def test_orientation_convention(self):
e = 0.5
orb0 = np.array([self.a, e, 0, 0, 0, 0], dtype=np.float64)
q = self.a * (1 - e)
Q = self.a * (1 + e)
l = self.a * (1 - e**2)
orb = orb0.copy()
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], q, decimal=6)
orb = orb0.copy()
orb[5] = 90
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[1], l, decimal=6)
orb = orb0.copy()
orb[3] = 180
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], -q, decimal=6)
orb[5] = 180
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], Q, decimal=6)
orb = orb0.copy()
orb[3] = 90
orb[4] = 90
orb[5] = 180
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], Q, decimal=6)
orb = orb0.copy()
orb[2] = 90
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], q, decimal=6)
nt.assert_almost_equal(x[1], 0, decimal=6)
orb[3] = 90
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], 0, decimal=6)
nt.assert_almost_equal(x[1], 0, decimal=6)
nt.assert_almost_equal(x[2], q, decimal=6)
orb[4] = 180
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], 0, decimal=6)
nt.assert_almost_equal(x[1], 0, decimal=6)
nt.assert_almost_equal(x[2], q, decimal=6)
orb = orb0.copy()
orb[2] = 45
orb[3] = 90
orb[4] = 90
x = kep.kep_to_cart(orb, mu=self.mu, degrees=True)
nt.assert_almost_equal(x[0], -q * np.sqrt(2) * 0.5, decimal=6)
nt.assert_almost_equal(x[1], 0, decimal=6)
nt.assert_almost_equal(x[2], q * np.sqrt(2) * 0.5, decimal=6)
def test_cart_kep_loop_degradation(self):
orb_init = np.array([self.a, 0.2, 23.0, 136.0, 44.0, 10.0],
dtype=np.float64)
x = kep.kep_to_cart(orb_init, mu=self.mu, degrees=True)
x_ref = x.copy()
for ind in range(200):
o = kep.cart_to_kep(x, mu=self.mu, degrees=True)
x = kep.kep_to_cart(o, mu=self.mu, degrees=True)
nt.assert_array_almost_equal(x, x_ref, decimal=6)
def test_kep_to_cart_Omega_inc(self):
self.orb_init[1] = 0.8
self.orb_init[2] = 45.0
self.orb_init[3] = 90.0
self.orb_init[4] = 90.0
nu = np.degrees(np.array([0.0], dtype=np.float64))
res = nu.size
o = np.empty((6, res), dtype=np.float64)
for i in range(res):
o[:5, i] = self.orb_init
o[5, i] = nu[i]
x = kep.kep_to_cart(o, mu=self.mu, degrees=True)
#rotates counterclockwise in orbital plane
r = np.sqrt(np.sum(x[:3, :]**2, axis=0))
nt.assert_almost_equal(
r[0] / self.R_e,
(1.0 - self.orb_init[1]) * self.orb_init[0] / self.R_e,
decimal=3,
)
#check quadrant of periapsis
assert x[2, 0] > 0.0 and x[0, 0] < 0.0 and np.abs(
x[1, 0] / self.R_e) < 1e-3
def test_kep_to_cart_omega_inc(self):
self.orb_init[1] = 0.8
self.orb_init[2] = 90.0
self.orb_init[3] = 90.0
nu = np.degrees(np.array([0.0], dtype=np.float64))
res = nu.size
o = np.empty((6, res), dtype=np.float64)
for i in range(res):
o[:5, i] = self.orb_init
o[5, i] = nu[i]
x = kep.kep_to_cart(o, mu=self.mu, degrees=True)
#rotates counterclockwise in orbital plane
r = np.sqrt(np.sum(x[:3, :]**2, axis=0))
nt.assert_almost_equal(
r[0] / self.R_e,
(1.0 - self.orb_init[1]) * self.orb_init[0] / self.R_e,
decimal=3,
)
#check periapsis lies on +z axis
nt.assert_almost_equal(
x[2, 0] / self.R_e,
np.linalg.norm(x[:, 0]) / self.R_e,
decimal=3,
)
def test_kep_to_cart_ecc(self):
self.orb_init[1] = 0.8
nu = np.degrees(
np.array([0, np.pi * 0.5, 1.5 * np.pi, np.pi], dtype=np.float64))
res = nu.size
o = np.empty((6, res), dtype=np.float64)
for i in range(res):
o[:5, i] = self.orb_init
o[5, i] = nu[i]
x = kep.kep_to_cart(o, mu=self.mu, degrees=True)
r = np.sqrt(np.sum(x[:3, :]**2, axis=0))
v = np.sqrt(np.sum(x[3:, :]**2, axis=0))
#test true anomaly = 0 is periapsis
assert np.all(r[0] < r[1:]), 'nu=0 is not periapsis'
assert np.all(r[3] > r[:3]), 'nu=pi is not apoapsis'
assert x[0, 0] > 0.0, 'periapsis NOT to +x'
assert x[0, 3] < 0.0, 'apoapsis NOT to +x'
#test velocity, fast at peri slow at apo
assert np.all(v[0] > v[1:]), 'periapsis vel not fastest'
assert np.all(v[3] < v[:3]), 'apoapsis vel not slowest'
#test velocity is perp at peri and apo
nt.assert_almost_equal(x[3, 0] * 1e-3, 0.0, decimal=3)
nt.assert_almost_equal(x[3, 3] * 1e-3, 0.0, decimal=3)
#test ellipse oriented along x
nt.assert_almost_equal(x[1, 0] / self.R_e, 0.0, decimal=3)
nt.assert_almost_equal(x[1, 3] / self.R_e, 0.0, decimal=3)
#test orbital motion counter-clockwise
assert x[1, 1] > 0.0, 'orbital motion is not counter-clockwise'
assert x[1, 2] < 0.0, 'orbital motion is not counter-clockwise'
#test periapsis distance and apoapsis distance
nt.assert_almost_equal(
r[0] / self.R_e,
(1.0 - self.orb_init[1]) * self.orb_init[0] / self.R_e,
decimal=3,
)
nt.assert_almost_equal(
r[3] / self.R_e,
(1.0 + self.orb_init[1]) * self.orb_init[0] / self.R_e,
decimal=3,
)
def test_kep_to_cart_inc(self):
self.orb_init[2] = 45.0
nu = np.degrees(np.array([np.pi * 0.5], dtype=np.float64))
res = nu.size
o = np.empty((6, res), dtype=np.float64)
for i in range(res):
o[:5, i] = self.orb_init
o[5, i] = nu[i]
x = kep.kep_to_cart(o, mu=self.mu, degrees=True)
assert x[2, 0] > 0.0 and x[1, 0] > 0.0, '+y inclines towards +z'
def test_planar_detection(self):
'''Longitude of ascending node gets transfered to argument of periapsis in planar orbits. Test if this is true for retro-grade and pro-grade planar orbits.
'''
orb_in = np.array([self.a, 0.5, 0, 0, 45, 0], dtype=np.float64)
orb_ref = np.array([self.a, 0.5, 0, 45, 0, 0], dtype=np.float64)
x0 = kep.kep_to_cart(orb_in, mu=self.mu, degrees=True)
orb_out = kep.cart_to_kep(x0, mu=self.mu, degrees=True)
nt.assert_almost_equal(orb_ref, orb_out)
orb_in = np.array([self.a, 0.5, 180, 0, 45, 0], dtype=np.float64)
orb_ref = np.array([self.a, 0.5, 180, 360 - 45, 0, 0],
dtype=np.float64)
x1 = kep.kep_to_cart(orb_in, mu=self.mu, degrees=True)
orb_out = kep.cart_to_kep(x1, mu=self.mu, degrees=True)
#should be same but reversed velocity
x1[3:] = -x1[3:]
nt.assert_almost_equal(x0, x1)
nt.assert_almost_equal(orb_ref, orb_out)
def test_kep_to_cart_circ(self):
res = 100
nu = np.linspace(0, 360.0, num=res, dtype=np.float64)
o = np.empty((6, res), dtype=np.float64)
for i in range(res):
o[:5, i] = self.orb_init
o[5, i] = nu[i]
x = kep.kep_to_cart(o, mu=self.mu, degrees=True)
r0 = np.ones((res, ), dtype=np.float64)
r0 *= self.a / self.R_e
r = np.sqrt(np.sum(x[:3, :]**2, axis=0)) / self.R_e
nt.assert_array_almost_equal(r0, r, decimal=3)
v0 = np.ones((res, ), dtype=np.float64)
v0 *= kep.orbital_speed(self.a, self.a, self.mu) * 1e-3
v = np.sqrt(np.sum(x[3:, :]**2, axis=0)) * 1e-3
nt.assert_array_almost_equal(v0, v, decimal=3)
#check perpendicular vel to rad
dot = np.sum(x[3:, :] * x[:3, :], axis=0)
nt.assert_array_almost_equal(dot,
np.zeros(dot.shape, dtype=np.float64),
decimal=3)
#check 0 inc in xy
nt.assert_array_almost_equal(x[2, :],
np.zeros((res, ), dtype=np.float64),
decimal=3)
nt.assert_array_almost_equal(x[5, :],
np.zeros((res, ), dtype=np.float64),
decimal=3)
def test_cart_kep_inverse(self):
a = np.linspace(self.a, self.a + self.R_e, num=2, dtype=np.float64)
e = np.linspace(0.0, 0.99, num=10, dtype=np.float64)
inc = np.linspace(0.0, 180.0, num=10, dtype=np.float64)
omega = np.linspace(0.0, 360.0, num=10, dtype=np.float64)
Omega = omega.copy()
nu = np.array([0, 45, 180], dtype=np.float64)
av, ev, incv, omegav, Omegav, nuv = np.meshgrid(
a, e, inc, omega, Omega, nu)
ait = np.nditer(av)
eit = np.nditer(ev)
incit = np.nditer(incv)
omegait = np.nditer(omegav)
Omegait = np.nditer(Omegav)
nuit = np.nditer(nuv)
o = np.empty((6, av.size), dtype=np.float64)
for ind in range(av.size):
o[0, ind] = next(ait)
o[1, ind] = next(eit)
o[2, ind] = next(incit)
o[3, ind] = next(omegait)
o[4, ind] = next(Omegait)
o[5, ind] = next(nuit)
x = kep.kep_to_cart(o, mu=self.mu, degrees=True)
o_calc = kep.cart_to_kep(x, mu=self.mu, degrees=True)
x_calc = kep.kep_to_cart(o_calc, mu=self.mu, degrees=True)
for ind in range(av.size):
try:
nt.assert_array_almost_equal(x[:3, ind] / o[0, ind],
x_calc[:3, ind] / o[0, ind],
decimal=6)
nt.assert_array_almost_equal(x[3:, ind] / o[0, ind],
x_calc[3:, ind] / o[0, ind],
decimal=6)
except AssertionError:
print(ind)
print(x[:3, ind] - x_calc[:3, ind])
print(o[:, ind])
print(o_calc[:, ind])
print(o_calc[:, ind] - o[:, ind])
raise
el = o[1, :] < kep.e_lim
il = o[2, :] < np.degrees(kep.i_lim)
il_ret = o[2, :] > 180 - np.degrees(kep.i_lim)
o_orig = o.copy()
o[3, el] = 0.0
o[4, il] = 0.0
o[4, il_ret] = 0.0
o[5, el] += o_orig[3, el]
o[5, np.logical_and(il, el)] += o_orig[4, np.logical_and(il, el)]
o[3, np.logical_and(il, np.logical_not(el))] += o_orig[
4, np.logical_and(il, np.logical_not(el))]
o[5, np.logical_and(il_ret, el)] -= o_orig[4,
np.logical_and(il_ret, el)]
o[3, np.logical_and(il_ret, np.logical_not(el))] -= o_orig[
4, np.logical_and(il_ret, np.logical_not(el))]
o[5, :] = np.mod(o[5, :] + 360.0, 360.0)
for ind in range(av.size):
test = np.isclose(o_calc[0, ind] / self.R_e,
o[0, ind] / self.R_e,
atol=1e-3)
test = np.logical_and(
test, np.isclose(o_calc[1, ind], o[1, ind], atol=1e-4))
test_ang = np.logical_or(
np.isclose(o_calc[2:, ind], o[2:, ind], atol=1e-7),
np.isclose(np.mod(o_calc[2:, ind] + 180.0, 360.0),
np.mod(o[2:, ind] + 180.0, 360.0),
atol=1e-7),
)
test = np.logical_and(test, test_ang)
if not np.all(test):
# x_ = kep.kep_to_cart(o_orig[:,ind], mu=self.mu, degrees=True)
# o_calc_ = kep.cart_to_kep(x_, mu=self.mu, degrees=True)
# x_calc_ = kep.kep_to_cart(o_calc_, mu=self.mu, degrees=True)
print(ind)
print(o_orig[:, ind])
print(o[:, ind])
print(o_calc[:, ind])
print(o_calc[:, ind] - o[:, ind])
assert np.all(test)
