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This is the UK Mirror of the HEASARC PIMMS pages, maintained by LEDAS.
Please refer any problems with these pages to ledas-help@star.le.ac.uk.

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PIMMS reads the list of missions from a file called pms_mssn.lst in the data directory. It then looks, for each mission (i.e., satellite), detector and filter combination, the appropriate calibration files for the effective area etc. Since this is a run-time process, the following items may not exactly correspond to what you see. For a listing of what is currently available, use the DIRECTORY command.

For active and near-future missions, we provide the latest effective area curves with PIMMS for proposal preparation purposes. If the effective area changes in-orbit, count rate to flux conversion factor for actual observations is time-dependent, which PIMMS is currently not well equipped to handle.


The Japanese X-ray satellite ASCA had 4 co-aligned telescopes, each having an effective area of ~250 cm^2 at 1 keV; there were two GIS (imaging gas scintillation proportional counters) and two SIS (Solid-state Imaging Spectrometer, X-ray CCDs) detectors. Count rates are given for a single GIS or a single SIS, as appropriate.


BBXRT is flown on the Shuttle with the ASTRO payload in December 1990. The effective area curve is that for pixel A0.


The Compton Gamma Ray Observatory OSSE instrument is now available as in PIMMS, primarily as an aid in Integral observation planning.

Chandra (AXAF)

The Chandra X-ray Observatory was formerly known as AXAF; starting with v2.7, PIMMS has switched to Chandra.

This version includes the Chandra instrument effective area curves appropriate for Cycle 11 proposers as provided by the Chandra X-ray Observatory Center, where the details of the instruments can be found. Older versions are available by request.

All effective areas assume an on-axis observation.

The 4 CCDs of the AXAF CCD Imaging Spectrometer Imaging array (ACIS-I) cover ~17 by 17 arcmin of sky with ~0.5 arcsec square pixels. PIMMS calculates the on-axis count rate uncorrected for pile-up (see below).

Two of the 6 ACIS-S CCDs are back-illuminated (BI), to improve the low energy effective areas. For imaging with ACIS-S, the observer will thus have the choice of FI/BI. Since the FI chips have a performance identical to that of the ACIS-I chips, only the BI chip option is separately available in PIMMS.

High Resolution Camera (HRC) covers a larger area of the sky with smaller pixels.

All effective areas for the gratings are for both positive and negative orders summed together.

ACIS-S will be the normal readout instrument for HETG (High Energy Transmission Grating) spectra. The curves use the flight instrument chip layout of 4 FI and 2 BI chips. PIMMS will provide count rates for both grating subsets (MEG and HEG) separately, or for the combination. A single observation provides both spectra simultaneously in a cross-shaped orientation. Since the energy response and spectral resolution of the two grating assemblies differ, separation of the output may be important for some users. In all cases the output is for isolated first order. The energy resolution of the ACIS instrument will allow the user to separate this from the higher order light. See the Science Instrument Notebook for more information. Count rate in the zeroth order image can also be calculated.

HRC-S is the normal readout instrument for LETG (Low Energy Transmission Grating) spectra. PIMMS currently allows determination of the count rates in the 0th order image; 1st order spectrum; and the higher orders; through the "normal" part of the UV/Ion shield. Note in practice, due to the lack of energy resolution of the HRC, isolation of the first order signal will require a combination of "normal" and "low-energy reject" mode observations which are likely to take roughly twice as long as the estimate provided by PIMMS. An alternative is to use the High Energy Suppression Filter (HESF) which effectively isolates first order from 0.05-0.44 keV.

LETG data can also be read out with the ACIS-S detectors; 0th and 1st order count rates for this combination can also be estimated with PIMMS.


Observations of bright sources with ACIS are limited by photon pile-ups (see Proposers Guide). This version of PIMMS includes a beta-test release of pile-up estimate (based on the separate pileup tool written at ASC). This feature, when turned on (by uncompressing the special files in the data directory), will provide you with an estimate of the degree of pile-up for ACIS imaging mode observations (ACIS-I, ACIS-S-BI, LETG-ACIS-S ORDER0, and HETG-ACIS-S ORDER0).

Note that this is valid only for point source observations on-axis.

Pile-up effect can be mitigated by placing the source off-axis --- the inferior PSF will spread the photons over many pixels. Quantitative analysis of this is not yet available in PIMMS. The other principal method of altering the frame time can be evaluated by PIMMS. For this purpose, the 'go' command of PIMMS for ACIS-I and ACIS-S-BI allows an optional numerical parameter. If given, it will be taken as the frame time (allowed range: 0.2-3.3 s), and gives the pile-up fraction accordingly. If absent, PIMMS will attempt to estimate the frame time at which the pile-up fraction is 10% (which is the rule-of-thumb number above which you will have a severe problem). For the two 0th order images, the default frame time of 3.3 s is assumed.

Constellation-X ("conx")

The Constellation X-ray Mission is a next generation X-ray observatory dedicated to high resolution spectroscopy. Currently, PIMMS includes effective area curves derived from simulation-grade response matrices released in 2008 February.


Currently PIMMS only have IPC and MPC effective area curves.


PIMMS currently has the effective area curves for the three channels of the spectrometer, which is used by GOs for pointed observations. Detectors are SW (70-190A), MW (140-480A) and LW (280-750A).


For the Low Energy telescopes, only the LE1/CMA effective area data are kept within PIMMS. Specify filter OPEN, LX3, LX4, ALP, or BRN. The ME effective area is for a half-array; GSPC area is also available.


Ginga is the 3rd Japanese X-ray astronomy satellite, which carried the LAC (Large Area Counter) array with an effective area of ~4000 cm^2. Count rate can be calculated for TOP layer of the detector only or BOTH.


Currently, only the A4 LED is supported.

The PIMMS set-up for this instrument is meant to make it straightforward to use the Levine et al (1984, ApJS 54, 281) catalog for XTE proposals. As an input, use the A+B+C combined count rate; as an output, A+B+C rate as well as the individual rate in the four bands (A through D) are given. One suggested use is to specify HEAO1 A4 as both input and output instrument: by an iterative process, the user can find a spectral model that reproduces the distribution of counts in different bands. Then switch to a different output instrument (in terms of energy range, LED matches the higher end of XTE PCA and the lower end of XTE HEXTE) keeping that model.


As of version 3.9f, PIMMS includes effegtive area curves for ISGRI and JEM-X instruments, based on calibration as of 2008 March. See Integral Science Data Centre for details of the mission.


For the German XRT, effective area curve with PSPC (filter OPEN or BRN) and HRI are available. Also, beginning with v2.3, the Snowden R bands (see Snowden et al 1994, ApJ 424, 714) are available as software filters (R1, R1R2, R4, R4R5, R4TOR7, R5, R6, R6R7, and R7). For the British WFC, filters S1, S2, P1 and P2 effective area curves are available; these are appropriate for the time of launch. Note the S1 and S2 sensitivity dropped to ~75% of initial value by the end of the survey, followed by a steeper decline to 15-20% of the original value after The Tumble. Non-survey (P1 and P2) filters have suffered much smaller degradation.


Although the official name for this Italian-Dutch satellite is now BeppoSAX, the mission name within PIMMS remains SAX. It was launched in Apr 1996 by an Atlas G-Centaur directly into a 600 km orbit at 3 degrees inclination. SAX carries 4 narrow field instruments (1 LECS, 2 MECS, 1 HPGSPC, 1 PDS), covering the energy band from 0.1 to 200 keV, and two Wide Field Cameras (WFC, 2-30 keV) which view the sky through a coded mask perpendicularly to the axis of the narrow field instruments. The LECS (0.1-10 keV) is an imaging gas scintillation proportional counter similar to the MECS but extends the energy range down to 0.1 keV. The MECS (1-10 keV) is an imaging gas scintillation proportional counter similar to the LECS. There are 2 working MECS on board SAX(a third unit developed a fault in May 1997). The count rate estimate is for the 2 MECS, starting with version 2.4b (previous versions estimated for 3 MECS). The HPGSPC is an high pressure gas scintillation proportional counter sensitive in the energy range 3-120 keV with a FOV of 1 deg. The PSD, phoswich detector system, consists in four phoswich units. The observations are carried out with two halves of the experiment alternatively pointing source and background region, providing a continuous monitoring of the background. The PSD is sensitive in the 15-300 keV energy bandwidth and has a FOV of 1.5 deg. The Wide field Cameras is position sensitive proportional counter sensitive in the 2-30 keV band. There are 2 WFC on board SAX. The FOV per unit is 20 deg X 20 deg with an angular resolution of a few arcmin.


Suzaku (formerly Astro-E2) is a Japanese-US X-ray astronomy satellite launched in July 2005. The current PIMMS implimentation is based on information from the instrument teams as of 2009 September, as collected by the Suzaku Guest Observer Facility.

The Hard-Xray Detector (HXD) is a non-imaging instrument with an effective area of ~300 cm2 featuring a compound-eye configuration and an extremely low background. It consists of two types of sensors, silicon PIN diodes and GSO crystal scintillators.

There are four units of the X-ray Imaging Spectrometer (XIS) on-board Suzaku, three with frontside-illuminated (FI) CCDs and one with a backside-illuminated (BI) CCD. Each XIS detector is located at the focus of a conical foil X-Ray Telescope (XRT) with a 4.75m focal length. The CCD pixels of XIS vastly oversamples the XRT PSF, thereby allowing high S/N spectroscopy with a relatively benign amount of photon pile-up.

PIMMS currently returns count rate per one unit of XIS, with no further instrument specific information.

The X-Ray Spectrometer (XRS) lost all its liquid helium cryogen and is no longer operational. The pre-launch estimate of the XRS effective area is included in PIMMS for historical purposes.


Swift is a multiwavlength gamma-ray burst observatory launched on 2004 November 20. Swift carries a wide-field (2 sr), coded-aperture Burst Alert Telescope (BAT, 15-150 keV); an X-Ray Telescope (XRT, 0.2-10 keV); and a UV/Optical Telescope (UVOT, 170-650 nm). The BAT response in PIMMS v3.6c and later yields the counts per fully illuminated detector, which matches the BAT analysis software default units. One detector has a geometric area of 0.16 cm2. An on-axis source illuminates 16384 detectors; PIMMS v3.6b and earlier calculated the total on-axis count rates (i.e., per 16384 detectors).

Note that PIMMS is primarily an X-ray tool, and extrapolation to the UV regime introduces additional uncertainties. In particular, PIMMS assumes EB-V = NH / 4.8 x 1021 and an average Milkyway extinction law.


Spectrum-X-Gamma (SXG) is a Russian-led international mission. This version of PIMMS supports the SODART X-ray telescope with LEPC and HEPC (both are Microstrip Proportional Counters) and with SIXA (Silicon Spectrometer).


XEUS (X-ray Evolving Universe Spectroscopy) mission is a potential follow-on to ESA's XMM mission. Currently, PIMMS includes effective area curves derived from simulation-grade response matrices made available in 2007.


XMM, the X-ray Multi-mirror Mission, is the second cornerstone of the European Space Agency (ESA) Horizon 2000 program. XMM is currently scheduled to be launched in January 2000. It consists of three coaligned high-throughput 7.5m focal length telescopes with six arc second (FWHM) angular resolution. The European Photon Imaging Camera (EPIC), which consists of two MOS and one PN CCD arrays, provide moderate spectral resolution over a30 arc minute field of view. High-resolution spectral information (E/dE~300) is provided by the Reflection Grating Spectrometer (RGS) that deflects half of the beam on two of the X-ray telescopes (those with the MOS arrays). The observatory also has a coaligned 30cm optical/UV telescope called the Optical Monitor (OM).

The count rates for the EPIC MOS are given for one instrument, calculated using the average effective area curves of MOS1 and MOS2. Note that, starting with V3.6, PIMMS now uses EPIC effective area curves for 15 arcsec radius extraction regions that are typically used for point sources observed on-axis.

The count rates for the EPIC MOS are given for one instrument (we have averaged the effective area curves for MOS1 and MOS2) not for pairs of instruments. Note that, starting with V3.6, PIMMS now uses EPIC effective area curves for 15 arcsec radius extraction regions that are typically used for point sources observed on-axis.

Starting with Version 3.9, PN rates are for PATTERN=0 events only.

For the RGS, count rates in three orders can be calculated separately. Even though the term 'filter' is used (because that's what the most common use of the third level of instrument specification in PIMMS), these do not represent physical filters. Data are taken in all three orders simultaneously, to be extracted into separate spectra using software filters.


XTE, which was launched in Dec 1995, carries the All-Sky Monitor (ASM), large area proportional counter array (PCA) and the high energy X-ray Timing Experiment (HEXTE).

PCA is a mechanically-collimated array of five xenon proportional counter units (PCUs) with a total effective area of ~7000 cm2; however, different observations are taken with difeerent numbers of PCUs on. Therefore, starting with PIMMS v2.7, user must supply the count rate per PCU when this is used as the input mission (from xte pca). When used as the output mission (inst xte pca), the first output is count rate per PCU summed over all energies and over all 3 xenon layers. Additional outputs (the rates in the 6 canonical PCA channels required on the proposal form and used in RECOMMD) are given for 3 and 2 PCU combinations, which are becoming more frequent (and the proposal form requires numbers for 3 PCUs). The effective area curves, channel boundaries and the extimated background rates are all appropriate for "Epoch 4" gain setting.

HEXTE consists of two clusters of detectors, with 4 scintillation detectors in each cluster. Count rates are given per cluster. Values are given for the total count rate, and the count rates in the 4 canonical HEXTE channels required on the proposal form and used in HEXTEmporize.

The quoted detection times assume two-cluster 16-s source/background beamswitching, i.e., one cluster measures background while the other is on-source. In this case, the "detection time" applies to the combined HEXTE instrument. For those bright source observations (source rate >> background rate) where a HEXTE cluster is selected to be in STARE mode, this detection time can be also interpreted as appropriate for a single HEXTE cluster. For the combined HEXTE detection time, divide by sqrt(2).


PIMMS can also calculate conversion to/from flux values not folded through any instrument responses can also be used. To use flux, the unit must be specified: ERGS for ergs/cm/cm/s or PHOTONS for photons/cm/cm/s. Also necessary is the energy range of interest, to be specified in the form 2.5-10 (for 2.5 to 10 keV), or 2.0-40 A (for a wavelength range of 2.0 to 40 A, or roughly 0.03-6 keV). Optional keyword UNABSORBED following the range will make PIMMS calculate flux with Nh set to 0.0; this is useful in relating the flux to the total bolometric luminosity of the X-ray source before interstellar absorption.

(Flux) Density

PIMMS can also calculate conversion to/from flux densities at a specific energy, rather than flux integrated over a range of energies. To use density, the unit must be specified: ERGS for ergs/cm/cm/s/keV or PHOTONS for photons/cm/cm/s/kev. Also necessary is the energy of interest (in keV). Alternatively, this can be specified as the wavelength in Angstroms, with the optional argument Angstrom, in which case flux density is in (ergs or photons)/cm/cm/s/A. Flux density can be UNABSORBED as in flux.


PIMMS now supports the use of 'model normalization'; for the power law model, for example, normalization is the flux at 1 keV. For models imported from XSPEC, a normalization of 1.0 is the flux level as simulated within XSPEC.

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