A method for Cloud Mapping in the Field of View of the Infra-Red Camera during the EUSO-SPB1 flight

TL;DR

This paper presents a new method for creating high-resolution cloudiness maps using infrared images from the EUSO-SPB1 balloon mission, aiding the analysis of ultra-high-energy cosmic ray data affected by clouds.

Contribution

It introduces an expert system-based approach for dense cloud mapping at IR-camera pixel resolution during balloon flights.

Findings

Cloudiness maps achieved with nearly 4 times higher resolution than UV-camera.

Effective image enhancement improves cloud detection accuracy.

Method applicable to uncalibrated IR data in atmospheric observations.

Abstract

EUSO-SPB1 was released on April 24th, 2017, from the NASA balloon launch site in Wanaka (New Zealand) and landed on the South Pacific Ocean on May 7th. The data collected by the instruments onboard the balloon were analyzed to search UV pulse signatures of UHECR (Ultra High Energy Cosmic Rays) air showers. Indirect measurements of UHECRs can be affected by cloud presence during nighttime, therefore it is crucial to know the meteorological conditions during the observation period of the detector. During the flight, the onboard EUSO-SPB1 UCIRC camera (University of Chicago Infra-Red Camera), acquired images in the field of view of the UV telescope. The available nighttime and daytime images include information on meteorological conditions of the atmosphere observed in two infra-red bands. The presence of clouds has been investigated employing a method developed to provide a dense cloudiness map for each available infra-red image. The final masks are intended to give pixel cloudiness information at the IR-camera pixel resolution that is nearly 4-times higher than the one of the UV-camera. In this work, cloudiness maps are obtained by using an expert system based on the analysis of different low-level image features. Furthermore, an image enhancement step was needed to be applied as a preprocessing step to deal with uncalibrated data.