def predict_pos(self, date, obscode=807):
"""
Computes ra, dec, and error ellipse at the date(s) and observatory specified.
Date is an ephem.date object.
Returns a corresponding dictionary with keywords
'ra' -- ra in ICRS coords, returned as an ephem.Angle object
'dec' -- dec in ICRS coords, ditto
'err' -- error ellipse (see below)
'elong' -- solar elongation in degrees
'opp' -- opposition angle in degrees
where the error ellipse, indexed by 'err', is itself a dictionary with keywords:
'a' -- semimajor axis in arcsec
'b' -- semiminor axis in arcsec
'PA' -- position angle in degrees, north through east
"""
p_in = self.orbit_abg
jd0 = orbfit.cvar.jd0 # zeropoint of time scale
# Create space for various useful matrices
sigxy = orbfit.dmatrix(1, 2, 1, 2)
derivs = orbfit.dmatrix(1, 2, 1, 2)
covecl = orbfit.dmatrix(1, 2, 1, 2)
coveq = orbfit.dmatrix(1, 2, 1, 2)
# Fill the OBSERVATION structure
futobs = orbfit.OBSERVATION()
futobs.obscode = obscode
futobs.obstime = (ephem.julian_date(date) - jd0) * orbfit.DAY
futobs.xe = -999 # force evaluation of earth3D
dx = orbfit.dvector(1, 6)
dy = orbfit.dvector(1, 6)
# Sometimes hangs in next line... why?
thetax, thetay = orbfit.kbo2d(p_in, futobs, dx, dy)
# Predicted position, in abg basis:
orbfit.predict_posn(p_in, self.cov_abg, futobs, sigxy)
solar_elongation = orbfit.elongation(
futobs) / orbfit.DTOR # solar elongation in degrees
opposition_angle = orbfit.opposition_angle(
futobs) / orbfit.DTOR # opposition angle in degrees
lat_ec, lon_ec = orbfit.proj_to_ec(
futobs.thetax, futobs.thetay, orbfit.cvar.lat0, orbfit.cvar.lon0,
derivs) # project to ecliptic coords
orbfit.covar_map(sigxy, derivs, covecl, 2, 2) # map the covariance
ra_eq, dec_eq = orbfit.ec_to_eq(
lat_ec, lon_ec, derivs) # transform to ICRS to compute ra, dec
if ra_eq < 0: ra_eq += 2 * np.pi # convert angle to (0,2pi) range
orbfit.covar_map(covecl, derivs, coveq, 2, 2) # map the covariance
# Compute ICRS error ellipse
c = orbfit.doubleArray(4) # stoopid workaround for double pointers...
orbfit.flatten_cov(coveq, 2, c)
covar_eq = np.array([c[i] for i in range(4)]).reshape(2, 2)
xx = covar_eq[0][0] * np.cos(dec_eq)**2
xy = covar_eq[0][1] * np.cos(dec_eq)
yy = covar_eq[1][1]
pos_angle = 0.5 * np.arctan2(2. * xy, (xx - yy)) * 180. / np.pi
pos_angle = 90 - pos_angle # convert to astronomy convention of measuring position angle North through East
bovasqrd = (xx + yy - np.sqrt((xx - yy)**2 +
(2 * xy)**2)) / (xx + yy +
np.sqrt((xx - yy)**2 +
(2 * xy)**2))
det = xx * yy - xy * xy
a = (det / bovasqrd)**(
1 / 4
) / orbfit.ARCSEC # semimajor, minor axes of error ellipse, in arcsec
b = (det * bovasqrd)**(1 / 4) / orbfit.ARCSEC
err_ellipse = dict(a=a, b=b, PA=pos_angle) # store as a dictionary
pos = dict(ra=ephem.hours(ra_eq),
dec=ephem.degrees(dec_eq),
err=err_ellipse,
elong=solar_elongation,
opp=opposition_angle)
return pos
def predict_pos(self, date, obscode=807):
"""
Computes ra, dec, and error ellipse at the date(s) and observatory specified.
Date is an ephem.date object.
Returns a corresponding dictionary with keywords
'ra' -- ra in ICRS coords, returned as an ephem.Angle object
'dec' -- dec in ICRS coords, ditto
'err' -- error ellipse (see below)
'elong' -- solar elongation in degrees
'opp' -- opposition angle in degrees
where the error ellipse, indexed by 'err', is itself a dictionary with keywords:
'a' -- semimajor axis in arcsec
'b' -- semiminor axis in arcsec
'PA' -- position angle in degrees, north through east
"""
p_in = self.orbit_abg
jd0 = orbfit.cvar.jd0 # zeropoint of time scale
# Create space for various useful matrices
sigxy = orbfit.dmatrix(1, 2, 1, 2)
derivs = orbfit.dmatrix(1, 2, 1, 2)
covecl = orbfit.dmatrix(1, 2, 1, 2)
coveq = orbfit.dmatrix(1, 2, 1, 2)
# Fill the OBSERVATION structure
futobs = orbfit.OBSERVATION()
futobs.obscode = obscode
futobs.obstime = (ephem.julian_date(date) - jd0) * orbfit.DAY
futobs.xe = -999 # force evaluation of earth3D
dx = orbfit.dvector(1, 6)
dy = orbfit.dvector(1, 6)
thetax, thetay = orbfit.kbo2d(p_in, futobs, dx, dy)
# Predicted position, in abg basis:
orbfit.predict_posn(p_in, self.cov_abg, futobs, sigxy)
solar_elongation = orbfit.elongation(futobs) / orbfit.DTOR # solar elongation in degrees
opposition_angle = orbfit.opposition_angle(futobs) / orbfit.DTOR # opposition angle in degrees
lat_ec, lon_ec = orbfit.proj_to_ec(
futobs.thetax, futobs.thetay, orbfit.cvar.lat0, orbfit.cvar.lon0, derivs
) # project to ecliptic coords
orbfit.covar_map(sigxy, derivs, covecl, 2, 2) # map the covariance
ra_eq, dec_eq = orbfit.ec_to_eq(lat_ec, lon_ec, derivs) # transform to ICRS to compute ra, dec
if ra_eq < 0:
ra_eq += 2 * np.pi # convert angle to (0,2pi) range
orbfit.covar_map(covecl, derivs, coveq, 2, 2) # map the covariance
# Compute ICRS error ellipse
c = orbfit.doubleArray(4) # stoopid workaround for double pointers...
orbfit.flatten_cov(coveq, 2, c)
covar_eq = np.array([c[i] for i in range(4)]).reshape(2, 2)
xx = covar_eq[0][0] * np.cos(dec_eq) ** 2
xy = covar_eq[0][1] * np.cos(dec_eq)
yy = covar_eq[1][1]
pos_angle = 0.5 * np.arctan2(2.0 * xy, (xx - yy)) * 180.0 / np.pi
pos_angle = 90 - pos_angle # convert to astronomy convention of measuring position angle North through East
bovasqrd = (xx + yy - np.sqrt((xx - yy) ** 2 + (2 * xy) ** 2)) / (
xx + yy + np.sqrt((xx - yy) ** 2 + (2 * xy) ** 2)
)
det = xx * yy - xy * xy
a = (det / bovasqrd) ** (1 / 4) / orbfit.ARCSEC # semimajor, minor axes of error ellipse, in arcsec
b = (det * bovasqrd) ** (1 / 4) / orbfit.ARCSEC
err_ellipse = dict(a=a, b=b, PA=pos_angle) # store as a dictionary
pos = dict(
ra=ephem.hours(ra_eq),
dec=ephem.degrees(dec_eq),
err=err_ellipse,
elong=solar_elongation,
opp=opposition_angle,
)
return pos
def predict_from_abg(abginfo, date, obscode=807):
p_in = abginfo['pbasis']
cov_abg = abginfo['cov_abg']
orbfit.cvar.jd0 = abginfo['jd0']
orbfit.cvar.xBary = abginfo['xBary']
orbfit.cvar.yBary = abginfo['yBary']
orbfit.cvar.zBary = abginfo['zBary']
orbfit.cvar.lon0 = abginfo['lon0'] * np.pi / 180
orbfit.cvar.lat0 = abginfo['lat0'] * np.pi / 180
sigxy = orbfit.dmatrix(1, 2, 1, 2)
derivs = orbfit.dmatrix(1, 2, 1, 2)
covecl = orbfit.dmatrix(1, 2, 1, 2)
coveq = orbfit.dmatrix(1, 2, 1, 2)
# Fill the OBSERVATION structure
futobs = orbfit.OBSERVATION()
futobs.obscode = obscode
futobs.obstime = (ephem.julian_date(date) - orbfit.cvar.jd0) * orbfit.DAY
futobs.xe = -999 # force evaluation of earth3D
dx = orbfit.dvector(1, 6)
dy = orbfit.dvector(1, 6)
thetax, thetay = orbfit.kbo2d(p_in, futobs, dx, dy)
# Predicted position, in abg basis:
orbfit.predict_posn(p_in, cov_abg, futobs, sigxy)
solar_elongation = orbfit.elongation(
futobs) / orbfit.DTOR # solar elongation in degrees
opposition_angle = orbfit.opposition_angle(
futobs) / orbfit.DTOR # opposition angle in degrees
lat_ec, lon_ec = orbfit.proj_to_ec(futobs.thetax, futobs.thetay,
orbfit.cvar.lat0, orbfit.cvar.lon0,
derivs) # project to ecliptic coords
orbfit.covar_map(sigxy, derivs, covecl, 2, 2) # map the covariance
ra_eq, dec_eq = orbfit.ec_to_eq(
lat_ec, lon_ec, derivs) # transform to ICRS to compute ra, dec
eq = ephem.Equatorial(ephem.Ecliptic(lat_ec, lon_ec))
ra_eq2 = eq.ra * 180 / np.pi
dec_eq2 = eq.dec * 180 / np.pi
if ra_eq < 0: ra_eq += 2 * np.pi # convert angle to (0,2pi) range
# print ra_eq*180/np.pi, dec_eq*180/np.pi, ra_eq2, dec_eq2, ra_eq*180/np.pi-ra_eq2, dec_eq*180/np.pi-dec_eq2
orbfit.covar_map(covecl, derivs, coveq, 2, 2) # map the covariance
# print ephem.hours(ra_eq), ephem.degrees(dec_eq)
# Compute ICRS error ellipse
c2d = orbfit.doubleArray(4) # stoopid workaround for double pointers...
orbfit.flatten_cov(coveq, 2, c2d)
covar_eq = np.array([c2d[i] for i in range(4)]).reshape(2, 2)
xx = covar_eq[0][0] * np.cos(dec_eq)**2
xy = covar_eq[0][1] * np.cos(dec_eq)
yy = covar_eq[1][1]
pos_angle = 0.5 * np.arctan2(2. * xy, (xx - yy)) * 180. / np.pi
pos_angle = 90 - pos_angle # convert to astronomy convention of measuring position angle North through East
bovasqrd = (xx + yy - np.sqrt((xx - yy)**2 +
(2 * xy)**2)) / (xx + yy +
np.sqrt((xx - yy)**2 +
(2 * xy)**2))
det = xx * yy - xy * xy
a = (det / bovasqrd)**(
1 /
4) / orbfit.ARCSEC # semimajor, minor axes of error ellipse, in arcsec
b = (det * bovasqrd)**(1 / 4) / orbfit.ARCSEC
err_ellipse = dict(a=a, b=b, PA=pos_angle) # store as a dictionary
pos = dict(ra=ephem.hours(ra_eq),
dec=ephem.degrees(dec_eq),
err=err_ellipse,
elong=solar_elongation,
opp=opposition_angle)
return pos
def predict_from_abg(abginfo, date, obscode=807):
p_in = abginfo["pbasis"]
cov_abg = abginfo["cov_abg"]
orbfit.cvar.jd0 = abginfo["jd0"]
orbfit.cvar.xBary = abginfo["xBary"]
orbfit.cvar.yBary = abginfo["yBary"]
orbfit.cvar.zBary = abginfo["zBary"]
orbfit.cvar.lon0 = abginfo["lon0"] * np.pi / 180
orbfit.cvar.lat0 = abginfo["lat0"] * np.pi / 180
sigxy = orbfit.dmatrix(1, 2, 1, 2)
derivs = orbfit.dmatrix(1, 2, 1, 2)
covecl = orbfit.dmatrix(1, 2, 1, 2)
coveq = orbfit.dmatrix(1, 2, 1, 2)
# Fill the OBSERVATION structure
futobs = orbfit.OBSERVATION()
futobs.obscode = obscode
futobs.obstime = (ephem.julian_date(date) - orbfit.cvar.jd0) * orbfit.DAY
futobs.xe = -999 # force evaluation of earth3D
dx = orbfit.dvector(1, 6)
dy = orbfit.dvector(1, 6)
thetax, thetay = orbfit.kbo2d(p_in, futobs, dx, dy)
# Predicted position, in abg basis:
orbfit.predict_posn(p_in, cov_abg, futobs, sigxy)
solar_elongation = orbfit.elongation(futobs) / orbfit.DTOR # solar elongation in degrees
opposition_angle = orbfit.opposition_angle(futobs) / orbfit.DTOR # opposition angle in degrees
lat_ec, lon_ec = orbfit.proj_to_ec(
futobs.thetax, futobs.thetay, orbfit.cvar.lat0, orbfit.cvar.lon0, derivs
) # project to ecliptic coords
orbfit.covar_map(sigxy, derivs, covecl, 2, 2) # map the covariance
ra_eq, dec_eq = orbfit.ec_to_eq(lat_ec, lon_ec, derivs) # transform to ICRS to compute ra, dec
eq = ephem.Equatorial(ephem.Ecliptic(lat_ec, lon_ec))
ra_eq2 = eq.ra * 180 / np.pi
dec_eq2 = eq.dec * 180 / np.pi
if ra_eq < 0:
ra_eq += 2 * np.pi # convert angle to (0,2pi) range
# print ra_eq*180/np.pi, dec_eq*180/np.pi, ra_eq2, dec_eq2, ra_eq*180/np.pi-ra_eq2, dec_eq*180/np.pi-dec_eq2
orbfit.covar_map(covecl, derivs, coveq, 2, 2) # map the covariance
# print ephem.hours(ra_eq), ephem.degrees(dec_eq)
# Compute ICRS error ellipse
c2d = orbfit.doubleArray(4) # stoopid workaround for double pointers...
orbfit.flatten_cov(coveq, 2, c2d)
covar_eq = np.array([c2d[i] for i in range(4)]).reshape(2, 2)
xx = covar_eq[0][0] * np.cos(dec_eq) ** 2
xy = covar_eq[0][1] * np.cos(dec_eq)
yy = covar_eq[1][1]
pos_angle = 0.5 * np.arctan2(2.0 * xy, (xx - yy)) * 180.0 / np.pi
pos_angle = 90 - pos_angle # convert to astronomy convention of measuring position angle North through East
bovasqrd = (xx + yy - np.sqrt((xx - yy) ** 2 + (2 * xy) ** 2)) / (xx + yy + np.sqrt((xx - yy) ** 2 + (2 * xy) ** 2))
det = xx * yy - xy * xy
a = (det / bovasqrd) ** (1 / 4) / orbfit.ARCSEC # semimajor, minor axes of error ellipse, in arcsec
b = (det * bovasqrd) ** (1 / 4) / orbfit.ARCSEC
err_ellipse = dict(a=a, b=b, PA=pos_angle) # store as a dictionary
pos = dict(
ra=ephem.hours(ra_eq), dec=ephem.degrees(dec_eq), err=err_ellipse, elong=solar_elongation, opp=opposition_angle
)
return pos