SUIM project: measuring the upper atmosphere from the ISS by observations of the CXB transmitted through the Earth rim

TL;DR

The SUIM project aims to measure the Earth's upper atmosphere density at 60-110 km altitude by observing the cosmic X-ray background through the atmosphere using an X-ray camera on the ISS, providing continuous data on this poorly understood region.

Contribution

This paper introduces the development of a novel X-ray observation instrument, SUIM, designed for continuous atmospheric density measurements from the ISS, utilizing CXB transmission spectroscopy.

Findings

Design of the SUIM X-ray camera system completed

Development status of the SUIM project reported

Expected deployment on ISS in 2025

Abstract

The upper atmosphere at the altitude of 60-110 km, the mesosphere and lower thermosphere (MLT), has the least observational data of all atmospheres due to the difficulties of in-situ observations. Previous studies demonstrated that atmospheric occultation of cosmic X-ray sources is an effective technique to investigate the MLT. Aiming to measure the atmospheric density of the MLT continuously, we are developing an X-ray camera, "Soipix for observing Upper atmosphere as Iss experiment Mission (SUIM)", dedicated to atmospheric observations. SUIM will be installed on the exposed area of the International Space Station (ISS) and face the ram direction of the ISS to point toward the Earth rim. Observing the cosmic X-ray background (CXB) transmitted through the atmosphere, we will measure the absorption column density via spectroscopy and thus obtain the density of the upper atmosphere. The X-ray camera is composed of a slit collimator and two X-ray SOI-CMOS pixel sensors (SOIPIX), and will stand on its own and make observations, controlled by a CPU-embedded FPGA "Zynq". We plan to install the SUIM payload on the ISS in 2025 during the solar maximum. In this paper, we report the overview and the development status of this project.