def radec2strings(ra_radians, dec_radians, seperator=' '):
'''Format an (RA, Dec) pair (in radians) into a tuple of strings, with
configurable seperator (defaults to <space>)'''
ra_format = "%02.2d%c%02.2d%c%02.2d.%02.2d"
dec_format = "%s%02.2d%c%02.2d%c%02.2d.%d"
(rsign, ra ) = S.sla_dr2tf(2, ra_radians)
(dsign, dec) = S.sla_dr2af(1, dec_radians)
ra_str = ra_format % ( ra[0], seperator, ra[1], seperator, ra[2], ra[3] )
dec_str = dec_format % ( dsign, dec[0], seperator, dec[1], seperator, dec[2], dec[3] )
return (ra_str, dec_str)
def radec2strings(ra_radians, dec_radians, seperator=' '):
'''Format an (RA, Dec) pair (in radians) into a tuple of strings, with
configurable seperator (defaults to <space>).
There is no sign produced on the RA quantity unless ra_radians and dec_radians
are equal.'''
ra_format = "%s%02.2d%c%02.2d%c%02.2d.%02.2d"
dec_format = "%s%02.2d%c%02.2d%c%02.2d.%d"
(rsign, ra ) = S.sla_dr2tf(2, ra_radians)
(dsign, dec) = S.sla_dr2af(1, dec_radians)
if rsign == '+' and ra_radians != dec_radians: rsign = ''
ra_str = ra_format % ( rsign, ra[0], seperator, ra[1], seperator, ra[2], ra[3] )
dec_str = dec_format % ( dsign, dec[0], seperator, dec[1], seperator, dec[2], dec[3] )
return (ra_str, dec_str)
def compute_ephem(d, orbelems, sitecode, dbg=False, perturb=True, display=False):
'''Routine to compute the geocentric or topocentric position, magnitude,
motion and altitude of an asteroid or comet for a specific date and time
from a dictionary of orbital elements.
<orbelems> can be in one of two forms, so called "Eric format" as produced
by rise_set.moving_objects.read_neocp_orbit and used in the scheduler/RequestDB
or the format used by NEO exchange. Selection is automatically handled based on
whether the epoch of the elements dictionary key is 'epoch' (Eric format) or
'epochofel' (NEO exchange format)
'''
# Light travel time for 1 AU (in sec)
tau = 499.004783806
# Compute MJD for UTC
mjd_utc = datetime2mjd_utc(d)
# Compute epoch of the elements as a MJD
try:
epochofel = datetime.strptime(orbelems['epochofel'], '%Y-%m-%d %H:%M:%S')
except TypeError:
epochofel = orbelems['epochofel']
epoch_mjd = datetime2mjd_utc(epochofel)
logger.debug('Element Epoch= %.1f' % (epoch_mjd))
logger.debug('MJD(UTC) = %.15f' % (mjd_utc))
logger.debug(' JD(UTC) = %.8f' % (mjd_utc + 2400000.5))
# Convert MJD(UTC) to MJD(TT)
mjd_tt = mjd_utc2mjd_tt(mjd_utc)
logger.debug('MJD(TT) = %.15f' % (mjd_tt))
# Compute UT1-UTC
dut = ut1_minus_utc(mjd_utc)
logger.debug("UT1-UTC = %.15f" % (dut))
# Obtain precession-nutation 3x3 rotation matrix
# Should really be TDB but "TT will do" says The Wallace...
rmat = S.sla_prenut(2000.0, mjd_tt)
logger.debug(rmat)
# Obtain latitude, longitude of the observing site.
# Reverse longitude to get the more normal East-positive convention
# (site_num, site_name, site_long, site_lat, site_hgt) = S.sla_obs(0, 'SAAO74')
# site_long = -site_long
(site_name, site_long, site_lat, site_hgt) = get_sitepos(sitecode)
logger.debug("Site code/name, lat/long/height=%s %s %f %f %.1f" % (sitecode, site_name, site_long, site_lat, site_hgt))
if site_name == '?':
logger.debug("WARN: No site co-ordinates found, computing for geocenter")
pvobs = zeros(6)
else:
# Compute local apparent sidereal time
# Do GMST first which takes UT1 and then add East longitiude and the equation of the equinoxes
# (which takes TDB; but we use TT here)
#
gmst = S.sla_gmst(mjd_utc+(dut/86400.0))
stl = gmst + site_long + S.sla_eqeqx(mjd_tt)
logger.debug('GMST, LAST, EQEQX, GAST, long= %.17f %.17f %E %.17f %.17f' % (gmst, stl, S.sla_eqeqx(mjd_tt), gmst+S.sla_eqeqx(mjd_tt), site_long))
pvobs = S.sla_pvobs(site_lat, site_hgt, stl)
logger.debug("PVobs(orig)=%s\n %s" % (pvobs[0:3],pvobs[3:6]*86400.0))
# Apply transpose of precession/nutation matrix to pv vector to go from
# true equator and equinox of date to J2000.0 mean equator and equinox (to
# match the reference system of sla_epv)
#
pos_new = S.sla_dimxv(rmat, pvobs[0:3])
vel_new = S.sla_dimxv(rmat, pvobs[3:6])
pvobs_new = concatenate([pos_new, vel_new])
logger.debug("PVobs(new)=%s\n %s" % (pvobs_new[0:3],pvobs_new[3:6]*86400.0))
# Earth position and velocity
# Moderate precision/speed version. N.B different order of bary vs. heliocentric!
#(vel_bar, pos_bar, e_vel_hel, e_pos_hel) = S.sla_evp(mjd_tt, 2000.0)
# High precision/slowest version. N.B different order of bary vs. heliocentric sets
# and position vs velocity!
# N.B. velocities are AU/day not AU/sec !
# Also N.B. ! Must use heliocentric positions, not barycentric as normal as
# asteroid position from sla_planel is also heliocentric.
(e_pos_hel, e_vel_hel, e_pos_bar, e_vel_bar) = S.sla_epv(mjd_tt)
e_vel_hel = e_vel_hel/86400.0
logger.debug("Sun->Earth [X, Y, Z]=%s" % e_pos_hel)
logger.debug("Sun->Earth [X, Y, Z]= %20.15E %20.15E %20.15E" % (e_pos_hel[0], e_pos_hel[1], e_pos_hel[2]))
logger.debug("Sun->Earth [Xdot, Ydot, Zdot]=%s" % e_vel_hel)
logger.debug("Sun->Earth [Xdot, Ydot, Zdot]= %20.15E %20.15E %20.15E" % (e_vel_hel[0]*86400.0, e_vel_hel[1]*86400.0, e_vel_hel[2]*86400.0))
# Add topocentric offset in position and velocity
e_pos_hel = e_pos_hel + pvobs_new[0:3]
e_vel_hel = e_vel_hel + pvobs_new[3:6]
logger.debug("Sun->Obsvr [X, Y, Z]=%s" % e_pos_hel)
logger.debug("Sun->Obsvr [Xdot, Ydot, Zdot]=%s" % e_vel_hel)
# Asteroid position (and velocity)
comet = False
jform = 2
if 'elements_type' in orbelems and str(orbelems['elements_type']).upper() == 'MPC_COMET':
comet = True
jform = 3
# Perturb elements
# NEO exchange format
if comet == True:
p_orbelems = {'LongNode' : radians(orbelems['longascnode']),
'Inc' : radians(orbelems['orbinc']),
'ArgPeri' : radians(orbelems['argofperih']),
'SemiAxisOrQ' : orbelems['perihdist'],
'Ecc' : orbelems['eccentricity'],
}
orbelems['meananom'] = 0.0
epoch_mjd = datetime2mjd_utc(orbelems['epochofperih'])
else:
p_orbelems = {'LongNode' : radians(orbelems['longascnode']),
'Inc' : radians(orbelems['orbinc']),
'ArgPeri' : radians(orbelems['argofperih']),
'MeanAnom' : radians(orbelems['meananom']),
'SemiAxis' : orbelems['meandist'],
'Ecc' : orbelems['eccentricity']
}
p_orbelems['H'] = orbelems['abs_mag']
p_orbelems['G'] = orbelems['slope']
if perturb == True:
(p_epoch_mjd, p_orbelems['Inc'], p_orbelems['LongNode'], p_orbelems['ArgPeri'],
p_orbelems['SemiAxis'], p_orbelems['Ecc'], p_orbelems['MeanAnom'], j) = S.sla_pertel( jform, epoch_mjd, mjd_tt, epoch_mjd, radians(orbelems['orbinc']), radians(orbelems['longascnode']),
radians(orbelems['argofperih']), orbelems['meandist'], orbelems['eccentricity'],
radians(orbelems['meananom']))
else:
p_epoch_mjd = epoch_mjd
j = 0
if j != 0:
logger.error("Perturbing error=%s" % j)
r3 = -100.
delta = 0.0
ltt = 0.0
pos = zeros(3)
vel = zeros(3)
#rel_pos= [0.0, 0.0, 0.0]
while (fabs(delta - r3) > .01):
r3 = delta
if comet == True:
(pv, status) = S.sla_planel(mjd_tt - (ltt/86400.0), jform, p_epoch_mjd,
p_orbelems['Inc'], p_orbelems['LongNode'],
p_orbelems['ArgPeri'], p_orbelems['SemiAxisOrQ'], p_orbelems['Ecc'],
0.0, 0.0)
else:
(pv, status) = S.sla_planel(mjd_tt - (ltt/86400.0), jform, p_epoch_mjd,
p_orbelems['Inc'], p_orbelems['LongNode'],
p_orbelems['ArgPeri'], p_orbelems['SemiAxis'], p_orbelems['Ecc'],
p_orbelems['MeanAnom'], 0.0)
logger.debug("Sun->Asteroid [x,y,z]=%s %s" % (pv[0:3], status))
logger.debug("Sun->Asteroid [xdot,ydot,zdot]=%s %s" % (pv[3:6], status))
for i, e_pos in enumerate(e_pos_hel):
pos[i] = pv[i] - e_pos
for i, e_vel in enumerate(e_vel_hel):
vel[i] = pv[i+3] - e_vel
logger.debug("Earth->Asteroid [x,y,z]=%s" % pos)
logger.debug("Earth->Asteroid [xdot,ydot,zdot]=%s" % vel)
# geometric distance, delta (AU)
delta = sqrt(pos[0]*pos[0] + pos[1]*pos[1] + pos[2]*pos[2])
logger.debug("Geometric distance, delta (AU)=%s" % delta)
# Light travel time to asteroid
ltt = tau * delta
logger.debug("Light travel time (sec, min, days)=%s %s %s" % (ltt, ltt/60.0, ltt/86400.0))
# Correct position for planetary aberration
for i, a_pos in enumerate(pos):
pos[i] = a_pos - (ltt * vel[i])
logger.debug("Earth->Asteroid [x,y,z]=%s" % pos)
logger.debug("Earth->Asteroid [x,y,z]= %20.15E %20.15E %20.15E" % (pos[0], pos[1], pos[2]))
logger.debug("Earth->Asteroid [xdot,ydot,zdot]=%s %s %s" % (vel[0]*86400.0,vel[1]*86400.0,vel[2]*86400.0))
# Convert Cartesian to RA, Dec
(ra, dec) = S.sla_dcc2s(pos)
logger.debug("ra,dec=%s %s" % (ra, dec))
ra = S.sla_dranrm(ra)
logger.debug("ra,dec=%s %s" % (ra, dec))
(rsign, ra_geo_deg) = S.sla_dr2tf(2, ra)
(dsign, dec_geo_deg) = S.sla_dr2af(1, dec)
# Compute r, the Sun-Target distance. Correct for light travel time first
cposx = pv[0] - (ltt * pv[3])
cposy = pv[1] - (ltt * pv[4])
cposz = pv[2] - (ltt * pv[5])
r = sqrt(cposx*cposx + cposy*cposy + cposz*cposz)
logger.debug("r (AU) =%s" % r)
# Compute R, the Earth-Sun distance. (Only actually need R^2 for the mag. formula)
es_Rsq = (e_pos_hel[0]*e_pos_hel[0] + e_pos_hel[1]*e_pos_hel[1] + e_pos_hel[2]*e_pos_hel[2])
logger.debug("R (AU) =%s" % sqrt(es_Rsq))
logger.debug("delta (AU)=%s" % delta)
# Compute sky motion
sky_vel = compute_relative_velocity_vectors(e_pos_hel, e_vel_hel, pos, vel, delta, dbg)
logger.debug("vel1, vel2, r= %15.10lf %15.10lf %15.10lf" % (sky_vel[1], sky_vel[2], delta))
logger.debug("vel1, vel2, r= %15.10e %15.10e %15.10lf\n" % (sky_vel[1], sky_vel[2], delta))
total_motion, sky_pa, ra_motion, dec_motion = compute_sky_motion(sky_vel, delta, dbg)
mag = -99
# Compute phase angle, beta (Sun-Target-Earth angle)
beta = compute_phase_angle(r, delta, es_Rsq)
if comet == True:
# Calculate magnitude of comet
# Here 'H' is the absolute magnitude, 'kappa' the slope parameter defined in Meeus
# _Astronomical Algorithms_ p. 231, is equal to 2.5 times the 'G' read from the elements
if p_orbelems['H'] and p_orbelems['G']:
mag = p_orbelems['H'] + 5.0 * log10(delta) + 2.5 * p_orbelems['G'] * log10(r)
else:
phi1 = exp(-3.33 * (tan(beta/2.0))**0.63)
phi2 = exp(-1.87 * (tan(beta/2.0))**1.22)
# logger.debug("Phi1, phi2=%s" % phi1,phi2)
# Calculate magnitude of object
if p_orbelems['H'] and p_orbelems['G']:
mag = p_orbelems['H'] + 5.0 * log10(r * delta) - \
(2.5 * log10((1.0 - p_orbelems['G'])*phi1 + p_orbelems['G']*phi2))
az_rad, alt_rad = moon_alt_az(d, ra, dec, site_long, site_lat, site_hgt)
airmass = S.sla_airmas((pi/2.0)-alt_rad)
alt_deg = degrees(alt_rad)
phaseang_deg = degrees(beta)
# if display: print " %02.2dh %02.2dm %02.2d.%02.2ds %s%02.2dd %02.2d\' %02.2d.%01.1d\" V=%.1f %5.2f %.1f % 7.3f %8.4f" % ( ra_geo_deg[0],
if display: print " %02.2d %02.2d %02.2d.%02.2d %s%02.2d %02.2d %02.2d.%01.1d %02.1f V=%.1f %5.2f %.1f % 7.3f %8.4f" % ( ra_geo_deg[0],
ra_geo_deg[1], ra_geo_deg[2], ra_geo_deg[3],
dsign, dec_geo_deg[0], dec_geo_deg[1], dec_geo_deg[2], dec_geo_deg[3],
phaseang_deg, mag, total_motion, sky_pa, alt_deg, airmass )
# Compute South Polar Distance from Dec
dec_arcsec_decimal = dec_geo_deg[2] + dec_geo_deg[3]
dec_arcmin_decimal = dec_geo_deg[1] + (dec_arcsec_decimal/60.)
dec_deg_decimal = dec_geo_deg[0] + (dec_arcmin_decimal/60.)
if '+' in dsign:
spd = 90. + dec_deg_decimal
elif '-' in dsign:
spd = 90. - dec_deg_decimal
else:
spd = None
emp_line = (d, ra, dec, mag, total_motion, alt_deg, spd, beta)
return emp_line
def degrees2hms(self, deg):
"converts degrees to h:m:s format"
if deg == self.noValue:
return self.noValue
sign, arr = s.sla_dr2tf(4, deg*DEGTORAD)
return "%02d:%02d:%07.4f" % (arr[0], arr[1], arr[2]+0.0001*arr[3])