NAME:
mimiretc
PURPOSE:   (one line only)
Exposure time and throughput calculator for {\it Mimir}
DESCRIPTION:
This program is a non-blocking widget tool for grism and filter
combinations for Mimir, an infrared imaging spectrograph at Lowell
Observatory built in cooperation with Boston University.  This program
attempts to model the light passing through in the instrument and
possible being dispersed.  Along the way, the efficicncy of the
instrument is tallied and you get to see what will be collected at
the detector.

When this program starts, it expects to find a collection of files in the
current directory.  These files define the instrument and the throughput
of its individual components.  The first file that is read is 'mimir.info'.
This file has the following format:
1 Mimir_Info_v1.0
2 437.5       effective focal length of collimator in mm
3 132.195     effective focal length of camera in mm
4 27.0        pixel size of detector in microns
5 unity.dat
6 unity.dat
7 blank.dat
8 grism_jhk.dat
...
a :grism
sp.dat
...
b :filter

The line numbers do not appear in the file.  Trailing comments are ok only
on lines with numeric values (not with file names).  The first line is
the version ID tag.  Line 2 is the effective focal length of the collimator
in millimeters and is used only to determine pixel scale on the sky.
Line 3 is the effective focal length of the camera lens in mm.  This is
used to determine the translation from angular deviation after the grism
to pixels.  Line 4 is the size of the pixels on the detector in microns.

The balance of the file is a list of file names in two sections.  The first
section is a list of grisms.  The list is terminated with the line
":grism".  This grism list is made up of file names that point to grism
definition files.  The second section is a list of filters.  Again, the
filter list is a list of file names.

Grism files are in the following format:

1 Mimir_Grism_v1.0
2 120.0      Grooves/mm
3 29.986     Groove angle, degrees
4 1.52       Index of refraction for resin
5 29.3       Prism apex angle, degrees
6 1.42       Index of refraction for prism

The first line is the version id string.  The next five lines specify the
grism properties as indicated by the option comment strings.  DO NOT
include the line numbers in the file.

Filter files are two-column tables of numbers.  The first column is a
wavelength in microns and the second column is the fraction of light
transmitted at that wavelength (between 0 and 1).  This file does not
need to be tabulated on a regular grid.  Internally the program will
use linear interpolation to get intermediate values.  To ensure that
the file doesn't lead to non-physical values, make sure the first pair
and last pair of numbers have identical throughputs so that extrapolation
beyond the tabulated range will return a constant value.

A complete set of files (including some test entries) are stored in
ftp://ftp.lowell.edu/pub/buie/mimir/etc.  Get all the .dat and .info
files.

The File menu option of "postscript" causes a color postscript file to be
generated with all three plots (wavelength, angle, and pixel) to the file
idl.ps.

CATEGORY:
Utility
CALLING SEQUENCE:
mimiretc
INPUTS:
OPTIONAL INPUT PARAMETERS:
KEYWORD INPUT PARAMETERS:
OUTPUTS:
KEYWORD OUTPUT PARAMETERS:
COMMON BLOCKS:
SIDE EFFECTS:
RESTRICTIONS:
mimir.info is read only upon startup.  If you edit this file while the
program is running you will need to exit and restart to pick up the changes.
All other files are read whenever a plot is generated meaning you can edit
a grism or filter file, save it, replot and see the new values.
PROCEDURE:
MODIFICATION HISTORY:
written by Marc W. Buie, Lowell Observatory, 2002/11/26
2002/12/02, MWB, fixed set_plot bug on Windows platforms