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We present the technical realization of a compact system for performing experiments with cold Rb and K atoms in microgravity in the future. The whole system fits into a capsule to be used in the drop tower Bremen. One of the advantages of a microgravity environment is long time evolution of atomic clouds which yields higher sensitivities in atom interferometer measurements. We give a full description of the system containing an experimental chamber with ultra-high vacuum conditions, miniaturized laser systems, a high-power thulium-doped fiber laser, the electronics and the power management. In a two-stage magneto-optical trap atoms should be cooled to the low μK regime. The thulium-doped fiber laser will create an optical dipole trap which will allow further cooling to sub- μK temperatures. The presented system fulfills the demanding requirements on size and power management for cold atom experiments on a microgravity platform, especially with respect to the use of an optical dipole trap. A first test in microgravity, including the creation of a cold Rb ensemble, shows the functionality of the system. [ABSTRACT FROM AUTHOR]

The Modular X- and Gamma-ray Sensor (MXGS) is an imaging and spectral X- and Gamma-ray instrument mounted on the starboard side of the Columbus module on the International Space Station. Together with the Modular Multi-Spectral Imaging Assembly (MMIA) (Chanrion et al. this issue) MXGS constitutes the instruments of the Atmosphere-Space Interactions Monitor (ASIM) (Neubert et al. this issue). The main objectives of MXGS are to image and measure the spectrum of X- and γ -rays from lightning discharges, known as Terrestrial Gamma-ray Flashes (TGFs), and for MMIA to image and perform high speed photometry of Transient Luminous Events (TLEs) and lightning discharges. With these two instruments specifically designed to explore the relation between electrical discharges, TLEs and TGFs, ASIM is the first mission of its kind. With an imaging system and a large detector area MXGS will, for the first time, allow estimation of the location of the source region and characterization of the energy spectrum of individual events. The sensors have fast readout electronics to minimize pileup effects, giving high time resolution of photon detection for comparison with measurements on μs-time scales of lightning processes measured by the MMIA and other sensors in space or on the ground. The detectors cover the large energy range of the relevant photon energies. In this paper we describe the scientific objectives, design, performance, imaging capabilities and operational modes of the MXGS instrument. [ABSTRACT FROM AUTHOR]