hifast.radec Coordinate Transformation#

hifast.radec is for transforming celestial coordinates (RA, Dec) from the the trajectory of phase centre of the feed stored in a Office Open XML Workbook file(.xlsx, feed cabin file).

Example Usage#

python -m hifast.radec data/XXX_arcdrift-M01_F-specs_T.hdf5
# Alternatively,
python -m hifast.radec XXX_arcdrift_11_2020_XX_XX_22_54_09_000.xlsx

  • Supported File Types:

    • Input the path of an hdf5 file created by hifast.sep. Only the file for the M01 beam is required as it contains celestial coordinates for other beams as well. According to the file name and mjd in the file to find the corresponding feed cabin file (.xlsx) and then calculate the RA and Dec of each spectrum.

      The program sequentially searches for these directories:

      • your_HOME_dir/KY/ (create this directory for local processing; it’s unnecessary on the FAST server).

      • /data/hw1/FAST/KY/

      • /data31/KY/ (FAST server directories for feed files).

      The program then searches for the relevant feed cabin file in the first directory it finds. It calculates the RA-DEC from the feed file. Since the spectral records’ time sampling points differ from those in the feed file, interpolation is used to derive the final coordinates of the spectrum.

    • Input the path of a feed cabin file with a .xlsx extension. This is used to calculate the RA and Dec corresponding to the trajectory of feed cabin.

Parameters#

  • Key Parameters:

    • --ky_files: Manually specify the path of the feed file if the program automatically locates it. You can specify one or multiple files.

    • --tol: Normally, the feed file’s time range should cover that of the observed spectral lines. Use --tol 5 to allow extrapolation for RA and Dec when there is a 5-second gap in the celestial file records. Note that spectral data from extrapolated coordinates should be discarded.

    • --outdir: Specify the output file’s directory. For .hdf5 file inputs, it defaults to the input file’s directory; for .xlsx inputs, it defaults to the program’s run path.

    • --ky_fixed: For early Drift scans where the feed file only recorded a few minutes of feed cabin position, this parameter calculates Right Ascension and Declination for the entire spectrum based on these few minutes. Caution: The feed may not have remained stable during the drift, so this could affect accuracy.

    • --plot: This option plots and saves a figure of RA and Dec.

    Note

    If your computer does not have internet access, automatic download of IERS data will fail, leading to errors like:

    • IERSStaleWarning: leap-second file is expired.

    • astropy.utils.iers.iers.IERSRangeError: (some) times are outside of range covered by IERS table.

    • urllib.error.URLError: <urlopen error [Errno -2] Name or service not known>

    To resolve this, please use the IERS Offline Cache Updater tool to manually update the offline cache.

  • For additional parameter information, use: python -m hifast.radec -h | more.

Output#

The output file, named with the “-radec” suffix added to the input file, stores the celestial coordinates data. It can be read with h5py. Example:

import h5py
f = h5py.File('data/XXX_arcdrift-M01_F-specs_T-radec.hdf5', 'r')
S = f['S']
print(S.keys())
S['mjd'][:]