Mini-EUSO telescope on board the International Space Station for terrestrial and cosmic UV emission observation.

The Mini-EUSO telescope is designed to observe UV (300 -- 400 nm) Earth emission from a nadir-facing window in the Russian Zvezda module inside the International Space Station in the second half of 2019. As a pathfinder mission for Ultra High Energy Cosmic Rays detection from space, it will map the UV Earth's emission with a spatial-temporal resolution of 6.11 km every 2.5 $\mu$s offering also the opportunity to study a variety of atmospheric events such as Transient Luminous Events (TLEs), meteoroids, bioluminescence as well as searching for strange quark matter. Furthermore, Mini-EUSO could represent the first step in a roadmap of potential orbital debris removal via laser ablation. The instrument comprises a compact telescope with a large field of view ($\pm 22^{\circ}$), based on an optical system employing two Fresnel lenses. The light is focused onto an array of 36 Hamamatsu multi-anode photomultiplier tubes and the resulting signal is converted into digital, processed and stored via the electronics subsystems on board. In addition, Mini-EUSO contains two ancillary cameras for complementary measurements in the near infrared (1500 -- 1600 nm) and visible (400 - 780 nm) range and a 64 SiPM channels. The integration and the characterization of the instrument, currently underway at the University of Roma Tor Vergata, are at their final stage and results will be presented.