PIMMS can be run over the WWW using a browser, such as
Netscape, or run locally using the command-line interface
(CLI). PIMMS is part of the Proposal toolkit. The toolkit is
distributed with CIAO.
PIMMS is a tool for estimating the source flux or count
rate for a specific mission from either a count rate estimated by
a previous mission or flux in some energy bound.
It is very useful for simple source spectra,
but not for complicated spectral or spatial structures.
PIMMS also estimates the amount of Chandra ACIS pile-up
assuming a point source on-axis, and accounts for this when
estimating count rates. The
tool was developed at NASA-GSFC, and the CXC implemented its own
version for use as a Chandra proposal tool. Detailed
information concerning PIMMS is available at:
http://heasarc.gsfc.nasa.gov/docs/software/tools/pimms.html.
Cycle 9 Effective Areas: The calibration files required for
the command line interface
of PIMMS are included in CIAO 3.4. **There
is no CALDB version requirement for PIMMS.** It is also
possible to use the PIMMS effective area viewer online to view the latest
effective area curves.
ACIS Pile-up: As mentioned above, PIMMS estimates the effect
of pile-up on ACIS counting rates. However, if a grating is
inserted, the impacts of pile up are only estimated for the
counting rate of the zeroth order image.The pile-up fraction
in PIMMS software is defined as the
ratio of the number of frames with two or more spurious
pile-up events to the number of frames with a single,
unpiled event. Note that the command-line version of PIMMS
assumes that the entire ACIS bandpass is used.
RAYMOND-SMITH MODELS:
(1) The calculation only extends to 8 keV regardless of output AND input
energy ranges. Any input model will be truncated at 8 keV, no attempt
will be made to ''convert'' counts above 8 keV. Similarly, the output
gives flux/counts up to 8 keV.
(2) The available temperatures are
listed in a pop-up menu from which the user selects that closest to
his/her desired temperature.
PIMMS can be accessed via the URL:
http://cxc.harvard.edu/toolkit/pimms.jsp
A general help file for the Proposal Planning Toolkit is available by
clicking the 'HELP' button.
Descriptions for each parameter may be found by clicking
the appropriate parameter name.
The web version of PIMMS has some features not found in the
command-line version, such as background count rates for
Chandra mission, the ACIS frame time option,
and the truncation of energy at 8 keV in
Raymond-Smith Models.
BACKGROUND COUNT RATES:
The web version of PIMMS provides background in a 1.5''
radius circle for imaging (ACIS or HRC) observations. Extended
source size specification affects only background determination.
PIMMS also estimates the background per resolution element for
HRC-S/LETG spectra.
ACIS FRAME TIME:In the web version of PIMMS, the user can
either enter the ACIS frame time or
choose to have PIMMS calculate the most efficient frame time
for a given number of CCDs and sub-array.
In the latter case, PIMMS will
calculate the frame time that results in the least amount of
pile-up and will present the corresponding results. The actual
frame time used in performing these calculations can be
examined using the ''View Output'' button.
To run PIMMS in the interactive CLI mode, type 'prop_pimms'
at the Unix prompt.
The NASA HEASARC web site includes a
PIMMS user guide,
and there
is a 'HELP' command in PIMMS.
To view HELP, simply type 'help' or 'h' at the PIMMS prompt.
To exit or go up one level in HELP, hit the return key.
To exit PIMMS, type
either 'QUIT' or 'EXIT', or simply 'q' or 'e'.
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