Monitor of All-sky X-ray Image (MAXI) is an X-ray all-sky scanner, which will be attached on Exposed Facility of Japanese Experiment Module dubbed "Kibo" of International Space Station (ISS). MAXI will be launched by the Space Shuttle or the Japanese H-IIA Transfer Vehicle (HTV) in 2008. MAXI carries two types of X-ray cameras: Solid-state Slit Camera (SSC) for 0.5-10 keV and Gas Slit Camera (GSC) for 2-30 keV bands. Both have long narrow fields of view (FOV) made by a slit and orthogonally arranged collimator plates (slats). The FOV will sweep almost the whole sky once every 96 minutes by utilizing the orbital motion of ISS. Then the light curve of an X-ray point source become triangular shape in one transit. In this paper, we present the actual triangular response of the GSC collimator, obtained by our calibration. In fact they are deformed by gaps between the slats, leaning angle of the slats, and the effective width of the slats. We are measuring these sizes by shooting X-ray beams into the detector behind the collimator. We summarize the calibration and present the first compilation of the data to make the GSC collimator response, which will be useful for public users.
Monitor of All-sky X-ray Image(MAXI) is an X-ray all sky monitor, which will be attached to the Japanese Experiment Module (JEM) on the International Space Station (ISS) around the year 2008. MAXI carries two types of scientific instruments. The Gas Slit Camera(GSC) consists of twelve Xe filled one-dimensional position sensitive gas proportional counters sensitive to X-ray in 2-30 keV band. The Solid-state Slit Camera (SSC) is a set of X-ray CCD arrays sensitive to 0.5-10 keV photons. Both detectors are utilized in combination with a slit
and orthogonally arranged collimator plates to produce one-dimensional X-ray images along sky great circles. The instruments are now under fabrication and preflight testing. A detector response matrix (DRM) of GSC is also under development phase based on flight model calibration tests for counters and collimators. MAXI's
overall performance depends on not only hardware characteristics but on the fact that the field-of-view changes in time even during observations. To study this complicated situation, we are developing a software, DRM builder, and also a simulation software to evaluate "realistic" performance of GSC in ISS orbits.