# array.py
# a interferometric telescope array class
#
# Copyright (C) 2018 Andrew Chael
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
from __future__ import division
from __future__ import print_function
from builtins import str
from builtins import range
from builtins import object
import numpy as np
import copy
from astropy.time import Time
import matplotlib.pyplot as plt
import matplotlib
import ehtim.observing.obs_simulate as simobs
import ehtim.observing.obs_helpers as obsh
import ehtim.io.save
import ehtim.io.load
import ehtim.const_def as ehc
from ehtim.caltable import plot_tarr_dterms
###################################################################################################
# Array object
###################################################################################################
[docs]class Array(object):
"""A VLBI array of telescopes with site locations, SEFDs, and other data.
Attributes:
tarr (numpy.recarray): The array of telescope data with datatype DTARR
tkey (dict): A dictionary of rows in the tarr for each site name
ephem (dict): A dictionary of TLEs for each space antenna,
Space antennas have x=y=z=0 in the tarr
"""
def __init__(self, tarr, ephem={}):
self.tarr = tarr
self.ephem = ephem
# check to see if ephemeris is correct
for line in self.tarr:
if np.any(np.isnan([line['x'], line['y'], line['z']])):
sitename = str(line['site'])
try:
elen = len(ephem[sitename])
except NameError:
raise Exception('no ephemeris for site %s !' % sitename)
if elen != 3:
raise Exception('wrong ephemeris format for site %s !' % sitename)
# Dictionary of array indices for site names
self.tkey = {self.tarr[i]['site']: i for i in range(len(self.tarr))}
@property
def tarr(self):
return self._tarr
@tarr.setter
def tarr(self, tarr):
self._tarr = tarr
self.tkey = {tarr[i]['site']: i for i in range(len(tarr))}
[docs] def copy(self):
"""Copy the array object.
Args:
Returns:
(Array): a copy of the Array object.
"""
newarr = copy.deepcopy(self)
return newarr
[docs] def listbls(self):
"""List all baselines.
Args:
Returns:
numpy.array : array of baselines
"""
bls = []
for i1 in sorted(self.tarr['site']):
for i2 in sorted(self.tarr['site']):
if not ([i1, i2] in bls) and not ([i2, i1] in bls) and i1 != i2:
bls.append([i1, i2])
bls = np.array(bls)
return bls
[docs] def obsdata(self, ra, dec, rf, bw, tint, tadv, tstart, tstop,
mjd=ehc.MJD_DEFAULT, timetype='UTC', polrep='stokes',
elevmin=ehc.ELEV_LOW, elevmax=ehc.ELEV_HIGH,
no_elevcut_space=False,
tau=ehc.TAUDEF, fix_theta_GMST=False):
"""Generate u,v points and baseline uncertainties.
Args:
ra (float): the source right ascension in fractional hours
dec (float): the source declination in fractional degrees
tint (float): the scan integration time in seconds
tadv (float): the uniform cadence between scans in seconds
tstart (float): the start time of the observation in hours
tstop (float): the end time of the observation in hours
mjd (int): the mjd of the observation
timetype (str): how to interpret tstart and tstop; either 'GMST' or 'UTC'
polrep (str): polarization representation, either 'stokes' or 'circ'
elevmin (float): station minimum elevation in degrees
elevmax (float): station maximum elevation in degrees
no_elevcut_space (bool): if True, do not apply elevation cut to orbiters
tau (float): the base opacity at all sites, or a dict giving one opacity per site
fix_theta_GMST (bool): if True, stops earth rotation to sample fixed u,v points
Returns:
Obsdata: an observation object with no data
"""
obsarr = simobs.make_uvpoints(self, ra, dec, rf, bw,
tint, tadv, tstart, tstop,
mjd=mjd, polrep=polrep, tau=tau,
elevmin=elevmin, elevmax=elevmax,
no_elevcut_space=no_elevcut_space,
timetype=timetype, fix_theta_GMST=fix_theta_GMST)
uniquetimes = np.sort(np.unique(obsarr['time']))
scans = np.array([[time - 0.5 * tadv, time + 0.5 * tadv] for time in uniquetimes])
source = str(ra) + ":" + str(dec)
obs = ehtim.obsdata.Obsdata(ra, dec, rf, bw, obsarr, self.tarr,
source=source, mjd=mjd, timetype=timetype, polrep=polrep,
ampcal=True, phasecal=True, opacitycal=True,
dcal=True, frcal=True,
scantable=scans)
return obs
[docs] def make_subarray(self, sites):
"""Make a subarray from the Array object array that only includes the sites listed.
Args:
sites (list) : list of sites in the subarray
Returns:
Array: an Array object with specified sites and metadata
"""
all_sites = [t[0] for t in self.tarr]
mask = np.array([t in sites for t in all_sites])
subarr = Array(self.tarr[mask], ephem=self.ephem)
return subarr
[docs] def save_txt(self, fname):
"""Save the array data in a text file.
Args:
fname (str) : path to output array file
"""
ehtim.io.save.save_array_txt(self, fname)
return
[docs] def plot_dterms(self, sites='all', label=None, legend=True, clist=ehc.SCOLORS,
rangex=False, rangey=False, markersize=2 * ehc.MARKERSIZE,
show=True, grid=True, export_pdf=""):
"""Make a plot of the D-terms.
Args:
sites (list) : list of sites to plot
label (str) : title for plot
legend (bool) : add telescope legend or not
clist (list) : list of colors for different stations
rangex (list) : lower and upper x-axis limits
rangey (list) : lower and upper y-axis limits
markersize (float) : marker size
show (bool) : display the plot or not
grid (bool) : add a grid to the plot or not
export_pdf (str) : save a pdf file to this path
Returns:
matplotlib.axes
"""
# sites
if sites in ['all' or 'All'] or sites == []:
sites = list(self.tkey.keys())
if not isinstance(sites, list):
sites = [sites]
keys = [self.tkey[site] for site in sites]
axes = plot_tarr_dterms(self.tarr, keys=keys, label=label, legend=legend, clist=clist,
rangex=rangex, rangey=rangey, markersize=markersize,
show=show, grid=grid, export_pdf=export_pdf)
return axes
[docs] def add_site(self, site, coords, sefd=10000,
fr_par=0, fr_elev=0, fr_off=0,
dr=0.+0.j, dl=0.+0.j):
"""Add a ground station to the array
"""
tarr_old = self.tarr.copy()
ephem_old = self.ephem.copy()
tarr_newline = np.array((str(site), float(coords[0]), float(coords[1]), float(coords[2]),
float(sefd), float(sefd),
dr, dl,
float(fr_par), float(fr_elev), float(fr_off)), dtype=ehc.DTARR)
tarr_new = np.append(tarr_old, tarr_newline)
arr_out = Array(tarr_new, ephem_old)
return arr_out
[docs] def remove_site(self, site):
"""Remove a site from the array
"""
tarr_old = self.tarr.copy()
ephem_old = self.ephem.copy()
ephem_new = ephem_old.copy()
try:
tarr_new = np.delete(tarr_old.copy(), self.tkey[site])
if site in ephem_old.keys():
ephem_new.pop(site)
except:
raise Exception("could not find site %s to delete from Array!"%site)
arr_out = Array(tarr_new, ephem_new)
return arr_out
[docs] def add_satellite_tle(self, tlelist, sefd=10000):
"""Add an earth-orbiting satellite to the array from a TLE
Args:
tlearr (str) : 3 element list with [name, tle line 1, tle line 2] as strings
sefd (float) : assumed sefd for the array file (assumes sefdl = sefdr)
"""
satname = tlearr[0]
tarr_new = self.tarr.copy()
ephem_new = self.ephem.copy()
tarr_newline = np.array((str(satname), 0., 0., 0.,
float(sefd), float(sefd),
0., 0., 0., 0., 0.), dtype=ehc.DTARR)
tarr_new = np.append(tarr_new, tarr_newline)
ephem_new[satname] = tlearr
arr_out = Array(tarr_new, ephem_new)
return arr_out
[docs] def add_satellite_elements(self, satname,
perigee_mjd=Time.now().mjd,
period_days=1., eccentricity=0.,
inclination=0., arg_perigee=0., long_ascending=0.,
sefd=10000):
"""Add an earth-orbiting satellite to the array from simple keplerian elements
perfect keplerian orbit is assumed, no derivatives
Args:
perigee time given in mjd
period given in days
inclination, arg_perigee, long_ascending given in degrees
"""
tarr_new = self.tarr.copy()
ephem_new = self.ephem.copy()
tarr_newline = np.array((str(satname), 0., 0., 0.,
float(sefd), float(sefd),
0., 0., 0., 0., 0.), dtype=ehc.DTARR)
tarr_new = np.append(tarr_new, tarr_newline)
ephem_new[satname] = [perigee_mjd, period_days, eccentricity, inclination, arg_perigee, long_ascending]
arr_out = Array(tarr_new, ephem_new)
return arr_out
def plot_satellite_orbits(self, tstart_mjd=Time.now().mjd, tstop_mjd=Time.now().mjd+1, npoints=1000):
earth_radius_polar = 6357. #km
earth_radius_eq = 6378.
fig = plt.figure(figsize=(18,6))
gs = matplotlib.gridspec.GridSpec(1,3,width_ratios=[1,1,1])
satellites = self.ephem.keys()
for i,satellite in enumerate(satellites):
if i==0: color='k'
else: color=ehc.SCOLORS[i-1]
# get skyfield satelllite object
if len(self.ephem[satellite])==3: # TLE
line1 = self.ephem[satellite][1]
line2 = self.ephem[satellite][2]
sat = obsh.sat_skyfield_from_tle(satellite, line1, line2)
elif len(self.ephem[satellite])==6: #keplerian elements
elements = self.ephem[satellite]
sat = obsh.sat_skyfield_from_elements(satellite, tstart_mjd,
elements[0],elements[1],elements[2],elements[3],elements[4],elements[5])
else:
raise Exception("ephemeris format not recognized for %s"%satellite)
# get GCRS positions
fracmjds = np.linspace(tstart_mjd, tstop_mjd, npoints)
positions = obsh.orbit_skyfield(sat, fracmjds, whichout='gcrs')
positions *= 1.e-3 # convert to km
distances = np.sqrt(positions[0]**2 + positions[1]**2 + positions[2]**2)
maxdist = np.max(distances)
ax1 = fig.add_subplot(gs[0])
ax1.set_aspect(1)
plt.plot(positions[0], positions[1], color=color, marker='.',ls='None')
circle1 = matplotlib.patches.Circle((0, 0), earth_radius_eq, color='b')
plt.gca().add_patch(circle1)
plt.xlabel('x (km)')
plt.ylabel('y (km)')
plt.xlim(-1.1*maxdist, 1.1*maxdist)
plt.ylim(-1.1*maxdist, 1.1*maxdist)
plt.grid()
ax2 = fig.add_subplot(gs[1])
ax2.set_aspect(1)
plt.plot(positions[1], positions[2], color=color, marker='.',ls='None')
circle1 = matplotlib.patches.Ellipse((0, 0), 2*earth_radius_eq, 2*earth_radius_polar, color='b')
plt.gca().add_patch(circle1)
plt.xlabel('y (km)')
plt.ylabel('z (km)')
plt.xlim(-1.1*maxdist, 1.1*maxdist)
plt.ylim(-1.1*maxdist, 1.1*maxdist)
plt.grid()
ax3 = fig.add_subplot(gs[2])
ax3.set_aspect(1)
plt.plot(positions[0], positions[2], color=color, marker='.',ls='None', label=satellite)
circle1 = matplotlib.patches.Ellipse((0, 0), 2*earth_radius_eq, 2*earth_radius_polar, color='b')
plt.gca().add_patch(circle1)
plt.xlabel('x (km)')
plt.ylabel('z (km)')
plt.xlim(-1.1*maxdist, 1.1*maxdist)
plt.ylim(-1.1*maxdist, 1.1*maxdist)
plt.legend(frameon=False,loc='center left', bbox_to_anchor=(1, 0.5))
plt.grid()
plt.subplots_adjust(wspace=1)
ehc.show_noblock()
return
##########################################################################
# Array creation functions
##########################################################################
[docs]def load_txt(fname, ephemdir='ephemeris'):
"""Read an array from a text file.
Sites with x=y=z=0 are spacecraft, TLE ephemerides read from ephemdir.
Args:
fname (str) : path to input array file
ephemdir (str) : path to directory with TLE ephemerides for spacecraft
Returns:
Array: an Array object loaded from file
"""
return ehtim.io.load.load_array_txt(fname, ephemdir=ephemdir)