JCMT Heterodyne Integration Time Calculator

Introduction

This package contains the Python-based integration time calculator for JCMT heterodyne instruments. It is based on the original Perl HITEC software.

Usage

The integration time calculator (ITC) can be used in a Python program via a HeterodyneITC object. The main calculation methods are calculate_time, calculate_rms_for_elapsed_time and calculate_rms_for_int_time. Each of these takes an optional with_extra_output argument. If this is not specified, only the main answer is returned, but if a true value is given, a (result, extra) pair is returned, where extra is a dictionary of supplemental information.

Here is an example time calculation for a HARP jiggle-chop observation:

from jcmt_itc_heterodyne import \
    HeterodyneITC, HeterodyneITCError, HeterodyneReceiver

itc = HeterodyneITC()

try:
    (result, extra) = itc.calculate_time(
        rms=0.1,  # K TA*
        receiver=HeterodyneReceiver.HARP,
        map_mode=HeterodyneITC.JIGGLE,
        sw_mode=HeterodyneITC.BMSW,
        freq=345.796,  # GHz
        freq_res=0.488,  # MHz
        tau_225=0.1,
        zenith_angle_deg=30.0,
        is_dsb=False,
        dual_polarization=False,
        n_points=25,  # HARP5 pattern
        dim_x=None,
        dim_y=None,
        dx=None,
        dy=None,
        basket_weave=False,
        separate_offs=False,
        continuum_mode=False,
        sideband=None,
        if_freq=None,
        with_extra_output=True)

    print('Main result: {}'.format(result))
    print('Extra information: {!r}'.format(extra))

except HeterodyneITCError as e:
    print('Error: {}'.format(e))

For raster observations, the size of the map is specified via the dim_x and dim_y parameters. The pixel size is given by dx and dy for single pixel receivers. For array receivers, dy is the scan spacing.

The HeterodyneITC object also has various utility methods such as velocity_to_freq_res and estimate_zenith_angle_deg.

License

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/>