Where is Pandora above the earth? Where is Pandora looking?¶

It is possible to use PandoraSpacecraft to see where the boresight is pointed over time, and where the spacecraft is above the earth.

In [1]:

import numpy as np
import matplotlib.pyplot as plt
import pandoraspacecraft as psc
from astropy.time import Time
import astropy.units as u

import numpy as np import matplotlib.pyplot as plt import pandoraspacecraft as psc from astropy.time import Time import astropy.units as u

In [2]:

ps = psc.PandoraSpacecraft()

ps = psc.PandoraSpacecraft()

In [3]:

t = Time(np.linspace(2461135, 2461136, 10000), format='jd')

t = Time(np.linspace(2461135, 2461136, 10000), format='jd')

In the cell below we get the illumination of the earth by the sun directly under Pandora.

In [4]:

illum = ps.get_earth_illumination(t)

illum = ps.get_earth_illumination(t)

If the illumination is >90 degrees this tells us Pandora is over the "night" side of earth. If it is <90 degrees, Pandora is over the "day" side of earth.

In [5]:

fig, ax = plt.subplots(facecolor='white', dpi=150)
ax.plot(t.jd, illum, c='k')
ax.set(xlabel='Time [JD]', ylabel='Earth Illumination Angle [deg]')

fig, ax = plt.subplots(facecolor='white', dpi=150) ax.plot(t.jd, illum, c='k') ax.set(xlabel='Time [JD]', ylabel='Earth Illumination Angle [deg]')

Out[5]:

[Text(0.5, 0, 'Time [JD]'), Text(0, 0.5, 'Earth Illumination Angle [deg]')]

You can see that Pandora passes over the night and day side over the course of one orbit. This pattern changes slowly over the course of a year.

You can also get the angle between the pointing vector and any body

In [6]:

angle = ps.get_angle_to_body(t, direction="boresight", body="earth")

angle = ps.get_angle_to_body(t, direction="boresight", body="earth")

When we plot these against each other we can see how close Pandora is pointing towards the earth during the day and night.

In [7]:

fig, ax = plt.subplots(facecolor='white', dpi=150)
ax.scatter(angle, illum, c='k', s=1)
ax.set(xlabel='Angle to Earth [deg]', ylabel='Earth Illumination Angle [deg]')
ax.axhline(90, ls='--', color='grey')
ax.text(150, 91, 'Night', color='grey')
ax.text(150, 89, 'Day', color='grey', va='top')

fig, ax = plt.subplots(facecolor='white', dpi=150) ax.scatter(angle, illum, c='k', s=1) ax.set(xlabel='Angle to Earth [deg]', ylabel='Earth Illumination Angle [deg]') ax.axhline(90, ls='--', color='grey') ax.text(150, 91, 'Night', color='grey') ax.text(150, 89, 'Day', color='grey', va='top')

Out[7]:

Text(150, 89, 'Day')

We can also get the positiong that Pandora is looking at

In [8]:

ra, dec = ps.get_pointing_radec(t, direction='boresight')

ra, dec = ps.get_pointing_radec(t, direction='boresight')

This is the direction in RA and Declination.

In [9]:

fig, ax = plt.subplots(facecolor='white', dpi=150)
ax.scatter(ra, dec, c='k', s=1)
ax.set(xlabel='Right Ascension [deg]', ylabel='Declination [deg]')

fig, ax = plt.subplots(facecolor='white', dpi=150) ax.scatter(ra, dec, c='k', s=1) ax.set(xlabel='Right Ascension [deg]', ylabel='Declination [deg]')

Out[9]:

[Text(0.5, 0, 'Right Ascension [deg]'), Text(0, 0.5, 'Declination [deg]')]