Assembly and test of MEDUSA, a multi-spectral instrument for stratospheric Earth observation

MEDUSA is a lightweight high resolution camera, designed to operate at stratospheric altitudes mounted on a solar-powered unmanned aerial vehicle (UAV). The MEDUSA instrument targets applications such as crisis monitoring and large scale mapping, requiring high resolution images with regional coverage, flexible flight patterns, high update rates and long mission lengths (weeks to months). The instrument is subject to severe constraints on mass (< 2,5 kg), volume, power consumption and survivability in the stratospheric environment. Operating temperatures within the payload vary over several tens of degrees Celsius over the day-night cycle. Nonetheless, the instrument will be able to provide panchromatic and color images of 30 cm ground resolution at an altitude of 18000 m and a wide swath of 3000m. This ESA-PRODEX (PROgramme de Developpement d'Experiences scientifiques) funded project successfully passed the Critical Design Review in September 2007 and the assembly, integration and test (AIT) phase of the subsystems will be finalized by the end of 2008. Subsystem tests include an optical performance verification performed on optical compartment with a test-sensor assembly both at ambient and operational environmental conditions. The electronic subsystems and their interfaces are tested for functionality and performance in the operational temperature and pressure range. From early 2009 onwards, the MEDUSA system will be fully integrated including a custom designed wide swath MEDUSA CMOS frame sensor (10000x1200 pixels). The MEDUSA instrument will be ready for its first flight in spring of 2009. The detailed design of the optical instrument and its performances have been discussed in [1]. In this paper we will give an overview of the AIT status of the MEDUSA sensor and the optical system and an outlook on the system integration and test phase.