7,564 research outputs found
Orbital Debris-Debris Collision Avoidance
We focus on preventing collisions between debris and debris, for which there
is no current, effective mitigation strategy. We investigate the feasibility of
using a medium-powered (5 kW) ground-based laser combined with a ground-based
telescope to prevent collisions between debris objects in low-Earth orbit
(LEO). The scheme utilizes photon pressure alone as a means to perturb the
orbit of a debris object. Applied over multiple engagements, this alters the
debris orbit sufficiently to reduce the risk of an upcoming conjunction. We
employ standard assumptions for atmospheric conditions and the resulting beam
propagation. Using case studies designed to represent the properties (e.g. area
and mass) of the current debris population, we show that one could
significantly reduce the risk of nearly half of all catastrophic collisions
involving debris using only one such laser/telescope facility. We speculate on
whether this could mitigate the debris fragmentation rate such that it falls
below the natural debris re-entry rate due to atmospheric drag, and thus
whether continuous long-term operation could entirely mitigate the Kessler
syndrome in LEO, without need for relatively expensive active debris removal.Comment: 13 pages, 8 figures. Accepted for publication in Advances in Space
Researc
Flight Dynamics Operations of the TanDEM-X Formation
Since end of 2010 the German TerraSAR-X and TanDEM-X satellites are routinely operated as the first configurable single-pass Synthetic Aperture Radar interferometer in space. The two 1340 kg satellites fly in a 514 km sun-synchronous orbit. In order to collect sufficient measurements for the generation of a global digital elevation model and to demonstrate new interferometric SAR techniques and applications, more than three years of formation flying are foreseen with flexible baselines ranging from 150 m to few kilometers. As a prerequisite for the close formation flight an extensive flight dynamics system was established at DLR/GSOC, which comprises of GPS-based absolute and relative navigation and impulsive orbit and formation control. Daily formation maintenance maneuvers are performed by TanDEM-X to counterbalance natural and artificial disturbances. The paper elaborates on the routine flight dynamics operations and its interactions with mission planning and ground-station network. The navigation and formation control concepts and the achieved control accuracy are briefly outlined. Furthermore, the paper addresses non-routine operations experienced during formation acquisition, frequent formation reconfiguration, formation maintenance problems and space debris collision avoidance, which is even more challenging than for single-satellite operations. In particular two close approaches of debris are presented, which were experienced in March 2011 and April 2012. Finally, a formation break-up procedure is discussed which could be executed in case of severe onboard failures
NASA Automated Rendezvous and Capture Review. Executive summary
In support of the Cargo Transfer Vehicle (CTV) Definition Studies in FY-92, the Advanced Program Development division of the Office of Space Flight at NASA Headquarters conducted an evaluation and review of the United States capabilities and state-of-the-art in Automated Rendezvous and Capture (AR&C). This review was held in Williamsburg, Virginia on 19-21 Nov. 1991 and included over 120 attendees from U.S. government organizations, industries, and universities. One hundred abstracts were submitted to the organizing committee for consideration. Forty-two were selected for presentation. The review was structured to include five technical sessions. Forty-two papers addressed topics in the five categories below: (1) hardware systems and components; (2) software systems; (3) integrated systems; (4) operations; and (5) supporting infrastructure
Vision technology/algorithms for space robotics applications
The thrust of automation and robotics for space applications has been proposed for increased productivity, improved reliability, increased flexibility, higher safety, and for the performance of automating time-consuming tasks, increasing productivity/performance of crew-accomplished tasks, and performing tasks beyond the capability of the crew. This paper provides a review of efforts currently in progress in the area of robotic vision. Both systems and algorithms are discussed. The evolution of future vision/sensing is projected to include the fusion of multisensors ranging from microwave to optical with multimode capability to include position, attitude, recognition, and motion parameters. The key feature of the overall system design will be small size and weight, fast signal processing, robust algorithms, and accurate parameter determination. These aspects of vision/sensing are also discussed
Double Deep Q-Learning and Faster R-CNN-Based Autonomous Vehicle Navigation and Obstacle Avoidance in Dynamic Environment
Autonomous vehicle navigation in an unknown dynamic environment is crucial for both supervised- and Reinforcement Learning-based autonomous maneuvering. The cooperative fusion of these two learning approaches has the potential to be an effective mechanism to tackle indefinite environmental dynamics. Most of the state-of-the-art autonomous vehicle navigation systems are trained on a specific mapped model with familiar environmental dynamics. However, this research focuses on the cooperative fusion of supervised and Reinforcement Learning technologies for autonomous navigation of land vehicles in a dynamic and unknown environment. The Faster RCNN, a supervised learning approach, identifies the ambient environmental obstacles for untroubled maneuver of the autonomous vehicle. Whereas, the training policies of Double Deep Q-Learning, a Reinforcement Learning approach, enable the autonomous agent to learn effective navigation decisions form the dynamic environment. The proposed model is primarily tested in a gaming environment similar to the real-world. It exhibits the overall efficiency and effectiveness in the maneuver of autonomous land vehicles.publishedVersio
Beyond swarm intelligence: The Ultraswarm
This paper explores the idea that it may be possible to
combine two ideas â UAV flocking, and wireless cluster
computing â in a single system, the UltraSwarm. The
possible advantages of such a system are considered, and
solutions to some of the technical problems are identified.
Initial work on constructing such a system based around
miniature electric helicopters is described
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