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Last modified: 20 Dec 2016


Adding Old Chandra Calibration Data to PIMMS

CIAO 4.9 Science Threads



The Portable, Interactive Multi-Mission Simulator, PIMMS package allows users to estimate the expected number of counts for various spectral models for different instrument/telescope configuration, including Chandra. The version available from GSFC only includes the latest Chandra calibrations for the current proposal cycle. Sometimes users may want to compare prior predictions with current calibration which requires having the old Chandra calibration curves available. This thread shows how to download the previous calibration files and install them in PIMMS.


The CXC strongly urges users not to use PIMMS to analyze observed data. At best, the prior cycle (or AO, Announcement of Opportunity) calibration curves were a best-guess at what the calibrations would be at the aim point, a year into the future. During the lifetime of the mission the detectors have changed due to increased CTI and contamination buildup and our understanding of these has resulted in some large changes from year to year that are not accounted for in prior years predictions. Users who want a simple conversion from counts to flux assuming a model should make use of the modelflux tool.

For a detailed analysis of the types of errors introduced, users should consult the Pitfalls using PIMMS for Observed Data page.


Users who want to have access to PIMMS calibration data for Chandra AO 3 to the present can follow this thread.

Related Links:

Last Update: 20 Dec 2016 - Updated with cycle 19 files.


Getting Started

PIMMS is not provided by the CXC. Users must download and install their own copy from the NASA's HEASARC site.

To use the Chandra calibration files with PIMMS, you must be using PIMMS version 4.6b (released Jan 25, 2013) or higher. Previous versions could not accommodate the large number of calibration files Chandra provides. The version of PIMMS is printed to the screen when the application starts.

unix% pimms 
*** PIMMS version 4.8c ***
    2016 Sep 99th Release
    Reading mission directory, please wait
* Current model is BREMSSTRAHLUNG, kT=  10.0000 keV; NH =  1.000E+21
   <--- Use 'MODEL' command to change
        and 'PLASMA' command to switch among APEC/mekal/RS
* By default, input rate is taken to be
 Flux (      2.000-     10.000 keV) in ergs/cm/cm/s
   <--- Use 'FROM' command to change the default
* Simulation product will be
 Count rate in CHANDRA-AO19 ACIS-I
   <--- Use 'INSTRUMENT' command to switch to another instrument

If you do not have PIMMS version 4.6b or greater then you will need to install it prior to continuing.

Download Chandra PIMMS files

The predicted Chandra calibration curves for PIMMS are available for proposal cycles 3 (2001) to 19 (current). Cycles 1 and 2 are not available.

Download this tar file, 19Mb.

Install Files

For most users installation will be as simple as uncompressing and untarring the tar file

unix% cd /soft/pimms
unix% /bin/ls 
data  models  pimms  pimms.tex  sample  source
unix% gunzip /tmp/pimmsfiles03-19.tar.gz
unix% tar xvf /tmp/pimmsfiles03-19.tar
-r--r--r-- user/group    44032 2007-11-20 18:01:13 data/chandra-ao10_acis-i_.area
-r--r--r-- user/group        4 2007-11-09 11:52:36 data/chandra-ao10_acis-i_.special
-r--r--r-- user/group    44032 2007-11-20 18:01:14 data/chandra-ao10_acis-s_.area
-r--r--r-- user/group        4 2007-11-09 11:52:43 data/chandra-ao10_acis-s_.special
-r--r--r-- user/group    44032 2007-11-20 18:01:16 data/chandra-ao10_hetg-acis-i_order0.area
-r--r--r-- user/group        4 2007-11-09 11:52:49 data/chandra-ao10_hetg-acis-i_order0.special

Note: These instructions assume that no other additions or modifications have been made to the PIMMS file that indexes the available missions and calibrations. If you have made local edits to data/pms_mssn.lst you need to merge those changes with the file provided.

Verify Installation

Each cycle (AO) of the Chandra files are available by number: for example CHANDRA-AO9, CHANDRA-AO11, etc.

Before installing the prior years, users will see the following error:

Unknown mission name
Type 'directory' for a list of valid mission names
ERROR selecting output mission

After installation, the old predicted curves will simply be available



29 Jan 2013 Initial version.
13 Dec 2013 Updated with cycle 16 files.
17 Dec 2014 Updated with cycle 17 files.
14 Dec 2015 Updated with cycle 18 files.
20 Dec 2016 Updated with cycle 19 files.

Last modified: 20 Dec 2016
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