mktrace

Refine a STIS trace table.

• A trace is generated from the science file and a trace center is computed.
• The two traces bracketing the trace center are extracted from the trace table and interpolated
• The correction is computed as the difference between the linear fit to the science and interpolated traces
• The correction is applied to all traces in the trace file for that particular OPT_ELEM and CENWAVE
• A new trace table is written to the current directory and the relevant keywords are updates in the header of the input file.

Examples

Simple example of running mktrace on a STIS file named ‘file.fits’:

>>> import mktrace
>>> mktrace.mktrace('file.fits', [tracecen=509.4], [weights=[(x1,x2),(x3,x4)])

Authors:

• Author (IDL): Linda Dressel
• Python version: Nadia Dencheva

class stistools.mktrace.Trace(file, kwinfo)

Trace class for a crj or flt file.

Notes

tr=Trace(file) file is a crj or flt file.

opt_elem, cenwave, sporder are read from the header of the science file a2center is a2center of the trace generated from the science file

tr_ind= tr.getTraceInd(a2center)

tr_ind is the index of the row in the trace file which brackets from below a2center as computed fro the generated trace

tr.readTrace(tr_ind)

a2center = tr.generateTrace(…)

Methods

gFitTrace(specimage, y1, y2)	Fit a gaussian to each column of an image.
generateTrace(data, kwinfo[, tracecen, wind])	Generates a trace from a science file.
getTraceInd(a2center)	Finds the first trace in the trace table whose A2CENTER is larger than the specified a2center.
openTraceFile(filename)	Returns a spectrum trace table
readTrace(tr_ind)	reads the specified row from the 1dttab.fits
writeTrace(fname, sciline, refline, …)	The ‘writeTrace’ method performs the following steps:

gFitTrace(specimage, y1, y2)

Fit a gaussian to each column of an image.

generateTrace(data, kwinfo, tracecen=0.0, wind=None)

Generates a trace from a science file.

getTraceInd(a2center)

Finds the first trace in the trace table whose A2CENTER is larger than the specified a2center.

openTraceFile(filename)

Returns a spectrum trace table

readTrace(tr_ind)

reads the specified row from the 1dttab.fits

writeTrace(fname, sciline, refline, interp_trace, trace1024, tr_ind, a2disp_ind)

The ‘writeTrace’ method performs the following steps:

• Adds sciline-refline to all traces with the relevent OPT_ELEM, CENWAVE and SPORDER.
• Writes the new trace table to the current directory.
• Updates the SPTRCTAB keyword in the header to point to the new table.
• Writes out fits files with the
  • science trace - ‘_sci’
  • the fit to the science trace - ‘_scifit’
  • the interpolated trace - ‘_interp’
  • the linear fit to the interpolated trace - ‘_interpfit’

stistools.mktrace.interp(y, n)

Given a 1D array of size m, interpolates it to a size n (m < n).

stistools.mktrace.mktrace(fname, tracecen=0.0, weights=None)

Refine a stis spectroscopic trace.