def Ls(et, return_marsyear=False):
"""Convert string or SPICE ET to Mars solar longitude. Requires SPICE
kernels.
Parameters
----------
et : float or str
Time to convert, either an ET or a format understood
by spiceypy.str2et.
return_marsyear : bool
Whether to return the Mars Year of the input date.
Returns
-------
Ls : float
Mars Solar Longitude
marsyear : int
Mars Year, if requested.
"""
et = check_et(et)
ls = spice.lspcn('MARS', et, 'NONE')
ls = ls * 180 / np.pi
if not return_marsyear:
return ls
marsyear = np.searchsorted(marsyearbounds_et, et)
return ls, marsyear
def spice_positions(self, et: float):
"""Calculate MAVEN spacecraft position, Mars solar longitude, and the
subsolar position for a given ephemeris time.
Parameters
----------
et
Input epoch in ephemeris seconds past J2000.
Returns
-------
et : array
The input ephemeris times. Just givin'em back.
subsc_lat : array
Sub-spacecraft latitudes in degrees.
subsc_lon : array
Sub-spacecraft longitudes in degrees.
sc_alt_km : array
Sub-spacecraft altitudes in kilometers.
ls : array
Mars solar longitudes in degrees.
subsolar_lat : array
Sub-solar latitudes in degrees.
subsolar_lon : array
Sub-solar longitudes in degrees.
mars_sun_km: array
"""
spoint, trgepc, srfvec = \
spice.subpnt('Intercept: ellipsoid', self.__target, et, 'IAU_MARS',
self.__abcorr, self.__observer)
_, _, srvec_sun = \
spice.subpnt('Intercept: ellipsoid', self.__target, et, 'IAU_MARS',
self.__abcorr, 'SUN')
rpoint, colatpoint, lonpoint = spice.recsph(spoint)
if lonpoint > np.pi:
lonpoint -= 2 * np.pi
subsc_lat = 90 - np.degrees(colatpoint)
subsc_lon = np.degrees(lonpoint)
sc_alt_km = np.sqrt(np.sum(srfvec**2))
mars_sun_km = np.sqrt(np.sum(srvec_sun**2))
# calculate subsolar position
sspoint, strgepc, ssrfvec = \
spice.subslr('Intercept: ellipsoid', self.__target, et, 'IAU_MARS',
self.__abcorr, self.__observer)
srpoint, scolatpoint, slonpoint = spice.recsph(sspoint)
if slonpoint > np.pi:
slonpoint -= 2 * np.pi
subsolar_lat = 90 - np.degrees(scolatpoint)
subsolar_lon = np.degrees(slonpoint)
ls = np.degrees(spice.lspcn(self.__target, et, self.__abcorr))
return et, subsc_lat, subsc_lon, sc_alt_km, ls, subsolar_lat, \
subsolar_lon, mars_sun_km
def spice_positions(et):
"""
Calculates MAVEN spacecraft position, Mars solar longitude, and subsolar position for a given ephemeris time.
Parameters
----------
et : float
Input epoch in ephemeris seconds past J2000.
Returns
-------
et : array
The input ephemeris times. Just givin'em back.
subsc_lat : array
Sub-spacecraft latitudes in degrees.
subsc_lon : array
Sub-spacecraft longitudes in degrees.
sc_alt_km : array
Sub-spacecraft altitudes in kilometers.
ls : array
Mars solar longitudes in degrees.
subsolar_lat : array
Sub-solar latitudes in degrees.
subsolar_lon : array
Sub-solar longitudes in degrees.
"""
# do a bunch of SPICE stuff only Justin understands...
target = 'Mars'
abcorr = 'LT+S'
observer = 'MAVEN'
spoint, trgepc, srfvec = spice.subpnt('Intercept: ellipsoid', target, et, 'IAU_MARS', abcorr, observer)
rpoint, colatpoint, lonpoint = spice.recsph(spoint)
if lonpoint > np.pi:
lonpoint -= 2 * np.pi
subsc_lat = 90 - np.degrees(colatpoint)
subsc_lon = np.degrees(lonpoint)
sc_alt_km = np.sqrt(np.sum(srfvec ** 2))
# calculate subsolar position
sspoint, strgepc, ssrfvec = spice.subslr('Intercept: ellipsoid', target, et, 'IAU_MARS', abcorr, observer)
srpoint, scolatpoint, slonpoint = spice.recsph(sspoint)
if slonpoint > np.pi:
slonpoint -= 2 * np.pi
subsolar_lat = 90 - np.degrees(scolatpoint)
subsolar_lon = np.degrees(slonpoint)
# calculate solar longitude
ls = spice.lspcn(target, et, abcorr)
ls = np.degrees(ls)
# return the position information
return et, subsc_lat, subsc_lon, sc_alt_km, ls, subsolar_lat, subsolar_lon
def writeTimeLsToFile():
"""make list of time vs ls"""
SPICE_TARGET = "MARS"
SPICE_ABERRATION_CORRECTION = "None"
DATETIME_FORMAT = "%d/%m/%Y %H:%M"
from datetime import datetime, timedelta
linesToWrite = []
datetimeStart = datetime(2018, 3, 1, 0, 0, 0, 0)
for hoursToAdd in range(0, 24*31*12*3, 6): #3 years
newDatetime = (datetimeStart + timedelta(hours=hoursToAdd)).strftime(DATETIME_FORMAT)
ls = sp.lspcn(SPICE_TARGET, sp.utc2et(str(datetimeStart + timedelta(hours=hoursToAdd))), SPICE_ABERRATION_CORRECTION) * sp.dpr()
linesToWrite.append("%s\t%0.1f" %(newDatetime, ls))
writeOutput("Time_vs_Ls.txt", linesToWrite)
def ls(self, utc, body='Saturn', abcorr='CN+S'):
"""Planetocentric longitude of the sun, as seen from a specified body.
Related orbital seasonal parameter:
- Vernal equinox: Ls = 0º
- Summer solstice: Ls = 90º
- Autumnal equinox: Ls = 180º
- Winter solstice: Ls = 270º
Warning
-------
For the moons the solar longitude must be computed
for the parent body (ie. Saturn for Titan) otherwise
the output value does not provide the correct orbital
seasomal location. Generaly this approximation is
within a fraction of moon's orbit.
Parameters
----------
utc: str
Input time in UTC format.
body: str, optional
Name of the central body.
abcorr: str, optional
Aberration correction.
Returns
-------
float
Solar longitude (in degrees).
"""
et = spice.str2et(utc)
return np.degrees(spice.lspcn(body, et, abcorr))
def f(_t):
return spiceypy.lspcn(body, _t, correction)
def lsubs(et):
return sp.lspcn("MARS", et, abcorr) * sp.dpr()
def l_s(self):
return np.rad2deg(spice.lspcn(self.target, self.et, self.corr))
def _get_l_s(self):
return np.rad2deg(spice.lspcn(self.target, self.et, self.corr))