Adding Old Chandra Calibration Data to PIMMS
CIAO 4.10 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.
- HEASARC PIMMS
- CXC Web Pimms includes all available Chandra observation cycles
- Model Flux
- Pitfalls using PIMMS for Observed Data
Last Update: 21 Dec 2017 - Updated with cycle 20 files.
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 4.8e *** 2017 Aug 18th 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-AO20 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 20 (current). Cycles 1 and 2 are not available.
Download this tar file, 19Mb.
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 pimms_install.guide sample source unix% gunzip /tmp/pimmsfiles03-20.tar.gz unix% tar xvf /tmp/pimmsfiles03-20.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.
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:
PIMMS > FROM CHANDRA-AO20 ACIS-I 0.2-10 Unknown mission name Type 'directory' for a list of valid mission names ERROR selecting output mission PIMMS >
After installation, the old predicted curves will simply be available
PIMMS > FROM CHANDRA-AO20 ACIS-I 0.2-10 PIMMS >
|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.|
|21 Dec 2017||Updated with cycle 20 files.|