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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.


AstroSat is India's first observatory for X-ray and multi-wavelength observations. This version of PIMMS includes effective area curves for Cadmium Zinc Telluride Imager (CZTI), Soft X-ray Telescope (SXT), and one fully functioning unit of Large Area X-ray Proportional Counter (LAXPCA), as provided by Astrosat Science Support Cell (ASSC) in 2023 May.


Athena (Advanced Telescope for High ENergy Astrophysics) is an ESA "Cosmic Vision" mission selected as one of the L(arge)-class missions, to be launched in the early 2030s. See the Community Support Portal for further details of the mission.

Version 4.10 of PIMMS contains effective area curves for the proposed X-IFU (X-ray Integral Field Unit) instrument produced in late 2018, taken from this page. Since this is a high spectral resolution instrument, PIMMS should be used only to judge whether a spectral resolution is worthwhile, and if so, to provide the initial guess as to the likely exposure time needed. Note also that PIMMS assumes 100% throughput in estimating the count rates. The actual throughput will be less in a count-rate dependent manner.


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, the mission name PIMMS has been changed to Chandra.

This version includes the Chandra instrument effective area curves appropriate for Cycle 26 proposers as provided by the Chandra X-ray Observatory Center, where the details of the instruments can be found. Older versions of the effective area curves 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.


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.


PIMMS currently contains supports for A1 and A4 LED instruments.

The PIMMS set-up for the A4 LED 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.

For the A1 instruments, effective area curves for two gain settings, AGCL and AGCP. Both are normalized to produce count rates per square cm to allow direct comparison with HEAO-1 A1 X-ray Source Catalog (Wood et al. 1984, ApJSupp, 56, 507; also available online). The AGCP version is applicable to the majority of sources, while the AGCL setting is appropriate for sources at ecliptic longitudes in the 230-265 and 50-85 deg ranges (but excluding those at ecliptic latitude >+80 or <-80). The effective area curves were digitized from Fig. 7 of Wood et al. by Koji Mukai, while Dr. Kent Wood of NRL kindly provided additional information.


Hitomi (formerly ASTRO-H) is the Japanese-led international X-ray observatory with a substantial US contribution, and was launched on February 175h, 2016. PIMMS v4.8b contains effective area curves for the 4 instruments based on preliminary calibration available as of 2015 July. They will be updated with in-orbit calibration in the near future.

Soft X-ray Spectrometer (SXS) is an X-ray microcalorimeter based instrument located at the focus of an imaging soft X-ray telescope (SXT-S). We provide four files corresponding to the current set of science filters (open, 25 micron Be, and 50 micron Be, as well as the optical blocking filter, OBF). These files are appropriate for point sources on-axis, adding counts in all pixels of the 6x6 array. For the detector, the baseline design of 7 eV resolution and XRS filters, is assumed. For bright sources, SXS suffers from a photon pile-up effect: the fraction of events that can be detected at the full resolution will decrease for higher count rate source. The current provides a preliminary estimate of this effect, the accuracy of which is under investigation.

Soft X-ray Imager (SXI) is an CCD based instrument located at the focus of a soft X-ray telescope (SXT-I). The effective area curve is appropriate for a point source observed on-axis, analyzed with a 1.8 arcmin radius extraction region.

Hard X-ray Imager (HXI) is a CdTe imaging detector behind 4 Si layers. There are two units, each located at the focus of an imaging, multi-layer, hard X-ray telescope (HXT). The effective area curves are for one HXI unit for an on-axis point source with 1.8 arcmin extraction region. Two choices are offered for top layer only and and for all layers.

Soft Gamma-ray Detector (SGD) is a narrow field-of-view Compton telescope operating in the 10-600 keV range. Its sensitivity at 300 keV is 10 times better than that of the Suzaku HXD. The current version provides preliminary estimates of the exposure times neceesary for 3 and 5 sigma detections with SGD, the accuracy of which is under investigation.


As of version 3.9f, PIMMS includes effegtive area curves for ISGRI and JEM-X instruments. See Integral Science Data Centre for details of the mission. Even though two near-identical units of Integral JEM-X are opretaional since 2010 October, PIMMS continue to provide count rates for a single unit, based on calibration as of 2008 March. This is reflected in the mission-specific comments since PIMMS v4.3. In Version 4.11a, the ISGRI effective area curve was updated based on the latest calibration as of 2020 August.


IXPE (Imagine X-ray Polarimetry Explorer) is a NASA small explorer (SMEX) mission with Italian participation to measure the linear polarization of celestial X-ray sources that was launched in 2021 December. As such, count rates as such are not of primary interest to IXPE users; PIMMS uses the predicted IXPE count rates to estimate, and display, the minimum detectable polarization (MDP) levels in percent for 10,000 s and 100,000s exposres. In fact, the users may be primarily interested in the exposure time necessary to reach a certain MDP level. For this purpose, the 'go' command of IXPE allows an optional numerical parameter. If given, it will be taken the percent polarization of interest, and the exposure time needed to reach that MDP level will be calculated and displayed. See this page at NASA Marshall Space Flight Center for further details.


MAXI (Monitor of All-sky X-ray Image) is an all-sky monitor on-board the International Space Station. MAXI payload includes two types of X-ray cameras, the Gas Slit Camera (GSC) and the Solid-state Slit Camera (SSC). PIMMS v4.7 contains effective area curve files provided by the MAXI team in mid-2013, normalized to produce count rates per square cm. More information on MAXI can be obtaeind from MAXI home page at Riken.


NICER (the Neutron star Interior Composition ExploreR) is a payload on the International Space Station for X-ray astrophysics. It achieves a high effective area, particularly in the 1 keV band, using a set of 56 concentrators, each with a dedicated silicon drift detector. Since NICER is not a true imaging instrument, PIMMS provide typical background levels and estimated time for 5-sigma detection (one with purely statistical errors, one with additional 10% systematic errors on the background rates) in two pre-defined energy ranges.

Note that the broadband background rate reported by PIMMS v4.9/v4.9a included background counts below 0.2 keV, where the rate is very high. This is outside the nominal energy range of NICER and resulted in more pessimistic estimates of the signal-to-noise than were appropriate.

The current effective-area file were provided by the NICER project in 2020 August and is appropriate for preparation of Cycle 3 proposals.


NuSTAR is an X-ray satellite with 10-meter focusing length and two side-by-side focal plane modules, each with 4 detectors. The count rate calculated by PIMMS reflects the total from both modules for a 50% PSF extraction region. In Version 4.7, the NuSTAR effective area curve file and related mission specific information were updated to reflect post-launch understanding, based on the response and background files for simulation released in 2013 August. For further details about this mission, see the mission web site.


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.


Spectr-Roentgen-Gamma (SRG) is a Russian-German mission with two instruments, ART-XC and eROSITA. This version of PIMMS includes the effective area curve for eROSITA only. See the MPG page for further details.


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 2012 September for the HXD and 2014 December for the XIS, as collected by the Suzaku Guest Observer Facility.

Note, however, that AO-10 proposals must not require the HXD to achieve its core scientific objectives, as the satellite is operated without the HXD for the majority of time.

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, although XIS-2 (with an FI chip) has become inoperative in November, 2006. 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.


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 each (we have averaged of MOS1 and MOS2 effective area curves), not for pairs of instruments. Starting with PIMMS v4.1, the EPIC count rates are given for PATTERN=0-12 (for MOS)/PATTERN=0-4 (pn) events over a large (5 arcmin) extraction region. This reverses the practice adoptied in v3.6 to use a 15 arcse radius extraction region, and that adopted in v3.9c to report only the PATTERN=0 count rates for PN. Starting with v4.11, PIMMS no longer provides information on timing and burst options for PN if thin or medium filter is specified, reflecting the new policy by the project. These options continue to be supported for PN observations only when using the thick filter.

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.

For the OM, we provide effective area curves derived from the version 2.0 rsponse files provided at this ESA page.

Current version of PIMMS contains effective area curves appropriate for AO-20 proposals.


XRISM is the Japan-led mission with two instruments, the microcalorimeter based Resolve instrument and wide field CCD instrument, Xtend. This version of PIMMS reflect the status of Resolve as of 2024 January, in which the gate valve (entrance door) has not opened, reducing the effective area particularly for soft photons. See the XRISM GOF home page for more.


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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This file was last modified on Friday, 02-Feb-2024 15:11:44 EST