Investigation of atmospheric instability for communication experiments with the ESA's geostationary satellite ARTEMIS

The investigations of the atmospheric turbulence instability are carried out. The observations of different stars and different positions of stars in the sky performed with the AZT-2 telescope (diameter of 0.7 m) of the Main Astronomical Observatory, Kyiv, Ukraine, and at the Optical Ground Station (the 1.0-m telescope) of ESA at Canary Islands are described. Short exposures (40 ms) with CCD cameras in focal plane of objectives with the filters were used. The calculations of middle positions of star images were performed. The deviation of star’s image positions from the middle position was also performed. The atmospheric attenuation and FWHM (Full Width Half Maximum) function were calculated using the MIDAS/ROMAFOT software package. The results of analyses of experimental data obtained due to observations in different regions are also presented

Free-Space distribution of entanglement and single photons over 144 km

Quantum Entanglement is the essence of quantum physics and inspires fundamental questions about the principles of nature. Moreover it is also the basis for emerging technologies of quantum information processing such as quantum cryptography, quantum teleportation and quantum computation. Bell's discovery, that correlations measured on entangled quantum systems are at variance with a local realistic picture led to a flurry of experiments confirming the quantum predictions. However, it is still experimentally undecided whether quantum entanglement can survive global distances, as predicted by quantum theory. Here we report the violation of the Clauser-Horne-Shimony-Holt (CHSH) inequality measured by two observers separated by 144 km between the Canary Islands of La Palma and Tenerife via an optical free-space link using the Optical Ground Station (OGS) of the European Space Agency (ESA). Furthermore we used the entangled pairs to generate a quantum cryptographic key under experimental conditions and constraints characteristic for a Space-to-ground experiment. The distance in our experiment exceeds all previous free-space experiments by more than one order of magnitude and exploits the limit for ground-based free-space communication; significantly longer distances can only be reached using air- or space-based platforms. The range achieved thereby demonstrates the feasibility of quantum communication in space, involving satellites or the International Space Station (ISS).Comment: 10 pages including 2 figures and 1 table, Corrected typo

LISA technology and instrumentation

This article reviews the present status of the technology and instrumentation for the joint ESA/NASA gravitational wave detector LISA. It briefly describes the measurement principle and the mission architecture including the resulting sensitivity before focussing on a description of the main payload items, such as the interferomtric measurement system, comprising the optical system with the optical bench and the telescope, the laser system, and the phase measurement system; and the disturbance reduction system with the inertial sensor, the charge control system, and the micropropulsion system. The article touches upon the requirements for the different subsystems that need to be fulfilled to obtain the overall sensitivity.Comment: 37 pages, 18 figures, submitted to CQ

Photothermische Interferometrie zur zerstoerungsfreien Materialpruefung

SIGLETIB Hannover: RO 43(8) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Direct Measurements of Laser Communication Point-Ahead Angles from the Artemis Geostationary Satellite Through Clouds

Laser experiments with ARTEMIS geostationary satellite have been performed in partly cloudy weather using the developed system for the telescope. It has been found that the part of the laser beam is observed simultaneously at the points in direction of the velocity vector where the satellite would arrive at when the laser light reaches the telescope. These results agree with the theory of relativity for light aberration in transition from fixed to moving coordinate system. Observation results open the way for research and development of systems to compensate atmospheric turbulence in laser communications between ground stations and satellites through the atmosphere

DARWIN nulling interferometer breadboard II: design and manufacturing

Nulling interferometry is a direct method to detect earth-like planets. To determine whether a planet is earth-like spectrometry can be performed which requires a broadband optical input signal from the planet. Nulling interferometry should decrease the broadband (λ ≈ 6-18μm) star signal by about a factor of 106. For an ESA contract a nulling interferometer breadboard has been designed, manufactured and tested by TNO TPD together with and as subcontractor of Astrium GmbH in Germany. The set-up enables testing of two different phase shifter types (dispersive phase shifting and field reversal), two different star/planet simulator designs and consists of three sources, a star source, a planet source and a control source. The optical path difference is actively stabilized using an adaptive control scheme and a piezo activated cat's-eye delay-line. The bandwidth of one star source equals 1550 ± 15nm. First tests with this source at TNO TPD resulted in an optical path length stability of 0.5nm rms and a stable, repeatable nulling depth of 30000 (3.3·10-5)

Oberflaechendynamik mittels photothermischer Waermewellenanalyse und Lasertechnik Abschlussbericht

TIB Hannover: FR 2735+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman