Developments of engineering model of the X-ray CCD camera of the MAXI experiment onboard the International Space Station

Abstract

MAXI, Monitor of All-sky X-ray Image, is an X-ray observatory on the Japanese Experimental Module (JEM) Exposed Facility (EF) on the International Space Station (ISS). MAXI is a slit scanning camera which consists of two kinds of X-ray detectors: one is a one-dimensional position-sensitive proportional counter with a total area of ∼5000 cm 2 , the Gas Slit Camera (GSC), and the other is an X-ray CCD array with a total area ∼200 cm 2 , the Solid-state Slit Camera (SSC). The GSC subtends a field of view with an angular dimension of 1°×180° while the SSC subtends a field of view with an angular dimension of 1° times a little less than 180°. In the course of one station orbit, MAXI can scan almost the entire sky with a precision of 1° and with an X-ray energy range 0.5– 30 keV . We have developed an engineering model (EM) for all components of the SSC. Their performance test is underway. We have also developed several kinds of CCDs fabricated from different wafers. Since the thermal condition of the ISS is not suitable for the CCD operation, the operating temperature of the CCD is estimated to be −85° to −50°C at the end of mission life. We therefore carefully need to choose CCD considering not only detection efficiency and readout noise but also the dark current. Here we report the current status of the EM of the SSC and the X-ray responsivity of CCDs.