def compute_lsrk(self):
""" Computes the LSR in km/s
uses the MJD, RA and DEC of observation to compute
along with the telescope location. Requires pyslalib
"""
ra = Angle(self.header[b'src_raj'], unit='hourangle')
dec = Angle(self.header[b'src_dej'], unit='degree')
mjdd = self.header[b'tstart']
rarad = ra.to('radian').value
dcrad = dec.to('radian').value
last = self.compute_lst()
tellat = np.deg2rad(self.coords[0])
tellong = np.deg2rad(self.coords[1])
# convert star position to vector
starvect = s.sla_dcs2c(rarad, dcrad)
# velocity component in ra,dec due to Earth rotation
Rgeo = s.sla_rverot(tellat, rarad, dcrad, last)
# get Barycentric and heliocentric velocity and position of the Earth.
evp = s.sla_evp(mjdd, 2000.0)
dvb = evp[0] # barycentric velocity vector, in AU/sec
dpb = evp[1] # barycentric position vector, in AU
dvh = evp[2] # heliocentric velocity vector, in AU/sec
dph = evp[3] # heliocentric position vector, in AU
# dot product of vector to object and heliocentric velocity
# convert AU/sec to km/sec
vcorhelio = -s.sla_dvdv(starvect, dvh) * 149.597870e6
vcorbary = -s.sla_dvdv(starvect, dvb) * 149.597870e6
# rvlsrd is velocity component in ra,dec direction due to the Sun's
# motion with respect to the "dynamical" local standard of rest
rvlsrd = s.sla_rvlsrd(rarad, dcrad)
# rvlsrk is velocity component in ra,dec direction due to i
# the Sun's motion w.r.t the "kinematic" local standard of rest
rvlsrk = s.sla_rvlsrk(rarad, dcrad)
# rvgalc is velocity component in ra,dec direction due to
#the rotation of the Galaxy.
rvgalc = s.sla_rvgalc(rarad, dcrad)
totalhelio = Rgeo + vcorhelio
totalbary = Rgeo + vcorbary
totallsrk = totalhelio + rvlsrk
totalgal = totalbary + rvlsrd + rvgalc
return totallsrk
def rvel(self, mjdd, radeg, decdeg):
global tellat, tellong, telelev
last = self.hlst(mjdd) # apparent LST in radians
# convert ra,dec to radians
rarad = radeg * math.pi / 180.0
dcrad = decdeg * math.pi / 180.0
# convert star position to vector
starvect = s.sla_dcs2c(rarad, dcrad)
# velocity component in ra,dec due to Earth rotation
Rgeo = s.sla_rverot(tellat, rarad, dcrad, last)
# get Barycentric and heliocentric velocity and position of the Earth.
evp = s.sla_evp(mjdd, 2000.0)
dvb = evp[0] # barycentric velocity vector, in AU/sec
dpb = evp[1] # barycentric position vector, in AU
dvh = evp[2] # heliocentric velocity vector, in AU/sec
dph = evp[3] # heliocentric position vector, in AU
# dot product of vector to object and heliocentric velocity
# convert AU/sec to km/sec
vcorhelio = -s.sla_dvdv(starvect, dvh) * 149.597870e6
vcorbary = -s.sla_dvdv(starvect, dvb) * 149.597870e6
# rvlsrd is velocity component in ra,dec direction due to the Sun's motion with
# respect to the "dynamical" local standard of rest
rvlsrd = s.sla_rvlsrd(rarad, dcrad)
# rvlsrk is velocity component in ra,dec direction due to the Sun's motion with
# respect to the "kinematic" local standard of rest
rvlsrk = s.sla_rvlsrk(rarad, dcrad)
# rvgalc is velocity component in ra,dec direction due to the rotation of the Galaxy.
rvgalc = s.sla_rvgalc(rarad, dcrad)
totalhelio = Rgeo + vcorhelio
totalbary = Rgeo + vcorbary
totallsrk = totalhelio + rvlsrk
totalgal = totalbary + rvlsrd + rvgalc
# ('UTHr', 'LST', 'Geo', 'Helio', 'Total Helio', 'LSRK', 'Galacto')
#(hour,last*12.0/math.pi,Rgeo,vcorb,totalhelio,totallsrk,totalgal)
# resulting velocities in km/sec
return ((mjdd, last * 12.0 / math.pi, Rgeo, totalhelio, totalbary,
totallsrk, totalgal))
def jd_to_hjd(t, target_position, debug=False):
"""Calculate the HJD timestamp corresponding to the JD given for the
current event.
Inputs:
t is an astropy Time object
target_position is a tuple of (RA, Dec) in decimal degrees
Outputs:
hjd float
"""
if debug == True:
print 'TIME JD: ',t, t.jd
# Calculate the MJD (UTC) timestamp:
mjd_utc = t.jd - 2400000.5
if debug == True:
print 'TIME MJD_UTC: ',mjd_utc
# Correct the MJD to TT:
mjd_tt = mjd_utc2mjd_tt(mjd_utc)
if debug == True:
print 'TIME MJD_TT: ',mjd_tt, t.tt.jd
# Calculate Earth's position and velocity, both heliocentric
# and barycentric for this date
(earth_helio_position, vh, pb, vb) = S.sla_epv( mjd_tt )
if debug == True:
print 'Earth Cartesian position: ',earth_helio_position
print 'Target cartesian position: ', target_position
# Calculate the light travel time delay from the target to
# the Sun:
dv = S.sla_dvdv( earth_helio_position, target_position )
tcorr = dv * ( constants.au.value / constants.c.value )
if debug == True:
print 'TIME tcorr: ', tcorr, 's', (tcorr/60.0),'mins'
# Calculating the HJD:
hjd = mjd_tt + tcorr/86400.0 + 2400000.5
if debug == True:
print 'TIME HJD: ',hjd,'\n'
return hjd
def jd_to_hjd(t, target_position, debug=False):
"""Calculate the HJD timestamp corresponding to the JD given for the
current event.
Inputs:
t is an astropy Time object
target_position is a tuple of (RA, Dec) in decimal degrees
Outputs:
hjd float
"""
if debug == True:
print('TIME JD: ', t, t.jd)
# Calculate the MJD (UTC) timestamp:
mjd_utc = t.jd - 2400000.5
if debug == True:
print('TIME MJD_UTC: ', mjd_utc)
# Correct the MJD to TT:
mjd_tt = mjd_utc2mjd_tt(mjd_utc)
if debug == True:
print('TIME MJD_TT: ', mjd_tt, t.tt.jd)
# Calculate Earth's position and velocity, both heliocentric
# and barycentric for this date
(earth_helio_position, vh, pb, vb) = S.sla_epv(mjd_tt)
if debug == True:
print('Earth Cartesian position: ', earth_helio_position)
print('Target cartesian position: ', target_position)
# Calculate the light travel time delay from the target to
# the Sun:
dv = S.sla_dvdv(earth_helio_position, target_position)
tcorr = dv * (constants.au.value / constants.c.value)
if debug == True:
print('TIME tcorr: ', tcorr, 's', (tcorr / 60.0), 'mins')
# Calculating the HJD:
hjd = mjd_tt + tcorr / 86400.0 + 2400000.5
if debug == True:
print('TIME HJD: ', hjd, '\n')
return hjd