An analysis tool for collision avoidance manoeuvres using aerodynamic drag

Aerodynamic collision avoidance manoeuvres provide an opportunity for satellites in Low Earth Orbits to reduce the risk during close encounters. With rising numbers of satellites and objects in orbit, satellites experience close encounters more frequently. Especially those satellites without thrusting capabilities face the problem of not being able to performimpulsive evasive manoeuvres. For satellites in Low Earth Orbits, though, perturbing forces due to aerodynamic drag may be used to influence their trajectories, thus offering a possibility to avoid collisions. This work introduces a tool for the analysis of aerodynamic collision avoidance manoeuvres. Current space-weather data are employed to estimate the density the satellite encounters. Achievable in-track separation distances following a variation of the ballistic coefficient through a change in attitude are then derived by evaluating an analytical equation from literature. Considering additional constraints for the attitude, e.g., charging phases, and uncertainties in the used parameters, the influence of a manoeuvre on the conjunction geometry and the collision probability is examined. The university satellite Flying Laptop of the University of Stuttgart is used as an exemplary satellite for analysis, which show the general effectiveness of evasive manoeuvres employing aerodynamic drag. First manoeuvring strategies can be deducted and the influence of parameter uncertainties is assessed.Comment: 18 pages, 13 figure

Measurement of spin observables in the quasifree np→{pp}_{s}π^{−} reaction at 353 MeV

none57The transverse spin correlations Ax,x and Ay,y have been measured in the d⃗p⃗→pspec{pp}sπ− reaction at COSY-ANKE at 353 MeV per nucleon. Here {pp}s denotes a proton-proton pair with low excitation energy, which is dominantly in the 1S0 state. By measuring three protons in the final state it was possible to extract events where there was a spectator proton pspec so that the reaction could be interpreted in terms of quasifree n⃗ p⃗→{pp}sπ−. The proton and neutron analyzing powers in this reaction were also deduced from this data set by averaging over the polarizations of the deuteron beam and hydrogen target, respectively. The values of Ay were shown to be consistent with a refined analysis of our earlier results obtained with a polarized proton incident on a deuterium target. Taking these data in combination with our previous measurements of the differential cross sections and analyzing powers in the p⃗p→{pp}s π0 reaction, a more robust partial wave decomposition was achieved. Three different acceptable solutions were found, and the only way of resolving this ambiguity without further theoretical input would be through a measurement of the mixed spin-correlation parameter Ax,z.noneS. Dymov;V. Shmakova;T. Azaryan;S. Barsov;V. Baru;P. Benati;D. Chiladze;A. Dzyuba;R. Engels;M. Gaisser;R. Gebel;K. Grigoryev;P. Goslawski;G. Guidoboni;M. Hartmann;A. Kacharava;V. Kamerdzhiev;A. Khoukaz;V. Komarov;P. Kulessa;A. Kulikov;V. Kurbatov;A. Lehrach;P. Lenisa;V. Lensky;N. Lomidze;B. Lorentz;G. Macharashvili;R. Maier;D. Mchedlishvili;S. Merzliakov;M. Mielke;M. Mikirtychyants;S. Mikirtytchiants;M. Nioradze;D. Oellers;H. Ohm;A. Polyanskiy;M. Papenbrock;D. Prasuhn;F. Rathmann;V. Serdyuk;H. Seyfarth;E. Steffens;H. J. Stein;H. Stockhorst;H. Ströher;M. Tabidze;S. Trusov;D. Tsirkov;Yu. Uzikov;Yu. Valdau;Ch. Weidemann;C. Wilkin;P. Wüstner;Q. J. Ye;M. ZhabitskyS., Dymov; V., Shmakova; T., Azaryan; S., Barsov; V., Baru; Benati, Paolo; D., Chiladze; A., Dzyuba; R., Engels; M., Gaisser; R., Gebel; K., Grigoryev; P., Goslawski; Guidoboni, Greta; M., Hartmann; A., Kacharava; V., Kamerdzhiev; A., Khoukaz; V., Komarov; P., Kulessa; A., Kulikov; V., Kurbatov; A., Lehrach; Lenisa, Paolo; V., Lensky; N., Lomidze; B., Lorentz; G., Macharashvili; R., Maier; D., Mchedlishvili; S., Merzliakov; M., Mielke; M., Mikirtychyants; S., Mikirtytchiants; M., Nioradze; D., Oellers; H., Ohm; A., Polyanskiy; M., Papenbrock; D., Prasuhn; F., Rathmann; V., Serdyuk; H., Seyfarth; E., Steffens; H. J., Stein; H., Stockhorst; H., Ströher; M., Tabidze; S., Trusov; D., Tsirkov; Uzikov, Y. u.; Valdau, Y. u.; Weidemann, C. h.; C., Wilkin; P., Wüstner; Q. J., Ye; M., Zhabitsk

Test of Time-Reversal Invariance in Proton-Deuteron Scattering at COSY

We propose to perform a novel (P-even, T-odd) null test of time-reversal invariance to an experimental accuracy of 10-6. The parity conserving time-reversal violating observable is the total cross-section asymmetry Ay,xz. The measurement is planned as an internal target transmission experiment at the cooler synchrotron COSY. Ay,xz is measured using a polarized proton beam with an energy of 135 MeV and a tensor polarized deuteron target. Since the experiment has to be staged, with the current request we ask for the two weeks of beam time by the end of 2012 for studies of bunched beam life time

Polarization of a stored beam by spin-filtering

The PAX Collaboration has successfully performed a spin-filtering experiment with protons at the COSY-ring. The measurement allowed the determination of the spin-dependent polarizing cross section, that compares well with the theoretical prediction from the nucleon-nucleon potential. The test confirms that spin-filtering can be adopted as a method to polarize a stored beam and that the present interpretation of the mechanism in terms of the proton-proton interaction is correct. The outcome of the experiment is of utmost importance in view of the possible application of the method to polarize a beam of stored antiprotons.QC 20121212</p

Measurement of deuteron carbon vector analyzing powers in the kinetic energy range 170–380 MeV

A measurement of vector analyzing powers in elastic deuteron-carbon scattering has been performed at the Cooler Synchrotron COSY of Forschungszentrum Jülich, Germany. Seven kinetic beam energies between 170 and 380 MeV have been used. A vector-polarized beam from a polarized deuteron source was injected, accelerated to the final desired energy and stored in COSY. A thin needle-shaped diamond strip was used as a carbon target, onto which the beam was slowly steered. Elastically scattered deuterons were identified in the forward direction using various layers of scintillators and straw tubes. Where data exist in the literature (at 200 and 270 MeV), excellent agreement of the angular shape was found. The beam polarization of the presented data was deduced by fitting the absolute scale of the analyzing power to these references. Our results extend the world data set and are necessary for polarimetry of future electric dipole moment searches at storage rings. They will as well serve as an input for theoretical description of polarized hadron-hadron scattering