Remote sensing of water clouds temperature with an IR camera on board the ISS in the frame of JEM-EUSO Mission

Abstract

The Extreme Universe Space Observatory (EUSO) is an astronomical telescope that will be hosted by the Japan Experiment Module (JEM) on the International Space Station (ISS). The telescope will determine Ultra High Energy Cosmic Rays properties by measuring the UV fluorescence light emitted by the particles generated in the interaction between the cosmic rays and the atmosphere. Therefore, cloud information is crucial for a proper interpretation of the data. To obtain the cloud top height an IR camera is being designed. The design is constrained by JEM-EUSO requirements which are mainly the instrument weight, power and data rate. These requirements have led to a bi-spectral camera option with 1 μm-wide bands centered at 10.8 and 12 μm. The bi-spectral design has allowed us to develop a Split Window Algorithm to correct the atmospheric effects and retrieve the cloud temperature from the brightness temperatures in the bands aforementioned. The algorithm has been checked in synthetic scenarios at pixel level. The simulations consider clouds at different levels with diverse atmospheric conditions. The results show that the algorithm is able to retrieve the temperature with accuracy much better than the required one by the JEM-EUSO mission of 3K. It has also been tested in 2D real scenarios (MODIS images). The algorithm has been applied to MODIS brightness temperatures in bands 31 and 32 which are similar to those of the IR camera. The temperatures retrieved by the algorithm are in a very good agreement with the cloud top temperatures given by MODIS.