def get_orbit_number(self, utc_time, tbus_style=False):
"""Calculate orbit number at specified time.
Optionally use TBUS-style orbit numbering (TLE orbit number + 1)
"""
try:
dt = astronomy._days(utc_time - self.orbit_elements.an_time)
orbit_period = astronomy._days(self.orbit_elements.an_period)
except AttributeError:
pos_epoch, vel_epoch = self.get_position(self.tle.epoch,
normalize=False)
if np.abs(pos_epoch[2]) > 1 or not vel_epoch[2] > 0:
# Epoch not at ascending node
self.orbit_elements.an_time = self.get_last_an_time(
self.tle.epoch)
else:
# Epoch at ascending node (z < 1 km) and positive v_z
self.orbit_elements.an_time = self.tle.epoch
self.orbit_elements.an_period = self.orbit_elements.an_time - \
self.get_last_an_time(self.orbit_elements.an_time
- timedelta(minutes=10))
dt = astronomy._days(utc_time - self.orbit_elements.an_time)
orbit_period = astronomy._days(self.orbit_elements.an_period)
orbit = int(self.tle.orbit + dt / orbit_period +
self.tle.mean_motion_derivative * dt**2 +
self.tle.mean_motion_sec_derivative * dt**3)
if tbus_style:
orbit += 1
return orbit
def propagate(self, utc_time):
kep = {}
ts = astronomy._days(utc_time - self.t_0) * XMNPDA
em = self.eo
xinc = self.xincl
xmp = self.xmo + self.xmdot * ts
xnode = self.xnodeo + ts * (self.xnodot + ts * self.xnodcf)
omega = self.omegao + self.omgdot * ts
if self.mode == SGDP4_ZERO_ECC:
raise NotImplementedError('Mode SGDP4_ZERO_ECC not implemented')
elif self.mode == SGDP4_NEAR_SIMP:
raise NotImplementedError('Mode "Near-space, simplified equations"'
' not implemented')
elif self.mode == SGDP4_NEAR_NORM:
delm = self.xmcof * \
((1.0 + self.eta * np.cos(xmp))**3 - self.delmo)
temp0 = ts * self.omgcof + delm
xmp += temp0
omega -= temp0
tempa = 1.0 - \
(ts *
(self.c1 + ts * (self.d2 + ts * (self.d3 + ts * self.d4))))
tempe = self.bstar * \
(self.c4 * ts + self.c5 * (np.sin(xmp) - self.sinXMO))
templ = ts * ts * \
(self.t2cof + ts *
(self.t3cof + ts * (self.t4cof + ts * self.t5cof)))
a = self.aodp * tempa**2
e = em - tempe
xl = xmp + omega + xnode + self.xnodp * templ
else:
raise NotImplementedError('Deep space calculations not supported')
if np.any(a < 1):
raise Exception('Satellite crased at time %s', utc_time)
elif np.any(e < ECC_LIMIT_LOW):
raise ValueError('Satellite modified eccentricity to low: %s < %e'
% (str(e[e < ECC_LIMIT_LOW]), ECC_LIMIT_LOW))
e = np.where(e < ECC_EPS, ECC_EPS, e)
e = np.where(e > ECC_LIMIT_HIGH, ECC_LIMIT_HIGH, e)
beta2 = 1.0 - e**2
# Long period periodics
sinOMG = np.sin(omega)
cosOMG = np.cos(omega)
temp0 = 1.0 / (a * beta2)
axn = e * cosOMG
ayn = e * sinOMG + temp0 * self.aycof
xlt = xl + temp0 * self.xlcof * axn
elsq = axn**2 + ayn**2
if np.any(elsq >= 1):
raise Exception('e**2 >= 1 at %s', utc_time)
kep['ecc'] = np.sqrt(elsq)
epw = np.fmod(xlt - xnode, 2 * np.pi)
# needs a copy in case of an array
capu = np.array(epw)
maxnr = kep['ecc']
for i in range(10):
sinEPW = np.sin(epw)
cosEPW = np.cos(epw)
ecosE = axn * cosEPW + ayn * sinEPW
esinE = axn * sinEPW - ayn * cosEPW
f = capu - epw + esinE
if np.all(np.abs(f) < NR_EPS):
break
df = 1.0 - ecosE
# 1st order Newton-Raphson correction.
nr = f / df
# 2nd order Newton-Raphson correction.
nr = np.where(np.logical_and(i == 0, np.abs(nr) > 1.25 * maxnr),
np.sign(nr) * maxnr,
f / (df + 0.5 * esinE * nr))
epw += nr
# Short period preliminary quantities
temp0 = 1.0 - elsq
betal = np.sqrt(temp0)
pl = a * temp0
r = a * (1.0 - ecosE)
invR = 1.0 / r
temp2 = a * invR
temp3 = 1.0 / (1.0 + betal)
cosu = temp2 * (cosEPW - axn + ayn * esinE * temp3)
sinu = temp2 * (sinEPW - ayn - axn * esinE * temp3)
u = np.arctan2(sinu, cosu)
sin2u = 2.0 * sinu * cosu
cos2u = 2.0 * cosu**2 - 1.0
temp0 = 1.0 / pl
temp1 = CK2 * temp0
temp2 = temp1 * temp0
# Update for short term periodics to position terms.
rk = r * (1.0 - 1.5 * temp2 * betal * self.x3thm1) + \
0.5 * temp1 * self.x1mth2 * cos2u
uk = u - 0.25 * temp2 * self.x7thm1 * sin2u
xnodek = xnode + 1.5 * temp2 * self.cosIO * sin2u
xinck = xinc + 1.5 * temp2 * self.cosIO * self.sinIO * cos2u
if np.any(rk < 1):
raise Exception('Satellite crased at time %s', utc_time)
temp0 = np.sqrt(a)
temp2 = XKE / (a * temp0)
rdotk = ((XKE * temp0 * esinE * invR - temp2 * temp1 * self.x1mth2 * sin2u) *
(XKMPER / AE * XMNPDA / 86400.0))
rfdotk = ((XKE * np.sqrt(pl) * invR + temp2 * temp1 *
(self.x1mth2 * cos2u + 1.5 * self.x3thm1)) *
(XKMPER / AE * XMNPDA / 86400.0))
kep['radius'] = rk * XKMPER / AE
kep['theta'] = uk
kep['eqinc'] = xinck
kep['ascn'] = xnodek
kep['argp'] = omega
kep['smjaxs'] = a * XKMPER / AE
kep['rdotk'] = rdotk
kep['rfdotk'] = rfdotk
return kep