def test_atmospheric_demise():
# Test an orbital decay that hits Earth. No analytic solution.
R = Earth.R.to(u.km).value
orbit = Orbit.circular(Earth, 230 * u.km)
t_decay = 48.2179 * u.d # not an analytic value
# parameters of a body
C_D = 2.2 # dimentionless (any value would do)
A_over_m = ((np.pi / 4.0) * (u.m**2) / (100 * u.kg)).to_value(
u.km**2 / u.kg) # km^2/kg
# parameters of the atmosphere
rho0 = rho0_earth.to(u.kg / u.km**3).value # kg/km^3
H0 = H0_earth.to(u.km).value # km
tofs = [365] * u.d # actually hits the ground a bit after day 48
lithobrake_event = LithobrakeEvent(R)
events = [lithobrake_event]
rr, _ = cowell(
Earth.k,
orbit.r,
orbit.v,
tofs,
ad=atmospheric_drag_exponential,
R=R,
C_D=C_D,
A_over_m=A_over_m,
H0=H0,
rho0=rho0,
events=events,
)
assert_quantity_allclose(norm(rr[0].to(u.km).value), R,
atol=1) # below 1km
assert_quantity_allclose(lithobrake_event.last_t, t_decay, rtol=1e-2)
# make sure having the event not firing is ok
tofs = [1] * u.d
lithobrake_event = LithobrakeEvent(R)
events = [lithobrake_event]
rr, _ = cowell(
Earth.k,
orbit.r,
orbit.v,
tofs,
ad=atmospheric_drag_exponential,
R=R,
C_D=C_D,
A_over_m=A_over_m,
H0=H0,
rho0=rho0,
events=events,
)
assert lithobrake_event.last_t == tofs[-1]
def test_atmospheric_demise_coesa76():
# Test an orbital decay that hits Earth. No analytic solution.
R = Earth.R.to(u.km).value
orbit = Orbit.circular(Earth, 250 * u.km)
t_decay = 7.17 * u.d
# Parameters of a body
C_D = 2.2 # Dimensionless (any value would do)
A_over_m = ((np.pi / 4.0) * (u.m**2) / (100 * u.kg)).to_value(
u.km**2 / u.kg) # km^2/kg
tofs = [365] * u.d
lithobrake_event = LithobrakeEvent(R)
events = [lithobrake_event]
coesa76 = COESA76()
def f(t0, u_, k):
du_kep = func_twobody(t0, u_, k)
# Avoid undershooting H below attractor radius R
H = max(norm(u_[:3]), R)
rho = coesa76.density((H - R) * u.km).to_value(u.kg / u.km**3)
ax, ay, az = atmospheric_drag(
t0,
u_,
k,
C_D=C_D,
A_over_m=A_over_m,
rho=rho,
)
du_ad = np.array([0, 0, 0, ax, ay, az])
return du_kep + du_ad
rr, _ = cowell(
Earth.k,
orbit.r,
orbit.v,
tofs,
events=events,
f=f,
)
assert_quantity_allclose(norm(rr[0].to(u.km).value), R,
atol=1) # Below 1km
assert_quantity_allclose(lithobrake_event.last_t, t_decay, rtol=1e-2)
def test_atmospheric_demise_coesa76():
# Test an orbital decay that hits Earth. No analytic solution.
R = Earth.R.to(u.km).value
orbit = Orbit.circular(Earth, 250 * u.km)
t_decay = 7.17 * u.d
# parameters of a body
C_D = 2.2 # dimentionless (any value would do)
A_over_m = ((np.pi / 4.0) * (u.m**2) / (100 * u.kg)).to_value(
u.km**2 / u.kg) # km^2/kg
tofs = [365] * u.d
lithobrake_event = LithobrakeEvent(R)
events = [lithobrake_event]
coesa76 = COESA76()
def f(t0, u_, k):
du_kep = func_twobody(t0, u_, k)
ax, ay, az = atmospheric_drag_model(t0,
u_,
k,
R=R,
C_D=C_D,
A_over_m=A_over_m,
model=coesa76)
du_ad = np.array([0, 0, 0, ax, ay, az])
return du_kep + du_ad
rr, _ = cowell(
Earth.k,
orbit.r,
orbit.v,
tofs,
events=events,
f=f,
)
assert_quantity_allclose(norm(rr[0].to(u.km).value), R,
atol=1) # below 1km
assert_quantity_allclose(lithobrake_event.last_t, t_decay, rtol=1e-2)
def test_atmospheric_demise():
# Test an orbital decay that hits Earth. No analytic solution.
R = Earth.R.to(u.km).value
orbit = Orbit.circular(Earth, 230 * u.km)
t_decay = 48.2179 * u.d
# parameters of a body
C_D = 2.2 # dimentionless (any value would do)
A = ((np.pi / 4.0) * (u.m**2)).to(u.km**2).value # km^2
m = 100 # kg
# parameters of the atmosphere
rho0 = rho0_earth.to(u.kg / u.km**3).value # kg/km^3
H0 = H0_earth.to(u.km).value # km
tofs = [365] * u.d # actually hits the ground a bit after day 48
lithobrake_event = LithobrakeEvent(R)
events = [lithobrake_event]
rr, _ = cowell(
Earth.k,
orbit.r,
orbit.v,
tofs,
ad=atmospheric_drag,
R=R,
C_D=C_D,
A=A,
m=m,
H0=H0,
rho0=rho0,
events=events,
)
assert_quantity_allclose(norm(rr[0].to(u.km).value), R,
atol=1) # below 1km
# last_t is not an analytic value
assert_quantity_allclose(lithobrake_event.last_t, t_decay, rtol=1e-2)
def test_atmospheric_demise_coesa76():
# Test an orbital decay that hits Earth. No analytic solution.
R = Earth.R.to(u.km).value
orbit = Orbit.circular(Earth, 250 * u.km)
t_decay = 7.17 * u.d
# parameters of a body
C_D = 2.2 # dimentionless (any value would do)
A = ((np.pi / 4.0) * (u.m**2)).to(u.km**2).value # km^2
m = 100 # kg
tofs = [365] * u.d
lithobrake_event = LithobrakeEvent(R)
events = [lithobrake_event]
coesa76 = COESA76()
rr, _ = cowell(
Earth.k,
orbit.r,
orbit.v,
tofs,
ad=atmospheric_drag_model,
R=R,
C_D=C_D,
A=A,
m=m,
model=coesa76,
events=events,
)
assert_quantity_allclose(norm(rr[0].to(u.km).value), R,
atol=1) # below 1km
assert_quantity_allclose(lithobrake_event.last_t, t_decay, rtol=1e-2)
def test_LOS_event_with_lithobrake_event_raises_warning_when_satellite_cuts_attractor(
):
r2 = np.array([-500, 1500, 4012.09]) << u.km
v2 = np.array([5021.38, -2900.7, 1000.354]) << u.km / u.s
orbit = Orbit.from_vectors(Earth, r2, v2)
tofs = [100, 500, 1000, 2000] << u.s
# Propagate the secondary body to generate its position coordinates.
rr, vv = cowell(
Earth.k,
orbit.r,
orbit.v,
tofs,
)
pos_coords = rr # Trajectory of the secondary body.
r1 = np.array([0, -5010.696, -5102.509]) << u.km
v1 = np.array([736.138, 2989.7, 164.354]) << u.km / u.s
orb = Orbit.from_vectors(Earth, r1, v1)
los_event = LosEvent(Earth, pos_coords, terminal=True)
tofs = [
0.003, 0.004, 0.01, 0.02, 0.03, 0.04, 0.07, 0.1, 0.2, 0.3, 0.4, 1, 3
] << u.s
lithobrake_event = LithobrakeEvent(Earth.R.to_value(u.km))
events = [lithobrake_event, los_event]
r, v = cowell(
Earth.k,
orb.r,
orb.v,
tofs,
events=events,
)
assert lithobrake_event.last_t < los_event.last_t
C_D = 2.2
A_over_m = (((4 * np.pi * 0.0144) / 4.0) * (u.m**2) / (48 * u.kg)).to_value(
u.km**2 / u.kg)
B = C_D * A_over_m
rho0 = rho0_earth.to(u.kg / u.km**3).value
H0 = H0_earth.to(u.km).value
orbit = Orbit.circular(Earth,
200 * u.km,
epoch=Time(0.0, format="jd", scale="tdb"))
tofs = TimeDelta(np.linspace(0 * u.h, 100000000 * u.d, num=200))
from poliastro.twobody.events import LithobrakeEvent
lithobrake_event = LithobrakeEvent(R)
events = [lithobrake_event]
rr = propagate(
orbit,
tofs,
method=cowell,
ad=atmospheric_drag_exponential,
R=R,
C_D=C_D,
A_over_m=A_over_m,
H0=H0,
rho0=rho0,
events=events,
)