IRAC Science Data Simulator (ISDS) Version 9 Jul 03
Note: At the time of this writing (11/08/06) the ISDS is no longer under active development.
It has not been updated since the time of launch. It is recommended that users who seek sample data start instead with the Legacy Program data, which may be downloaded from the Popular Products web site.
Please read the known limitations web page.
 |  |
| Truth Image of NGC 2623 made from the Digital Sky Survey
(left), and a simulated IRAC 5.8 micron data frame (right). |
Updated Version of the ISDS (July 9, 2003).
To install, click on the "installation" button above. It is a complete
replacement for your current ISDS installation and fixes a number of bugs.
Please report bugs found in this version to the SSC Helpdesk
(help@spitzer.caltech.edu).
The IRAC Science Data Simulator is an IRAF package designed to
simulate the IRAC data taking process, including the simulation of most
instrumental effects. It can also be used to produce data similar to the
SSC Basic Calibrated Data product. It was written by Matthew Ashby of the
IRAC Instrument Team at SAO on their behalf. It has been kindly released
to the Spitzer community in the hopes that it will enable Spitzer users to
better understand what they can expect from their data in terms of
instrument artifacts, noise, and data-taking procedures. With the ISDS
you will be able to make simulated data for your observations, which will
at least provide a good visualization of what your data will look like.
The ISDS is released on a shared-risk basis. The simulator is known
to have some bugs and inaccuracies. Please be sure to read the known limitations section and all accompanying
documentation.
What the ISDS does:
- Simulate the data-taking process, including fowler-sampling and the
camera internal byte-packing and packaging.
- Simulate the telescope pointing, including the mapping and dithering
patterns specified in the AOT.
- Simulate the known noise and artifact sources, including: dark current,
flat-fielding, read noise, shot noise, non-linearity, latency, bias
fluctuations, muxbleed, cosmic rays, infrared background, and the limited
bandwidth of the cables.
What the ISDS does not do:
- Model the infrared sky. Users must supply their own calibrated
"truth images" which represent their targets. The ISDS does contain a
simple model for the infrared background, which is modeled as a uniform
contant across the frame.
- Model the PSF or other optical effects. Users must pre-convolve their
data with the Spitzer PSF, which may either be generated via STinyTim or
acquired directly from the SSC.
- Create observation scripts directly, users must pre-make these using
Spot.
What You'll Need:
- A unix computer with around 300MB of free disk. The ISDS was developed
under Solaris on an
UltraSparc.
- A functional copy of IRAF 2.11.
- AOR files, which in turn means you'll need a working copy of Spot, the
SSC proposal tool.
- "Truth Images" which represent (at least your idea of) the infrared
sky at each of the four IRAC wavelengths. These should be in FITS format,
and convolved with the IRAC point spread function. That means you'll also
need the IRAC PSF.
For a complete discussion of the ISDS, Matthew Ashby has written
this document, describing it in
considerable detail. Please send comments/questions to the Spitzer helpdesk.
Jason Surace.
Last update 9 jul 03 by L. Rebull