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# Copyright (c) 2017 Weitian LI <liweitianux@live.com>
# MIT license
"""
Chandra ACIS utilities
"""
import math
import subprocess
import re
class ACIS:
"""
Chandra ACIS detector properties and utilities.
References
----------
[1] CIAO - dictionary - ACIS (advanced camera for imaging and spectroscopy)
http://cxc.harvard.edu/ciao/dictionary/acis.html
[2] CIAO - Dictionary - PI (pulse invariant)
http://cxc.harvard.edu/ciao/dictionary/pi.html
"""
# Pixel size
pixel2arcsec = 0.492 # [arcsec]
# Number of channels
nchannel = 1024
# Channel energy width
echannel = 14.6 # [eV]
@classmethod
def energy2channel(self, energy):
"""
Convert energy [eV] to channel number.
"""
return math.floor(energy/self.echannel + 1)
@classmethod
def get_type(self, filepath):
"""
Determine the Chandra ACIS type (``I`` or ``S``) according the
active ACIS chips.
Parameters
----------
filepath : str
Path to the input FITS file
Returns
-------
acis_type : str
``I`` if ACIS-I, ``S`` if ACIS-S;
otherwise, ``ValueError`` raised.
"""
subprocess.check_call(["punlearn", "dmkeypar"])
detnam = subprocess.check_output([
"dmkeypar", "infile=%s" % filepath, "keyword=DETNAM", "echo=yes"
]).decode("utf-8").strip()
if re.match(r"^ACIS-0123", detnam):
return "I"
elif re.match(r"^ACIS-[0-6]*7", detnam):
return "S"
else:
raise ValueError("unknown chip combination: %s" % detnam)
def get_chips_str(self, filepath, sep=":"):
"""
Return a string of the chips of interest according to the
active ACIS type.
Parameters
----------
filepath : str
Path to the input FITS file
sep : str, optional
Separator to join the chip ranges, e.g., 0:3, 0-3
Returns
-------
chips : str
``0:3`` if ACIS-I, ``7`` if ACIS-S;
otherwise, ``ValueError`` raised.
"""
acis_type = self.get_type(filepath)
if acis_type == "I":
return sep.join(["0", "3"])
elif acis_type == "S":
return "7"
else:
raise ValueError("unknown ACIS type")
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