)

Validates the parameters of a leg before adding it to the mission sequence.
addBurn(name: str, dV: ImpulsiveBurn) → None#

Adds an impulsive burn to the mission sequence.

Inserts an impulsive burn event, modifying the spacecraft’s velocity instantaneously. The burn is added between two propagation legs, and a corresponding velocity update (dv_man) is introduced in the next leg.

Parameters:

  • name (str) – The name of the impulsive burn.

  • dV (ImpulsiveBurn) – The impulsive burn model defining the velocity change.

Return type:

None

addLeg(name, period: ArrayWUnits, state_vector, dt: ArrayWUnits = None, epochs=None) → None#

Adds a propagation leg to the mission sequence.

Defines a new segment (leg) in the mission sequence, where the spacecraft propagates under the specified dynamical model. The user must specify either a time step (dt) or a predefined list of epochs (epochs). The number of integration steps is computed accordingly.

Parameters:

  • name (str) – The name of the leg.

  • period (ArrayWUnits) – The total duration of the leg in seconds.

  • state_vector (StateArray) – The initial state of the spacecraft for the leg.

  • dt (ArrayWUnits, optional) – The time step used to discretize the propagation period. Required if epochs is not provided. Defaults to None.

  • epochs (EpochArray, optional) – Predefined epochs for the propagation instead of computing them using period and dt. If provided, dt must be None. Defaults to None.

Return type:

None

check_sequence_consistency() → None#

Checks the consistency of the mission sequence.

Ensures that the mission sequence follows logical constraints, such as epoch continuity between legs, proper state vector propagation, and a valid ordering of estimated parameters.

Return type:

None

validate_impulsive_burn(name: str, dV: ImpulsiveBurn) → None#

Validates the parameters of an impulsive burn before adding it.

Ensures that the burn name is unique, follows a valid mission sequence structure, and conforms to expected data types.

Parameters:

  • name (str) – The name of the impulsive burn.

  • dV (ImpulsiveBurn) – The impulsive burn model.

Return type:

None

validate_leg(name: str, period: ArrayWUnits, dt: ArrayWUnits, state_vector: StateArray, epochs_vec: EpochArray = None) → None#

Validates the parameters of a leg before adding it to the mission sequence.

Ensures that the provided leg parameters meet structural and logical requirements. It checks for correct data types, consistent state vector definitions, and the presence of necessary inputs.

Parameters:

  • name (str) – The name of the leg.

  • period (ArrayWUnits) – The duration of the leg in seconds.

  • dt (ArrayWUnits) – The time step for discretization in seconds.

  • state_vector (StateArray) – The state vector representing the spacecraft’s state during the leg.

  • epochs_vec (EpochArray, optional) – Predefined epochs. Defaults to None.

Return type:

None

property dts: list[ArrayWUnits] | None#

List of time step lengths used for integration in each segment.

property epochs_vec: list[EpochArray]#

List of EpochArray objects defining the timestamps associated with each mission phase.

property last_idx: list[int]#

Indices marking the last step of each segment within the overall timeline.

property models: list[StateArray] | list[ImpulsiveBurn]#

List of state models, representing either propagation states or impulsive maneuvers.

property name: str#

The name of the mission sequence.

property names: list[str]#

List of names corresponding to each sequence segment.

property num_steps: list[int] | None#

Number of integration steps per leg, or None for impulsive burns.

property periods: list[ArrayWUnits] | list[None]#

List of time durations for each leg in the sequence, or None for impulsive burns.

property propagator: Propagator#

The propagator associated with the mission sequence.

property states_n: list[int] | None#

List of the number of states in each leg, or None for impulsive burns.

property types: list[str]#

List of segment types, such as "Leg" (propagation phase) or "Impulsive Burn".