EUSO-SPB1 mission and science

The Extreme Universe Space Observatory on a Super Pressure Balloon 1 (EUSO-SPB1) was launched in 2017 April from Wanaka, New Zealand. The plan of this mission of opportunity on a NASA super pressure balloon test flight was to circle the southern hemisphere. The primary scientific goal was to make the first observations of ultra-high-energy cosmic-ray extensive air showers (EASs) by looking down on the atmosphere with an ultraviolet (UV) fluorescence telescope from suborbital altitude (33 km). After 12 days and 4 h aloft, the flight was terminated prematurely in the Pacific Ocean. Before the flight, the instrument was tested extensively in the West Desert of Utah, USA, with UV point sources and lasers. The test results indicated that the instrument had sensitivity to EASs of ⪆ 3 EeV. Simulations of the telescope system, telescope on time, and realized flight trajectory predicted an observation of about 1 event assuming clear sky conditions. The effects of high clouds were estimated to reduce this value by approximately a factor of 2. A manual search and a machine-learning-based search did not find any EAS signals in these data. Here we review the EUSO-SPB1 instrument and flight and the EAS search

Cosmic ray oriented performance studies for the JEM-EUSO first level trigger

JEM-EUSO is a space mission designed to investigate Ultra-High Energy Cosmic Rays and Neutrinos (E > 5 ⋅ 1019 eV) from the International Space Station (ISS). Looking down from above its wide angle telescope is able to observe their air showers and collect such data from a very wide area. Highly specific trigger algorithms are needed to drastically reduce the data load in the presence of both atmospheric and human activity related background light, yet retain the rare cosmic ray events recorded in the telescope. We report the performance in offline testing of the first level trigger algorithm on data from JEM-EUSO prototypes and laboratory measurements observing different light sources: data taken during a high altitude balloon flight over Canada, laser pulses observed from the ground traversing the real atmosphere, and model landscapes reproducing realistic aspect ratios and light conditions as would be seen from the ISS itself. The first level trigger logic successfully kept the trigger rate within the permissible bounds when challenged with artificially produced as well as naturally encountered night sky background fluctuations and while retaining events with general air-shower characteristics

Performance of the EUSO-Balloon FUV camera

International audienceJEM-EUSO [1] is intended to be a space-borne fruorescence telescope onboard of JEM/EF(Japanese Experimental Modeul/Exposure Facility) on the International Space Station (ISS). Themain goal of the JEM-EUSO project is to detect the Extensive Air Showers (EAS) produced bythe Extreme Energy Cosmic Rays (EECRs) with energies above 1019eV from the extragalacticobjects. As a pathfinder, the JEM-EUSO collaboration is currently developing a balloon-bornefluorescence telescope experiment, called EUSO-Balloon, funded by CNES, the French spaceagency. It will perform end-to-end tests of the JEM-EUSO subsystems and instrumental concept,and measure the UV background for space-based EECR detectors. It involves several French institutes(LAL, APC and IRAP) as well as several key institutes of the JEM-EUSO collaboration.The EUSO-Balloon instrument consists of an UV telescope and an infrared camera. The UVtelescope will be operated at an altitude of 40 km to observe the background and possibly signalphotons in the fluorescence UV range (290-430 nm), which are emitted along shower tracks generatedby ultra high energy cosmic rays with energies above 1018eV interacting with the earth’satmosphere. The balloon experiment will be equipped with electronics and acquisition systems,as close as possible to the ones designed for the UV telescope of main JEM-EUSO instrument.The past years have been devoted to the design, the fabrication and the tests of the prototypeboards of the PDM, of the digital processor, and the flight models of optics, electronics and theIR camera for EUSO-Balloon.Here we focus on the PDM, the core element of the JEM-EUSO focal surface. We first describeall key items of the PDM, from the photodetectors to the FPGA board, the first stage of the dataprocessing (DP). We then report on the tests carried out on the integration to assess their functionalityand their suitability for a balloon mission

Absolute calibration of the photon detector module of the EUSO-Balloon experiment and immprovements for future missions

International audienceEUSO-Balloon is a balloon borne mission operated by CNES during a one-night flight in August 2014 over the Ontario forest, in Canada, at 38 km altitude. The payload is a technological demonstrator for the Extreme Universe Space Observatory (JEM-EUSO) aiming at the detection of Extensive Air Showers (EAS) induced by Ultra High Energy Cosmic Rays (UHECR) from the International Space Station (ISS). The photon detection module of EUSO-Balloon consists in a square assembly of 36 Multi-Anodes Photomultiplier Tubes for a total of 2,304 pixels. The characterization at the single photoelectron level in laboratory has been processed before flight in a dedicated black box. After-flight calibration to check possible decrease of gain and efficiency of PMTs has been also carried out. Finally we discuss the upgrade of the detector module to improve the gain and the signal to noise ratio as well as the dynamic range of the readout electronics. The significant progresses made on these aspects represent a first milestone for the R&D of future EUSO-like missions

Photoelectron counting rate measurements in the UV camera during the EUSO-BALLOON night flight

International audienceEUSO-Balloon is a prototype for the future space telescope JEM-EUSO aiming to detect UV emissions in the Earth's atmosphere (cosmic air showers, meteorites, airglow, etc). It successfully completed its first flight operated by the CNES over Ontario, Canada, in August 2014. One of the main goals is to measure the photoelectron rate performed by its UV camera. These measurements, corrected from noise contamination, are presented including their time variation. a particular emphasis is put on the determination of the statistical and systematic errors using the relative calibration that was made for all the 2304 pixels. Possible improvements of these performances are discussed in the perspective of future flights

Performance of the EUSO-Balloon electronics

International audienceThe 24th of August 2014, the EUSO-Balloon instrument went for a night flight for several hours, 40 km above Timmins (Canada) balloon launching site, concretizing the hard work of an important part of the JEM-EUSO collaboration started 3 years before. This instrument consists of a telescope made of two lenses and a complex electronic chain divided in two main sub-systems: the PDM (Photo Detector Module) and the DP (Data Processor). Each of them is made of several innovative elements developed and tested in a short time. This paper presents their performances before and during the flight

Implementation of the first level trigger for ultra-high-energy cosmic ray (UHECR) detection from space with JEM-EUSO: Initial test results

International audienceThe JEM-EUSO Collaboration aims to study Ultra-High-Energy Cosmic Ray (UHECR) using a novel approach of looking down from space and using the atmosphere as a large detector to achieve a large effective area and therefore high-statistics on these events for the first time. For this purpose we have been developing a series of pathfinders operating from the ground, high altitude balloons and space, all sharing the same electronics, in particular the central data acquisition system. We report on the implementation and successful testing of the first-level trigger (L1) within the FPGA of the photo-detection module (PDM) board, which processes the signals from 36 64-pixel MAPMTs with a time unit of 2.5 μs to detect the passage of light from cosmic ray generated air-showers

Mini-EUSO Mission to Study Earth UV Emissions on board the ISS

International audienceMini-EUSO is a telescope observing the Earth in the ultraviolet band from the International Space Station. It is a part of the JEM-EUSO program, paving the way to future larger missions, such as K-EUSO and POEMMA, devoted primarily to the observation of ultrahigh-energy cosmic rays from space. Mini-EUSO is capable of observing extensive air showers generated by ultrahigh-energy cosmic rays with an energy above 1021 eV and to detect artificial showers generated with lasers from the ground. Other main scientific objectives of the mission are the search for nuclearites and strange quark matter, the study of atmospheric phenomena such as transient luminous events, meteors, and meteoroids, the observation of sea bioluminescence and of artificial satellites and man-made space debris. Mini-EUSO will map the nighttime Earth in the UV range (290–430 nm), with a spatial resolution of about 6.3 km and a temporal resolution of 2.5 μs, through a nadir-facing UV-transparent window in the Russian Zvezda module. The instrument, launched on 2019 August 22, from the Baikonur Cosmodrome, is based on an optical system employing two Fresnel lenses and a focal surface composed of 36 multianode photomultiplier tubes, 64 channels each, for a total of 2304 channels with single-photon counting sensitivity and an overall field of view of 44°. Mini-EUSO also contains two ancillary cameras to complement measurements in the near-infrared and visible ranges. In this paper, we describe the detector and present the various phenomena observed in the first months of operations