# Preliminaries

1. pip install jplephem
2. pip install sgp4
3. Put de430.bsp ephemeris into Spacecraft_Testbed/Information/Celestial_Bodies/Ephemerides.


In [1]:

# Import the Celestial Body class
from Spacecraft_Testbed.Body import Celestial_Body
# Importy NumPy tools for math stuff
from numpy import linspace




In [2]:

# Instantiate Earth and Jupiter
Earth = Celestial_Body('Earth')
Jupiter = Celestial_Body('Jupiter')




In [3]:

# Define Julian date of interest (March 20)
March20  = 2457832.5 # Initial time




In [4]:

# Calculate position and velocity of Earth
# with respect to the solar system barycentre

# On March 20
p, v = Earth.Position_and_Velocity(March20)
print "Position: " + str(p)
print "Velocity: " + str(v)




Position: [ -1.48489812e+11   2.21189805e+09   9.34648913e+08]
Velocity: [  -848.17837498 -27419.97431137 -11886.18017189]




In [5]:

# Examine the Chinese weather satellite Fengyun 1C debris fragements
frag1 = Earth.Satellites.Fengyun_1C.Fengyun_1C_Deb_102
frag2 = Earth.Satellites.Fengyun_1C.Fengyun_1C_Deb_105
# Examine the Iridium debris fragement 4
frag3 = Earth.Satellites.Iridium_33.Iridium_33_Deb_4
# and Breeze debris fragement 1
frag4 = Earth.Satellites.Cosmos_2251.Cosmos_2251_Deb_1




In [6]:

# These positions and velocities can be shown as well
print frag1.Position_and_Velocity(March20) # WRT SS barycentre




[[ -1.48485429e+11   2.20762439e+09   9.38126603e+08]
[  1.01969851e+03  -3.09831481e+04  -1.82752110e+04]]




In [7]:

# WRT other planets and fragements (all derrived from the body class)
print frag3.Position_and_Velocity_WRT(Earth, March20) # WRT Earth




[[  4.43878512e+06  -4.06131326e+06   3.82475823e+06]
[ -2.57981748e+03   3.11725590e+03   6.29035932e+03]]




In [8]:

# WRT another fragement
print frag4.Position_and_Velocity_WRT(frag1, March20)




[[  1.28717072e+06   5.51727170e+06   6.76550714e+05]
[ -6.42861377e+03   5.15034098e+03   1.20931045e+04]]




In [9]:

# WRT Jupiter
print frag2.Position_and_Velocity_WRT(Jupiter, March20)




[[  6.33120497e+11   2.22664442e+11   7.64038207e+10]
[ -5.51975218e+03  -1.35438198e+04  -3.96318645e+02]]




In [10]:

# Earth WRT Mars
print Earth.Position_and_Velocity_WRT(Celestial_Body('Mars'), March20)




[[ -2.57966193e+11  -1.77399718e+11  -7.84660765e+10]
[  1.94062670e+04  -3.98292685e+04  -1.81245049e+04]]



Remeber that position and velocity are given in $m$ and $\frac{m}{s}$, respectively.