The Atmospheric Monitoring System of the JEM-EUSO space mission

Abstract

Abstract. An Atmospheric Monitoring System (AMS) is mandatory and a key element of a space-based mission which aims to detect Ultra-High Energy Cosmic Rays (UHECR). JEM-EUSO has a dedicated atmospheric monitoring system that plays a fundamental role in our understanding of the atmospheric conditions in the Field of View (FoV) of the telescope. Our AMS consists of an infrared camera and a LIDAR device that are being fully designed with space qualification to fulfil the scientific requirements of this space mission. This AMS will provide information of the cloud cover in the FoV of JEM-EUSO, as well as measurements of the cloud top altitudes with an accuracy of 500 m and the optical depth profile of the atmosphere transmittance in the direction of each air shower with an accuracy of 0.15 degree and a resolution of 500 m. This will ensure that the energy of the primary UHECR and the depth of maximum development of the EAS (Extensive Air Shower) are measured with an accuracy better than 30% and 120 g/cm 2 , for EAS occurring either in the clear sky or with the EAS depth of maximum development above optically thick cloud layers. Moreover novel stereoscopic and radiometric retrieval techniques are under development to infer the Cloud Top Height (CTH) from the brightness temperature patterns obtained from the infrared camera. is compared to that of clear sky signal (green line). Now the fluorescence radiation suffers absorption but the Cherenkov peak takes place on ground due to the fact that the cirrus clouds are thin clouds.

The JEM-EUSO mission: Context and status

“…In addition, the atmospheric conditions (such as the cloud coverage) observed along the orbit are variable and affect the detection acceptance. For these reasons, an infrared camera and a LIDAR [4] are used to continuously monitor the field of view.…”

“…The electronics record the signals generated by the UV photons of the EAS in the FS, providing a kinematic reproduction of each track. A new type of front-end ASIC has been developed, which has both functions of single photon counting and 09001-p. 4 charge integration in a chip with 64 channels [12,13]. Radiation tolerance of the electronic circuits in space environment is also required.…”

Implementation in OFFline of the reconstruction code of the Infrared Camera of the JEM-EUSO Space Mission.

“…Due to the variable nature of the atmosphere an on-time Atmospheric Monitoring (AM) system is one of the most important tasks, and a key element of the space-based mission. Such a dedicated on-site AM system has been designed for the understanding of the atmospheric conditions in the Field of View (FoV) of the main telescope [4,5,6,7]. The EUSO AM system consists of a Long Wave Infrared (LWIR) camera [8,9] and a LIDAR.…”

Retrieving cloud top height in the JEM-EUSO cosmic-ray observation system

“…In order to monitor the atmospheric conditions and the cloud coverage in the JEM-EUSO FoV a state-of-art Atmospheric Monitoring System (AMS) will be included in the system [3]. The AMS is crucial to estimate the effective exposure with high accuracy and to increase the confidence level in the EECR events.…”