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Abstract:We report on design, manufacture, and testing of a Slewing Mirror Telescope (SMT), the first of its kind and a part of Ultra-Fast Flash Observatory-pathfinder (UFFO-p) for space-based prompt measurement of early UV/optical light curves from Gamma-Ray Bursts (GRBs). Using a fast slewing mirror of 150 mm diameter mounted on a 2 axis gimbal stage, SMT can deliver the images of GRB optical counterparts to the intensified CCD detector within 1.5~1.8 s over ± 35 degrees in the slewing field of view. Its Ritchey-Chrétien telescope of 100 mm diameter provides a 17 × 17 arcmin 2 instantaneous field of view. Technical details of design, construction, the laboratory performance tests in space environments for this unique SMT are described in conjunction with the plan for in-orbit operation onboard the Lomonosov satellite in 2013.

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The Extreme Universe Space Observatory on board the Japanese Experiment\ud Module of the International Space Station, JEM-EUSO, is being designed\ud to search from space ultra-high energy cosmic rays. These are charged\ud particles with energies from a few 10(19) eV to beyond 10(20) eV, at the\ud very end of the known cosmic ray energy spectrum. JEM-EUSO will also\ud search for extreme energy neutrinos, photons, and exotic particles,\ud providing a unique opportunity to explore largely unknown phenomena in\ud our Universe. The mission, principally based on a wide field of view (60\ud degrees) near-UV telescope with a diameter of similar to 2.5 m, will\ud monitor the earth's atmosphere at night, pioneering the observation from\ud space of the ultraviolet tracks (290-430 nm) associated with giant\ud extensive air showers produced by ultra-high energy primaries\ud propagating in the earth's atmosphere. Observing from an orbital\ud altitude of similar to 400 km, the mission is expected to reach an\ud instantaneous geometrical aperture of A (g e o) a parts per thousand yen\ud 2 x 10(5) km(2) sr with an estimated duty cycle of similar to 20 \%.\ud Such a geometrical aperture allows unprecedented exposures,\ud significantly larger than can be obtained with ground-based experiments.\ud In this paper we briefly review the history of space-based search for\ud ultra-high energy cosmic rays. We then introduce the special issue of\ud Experimental Astronomy devoted to the various aspects of such a\ud challenging enterprise. We also summarise the activities of the on-going\ud JEM-EUSO program

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.