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Bremen, Germany

Kurtz J.,University of New South Wales | Wittig S.,OHB System AG | O'Byrne S.,University of New South Wales
Journal of Aircraft | Year: 2016

This paper presents the investigation of the applicability of a counterpropagating laser airspeed sensor system to measure airflow velocity in the subsonic-to-transonic aircraft flight regimes. The system uses the Doppler shift of an absorption line in the A-band of molecular oxygen near 760 nm combined with an independent measurement of the static pressure and temperature to determine the true airspeed. The unique experimental arrangement using laser diodes allows the possibility for fully analog signal processing, while the size and weight of the system would be appropriate for most commercial aircraft or unmanned aerial vehicles flying today. Static pressure and velocity regimes were investigated in wind-tunnel tests from static pressures of 20 to 150 kPa (altitude equivalent 40,000 ft to subsea-level) and airspeeds of 5 to 380 m/s. It is concluded that counterpropagating laser airspeed sensor is a viable airspeed instrument for these aircraft flight regimes as well as a safety-enhancing possible alternative or supplement to pitot-based air data systems. © Copyright 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. Source


Oumer N.W.,German Aerospace Center | Panin G.,German Aerospace Center | Mulbauer Q.,OHB System AG | Tseneklidou A.,TU Munich
Acta Astronautica | Year: 2015

This paper proposes ground-in-the-loop, model-based visual localization system based on transmitted images to ground, to aid rendezvous and docking maneuvers between a servicer and a target satellite. In particular, we assume to deal with a partially cooperative target, i.e. passive and without fiducial markers, but supposed at least to keep a controlled attitude, up to small fluctuations, so that the approach mainly involves translational motion. For the purpose of localization, video cameras provide an effective and relatively inexpensive solution, working at a wide range of distances with an increasing accuracy and robustness during the approach. However, illumination conditions in space are especially challenging, due to the direct sunlight exposure and to the glossy surface of a satellite, that creates strong reflections and saturations and therefore a high level of background clutter and missing detections. We employ a monocular camera for mid-range tracking (20-5m) and stereo camera at close-range (5-0.5m), with the respective detection and tracking methods, both using intensity edges and robustly dealing with the above issues. Our tracking system has been extensively verified at the facility of the European Proximity Operations Simulator (EPOS) of DLR, which is a very realistic ground simulation able to reproduce sunlight conditions through a high power floodlight source, satellite surface properties using multilayer insulation foils, as well as orbital motion trajectories with ground-truth data, by means of two 6 DOF industrial robots. Results from this large dataset show the effectiveness and robustness of our method against the above difficulties. © 2015 IAA. All rights reserved. Source


Hornig A.,University of Stuttgart | Homeister M.,OHB System AG
Acta Astronautica | Year: 2015

In the current wake of mission plans to the Moon and to Earth-Moon Libration points (EML) by several agencies and organizations, TYCHO identifies the key role of telecommunication provision for the future path of lunar exploration. It demonstrates an interesting extension to existing communication methods to the Moon and beyond by combining innovative technology with a next frontier location and the commercial space communication sector. It is evident that all communication systems will rely on direct communication to Earth ground stations. In case of EML-2 missions around HALO orbits or bases on the far side of the Moon, it has to be extended by communication links via relay stations. The innovative approach is that TYCHO provides this relay communication to those out-of-sight lunar missions as a service. TYCHO will establish a new infrastructure for future missions and even create a new market for add-on relay services. The TMA-0 satellite is TYCHO's first phase and a proposed demonstrator mission to the Earth-Moon Libration point EML-4. It demonstrates relay services needed for automated exploratory and manned missions (Moon bases) on the rim (>90°E and >90°W) and far side surface, to lunar orbits and even to EML-2 halo orbits (satellites and space stations). Its main advantage is the permanent availability of communication coverage. This will provide full access to scientific and telemetry data and furthermore to crucial medical monitoring and safety. The communication subsystem is a platform for conventional communication but also a test-bed for optical communication with high data-rate LASER links to serve the future needs of manned bases and periodic burst data-transfer from lunar poles. The operational TMA-1 satellite is a stand-alone mission integrated into existing space communication networks to provide open communication service to external lunar missions. Therefore the long-time stable libration points EML-4 and -5 are selected to guarantee an operation time of up to 10 years. It also enables measurements of the libration point environment with the scientific payloads. This includes sensors for space dust, solar and cosmic radiation activity for satellite lifetime estimation and lunar crew protection by providing early-warning systems. The paper describes the mission concept and the pre-design of the demonstrator satellite according to the operational mission requirements, advantages and benefits of this service. The concept was awarded with the Space Generation Advisory Council and OHB Scholarship in 2011 and the concept study is conducted at the Institute of Space Systems (IRS) [1] of the University of Stuttgart and OHB-System, Bremen [2]. © 2014 IAA. Published by Elsevier Ltd. All rights reserved. Source


Kurtz J.,University of New South Wales | Wittig S.M.,OHB System AG | O'Byrne S.,University of New South Wales
31st AIAA Aerodynamic Measurement Technology and Ground Testing Conference | Year: 2015

This paper presents an investigation of the applicability of a counter-propagating laser air speed sensor (COPLASS) system to measure air flow velocity in the subsonic-to-transonic aircraft flight regimes. The system uses the Doppler shift of an absorption line in the A-band of molecular oxygen near 760 nm, combined with an independent measurement of the static pressure, to determine the true air speed. The experimental arrangement allows for the possibility of fully analog signal-processing, while the size and weight of the system would be appropriate for most commercial aircraft or unmanned aerial vehicles flying today. Static pressure and velocity regimes were investigated in wind tunnel tests from static pressures of 20 to 150 kPa (altitude equivalent 40,000 feet to sub sea-level) and air speeds from 5 to 380 m/s. We conclude that COPLASS is a viable instrument for measuring true air speed in these aircraft flight regimes. © 2015, American Institute of Aeronautics and Astronautics Inc, AIAA. Source


Hager P.B.,TU Munich | Parzinger S.,TU Munich | Haarmann R.,OHB System AG | Walter U.,TU Munich
Advances in Space Research | Year: 2015

The requirements for the design of rovers and sample collecting devices for the Moon are driven by the harsh and diverse thermal lunar environment. Local lunar surface temperatures are governed by boulders and craters. The present work quantifies the changes in solar and infrared heat fluxes qSol and qIR impinging on a rover or a sample collecting device, on the surface of the Moon, by combining lunar surface models, spacecraft and manipulator models, and transient thermal calculations. The interaction between a rover, boulders, and craters was simulated for three solar elevation angles (θ = 2°, 10°, and 90°), resembling lunar surface temperatures of Treg = 170, 248, and 392 K, respectively. Infrared and solar heat fluxes for paths in the vicinity of a single boulder, a field of five boulders, and a single crater were compared to a path on an unobstructed surface. The same heat fluxes were applied to closed and open sample collecting devices to investigate the temperature development of the transported regolith sample. The results show how total received infrared heat on a rover may increase by up to 331%, over the course of a transit in front of sunlit boulders compared to the same transit over an unobstructed plane. Temporary this leads to a 12-fold increased infrared heat flux at closest distance to the obstacle. A transit through a small bowl shaped crater on the other hand may decrease total received solar heat by as much as 86%. Relative as well as absolute influence of surface features on received heat fluxes increases significantly towards smaller solar elevation angles. The temperature of pristine samples, transported in closed or open sample collecting devices, increase from 120 to 150 K within 1 to 1.3 h if exposed to direct solar illumination and infrared heat. Protection from solar illumination yields in 8-fold and 5-fold increased transport times for closed and open sample devices, respectively. Closed sample transporters dampen short exposure times to solar illumination but also lead to higher sample end temperatures in the same period. The degradation of absorptivity and emissivity, due to coverage with dust or scratches obtained during operation, will significantly alter the sample temperature in a negative manner. The results indicate that transient thermal analyses, that take into account the local lunar environment, are feasible and permit more detailed thermal envelopes for future rover missions to the surface of the Moon. © 2014 COSPAR. Published by Elsevier Ltd. All rights reserved. Source

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