Abstract
The main telescope of JEM-EUSO will determine Ultra High Energy Cosmic Ray properties by measuring the UV fluorescence light generated in the interaction between the cosmic rays and the atmosphere. Therefore, cloud information is crucial for a proper interpretation of the data. JEM-EUSO will observe the clouds in the field of view of the telescope making use of an atmospheric monitoring system, which consists of a LIDAR and an IR Camera. To retrieve the cloud top height from IR images two different methodologies will be used. The first one is based on stereo vision algorithms and requires two different views of the same scene. The second one is based on the relationship between the cloud top temperature and the cloud top height. From the IR camera the brightness temperature can be retrieved, thus the developed Split Window Algorithm retrieves the real cloud temperature from the brightness temperature in two spectral bands. This article presents a preliminary work, in which both methodologies are compared with the height given by MODIS. The stereo system is provided by the two geostationary satellites MSG-2 and MSG-3. The Split Window Algorithm has been tested in MODIS images of bands 31 and 32. This initial work is a first step to compare a very simplified version of both methodologies.
Highlights
JEM-EUSO [1] is the first space mission devoted to the exploration of the Universe through the detection of Extreme Energy (E > 60 EeV) Cosmic Rays (EECRs)
In order to check the performance of the splitwindow algorithm (SWA) to retrieve CTT in real scenarios, the algorithm has been applied to Moderate Resolution Image Spectroradiometer (MODIS) images
From all the products that MODIS provides we have used only some of them: brightness temperatures in channels 31 and 32 (IR camera bands), the cloud temperature, the emissivity and the cloud phase
Summary
JEM-EUSO [1] is the first space mission devoted to the exploration of the Universe through the detection of Extreme Energy (E > 60 EeV) Cosmic Rays (EECRs). Cosmic rays are observed by looking downward from the International Space Station (ISS) at the altitude of about 400 km from ground. JEM-EUSO will observe UV photon tracks produced by EECRs developing in the atmosphere and producing Extensive Air Showers (EAS). Clouds affect the Cherenkov signal received from EAS, as well as its reconstruction efficiency. Estimation accuracy depends on cloud coverage and cloud top height (CTH). The strength of the fluorescent light depends on the transparency of the atmosphere, on the cloud coverage and on the height of the cloud top [2]
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