WISE Background Predictor ("bgmodel")

Last modified: 03/18/2010, F. Masci

This document is organized as follows:

- Summary
- Some notes
- I/O synopsis 
- Examples

Summary:
 
The "bgmodel" program takes as input an observation time, R.A./Dec. of
a target, a wavelength or specific WISE band number, ephemeris files,
and a directory containing IR emission maps from IRAS and DIRBE. It returns
predicted values for the zodiacal emission, interstellar medium emission,
and the cosmic infrared background in MJy/sr. A FITS image can also be
provided, in which case values of the observation time (DATIME), 
R.A.(CRVAL1), and Dec.(CRVAL2) are read from the header. The header can
be optionally updated with values for the three background estimates
using keywords: ZODY_EST, ISM_EST, and CIB_EST.

At the time of writing, bgmodel can only be executed from within the
WISE "dev" environment.

Some Notes:
This program and the libraries it depends on (-ljbBG, -ljbSFD, -ljbcvtc)
were adopted from the Spitzer Science Center and modified for use on
WISE. Details of the IR emission models and maps are given in: 
http://ssc.spitzer.caltech.edu/warmmission/propkit/som/bg/background.pdf
The dust maps were retrieved from the Spitzer Science Center under:
/proj/ssc/Data/IRAC/SFD/ and copied into /wise/fmasci/bgmodel/dustmaps 
for use on WISE.

A superior set of maps, which give more accurate estimates of the 
sky brightness at 12 and 25 microns are the IRIS reprocessing of the
IRAS data (Bill Reach, private communication). For details see:
http://www.cita.utoronto.ca/~mamd/IRIS/IrisOverview.html
These have not been installed for WISE. The current default maps are 
sufficient for first order estimates of the zodiacal, ISM, and cosmic 
IR backgrounds.

The hardcoded WISE band definitions (-b input parameter) are as follows. 
These were obtained from:
http://www.astro.ucla.edu/~wright/WISE/passbands.html

BAND1                3.368 microns
BAND2                4.618 microns 
BAND3               12.082 microns 
BAND4               22.194 microns

I/O Synopsis:
When executed with no command-line arguments, the following usage synopsis
is written to the screen:

Program bgmodel (Perform background model predictions), Version 1.1

Usage: bgmodel
 -i    <Image> (Optional; if provided, -t,-ra,-dec read from header;
                header also updated with bckgnd keywords if -h specified)
 -b    <BandNumber> (Optional; any one of 1,2,3,4 as defined in
                     bgmodel.h file; overrides -w value)
 -w    <Wavelength> (Required if -b not specified, in microns)
 -t    <ObsTime> (Required if input image (-i) not given;
                  e.g: '2010-01-28T19:26:35' [=DATIME keyword])
 -ra   <RA> (Required if input image not given [=CRVAL1 keyword])
 -dec  <Dec> (Required if input image not given [=CRVAL2 keyword])
 -e    <Ephemeris_File> (Required)
 -p    <Leapsec_Kernel_File> (Required)
 -s    <Spk_Kernel_File> (Required)
 -m    <BkgdMap_Path> (Required)
 -d    (switch: prints debug statements)
 -v    (switch: verbose output)
 -h    (switch: update image header with bckgnd keywords)

Examples:
(1) Execute bgmodel via a script which returns background estimates for all
    WISE bands; see script: caustic:/wise/fmasci/bgmodel/driver/README
    Here are the steps:
    (i)  copy this script to your private directory;
    (ii) edit the script and update the following variables:
         # date-time string of observation:
           set datime = 2010-01-14T19:52:26.000
         # R.A./Dec. of target:
           set ra = 206.30676910035 
           set dec = 6.05442204469935
    (iii) ensure your environment is "dev" by typing at the prompt:
          % newcfg dev
    (iv)  execute as:
          % ./README
          and results will be written to the screen.

(2) Execute bgmodel standalone on a single WISE band, e.g., band 4. Note, the 
    "\" are used to break up the command-line to avoid wrap-around in this
    document.
    % newcfg dev
    % bgmodel -b 4 -t 2010-01-14T19:52:26.000 -ra 206.306769 -dec 6.054422  \
      -e /wise/fmasci/bgmodel/wise_extended.bsp \
      -s /wise/fops/ref/mos/naif/wise-planets.bsp \
      -p /wise/fops/ref/mos/naif/wise.tls \
      -m /wise/fmasci/bgmodel/dustmaps -v

(3) Execute bgmodel with an input WISE band 1 FITS image containing correct
    WCS and date-time keywords. The FITS header is also updated with values
    of the IR background components:
    % newcfg dev
    % bgmodel -b 1 -i /path/01157b123-w1-int-1b.fits \
      -e /wise/fmasci/bgmodel/wise_extended.bsp \
      -s /wise/fops/ref/mos/naif/wise-planets.bsp \
      -p /wise/fops/ref/mos/naif/wise.tls \
      -m /wise/fmasci/bgmodel/dustmaps -h -v

(4) Execute bgmodel using a specific (non-WISE) wavelength, e.g., 150 microns:
    % newcfg dev
    % bgmodel -w 150 -t 2010-01-14T19:52:26.000 -ra 206.306769 -dec 6.054422  \
      -e /wise/fmasci/bgmodel/wise_extended.bsp \
      -s /wise/fops/ref/mos/naif/wise-planets.bsp \
      -p /wise/fops/ref/mos/naif/wise.tls \
      -m /wise/fmasci/bgmodel/dustmaps -v


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