Ejemplo n.º 1
0
def readMS(fn, sbs, column='DATA'):
    """Return the visibilites and UVW coordinates from a SE607 LOFAR XST format file
    fn: XST filename
    column: string, data column
    sbs: 1-D array of subband IDs

    returns:
        vis: visibilities [4, Nsamples, Nsubbands]
        uvw: UVW coordinates [Nsamples, 3, Nsubbands]
        freqs: frequencies [Nsubbands]
        obsdata: [latitude, longitude, LST]
    """
    try:
        import casacore.tables as tbls
    except ImportError:
        print 'ERROR: could not import casacore.tables, cannot read measurement sets'
        exit(1)

    MS = tbls.table(fn, readonly=True)
    data_column = column.upper()
    uvw = MS.col('UVW').getcol() # [vis id, (u,v,w)]
    vis = MS.col(data_column).getcol() #[vis id, freq id, stokes id]
    vis = vis[:,sbs,:] #select subbands
    MS.close()

    # lat/long/lst information
    ANTS = tbls.table(fn + '/ANTENNA')
    positions = ANTS.col('POSITION').getcol()
    ant0Lat, ant0Long, ant0hgt = ecef.ecef2geodetic(positions[0,0], positions[0,1], positions[0,2], degrees=False) # use the first antenna in the table to get the array lat/long
    ANTS.close()
    SRC = tbls.table(fn + '/SOURCE')
    direction = SRC.col('DIRECTION').getcol()
    obsLat = direction[0,1]
    obsLong = ant0Long
    LSTangle = direction[0,0]
    SRC.close()

    # freq information, convert uvw coordinates
    SW = tbls.table(fn + '/SPECTRAL_WINDOW')
    freqs = SW.col('CHAN_FREQ').getcol()[0, sbs] # [nchan]
    print 'SUBBANDS:', sbs, '(', freqs/1e6, 'MHz)'
    SW.close()

    # TODO: check rotation reference is the same as with LOFAR data, north pole is dec=+90, ra=0
    # in order to accommodate multiple observations at different times/sidereal times all the positions need to be rotated relative to sidereal time 0
    print 'LST:',  LSTangle
    rotAngle = float(LSTangle) - obsLong # adjust LST to that of the Observatory longitutude to make the LST that at Greenwich
    # to be honest, the next two lines change the LST to make the images come out but i haven't worked out the coordinate transforms, so for now these work without justification
    rotAngle += np.pi
    rotAngle *= -1
    # Rotation matrix for antenna positions
    rotMatrix = np.array([[np.cos(rotAngle), -1.*np.sin(rotAngle), 0.],
                          [np.sin(rotAngle), np.cos(rotAngle),     0.],
                          [0.,               0.,                   1.]]) #rotate about the z-axis
    uvwRot = np.dot(uvw, rotMatrix).reshape(uvw.shape[0], uvw.shape[1], 1)
    uvwRotRepeat = np.repeat(uvwRot, len(sbs), axis=2)

    return np.transpose(vis, (2,0,1)), uvwRotRepeat, freqs, [obsLat, obsLong, LSTangle]
Ejemplo n.º 2
0
def readMS(fn, sbs, column='DATA'):
    """Return the visibilites and UVW coordinates from a Measurement Set
    fn: MS filename
    column: string, data column
    sbs: 1-D array of subband IDs

    returns:
        vis: visibilities [4, Nsamples, Nsubbands]
        uvw: UVW coordinates [Nsamples, 3, Nsubbands]
        freqs: frequencies [Nsubbands]
        obsdata: [latitude, longitude, LST]
    """
    try:
        import casacore.tables as tbls
    except ImportError:
        print 'ERROR: could not import casacore.tables, cannot read measurement sets'
        exit(1)

    MS = tbls.table(fn, readonly=True)
    data_column = column.upper()
    uvw = MS.col('UVW').getcol() # [vis id, (u,v,w)]
    vis = MS.col(data_column).getcol() #[vis id, freq id, stokes id]
    vis = vis[:,sbs,:] #select subbands
    MS.close()

    # lat/long/lst information
    ANTS = tbls.table(fn + '/ANTENNA')
    positions = ANTS.col('POSITION').getcol()
    ant0Lat, ant0Long, ant0hgt = ecef.ecef2geodetic(positions[0,0], positions[0,1], positions[0,2], degrees=False) # use the first antenna in the table to get the array lat/long
    ANTS.close()
    SRC = tbls.table(fn + '/SOURCE')
    direction = SRC.col('DIRECTION').getcol()
    obsLat = direction[0,1]
    obsLong = ant0Long
    LSTangle = direction[0,0]
    SRC.close()

    # freq information, convert uvw coordinates
    SW = tbls.table(fn + '/SPECTRAL_WINDOW')
    freqs = SW.col('CHAN_FREQ').getcol()[0, sbs] # [nchan]
    print 'SUBBANDS:', sbs, '(', freqs/1e6, 'MHz)'
    SW.close()

    # TODO: check rotation reference is the same as with LOFAR data, north pole is dec=+90, ra=0
    # in order to accommodate multiple observations at different times/sidereal times all the positions need to be rotated relative to sidereal time 0
    print 'LST:',  LSTangle
    rotAngle = float(LSTangle) - obsLong # adjust LST to that of the Observatory longitutude to make the LST that at Greenwich
    # to be honest, the next two lines change the LST to make the images come out but i haven't worked out the coordinate transforms, so for now these work without justification
    rotAngle += np.pi
    rotAngle *= -1
    # Rotation matrix for antenna positions
    rotMatrix = np.array([[np.cos(rotAngle), -1.*np.sin(rotAngle), 0.],
                          [np.sin(rotAngle), np.cos(rotAngle),     0.],
                          [0.,               0.,                   1.]]) #rotate about the z-axis
    uvwRot = np.dot(uvw, rotMatrix).reshape(uvw.shape[0], uvw.shape[1], 1)
    uvwRotRepeat = np.repeat(uvwRot, len(sbs), axis=2)

    return np.transpose(vis, (2,0,1)), uvwRotRepeat, freqs, [obsLat, obsLong, LSTangle]
Ejemplo n.º 3
0
def lofarArrayLatLong(lofarStation, arrayType='LBA'):
    """Return the Latitude, Longitude, Elevation of a LOFAR station
    lofarStation: instance, see lofarConfig.py
    arrayType: string, LOFAR array type

    returns: latitude (degs), longitude (degs), elevation (m)
    """
    #lon, lat, elev = lofarStation.antArrays.location[lofarConfig.rcuInfo[fDict['rcu']]['array_type']]
    arr_xyz = lofarStation.antField.location[arrayType]
    lat, lon, elev = ecef.ecef2geodetic(arr_xyz[0], arr_xyz[1], arr_xyz[2], degrees=True)
    print 'LON(deg):', lon, 'LAT(deg):', lat, 'ELEV(m):', elev

    return lat, lon, elev
Ejemplo n.º 4
0
def lofarArrayLatLong(lofarStation, arrayType='LBA'):
    """Return the Latitude, Longitude, Elevation of a LOFAR station
    lofarStation: instance, see lofarConfig.py
    arrayType: string, LOFAR array type

    returns: latitude (degs), longitude (degs), elevation (m)
    """
    #lon, lat, elev = lofarStation.antArrays.location[lofarConfig.rcuInfo[fDict['rcu']]['array_type']]
    arr_xyz = lofarStation.antField.location[arrayType]
    lat, lon, elev = ecef.ecef2geodetic(arr_xyz[0], arr_xyz[1], arr_xyz[2], degrees=True)
    print 'LON(deg):', lon, 'LAT(deg):', lat, 'ELEV(m):', elev

    return lat, lon, elev