In-Orbit Performance of MAXI Gas Slit Camera (GSC) on ISS

TL;DR

This paper reports the in-orbit performance, calibration, and operational stability of the MAXI Gas Slit Camera on the ISS, demonstrating its effective area, resolution, sky coverage, and background stability in space-based X-ray observations.

Contribution

It provides the first comprehensive in-orbit performance assessment and calibration of the MAXI GSC, confirming its capabilities and stability in space.

Findings

Effective area confirmed in 2-30 keV band

Spatial resolution of 1.5 degrees FWHM achieved

Sky coverage of 85% per orbit and 95% per day

Abstract

We report the in-orbit performance of the Gas Slit Camera (GSC) on the MAXI (Monitor of All-sky X-ray Image) mission carried on the International Space Station (ISS). Its commissioning operation started on August 8, 2009, confirmed the basic performances of the effective area in the energy band of 2--30 keV, the spatial resolution of the slit-and-slat collimator and detector with 1.5 degree FWHM, the source visibility of 40-150 seconds for each scan cycle, and the sky coverage of 85% per 92-minute orbital period and 95% per day. The gas gains and read-out amplifier gains have been stable within 1%. The background rate is consistent with the past X-ray experiments operated at the similar low-earth orbit if its relation with the geomagnetic cutoff rigidity is extrapolated to the high latitude. We also present the status of the in-orbit operation and the calibration of the effective area and the energy response matrix using Crab-nebula data.