simulation_start_epoch = 0.0 # s
# Load spice kernels
spice_interface.load_standard_kernels()
# Define settings for celestial bodies
bodies_to_create = ['Moon']
# Define coordinate system
global_frame_origin = 'Moon'
global_frame_orientation = 'ECLIPJ2000'
# Create body settings
# N.B.: all the bodies added after this function is called will automatically
# be placed in the same reference frame, which is the same for the full
# system of bodies
body_settings = environment_setup.get_default_body_settings(
bodies_to_create, global_frame_origin, global_frame_orientation)
# Create bodies
bodies = environment_setup.create_system_of_bodies(body_settings)
###########################################################################
# CREATE VEHICLE ##########################################################
###########################################################################
# Create vehicle object and add it to the existing system of bodies
bodies.create_empty_body('Vehicle')
# Set mass of vehicle
bodies.get_body('Vehicle').set_constant_mass(vehicle_mass)
###########################################################################
# CREATE ACCELERATIONS ####################################################
###########################################################################
# Define bodies that are propagated and their central bodies of propagation
def create_simulation_bodies(
itokawa_radius: float
) -> tudatpy.kernel.simulation.environment_setup.SystemOfBodies:
"""
It creates all the body settings and body objects required by the simulation.
Parameters
----------
itokawa_radius : float
Radius of Itokawa, assuming a spherical shape.
Returns
-------
tudatpy.kernel.simulation.environment_setup.SystemOfBodies
System of bodies to be used in the simulation.
"""
### CELESTIAL BODIES ###
# Define Itokawa body frame name
itokawa_body_frame_name = "Itokawa_Frame"
# Create default body settings for selected celestial bodies
bodies_to_create = ["Sun", "Earth", "Jupiter", "Saturn", "Mars"]
# Create default body settings for bodies_to_create, with "Earth"/"J2000" as
# global frame origin and orientation. This environment will only be valid
# in the indicated time range [simulation_start_epoch --- simulation_end_epoch]
body_settings = environment_setup.get_default_body_settings(
bodies_to_create, "SSB", "ECLIPJ2000")
# Add Itokawa body
body_settings.add_empty_settings("Itokawa")
# Gravity field definition
itokawa_gravity_field_settings = get_itokawa_gravity_field_settings(
itokawa_body_frame_name, itokawa_radius)
# Adds Itokawa settings
# Gravity field
body_settings.get(
"Itokawa").gravity_field_settings = itokawa_gravity_field_settings
# Rotational model
body_settings.get(
"Itokawa").rotation_model_settings = get_itokawa_rotation_settings(
itokawa_body_frame_name)
# Ephemeris
body_settings.get(
"Itokawa").ephemeris_settings = get_itokawa_ephemeris_settings(
itokawa_gravity_field_settings.gravitational_parameter)
# Shape (spherical)
body_settings.get("Itokawa").shape_settings = get_itokawa_shape_settings(
itokawa_radius)
# Create system of selected bodies
bodies = environment_setup.create_system_of_bodies(body_settings)
### VEHICLE BODY ###
# Create vehicle object
bodies.create_empty_body("Spacecraft")
bodies.get_body("Spacecraft").set_constant_mass(400.0)
# Create radiation pressure settings, and add to vehicle
reference_area_radiation = 4.0
radiation_pressure_coefficient = 1.2
radiation_pressure_settings = environment_setup.radiation_pressure.cannonball(
"Sun", reference_area_radiation, radiation_pressure_coefficient)
environment_setup.add_radiation_pressure_interface(
bodies, "Spacecraft", radiation_pressure_settings)
return bodies
