1 files changed, 91 insertions, 0 deletions
diff --git a/astro/chandra/blanksky_add_time.py b/astro/chandra/blanksky_add_time.py
new file mode 100755
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+++ b/astro/chandra/blanksky_add_time.py
@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+#
+# Aaron LI
+# 2015/06/16
+#
+# Changelogs:
+# 0.2.0, 2015/06/16, Aaron LI
+#   * append the new time column to the *last*, rather than inserting
+#     to the beginning
+#   * explicitly update header from the new generated table
+#
+# BUGS:
+#   * comments of columns will lost after modified by astropy.io.fits,
+#     which is a bug with this package
+#
+
+"""
+Add a time column for the chandra blanksky event file.
+The time data are generated with a uniform distribution
+between TSTART and TSTOP.
+"""
+
+__version__ = "0.2.0"
+__date__ = "2015/06/16"
+
+import sys
+import argparse
+
+import numpy as np
+try:
+    from astropy.io import fits
+except ImportError:
+    try:
+        import pyfits as fits
+    except ImportError:
+        raise ImportError("cannot import 'astropy.io.fits' or 'pyfits'")
+
+
+def add_time_column(fitsfile, blockname="EVENTS"):
+    """
+    Add a time column to the specified block of the input fits file.
+    The time data are generated with a uniform distribution
+    between TSTART and TSTOP.
+
+    Return:
+        A fits object with the new time column.
+    """
+    if isinstance(fitsfile, str):
+        fitsfile = fits.open(fitsfile)
+    table = fitsfile[blockname]
+    tstart = table.header["TSTART"]
+    tstop = table.header["TSTOP"]
+    counts = len(table.data)
+    time_data = np.random.uniform(tstart, tstop, counts)
+    time_col = fits.Column(name="time", format="1D", unit="s", array=time_data)
+    # NOTE: append the new time column to the *last*!
+    # Otherwise the TLMIN??/TLMAX?? keyword pairs, which record the
+    # minimum/maximum values of corresponding columns, will become
+    # *out of order*. Therefore the output FITS file causes weird problems
+    # with DS9 and DM tools.
+    newtable = fits.BinTableHDU.from_columns(
+            table.columns + fits.ColDefs([time_col]))
+    fitsfile[blockname].data = newtable.data
+    # update header
+    fitsfile[blockname].header.update(newtable.header)
+    return fitsfile
+
+
+def main():
+    parser = argparse.ArgumentParser(
+            description="Add a time column for Chandra blanksky event file.")
+    parser.add_argument("-V", "--version", action="version",
+            version="%(prog)s " + "%s (%s)" % (__version__, __date__))
+    parser.add_argument("infile", help="input chandra blanksky file")
+    parser.add_argument("outfile", nargs="?", default=None,
+            help="modified blanksky file. IN-PLACE modification if omitted.")
+    parser.add_argument("-C", "--clobber", dest="clobber",
+            action="store_true", help="overwrite output file if exists")
+    args = parser.parse_args()
+
+    newfits = add_time_column(args.infile)
+    if args.outfile:
+        newfits.writeto(args.outfile, clobber=args.clobber)
+    else:
+        newfits.writeto(args.infile, clobber=True)
+
+
+if __name__ == "__main__":
+    main()
+