5. Planning and Simulation Software

In this chapter, Suzaku software used for observation planning and simulation are explained.

5.1 Observation Planning Software

5.1.1 TAKO (Timeline Assembler, Keyword Oriented)

A planning software package named ``TAKO'' (for Timeline Assembler, Keyword Oriented) is developed for Suzaku by GSFC based on the methods used for ASCA and XTE.

This package is designed to accommodate Suzaku specific constraints. These constraints are determined in cooperation of ISAS and GSFC instrument and operations teams. Post-launch changes will be handled in a similar fashion. As has been the case for ASCA, a technician is employed by GSFC and stationed at ISAS to maintain and operate TAKO to produce regular observation schedules.

5.1.2 MAKI

MAKI is developed at GSFC for Suzaku and future multimission planning^5.1. Users may run MAKI through a Web browser (users will need to obtain and install the ``LHEA Plug-In''<sup>5.2</sup>). Users may place different satellite fields of view on a sky image to plan out observation (Euler angles are automatically calculated). These FOVs may be rotated, and MAKI will indicate if the roll is allowed or not by different colors for a given time period. Users can also view the sun angle visibility limits for several missions, as well as adding phase constraints. MAKI is expected to replace the ASCA command planning program ``adcongra'' which had similar but more primitive functions.

MAKI accepts a sky image file from ``SkyView''^5.3, or almost any FITS image files. It also lets users save and reload the results. In figure 5.1, an example of MAKI output is shown.

Figure 5.1: An examples of the MAKI plot. An XRS field of view is displayed on an optical image obtained from SkyView.

5.2 Simulation Software

Suzaku simulation software will have the following purposes. First, simulation software will be used to study technical feasibility of planned observations. Second, they will be used to determine instrumental responses in order to simulate and understand physical processes in the instruments. Third, they may be used in data analysis when instrument responses are difficult to determine and Monte Carlo approach is considered more effective. Finally, simulated data sets will be used to verify software for data analysis and processing.

5.2.1 Counting Rate Simulation - PIMMS

When planning observations, the first thing needed is to estimate the expected counting rates. For such a purpose, PIMMS (Portable, Interactive, Multi-Mission Simulator) has been developed at GSFC and already widely used in the community. Users will be able to estimate the expected counting rates for XIS and HXD by inputting the source flux and the spectral form. The source flux can be a physical unit (ergs s$^{-1}$ cm$^{-2}$) or counting rates from other satellites/instruments.

As of ver. 3.6 released in late 2004, PIMMS calculates expected counting rates for Suzaku. See details at
http://heasarc.gsfc.nasa.gov/docs/software/tools/pimms.html^5.4.

5.2.2 Spectral Simulation - XSPEC

The XSPEC spectral fitting package has the capability to simulate instrument dependent pulse-height spectra for given input photon spectra^5.5. To that end, XSPEC requires not only the effective area and efficiency (ARFs - Ancillary Response Files), but also the response matrices (RMF - Redistribution Matrix Files).

GOF has released a suite of the Suzaku response functions for spectral simulation purposes. See,
http://heasarc.gsfc.nasa.gov/docs/suzaku/aehp_prop_tools.html for details.

5.2.3 XRT Ray-Tracing Library - libxrrt

The ray-tracing package, named ``xrrt'', was developed at GSFC ADF (Astrophysics Data Facility) in cooperation with ISAS, Nagoya University and GSFC mirror team (code 662). The package is written in C++. It is available as a function library (section 4.3) for use by other FTOOLS such as xissim.

The ray-tracing package will be used to determine physical parameters of the mirrors which are difficult to measure (e.g., surface densities), by comparing the actual data and simulations. XRT responses such as point spread functions and effective areas will be determined through iterations of the ray-tracing simulations and actual calibration data.

The ray tracing package is also useful to simulate observations when making plans or analyzing data. For example, if there are bright sources outside of the field of view, amounts of the stray-lights can be estimated through the ray-tracing simulations.

5.2.4 Suzaku XIS Event Simulator xissim

A simple simulation with XSPEC does not work in estimating contamination from nearby sources or a position dependent spectrum of extended sources, coupled with the image quality. Such estimates are sometimes necessary for proposing new Suzaku observations or comparing the observing data with the faked data of a complicated model through Monte Carlo simulations. The instrument team has developed the photon-by-photon simulator of XIS events, xissim^5.6. The simulator is comprise of two tasks: mkphlist, which fakes incident photons from celestial sources in the XIS FOV, and xissim, which simulates XIS events of the faked photons, taking into account the XRT efficiency and the XIS response. The software outputs photon event files as the real observing data, so uses can analyze the simulated data with the generic XANADU software.