ORBIT PRECISION ANALYSIS OF SMALL MAN-MADE SPACE OBJECTS IN LEO BASED ON RADAR TRACKING MEASUREMENTS

Abstract: The German Space Operations Center (GSOC

Bose-Einstein Condensate in Weak 3d Isotropic Speckle Disorder

The effect of a weak three-dimensional (3d) isotropic laser speckle disorder on various thermodynamic properties of a dilute Bose gas is considered at zero temperature. First, we summarize the derivation of the autocorrelation function of laser speckles in 1d and 2d following the seminal work of Goodman. The goal of this discussion is to show that a Gaussian approximation of this function, proposed in some recent papers, is inconsistent with the general background of laser speckle theory. Then we propose a possible experimental realization for an isotropic 3d laser speckle potential and derive its corresponding autocorrelation function. Using a Fourier transform of that function, we calculate both condensate depletion and sound velocity of a Bose-Einstein condensate as disorder ensemble averages of such a weak laser speckle potential within a perturbative solution of the Gross-Pitaevskii equation. By doing so, we reproduce the expression of the normalfluid density obtained earlier within the treatment of Landau. This physically transparent derivation shows that condensate particles, which are scattered by disorder, form a gas of quasiparticles which is responsible for the normalfluid component

Quantifying Lgr5-positive stem cell behaviour in the pyloric epithelium

10.1038/srep21923Scientific Reports62192

Autonomous Tracking of Space Objects with the FGAN Tracking and Imaging Radar

This paper presents the first progress made at FGAN/FHR-RWA towards the development of a robust autonomous method for the tracking of space objects with the Tracking and Imaging Radar (TIRA). For the acquisition phase an algorithm based on a Least-Squares Estimation of the state vector and f and g series will be presented and tested. For the tracking phase the suitability of the Extended Kalman Filter in mixed coordinates (EKF) and of the Piecewise-Constant Acceleration Converted Measurements Kalman Filter (PCA-CMKF) will be evaluated

Determination of physical characteristics of space debris Final report

Orbital debris emerged as a new reality in space nearly unnoticed for many years. Before 1984, information about relatively large debris (>10 cm) were available from the NORAD catalogue only. Little was known about medium and small sized debris. Today it is assumed, that 94% of about 8.000 trackable objects in orbit around the Earth are space debris. These objects pose a hazard to large spacecraft planned to operate for long periods of time. The major sources of debris are breakups resulting from explosions and collisions of satellites. One of the problems is, that the physical characteristics of space debris like size, shape, and mass - even of larger space debris - are not very well known. The objective of this study, which was contracted with the German Space Agency DARA, is to characterize and compare debris shapes and sizes from different types of satellite breakups. The Tracking and Imaging Radar of FGAN-FHP was employed to measure a number of space objects selected by NASA. NASA provided up-to-date orbital elements to support the measurements. FGAN analysed the collected narrowband and highly resolved radar data to gain information on the physical characteristics. NASA conducted infrared, optical, and radar observations for the same objects in order to compare size and attitude results of as many objects as possible. This report contains descriptions of measurement and analysis techniques for space debris observations and a comprehensive summary of the results achieved. A total of 44 objects (including 4 different radar calibration satellites) were frequently measured and analysed resulting in estimates of size, shape, intrinsic motion, mass, orbit, and orbital lifetime. The results are useful for modelling and validation of fragmentation events, for concept development of space based detection and warning methods, and for considerations of active removal techniques. (orig.)SIGLEAvailable from TIB Hannover: RR 6936(6-95)+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie, Bonn (Germany); Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA) GmbH, Bonn (Germany)DEGerman