Convex Light Curves

Simulates torque-free rigid body motion for a simple object and computes the light curve

import matplotlib.pyplot as plt
import numpy as np
import seaborn as sns

import mirage as mr

To keep things simple, we’ll just use a cube for this demo

obj = mr.SpaceObject('cube.obj')
brdf = mr.Brdf('diffuse', cd=1.0, cs=0.0)

Computing the quaternion time history of the object

teval = np.linspace(0, 10, 1000)
q, _ = mr.propagate_attitude_torque_free(
    quat0=np.array([0.0, 0.0, 0.0, 1.0]),
    omega0=np.array([1.0, 1.0, 1.0]),
    itensor=np.diag([1, 2, 3]),
    teval=teval,
)
dcm = mr.quat_to_dcm(q)  # Converting to quaternion

Transforming fixed inertial Sun and Observer vectors into the body frame

svi = np.array([[1, 0, 0]])
# Sun vector in the inertial frame
svb = mr.stack_mat_mult_vec(dcm, svi)
# Sun vector in the body frame
ovi = np.array([[0, 1, 0]])
# Observer vector in the inertial frame
ovb = mr.stack_mat_mult_vec(dcm, ovi)
# Observer vector in the body frame

lc = obj.convex_light_curve(brdf, svb, ovb)

plt.figure()
sns.lineplot(x=teval, y=lc)
plt.title('Convex Light Curves')
plt.xlabel('Time [s]')
plt.ylabel('Normalized brightness')
plt.grid()
plt.show()