def carrington_rotation_number(t='now'):
"""
Return the Carrington Rotation number
"""
jd = julian_day(t)
result = (1. / 27.2753) * (jd - 2398167.0) + 1.0
return result
def carrington_rotation_number(t='now'):
"""
Return the Carrington Rotation number
"""
jd = julian_day(t)
result = (1. / 27.2753) * (jd - 2398167.0) + 1.0
return result
def test():
"""
Print out a summary of Solar ephemeris
A correct answer set to compare to
Solar Ephemeris for 1-JAN-01 00:00:00
Distance (AU) = 0.98330468
Semidiameter (arc sec) = 975.92336
True (long, lat) in degrees = (280.64366, 0.00000)
Apparent (long, lat) in degrees = (280.63336, 0.00000)
True (RA, Dec) in hrs, deg = (18.771741, -23.012449)
Apparent (RA, Dec) in hrs, deg = (18.770994, -23.012593)
Heliographic long. and lat. of disk center in deg = (217.31269, -3.0416292)
Position angle of north pole in deg = 2.0102649
Carrington Rotation Number = 1971.4091 check!
"""
t = '2001-01-01T00:00:00'
swpy_jd = swdt.julian_day(t)
sunpy_jd = sunt.julian_day(t)
print "SWPY JD: {}, SUNPY JD: {}".format(swpy_jd,sunpy_jd)
print "Sun-earth distance: {}, {}".format(
sun.sunearth_distance(t),
ssun.sunearth_distance(t))
print "Solar semidiameter angular size: {}, {}".format(
sun.solar_semidiameter_angular_size(t),
sun.solar_semidiameter_angular_size(t))
print "True longitude: {}, {}".format(sun.true_longitude(t),
ssun.true_longitude(t))
print "Apparent Longitude: {}, {}".format(sun.apparent_longitude(t),
ssun.apparent_longitude(t))
print "True R.A.: {}, {}".format(
sun.true_rightascension(t),
ssun.true_rightascension(t))
print "True Dec.: {}, {}".format(sun.true_declination(t),
ssun.true_declination(t))
print "Apparent R.A.: {}, {}".format(
sun.apparent_rightascension(t),
ssun.apparent_rightascension(t))
print "Apparent Dec.: {}, {}".format(sun.apparent_declination(t),
ssun.apparent_declination(t))
print "Heliographic center: {}, {}".format(sun.heliographic_solar_center(t),
ssun.heliographic_solar_center(t))
print "Position angle of north pole [deg]: {}, {}".format(sun.solar_north(t),
ssun.solar_north(t))
print "Carrington rotation number: {}, {}".format(sun.carrington_rotation_number(t),
ssun.carrington_rotation_number(t))
def heliographic_solar_center(t='now'):
"""Returns the position of the solar center in heliographic coordinates."""
jd = julian_day(t)
T = julian_centuries(t)
# Heliographic coordinates in degrees
theta = ((jd - 2398220)*360/25.38) * u.deg
i = 7.25 * u.deg
k = (74.3646 + 1.395833 * T) * u.deg
lamda = true_longitude(t) - 0.00569 * u.deg
diff = lamda - k
# Latitude at center of disk (deg):
he_lat = np.degrees(np.arcsin(np.sin(diff)*np.sin(i)))
# Longitude at center of disk (deg):
y = -np.sin(diff)*np.cos(i)
x = -np.cos(diff)
rpol = (np.arctan2(y, x))
he_lon = rpol - theta
return [Longitude(he_lon), Latitude(he_lat)]
def heliographic_solar_center(t='now'):
"""Returns the position of the solar center in heliographic coordinates."""
jd = julian_day(t)
T = julian_centuries(t)
# Heliographic coordinates in degrees
theta = ((jd - 2398220)*360/25.38) * u.deg
i = 7.25 * u.deg
k = (74.3646 + 1.395833 * T) * u.deg
lamda = true_longitude(t) - 0.00569 * u.deg
diff = lamda - k
# Latitude at center of disk (deg):
he_lat = np.arcsin(np.sin(diff)*np.sin(i))
# Longitude at center of disk (deg):
y = -np.sin(diff)*np.cos(i)
x = -np.cos(diff)
rpol = (np.arctan2(y, x))
he_lon = rpol - theta
return (Longitude(he_lon.to(u.deg)), Latitude(he_lat.to(u.deg)))
def heliographic_solar_center(t=None):
"""Returns the position of the solar center in heliographic coordinates."""
jd = julian_day(t)
T = julian_centuries(t)
# Heliographic coordinates in degrees
theta = (jd - 2398220) * 360 / 25.38
i = 7.25
k = 74.3646 + 1.395833 * T
lamda = true_longitude(t) - 0.00569
#omega = apparent_longitude(t)
#lamda2 = lamda - 0.00479 * math.sin(np.radians(omega))
diff = np.radians(lamda - k)
# Latitude at center of disk (deg):
he_lat = np.degrees(math.asin(math.sin(diff) * math.sin(np.radians(i))))
# Longitude at center of disk (deg):
y = -math.sin(diff) * math.cos(np.radians(i))
x = -math.cos(diff)
rpol = cmath.polar(complex(x, y))
he_lon = np.degrees(rpol[1]) - theta
he_lon = he_lon % 360
if he_lon < 0:
he_lon = he_lon + 360.0
return [he_lon, he_lat]
def heliographic_solar_center(t=None):
"""Returns the position of the solar center in heliographic coordinates."""
jd = julian_day(t)
T = julian_centuries(t)
# Heliographic coordinates in degrees
theta = (jd - 2398220)*360/25.38
i = 7.25
k = 74.3646 + 1.395833 * T
lamda = true_longitude(t) - 0.00569
#omega = apparent_longitude(t)
#lamda2 = lamda - 0.00479 * math.sin(np.radians(omega))
diff = np.radians(lamda - k)
# Latitude at center of disk (deg):
he_lat = np.degrees(np.arcsin(np.sin(diff)*np.sin(np.radians(i))))
# Longitude at center of disk (deg):
y = -np.sin(diff)*np.cos(np.radians(i))
x = -np.cos(diff)
rpol = cmath.polar(complex(x,y))
he_lon = np.degrees(rpol[1]) - theta
he_lon = he_lon % 360
if he_lon < 0:
he_lon = he_lon + 360.0
return [he_lon, he_lat]
def _sun_pos(date):
"""
Calculate solar ephemeris parameters. Allows for planetary and lunar
perturbations in the calculation of solar longitude at date and various
other solar positional parameters. This routine is a truncated version of
Newcomb's Sun and is designed to give apparent angular coordinates (T.E.D)
to a precision of one second of time. This function replicates the SSW/
IDL function "sun_pos.pro". This function is assigned to be
internal at the moment as it should really be replaced by accurate
ephemeris calculations in the part of SunPy that handles ephemeris.
Parameters
-----------
date : `sunpy.time.time`
Time at which the solar ephemeris parameters are calculated. The
input time can be in any acceptable time format.
Returns
-------
A dictionary with the following keys with the following meanings:
longitude - Longitude of sun for mean equinox of date (degs)
ra - Apparent RA for true equinox of date (degs)
dec - Apparent declination for true equinox of date (degs)
app_long - Apparent longitude (degs)
obliq - True obliquity (degs)
Notes
-----
SSWIDL code equivalent:
http://hesperia.gsfc.nasa.gov/ssw/gen/idl/solar/sun_pos.pro
Examples
--------
>>> sp = _sun_pos('2013-03-27')
"""
# Fractional Julian day with correct offset
dd = julian_day(date) - 2415020.0
# form time in Julian centuries from 1900.0
t = dd / 36525.0
# form sun's mean longitude
l = (279.6966780 + np.mod(36000.7689250 * t, 360.00)) * 3600.0
# allow for ellipticity of the orbit (equation of centre) using the Earth's
# mean anomaly ME
me = 358.4758440 + np.mod(35999.049750 * t, 360.0)
ellcor = (6910.10 - 17.20 * t) * np.sin(np.deg2rad(me)) + \
72.30 * np.sin(np.deg2rad(2.0 * me))
l = l + ellcor
# allow for the Venus perturbations using the mean anomaly of Venus MV
mv = 212.603219 + np.mod(58517.8038750 * t, 360.0)
vencorr = 4.80 * np.cos(np.deg2rad(299.10170 + mv - me)) + \
5.50 * np.cos(np.deg2rad(148.31330 + 2.0 * mv - 2.0 * me)) + \
2.50 * np.cos(np.deg2rad(315.94330 + 2.0 * mv - 3.0 * me)) + \
1.60 * np.cos(np.deg2rad(345.25330 + 3.0 * mv - 4.0 * me)) + \
1.00 * np.cos(np.deg2rad(318.150 + 3.0 * mv - 5.0 * me))
l = l + vencorr
# Allow for the Mars perturbations using the mean anomaly of Mars MM
mm = 319.5294250 + np.mod(19139.858500 * t, 360.0)
marscorr = 2.0 * np.cos(np.deg2rad(343.88830 - 2.0 * mm + 2.0 * me)) + \
1.80 * np.cos(np.deg2rad(200.40170 - 2.0 * mm + me))
l = l + marscorr
# Allow for the Jupiter perturbations using the mean anomaly of Jupiter MJ
mj = 225.3283280 + np.mod(3034.69202390 * t, 360.00)
jupcorr = 7.20 * np.cos(np.deg2rad(179.53170 - mj + me)) + \
2.60 * np.cos(np.deg2rad(263.21670 - mj)) + \
2.70 * np.cos(np.deg2rad(87.14500 - 2.0 * mj + 2.0 * me)) + \
1.60 * np.cos(np.deg2rad(109.49330 - 2.0 * mj + me))
l = l + jupcorr
# Allow for the Moons perturbations using the mean elongation of the Moon
# from the Sun D
d = 350.73768140 + np.mod(445267.114220 * t, 360.0)
mooncorr = 6.50 * np.sin(np.deg2rad(d))
l = l + mooncorr
# Note the original code is
# longterm = + 6.4d0 * sin(( 231.19d0 + 20.20d0 * t )*!dtor)
longterm = 6.40 * np.sin(np.deg2rad(231.190 + 20.20 * t))
l = l + longterm
l = np.mod(l + 2592000.0, 1296000.0)
longmed = l / 3600.0
# Allow for Aberration
l = l - 20.5
# Allow for Nutation using the longitude of the Moons mean node OMEGA
omega = 259.1832750 - np.mod(1934.1420080 * t, 360.0)
l = l - 17.20 * np.sin(np.deg2rad(omega))
# Form the True Obliquity
oblt = 23.4522940 - 0.01301250 * t + \
(9.20 * np.cos(np.deg2rad(omega))) / 3600.0
# Form Right Ascension and Declination
l = l / 3600.0
ra = np.rad2deg(np.arctan2(np.sin(np.deg2rad(l)) * \
np.cos(np.deg2rad(oblt)), np.cos(np.deg2rad(l))))
if isinstance(ra, np.ndarray):
ra[ra < 0.0] += 360.0
elif ra < 0.0:
ra = ra + 360.0
dec = np.rad2deg(np.arcsin(np.sin(np.deg2rad(l)) *
np.sin(np.deg2rad(oblt))))
# convert the internal variables to those listed in the top of the
# comment section in this code and in the original IDL code. Quantities
# are assigned following the advice in Astropy "Working with Angles"
return {"longitude": Longitude(longmed, u.deg),
"ra": Longitude(ra, u.deg),
"dec": Latitude(dec, u.deg),
"app_long": Longitude(l, u.deg),
"obliq": Angle(oblt, u.deg)}
def _calc_P_B0_SD(date):
"""
To calculate the solar P, B0 angles and the semi-diameter as seen from
Earth. This function is assigned as being internal as these quantities
should be calculated in a part of SunPy that can calculate these quantities
accurately.
Parameters
-----------
date: `sunpy.time.time`
the time at which to calculate the solar P, B0 angles and the
semi-diameter.
Returns
-------
A dictionary with the following keys with the following meanings:
p - Solar P (position angle of pole) (degrees)
b0 - latitude of point at disk centre (degrees)
sd - semi-diameter of the solar disk in arcminutes
Notes
-----
SSWIDL code equivalent:
http://hesperia.gsfc.nasa.gov/ssw/gen/idl/solar/pb0r.pro
"""
# number of Julian days since 2415020.0
de = julian_day(parse_time(date)) - 2415020.0
# get the longitude of the sun etc.
sun_position = _sun_pos(date)
longmed = sun_position["longitude"].to(u.deg).value
#ra = sun_position["ra"]
#dec = sun_position["dec"]
appl = sun_position["app_long"].to(u.deg).value
oblt = sun_position["obliq"].to(u.deg).value
# form the aberrated longitude
Lambda = longmed - (20.50 / 3600.0)
# form longitude of ascending node of sun's equator on ecliptic
node = 73.6666660 + (50.250 / 3600.0) * ((de / 365.250) + 50.0)
arg = Lambda - node
# calculate P, the position angle of the pole
p = np.rad2deg(
np.arctan(-np.tan(np.deg2rad(oblt)) * np.cos(np.deg2rad(appl))) +
np.arctan(-0.127220 * np.cos(np.deg2rad(arg))))
# B0 the tilt of the axis...
b = np.rad2deg(np.arcsin(0.12620 * np.sin(np.deg2rad(arg))))
# ... and the semi-diameter
# Form the mean anomalies of Venus(MV),Earth(ME),Mars(MM),Jupiter(MJ)
# and the mean elongation of the Moon from the Sun(D).
t = de / 36525.0
mv = 212.60 + np.mod(58517.80 * t, 360.0)
me = 358.4760 + np.mod(35999.04980 * t, 360.0)
mm = 319.50 + np.mod(19139.860 * t, 360.0)
mj = 225.30 + np.mod(3034.690 * t, 360.0)
d = 350.70 + np.mod(445267.110 * t, 360.0)
# Form the geocentric distance(r) and semi-diameter(sd)
r = 1.0001410 - (0.0167480 - 0.00004180 * t) * np.cos(np.deg2rad(me)) \
- 0.000140 * np.cos(np.deg2rad(2.0 * me)) \
+ 0.0000160 * np.cos(np.deg2rad(58.30 + 2.0 * mv - 2.0 * me)) \
+ 0.0000050 * np.cos(np.deg2rad(209.10 + mv - me)) \
+ 0.0000050 * np.cos(np.deg2rad(253.80 - 2.0 * mm + 2.0 * me)) \
+ 0.0000160 * np.cos(np.deg2rad(89.50 - mj + me)) \
+ 0.0000090 * np.cos(np.deg2rad(357.10 - 2.0 * mj + 2.0 * me)) \
+ 0.0000310 * np.cos(np.deg2rad(d))
sd_const = constants.radius / constants.au
sd = np.arcsin(sd_const / r) * 10800.0 / np.pi
return {"p": Angle(p, u.deg),
"b0": Angle(b, u.deg),
"sd": Angle(sd.value, u.arcmin),
"l0": Angle(0.0, u.deg)}
def pb0r(date, stereo=None, soho=False, arcsec=False):
# Ejemplo:
# >> from cjd_pylib import pb0r
# >> A = pb0r.pb0r('2014-06-17T09:35:00')
# {'p': -8.8133708, 'b0': 1.2762924, 'l0': 0.0, 'sd': 15.732692}
"""To calculate the solar P, B0 angles and the semi-diameter.
Parameters
-----------
date: a date/time object - the date/time specified in any CDS format
stereo: { 'A' | 'B' | None }
calculate the solar P, B0 angles and the semi-diameter from the point
of view of either of the STEREO spacecraft.
soho: { False | True }
calculate the solar P, B0 angles and the semi-diameter from the point
of view of the SOHO spacecraft. SOHO sits at the Lagrange L1 point
which is about 1% closer to the Sun than the Earth. Implementation
of this seems to require the ability to read SOHO orbit files.
arcsec: { False | True }
return the semi-diameter in arcseconds.
Returns:
-------
A dictionary with the following keys with the following meanings:
p - Solar P (position angle of pole) (degrees)
b0 - latitude of point at disk centre (degrees)
sd - semi-diameter of the solar disk in arcminutes
See Also
--------
IDL code equavalent:
http://hesperia.gsfc.nasa.gov/ssw/gen/idl/solar/pb0r.pro
"""
if (stereo is not None) and soho:
raise ValueError("Cannot set STEREO and SOHO simultaneously")
# place holder for STEREO calculation
if stereo is not None:
raise ValueError("STEREO solar P, B0 and semi-diameter calcution" + \
" is not supported.")
# number of Julian days since 2415020.0
de = julian_day(date) - 2415020.0
# get the longitude of the sun etc.
sun_position = sun_pos(date)
longmed = sun_position["longitude"]
#ra = sun_position["ra"]
#dec = sun_position["dec"]
appl = sun_position["app_long"]
oblt = sun_position["obliq"]
# form the aberrated longitude
Lambda = longmed - (20.50 / 3600.0)
# form longitude of ascending node of sun's equator on ecliptic
node = 73.6666660 + (50.250 / 3600.0) * ((de / 365.250) + 50.0)
arg = Lambda - node
# calculate P, the position angle of the pole
p = np.rad2deg(\
np.arctan(-np.tan(np.deg2rad(oblt)) * np.cos(np.deg2rad(appl))) + \
np.arctan(-0.127220 * np.cos(np.deg2rad(arg))))
# B0 the tilt of the axis...
b = np.rad2deg(np.arcsin(0.12620 * np.sin(np.deg2rad(arg))))
# ... and the semi-diameter
# Form the mean anomalies of Venus(MV),Earth(ME),Mars(MM),Jupiter(MJ)
# and the mean elongation of the Moon from the Sun(D).
t = de / 36525.0
mv = 212.60 + np.mod(58517.80 * t, 360.0)
me = 358.4760 + np.mod(35999.04980 * t, 360.0)
mm = 319.50 + np.mod(19139.860 * t, 360.0)
mj = 225.30 + np.mod(3034.690 * t, 360.0)
d = 350.70 + np.mod(445267.110 * t, 360.0)
# Form the geocentric distance(r) and semi-diameter(sd)
r = 1.0001410 - (0.0167480 - 0.00004180 * t) * np.cos(np.deg2rad(me)) \
- 0.000140 * np.cos(np.deg2rad(2.0 * me)) \
+ 0.0000160 * np.cos(np.deg2rad(58.30 + 2.0 * mv - 2.0 * me)) \
+ 0.0000050 * np.cos(np.deg2rad(209.10 + mv - me)) \
+ 0.0000050 * np.cos(np.deg2rad(253.80 - 2.0 * mm + 2.0 * me)) \
+ 0.0000160 * np.cos(np.deg2rad(89.50 - mj + me)) \
+ 0.0000090 * np.cos(np.deg2rad(357.10 - 2.0 * mj + 2.0 * me)) \
+ 0.0000310 * np.cos(np.deg2rad(d))
sd_const = constants.radius / constants.au
sd = np.arcsin(sd_const / r) * 10800.0 / np.pi
# place holder for SOHO correction
if soho:
raise ValueError("SOHO correction (on the order of 1% " + \
"since SOHO sets at L1) not yet supported.")
if arcsec:
return {"p": p, "b0": b, "sd": sd * 60.0}
else:
return {"p": p, "b0": b, "sd": sd, "l0": 0.0}
def sun_pos(date, is_julian=False, since_2415020=False):
""" Calculate solar ephemeris parameters. Allows for planetary and lunar
perturbations in the calculation of solar longitude at date and various
other solar positional parameters. This routine is a truncated version of
Newcomb's Sun and is designed to give apparent angular coordinates (T.E.D)
to a precision of one second of time.
Parameters
-----------
date: a date/time object or a fractional number of days since JD 2415020.0
is_julian: { False | True }
notify this routine that the variable "date" is a Julian date
(a floating point number)
since_2415020: { False | True }
notify this routine that the variable "date" has been corrected for
the required time offset
Returns:
-------
A dictionary with the following keys with the following meanings:
longitude - Longitude of sun for mean equinox of date (degs)
ra - Apparent RA for true equinox of date (degs)
dec - Apparent declination for true equinox of date (degs)
app_long - Apparent longitude (degs)
obliq - True obliquity (degs)longditude_delta:
See Also
--------
IDL code equavalent:
http://hesperia.gsfc.nasa.gov/ssw/gen/idl/solar/sun_pos.pro
Examples
--------
>>> sp = sun_pos('2013-03-27')
"""
# check the time input
if is_julian:
# if a Julian date is being passed in
if since_2415020:
dd = date
else:
dd = date - 2415020.0
else:
# parse the input time as a julian day
if since_2415020:
dd = julian_day(date)
else:
dd = julian_day(date) - 2415020.0
# form time in Julian centuries from 1900.0
t = dd / 36525.0
# form sun's mean longitude
l = (279.6966780 + np.mod(36000.7689250 * t, 360.00)) * 3600.0
# allow for ellipticity of the orbit (equation of centre) using the Earth's
# mean anomaly ME
me = 358.4758440 + np.mod(35999.049750 * t, 360.0)
ellcor = (6910.10 - 17.20 * t) * np.sin(np.deg2rad(me)) + \
72.30 * np.sin(np.deg2rad(2.0 * me))
l = l + ellcor
# allow for the Venus perturbations using the mean anomaly of Venus MV
mv = 212.603219 + np.mod(58517.8038750 * t, 360.0)
vencorr = 4.80 * np.cos(np.deg2rad(299.10170 + mv - me)) + \
5.50 * np.cos(np.deg2rad(148.31330 + 2.0 * mv - 2.0 * me)) + \
2.50 * np.cos(np.deg2rad(315.94330 + 2.0 * mv - 3.0 * me)) + \
1.60 * np.cos(np.deg2rad(345.25330 + 3.0 * mv - 4.0 * me)) + \
1.00 * np.cos(np.deg2rad(318.150 + 3.0 * mv - 5.0 * me))
l = l + vencorr
# Allow for the Mars perturbations using the mean anomaly of Mars MM
mm = 319.5294250 + np.mod(19139.858500 * t, 360.0)
marscorr = 2.0 * np.cos(np.deg2rad(343.88830 - 2.0 * mm + 2.0 * me)) + \
1.80 * np.cos(np.deg2rad(200.40170 - 2.0 * mm + me))
l = l + marscorr
# Allow for the Jupiter perturbations using the mean anomaly of Jupiter MJ
mj = 225.3283280 + np.mod(3034.69202390 * t, 360.00)
jupcorr = 7.20 * np.cos(np.deg2rad(179.53170 - mj + me)) + \
2.60 * np.cos(np.deg2rad(263.21670 - mj)) + \
2.70 * np.cos(np.deg2rad(87.14500 - 2.0 * mj + 2.0 * me)) + \
1.60 * np.cos(np.deg2rad(109.49330 - 2.0 * mj + me))
l = l + jupcorr
# Allow for the Moons perturbations using the mean elongation of the Moon
# from the Sun D
d = 350.73768140 + np.mod(445267.114220 * t, 360.0)
mooncorr = 6.50 * np.sin(np.deg2rad(d))
l = l + mooncorr
# Note the original code is
# longterm = + 6.4d0 * sin(( 231.19d0 + 20.20d0 * t )*!dtor)
longterm = 6.40 * np.sin(np.deg2rad(231.190 + 20.20 * t))
l = l + longterm
l = np.mod(l + 2592000.0, 1296000.0)
longmed = l / 3600.0
# Allow for Aberration
l = l - 20.5
# Allow for Nutation using the longitude of the Moons mean node OMEGA
omega = 259.1832750 - np.mod(1934.1420080 * t, 360.0)
l = l - 17.20 * np.sin(np.deg2rad(omega))
# Form the True Obliquity
oblt = 23.4522940 - 0.01301250 * t + \
(9.20 * np.cos(np.deg2rad(omega))) / 3600.0
# Form Right Ascension and Declination
l = l / 3600.0
ra = np.rad2deg(np.arctan2(np.sin(np.deg2rad(l)) * \
np.cos(np.deg2rad(oblt)), np.cos(np.deg2rad(l))))
if isinstance(ra, np.ndarray):
ra[ra < 0.0] += 360.0
elif ra < 0.0:
ra = ra + 360.0
dec = np.rad2deg(np.arcsin(np.sin(np.deg2rad(l)) * \
np.sin(np.deg2rad(oblt))))
# convert the internal variables to those listed in the top of the
# comment section in this code and in the original IDL code.
return {"longitude": longmed, "ra": ra, "dec": dec, "app_long": l,
"obliq": oblt}
def pb0r(date, stereo=None, soho=False, arcsec=False):
# Ejemplo:
# >> from cjd_pylib import pb0r
# >> A = pb0r.pb0r('2014-06-17T09:35:00')
# {'p': -8.8133708, 'b0': 1.2762924, 'l0': 0.0, 'sd': 15.732692}
"""To calculate the solar P, B0 angles and the semi-diameter.
Parameters
-----------
date: a date/time object - the date/time specified in any CDS format
stereo: { 'A' | 'B' | None }
calculate the solar P, B0 angles and the semi-diameter from the point
of view of either of the STEREO spacecraft.
soho: { False | True }
calculate the solar P, B0 angles and the semi-diameter from the point
of view of the SOHO spacecraft. SOHO sits at the Lagrange L1 point
which is about 1% closer to the Sun than the Earth. Implementation
of this seems to require the ability to read SOHO orbit files.
arcsec: { False | True }
return the semi-diameter in arcseconds.
Returns:
-------
A dictionary with the following keys with the following meanings:
p - Solar P (position angle of pole) (degrees)
b0 - latitude of point at disk centre (degrees)
sd - semi-diameter of the solar disk in arcminutes
See Also
--------
IDL code equavalent:
http://hesperia.gsfc.nasa.gov/ssw/gen/idl/solar/pb0r.pro
"""
if (stereo is not None) and soho:
raise ValueError("Cannot set STEREO and SOHO simultaneously")
# place holder for STEREO calculation
if stereo is not None:
raise ValueError("STEREO solar P, B0 and semi-diameter calcution" + \
" is not supported.")
# number of Julian days since 2415020.0
de = julian_day(date) - 2415020.0
# get the longitude of the sun etc.
sun_position = sun_pos(date)
longmed = sun_position["longitude"]
#ra = sun_position["ra"]
#dec = sun_position["dec"]
appl = sun_position["app_long"]
oblt = sun_position["obliq"]
# form the aberrated longitude
Lambda = longmed - (20.50 / 3600.0)
# form longitude of ascending node of sun's equator on ecliptic
node = 73.6666660 + (50.250 / 3600.0) * ((de / 365.250) + 50.0)
arg = Lambda - node
# calculate P, the position angle of the pole
p = np.rad2deg(\
np.arctan(-np.tan(np.deg2rad(oblt)) * np.cos(np.deg2rad(appl))) + \
np.arctan(-0.127220 * np.cos(np.deg2rad(arg))))
# B0 the tilt of the axis...
b = np.rad2deg(np.arcsin(0.12620 * np.sin(np.deg2rad(arg))))
# ... and the semi-diameter
# Form the mean anomalies of Venus(MV),Earth(ME),Mars(MM),Jupiter(MJ)
# and the mean elongation of the Moon from the Sun(D).
t = de / 36525.0
mv = 212.60 + np.mod(58517.80 * t, 360.0)
me = 358.4760 + np.mod(35999.04980 * t, 360.0)
mm = 319.50 + np.mod(19139.860 * t, 360.0)
mj = 225.30 + np.mod(3034.690 * t, 360.0)
d = 350.70 + np.mod(445267.110 * t, 360.0)
# Form the geocentric distance(r) and semi-diameter(sd)
r = 1.0001410 - (0.0167480 - 0.00004180 * t) * np.cos(np.deg2rad(me)) \
- 0.000140 * np.cos(np.deg2rad(2.0 * me)) \
+ 0.0000160 * np.cos(np.deg2rad(58.30 + 2.0 * mv - 2.0 * me)) \
+ 0.0000050 * np.cos(np.deg2rad(209.10 + mv - me)) \
+ 0.0000050 * np.cos(np.deg2rad(253.80 - 2.0 * mm + 2.0 * me)) \
+ 0.0000160 * np.cos(np.deg2rad(89.50 - mj + me)) \
+ 0.0000090 * np.cos(np.deg2rad(357.10 - 2.0 * mj + 2.0 * me)) \
+ 0.0000310 * np.cos(np.deg2rad(d))
sd_const = constants.radius / constants.au
sd = np.arcsin(sd_const / r) * 10800.0 / np.pi
# place holder for SOHO correction
if soho:
raise ValueError("SOHO correction (on the order of 1% " + \
"since SOHO sets at L1) not yet supported.")
if arcsec:
return {p, b, sd * 60.0}
else:
return {p, b, sd}
def sun_pos(date, is_julian=False, since_2415020=False):
""" Calculate solar ephemeris parameters. Allows for planetary and lunar
perturbations in the calculation of solar longitude at date and various
other solar positional parameters. This routine is a truncated version of
Newcomb's Sun and is designed to give apparent angular coordinates (T.E.D)
to a precision of one second of time.
Parameters
-----------
date: a date/time object or a fractional number of days since JD 2415020.0
is_julian: { False | True }
notify this routine that the variable "date" is a Julian date
(a floating point number)
since_2415020: { False | True }
notify this routine that the variable "date" has been corrected for
the required time offset
Returns:
-------
A dictionary with the following keys with the following meanings:
longitude - Longitude of sun for mean equinox of date (degs)
ra - Apparent RA for true equinox of date (degs)
dec - Apparent declination for true equinox of date (degs)
app_long - Apparent longitude (degs)
obliq - True obliquity (degs)longditude_delta:
See Also
--------
IDL code equavalent:
http://hesperia.gsfc.nasa.gov/ssw/gen/idl/solar/sun_pos.pro
Examples
--------
>>> sp = sun_pos('2013-03-27')
"""
# check the time input
if is_julian:
# if a Julian date is being passed in
if since_2415020:
dd = date
else:
dd = date - 2415020.0
else:
# parse the input time as a julian day
if since_2415020:
dd = julian_day(date)
else:
dd = julian_day(date) - 2415020.0
# form time in Julian centuries from 1900.0
t = dd / 36525.0
# form sun's mean longitude
l = (279.6966780 + np.mod(36000.7689250 * t, 360.00)) * 3600.0
# allow for ellipticity of the orbit (equation of centre) using the Earth's
# mean anomaly ME
me = 358.4758440 + np.mod(35999.049750 * t, 360.0)
ellcor = (6910.10 - 17.20 * t) * np.sin(np.deg2rad(me)) + \
72.30 * np.sin(np.deg2rad(2.0 * me))
l = l + ellcor
# allow for the Venus perturbations using the mean anomaly of Venus MV
mv = 212.603219 + np.mod(58517.8038750 * t, 360.0)
vencorr = 4.80 * np.cos(np.deg2rad(299.10170 + mv - me)) + \
5.50 * np.cos(np.deg2rad(148.31330 + 2.0 * mv - 2.0 * me)) + \
2.50 * np.cos(np.deg2rad(315.94330 + 2.0 * mv - 3.0 * me)) + \
1.60 * np.cos(np.deg2rad(345.25330 + 3.0 * mv - 4.0 * me)) + \
1.00 * np.cos(np.deg2rad(318.150 + 3.0 * mv - 5.0 * me))
l = l + vencorr
# Allow for the Mars perturbations using the mean anomaly of Mars MM
mm = 319.5294250 + np.mod(19139.858500 * t, 360.0)
marscorr = 2.0 * np.cos(np.deg2rad(343.88830 - 2.0 * mm + 2.0 * me)) + \
1.80 * np.cos(np.deg2rad(200.40170 - 2.0 * mm + me))
l = l + marscorr
# Allow for the Jupiter perturbations using the mean anomaly of Jupiter MJ
mj = 225.3283280 + np.mod(3034.69202390 * t, 360.00)
jupcorr = 7.20 * np.cos(np.deg2rad(179.53170 - mj + me)) + \
2.60 * np.cos(np.deg2rad(263.21670 - mj)) + \
2.70 * np.cos(np.deg2rad(87.14500 - 2.0 * mj + 2.0 * me)) + \
1.60 * np.cos(np.deg2rad(109.49330 - 2.0 * mj + me))
l = l + jupcorr
# Allow for the Moons perturbations using the mean elongation of the Moon
# from the Sun D
d = 350.73768140 + np.mod(445267.114220 * t, 360.0)
mooncorr = 6.50 * np.sin(np.deg2rad(d))
l = l + mooncorr
# Note the original code is
# longterm = + 6.4d0 * sin(( 231.19d0 + 20.20d0 * t )*!dtor)
longterm = 6.40 * np.sin(np.deg2rad(231.190 + 20.20 * t))
l = l + longterm
l = np.mod(l + 2592000.0, 1296000.0)
longmed = l / 3600.0
# Allow for Aberration
l = l - 20.5
# Allow for Nutation using the longitude of the Moons mean node OMEGA
omega = 259.1832750 - np.mod(1934.1420080 * t, 360.0)
l = l - 17.20 * np.sin(np.deg2rad(omega))
# Form the True Obliquity
oblt = 23.4522940 - 0.01301250 * t + \
(9.20 * np.cos(np.deg2rad(omega))) / 3600.0
# Form Right Ascension and Declination
l = l / 3600.0
ra = np.rad2deg(np.arctan2(np.sin(np.deg2rad(l)) * \
np.cos(np.deg2rad(oblt)), np.cos(np.deg2rad(l))))
if isinstance(ra, np.ndarray):
ra[ra < 0.0] += 360.0
elif ra < 0.0:
ra = ra + 360.0
dec = np.rad2deg(np.arcsin(np.sin(np.deg2rad(l)) * \
np.sin(np.deg2rad(oblt))))
# convert the internal variables to those listed in the top of the
# comment section in this code and in the original IDL code.
return {"longitude": longmed, "ra": ra, "dec": dec, "app_long": l,
"obliq": oblt}
