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EUSO-TA is a on-ground telescope, installed at the Telescope Array (TA) site in Black Rock Mesa, Utah, USA in 2013. The main aim of the project is observation of Ultra High Energy Cosmic Rays (UHECR) through detection of ultraviolet light generated by cosmic-ray showers. EUSO-TA consists of two, 1 m 2 square Fresnel lenses with a field of view of about 10.6 • × 10.6 •. Light is focused on the Photo Detector Module (PDM), identical to the ones that are employed in the other EUSO missions' focal surfaces. The PDM is composed of 36 Hamamatsu multi-anode photomultipliers (64 channels per tube), for a total of 2304 channels. Front-End readout is performed by 36 ASICS, with trigger and readout tasks done by two acquisition boards that send the data to a CPU and storage system. The telescope is housed in a shed located in front of one of the fluorescence detectors of the TA experiment, pointing in the direction of the Electron Light Source and Central Laser Facility. After the installation in February 2013, the performance of the detector has been very good, with little (about one photoelectron) electronic noise and a Point Spread Function of stars compatible with expectations. Several ultra high energy cosmic rays and meteors have been observed. The limiting magnitude of 5.5 on summed frames has been established, with PSF of ∼ 2.5 pixels FWHM. Measurements of the UV background in different darkness conditions and moon phases and positions have been completed. EUSO-TA has been used for development of balloon and space flights within the EUSO framework.

EUSO-Balloon is a pathfinder mission for the Extreme Universe Space Observatory onboard the Japanese Experiment Module (JEM-EUSO). It was launched on the moonless night of the 25 th of August 2014 from Timmins, Canada. The flight ended successfully after maintaining the target altitude of 38 km for five hours. One part of the mission was a 2.5 hour underflight using a helicopter equipped with three UV light sources (LED, xenon flasher and laser) to perform an inflight calibration and examine the detectors capability to measure tracks moving at the speed of light. We describe the helicopter laser system and details of the underflight as well as how the laser tracks were recorded and found in the data. These are the first recorded laser tracks measured from a fluorescence detector looking down on the atmosphere. Finally, we present a first reconstruction of the direction of the laser tracks relative to the detector.