The objective of the R&D project CLAIRE was to prove the principle of a gamma-ray lens for nuclear astrophysics. CLAIRE's Laue diffraction lens has a diameter of 45 cm and a focal length of 277 cm; 556 germanium-silicon crystals are tuned to focus 170 keV photons onto a 1.5 cm diameter focal spot. Laboratory measurements of the individual crystals and the entire lens have been used to validate a numerical model that we use to estimate the lens performance for a source at infinity. During a stratospheric balloon flight on 2001 June 14, CLAIRE was directed at the Crab nebula by a pointing system able to stabilize the lens to within a few arcseconds of the target. In 72 min of valid pointing time, 33 photons from the Crab were detected in the 3 keV bandpass of the lens: CLAIRE's first light! The performance of CLAIRE's gamma-ray lens, namely the peak reflectivity for a polychromatic source (9±1%), has been confirmed by ground data obtained on a 205 meter long test range. CLAIRE's measured performance validates the principle of a Laue lens for nuclear astrophysics, opening the way for a space-borne gamma-ray lens telescope that will achieve one to two orders of magnitude improvement in sensitivity over present technologies

No abstract

The Faint Intergalactic Medium Redshifted Emission Balloon (FIREBall) is a mission designed to observe faint emission from the circumgalactic medium of moderate-redshift (z ∼ 0.7) galaxies for the first time. FIREBall observes a component of galaxies that plays a key role in how galaxies form and evolve, likely contains a significant amount of baryons, and has only recently been observed at higher redshifts in the visible. Here we report on the 2018 flight of the FIREBall-2 Balloon telescope, which occurred on 2018 September 22 from Fort Sumner, New Mexico. The flight was the culmination of a complete redesign of the spectrograph from the original FIREBall fiber-fed integral field unit to a wide-field multiobject spectrograph. The flight was terminated early owing to a hole in the balloon, and our original science objectives were not achieved. The overall sensitivity of the instrument and telescope was 90,000 LU, due primarily to increased noise from stray light. We discuss the design of the FIREBall-2 spectrograph, including modifications from the original FIREBall payload, and provide an overview of the performance of all systems. We were able to successfully flight-test a new pointing control system, a UV-optimized, delta-doped, and coated electron multiplying CCD, and an aspheric grating. The FIREBall-2 team is rebuilding the payload for another flight attempt in the fall of 2021, delayed from 2020 as a result of COVID-19.

FIREBALL (the Faint Intergalactic Redshifted Emission Balloon) is a balloon-borne 1m telescope coupled to an ultraviolet fiber-fed spectrograph. FIREBALL is designed to study the faint and diffuse emission of the intergalactic medium, until now detected primarily in absorption. FIREBALL is a path finding mission to test new technology and make new constraints on the temperature and density of this gas. We report on the first successful science flight of FIREBALL, in June 2009, which proved every aspect of the complex instrument performance, and provided the strongest measurements and constraints on IGM emission available from any instrument.

EUSO-BALLOON has been conceived as a pathfinder for JEM-EUSO, a mission concept for a spaceborne wide-field telescope monitoring the Earth's nighttime atmosphere with the objective of recording the ultraviolet light from tracks initiated by ultra-high energy cosmic rays. Through a series of stratospheric balloon flights performed by the French Space Agency CNES, EUSO-BALLOON will serve as a test-bench for the key technologies of JEM-EUSO. EUSO-BALLOON shall perform an end-to-end test of all subsystems and components, and prove the global detection chain while improving our knowledge of the atmospheric and terrestrial ultraviolet background. The ballooninstrument also has the potential to detect for the first time UV-light generated by atmospheric airshower from above, marking a key milestone in the development of UHECR science, and paving the way for any future large scale, space-based ultra-high energy cosmic ray observatory.