Alignment calibration of MAXI/GSC

Monitor of All-sky X-ray Image (MAXI) is the unprecedentedly sensitive all-sky X-ray monitor. MAXI is mounted on the Exposed Facility of Japanese Experiment Module on the International Space Station. MAXI has two types of slit and slat X-ray cameras: Gas Slit Camera (GSC) and Solid-state Slit Camera (SSC) sensitive for 2–30 and 0.5–12 keV bands, respectively. We calibrated the alignment of the GSC, then the position accuracy of X-ray point sources was significantly improved from about 1° to 0.2° (90% containment radius). This improvement of the position accuracy is essentially important to achieve various scientific objectives of MAXI.