def __init__(self, altitude, inclination, solarmodulation=None):
self.Alt = altitude # instrument altitude (km)
self.magl = inclination # orbit inclination (deg.)
self.geomlat = inclination # geomagnetic latitude (deg.) TODO
# The inclination was used to approximate the average Magnetic Latitude
""" solar modulation potential (MV): ~550 for solar minimum
~1100 for solar maximum
"""
if solarmodulation is None:
self.solmod = 650.
else:
self.solmod = solarmodulation
EarthRadius = R_earth.to('km').value
""" Average Geomagnetic cutoff in GV
for a dipole approximations
Equation 4 Smart et al. 2005
doi:10.1016/j.asr.2004.09.015
"""
R_E = R_earth.to('cm').value
# g 01 term (in units of G) from IGRF-12 for 2015
g10 = 29442 * 10**(-9) * 10**4 # G
M = g10 * R_E * 300 / 10**9 # GV/cm2
self.AvGeomagCutOff = (M / 4 * (1 + self.Alt / EarthRadius)**(-2.0) *
np.cos(np.deg2rad(self.geomlat))**4)
AtmosphereHeight = 40 # km
self.HorizonAngle = 90.0 + np.rad2deg(
np.arccos(
(EarthRadius + AtmosphereHeight) / (EarthRadius + self.Alt)))
def moon_distance(loc, t2, t3):
# Get the distance to the moon via the umbra diameter estimate
if isinstance(loc, type(u'')) or isinstance(loc, type('')):
loc = EarthLocation.of_address(loc)
# Location of Sun & Moon
sun = get_sun(t2)
moon = get_moon(t2, loc)
# Umbra size, from time and location
su = estimate_umbra(loc, t2, t3)
# Constants in km
re = R_earth.to(u.km).value
ds = sun.distance.to(u.km).value
rs = R_sun.to(u.km).value
rm = 1738.1
dm = (2 * rm - su) * ds / (2 * (rs - rm)) + re
print(
'Distance estimate: {:.7} km (Actual: {:.7}). Ratio: {:.2}. Difference: {:.7}'
.format(dm, moon.distance, moon.distance / (dm * u.km),
dm * u.km - moon.distance))
# moon.distance is from surface, not center
return dm, moon.distance.to(u.km).value + re
def test_vallado61(self):
alt_i = 191.34411 # km
alt_f = 35781.34857 # km
k = k_earth.to(units.km ** 3 / units.s ** 2).value
R = R_earth.to(units.km).value
expected_dv = 3.935224 # km/s
expected_t_trans = 5.256713 # h
r_i = R + alt_i
r_f = R + alt_f
dva, dvb, _, t_trans = hohmann(k, r_i, r_f)
dv = abs(dva) + abs(dvb)
assert_almost_equal(dv, expected_dv, decimal=2)
assert_almost_equal(t_trans / 3600, expected_t_trans, decimal=2)
def test_vallado62(self):
alt_i = 191.34411 # km
alt_b = 503873 # km
alt_f = 376310.0 # km
k = k_earth.to(units.km ** 3 / units.s ** 2).value
R = R_earth.to(units.km).value
expected_dv = 3.904057 # km/s
expected_t_trans = 593.919803 # h
r_i = R + alt_i
r_b = R + alt_b
r_f = R + alt_f
dva, dvb, dvc, _, _, t_trans1, t_trans2 = bielliptic(k, r_i, r_b, r_f)
dv = abs(dva) + abs(dvb) + abs(dvc)
t_trans = t_trans1 + t_trans2
assert_almost_equal(dv, expected_dv, decimal=2)
assert_almost_equal(t_trans / 3600, expected_t_trans, decimal=0)
def get_umbra(loc, t2):
# Get the real size of the umbra
sun = get_sun(t2)
moon = get_moon(t2, loc)
sun_altaz = sun.transform_to(AltAz(obstime=t2, location=loc))
# Constants in km
re = R_earth.to(u.km).value
ds = sun.distance.to(u.km).value
rs = R_sun.to(u.km).value
rm = 1738.1
alpha = np.arcsin((rs - rm) / (ds - moon.distance.to(u.km).value))
su = 2 * (rm / np.sin(alpha) -
(moon.distance.to(u.km).value - re)) * np.tan(alpha)
su / np.tan(sun_altaz.alt.to(u.rad)) # not 100% sure of this
return su
symbol : str, optional
Symbol for the body, default to None.
R : Quantity, optional
Radius of the body, default to 0 km.
"""
if not check_units((k, R), (u.m ** 3 / u.s ** 2, u.m)):
raise u.UnitsError("Units must be consistent")
self.k = k
self.name = name
self.symbol = symbol
self.R = R
def __str__(self):
return u"{} ({})".format(self.name, self.symbol)
def _repr_latex_(self):
"""Creates a LaTeX representation.
Used by the IPython notebook.
"""
return self.__str__()
Sun = Body(k=132712440018 * u.km ** 3 / u.s ** 2,
name="Sun", symbol=u"\u2609")
Earth = Body(k=398600 * u.km ** 3 / u.s ** 2,
name="Earth", symbol=u"\u2641", R=R_earth.to(u.km))
self.k = k
self.name = name
self.symbol = symbol
self.R = R
@classmethod
@u.quantity_input(k=u.km**3 / u.s**2, R=u.km)
def from_parameters(cls, k, name, symbol, R):
return cls(k, name, symbol, R)
def __str__(self):
return u"{0} ({1})".format(self.name, self.symbol)
def _repr_latex_(self):
"""Creates a LaTeX representation.
Used by the IPython notebook.
"""
return self.__str__()
Sun = Body.from_parameters(k=132712440018 * u.km**3 / u.s**2,
name="Sun",
symbol=u"\u2609",
R=695700 * u.km)
Earth = Body.from_parameters(k=398600 * u.km**3 / u.s**2,
name="Earth",
symbol=u"\u2641",
R=R_earth.to(u.km))
def estimate_umbra(loc, t2, t3, verbose=False):
# Estimate the size of the umbra from the contact times (not 100% sure on this yet)
delta_t = t3 - t2
# Location of Sun
sun = get_sun(t2)
sun_altaz = sun.transform_to(AltAz(obstime=t2, location=loc))
# Umbra size, from time and location
s_umbra = 2 * np.pi * R_earth * np.cos(loc.latitude.to(
u.rad)) / u.day * delta_t
s_umbra /= np.tan(sun_altaz.alt.to(
u.rad)) # correction for altitude (correct?)
su = s_umbra.to(u.km).value
# Extra corrections for projection/location from central line
# TODO: Need to check if this is the right approach
df = get_path()
df['sep'] = ang_sep(loc, df['clon'], df['clat']) * 2 * np.pi * R_earth.to(
u.km).value / 360.
ind = df[df['sep'] == min(df['sep'])].index[0]
# Replace with finer version
x2 = 41.
x1 = 0.
df_fine = pd.DataFrame(np.arange(x1, x2, 1), columns=['xval'])
df_fine['clat'] = make_fine('clat', ind, df, x1=x1, x2=x2)
df_fine['clon'] = make_fine('clon', ind, df, x1=x1, x2=x2)
df_fine['width'] = make_fine('width', ind, df, x1=x1, x2=x2)
# Get new best index
df_fine['sep'] = ang_sep(loc, df_fine['clon'],
df_fine['clat']) * 2 * np.pi * R_earth.to(
u.km).value / 360.
ind = df_fine[df_fine['sep'] == min(df_fine['sep'])].index[0]
df = df_fine
# Get the angle
factor = np.pi / 180
lat1 = df.loc[ind, 'clat'] * factor
lat2 = lat1
dlon = (df.loc[ind, 'clon'] - df.loc[ind - 1, 'clon']) * factor
theta1 = np.arctan2(
np.sin(dlon) * np.cos(lat2),
np.cos(lat1) * np.sin(lat2) -
np.sin(lat1) * np.cos(lat2) * np.cos(dlon)) / factor
lat2 = df.loc[ind - 1, 'clat'] * factor
theta2 = np.arctan2(
np.sin(dlon) * np.cos(lat2),
np.cos(lat1) * np.sin(lat2) -
np.sin(lat1) * np.cos(lat2) * np.cos(dlon)) / factor
theta = abs(theta1 - theta2)
# Modify the umbra size
# TODO: This still needs more work as it doesn't give an approximately correct value
ratio = 0.5 * df.loc[ind, 'width'] / (0.5 * df.loc[ind, 'width'] -
df.loc[ind, 'sep'])
su2 = su * ratio / np.cos(theta * factor)
if verbose:
print(df.loc[ind, ['clon', 'clat', 'width', 'sep']])
print('Angle: {} (Cosine: {})'.format(theta, np.cos(theta * factor)))
print('Ratio: {}'.format(ratio))
print('{} -> {}'.format(su, su2))
return su2
def get_observatory_info(self, time_delta=None):
"""Compute the lat/lon and altitude of HST.
Using the expstart and expend, generate a series MJD dates that correspond
to 1 minute intervals. Calculate the lat/lon and altitude at each
time step.
"""
altitude_list = []
lat_list = []
lon_list = []
# Break up the exposure into one minute intervals
if time_delta is None:
time_delta = self.metadata['expend'] - self.metadata['expstart']
num_intervals = 2*int(time_delta.to('minute').value)
expend = self.metadata['expend'].mjd
else:
expend= self.metadata['expstart'].mjd + time_delta/86400.0
num_intervals = int(np.round(time_delta/60))
# If the number of one minute intervals is less than 2, set the number
# of intervals to 5 (arbitrarily chosen)
if num_intervals < 2:
num_intervals = 5
# Generate MJD dates correspond to these one minute intervals
time_intervals = np.linspace(self.metadata['expstart'].mjd,
expend,
num_intervals,
endpoint=True)
# Generate the path to the engineering file
self._engineering_file()
# Using the telemetry data for the SPT file, compute HST (lon, lat, z)
if os.path.isfile(self.telemetry_file):
orbital_params = orbit.HSTOrbit(self.telemetry_file)
# compute coords at beginning and end of exposure
for t in time_intervals:
rect, vel = orbital_params.getPos(t)
r, ra, dec = rectToSph(rect)
altitude_list.append(r - R_earth.to('km').value)
lat = dec
lon = ra - 2 * np.pi * gmst(t)
if lon < 0:
lon += 2 * np.pi
lon /= DEGtoRAD
lat /= DEGtoRAD
lat_list.append(lat)
lon_list.append(lon)
self.metadata['latitude'] = np.asarray(lat_list)
self.metadata['longitude'] = np.asarray(lon_list)
self.metadata['altitude'] = np.asarray(altitude_list)
self.metadata['time_intervals'] = time_intervals
else:
LOG.info('SPT file not found, place it in the data directory')
# If the SPT file for some reason doesn't exist, save NaNs
self.metadata['altitude'] = np.nan
self.metadata['latitude'] = np.nan
self.metadata['longitude'] = np.nan
self.metadata['time_intervals'] = np.nan