Support Unobservability

This example shows how the support – the final construction of the object – is fundamentally unobservable from the light curve.

import numpy as np
import pyvista as pv

import mirage as mr
import mirage.vis as mrv

Defining the nominal object

obj = mrv.SpaceObject('cube.obj')

v2 = obj.v.copy()
for fi, ni in zip(obj.f, obj.face_normals):
    for vind in fi:
        v2[vind] += ni

obj2 = mrv.SpaceObject(vertices_and_faces=(v2, obj.f))

pl = pv.Plotter()
mrv.render_spaceobject(pl, obj)
mrv.render_spaceobject(pl, obj2, color='gray')
pl.show()

Calculating the irradiance difference for a change of 1 meter for one of the flat plates for an object in GEO

r_geo = 42164.0
r_plate = r_geo
r_plate2 = r_geo - 1e-3

irradiance_fraction_difference = 1 - (r_plate2 / r_plate) ** 2

print(
    f'The irradiance due to the closer plate is {irradiance_fraction_difference*100}% different'
)

The irradiance due to the closer plate is 4.743382919780714e-06% different

Figuring out the truncation losses in the CCD

obs = mr.Station(preset='pogs')
npix = obs.telescope.get_airy_disk_pixels()
ccd_signal = 1e4
trunc_variance = npix**2 / 24
trunc_std = np.sqrt(trunc_variance)

signal_difference = ccd_signal * irradiance_fraction_difference

print(f'The number of pixels in the airy disk is {npix}')
print(f'The standard deviation of the truncation noise is {trunc_std} ADU')
print(
    f'The difference in the signal due to plate distance is {signal_difference:.3e} ADU'
)
print(
    f'The truncation noise is {trunc_std / signal_difference} stronger than the signal difference'
)

SNR = signal_difference / np.sqrt(signal_difference + trunc_std)

print(f'The SNR is {SNR:.3e}')

The number of pixels in the airy disk is 53.72556416973795
The standard deviation of the truncation noise is 10.966684863251045 ADU
The difference in the signal due to plate distance is 4.743e-04 ADU
The truncation noise is 23119.965325839712 stronger than the signal difference
The SNR is 1.432e-04