Impact of tether cutting on onboard navigation during the Tethered Satellite Mission-1

The first Tethered Satellite System mission (TSS-1) is manifested for Shuttle Flight STS-44 in January of 1991. The TSS mission presents a new challenge to engineers, requiring advanced guidance, navigation and control concepts. Current NASA flight rules require that the navigational state of the Orbiter at deorbit burn be known to an accuracy of 20 nautical miles. Response of the Shuttle crew to this contingency may involve cutting the tether prior to a complete retrieval. The degradation of the navigational state accuracy as modelled by Shuttle navigation system is examined. Responses to the loss of communication scenario are proposed for two cases. The first case examines navigational performance during a nominal attitude profile. The second case is identical to the first, with the inclusion of modelled tether electrodynamical forces. Comparisons of trajectories propagated from the onboard navigational state vector and a reference ephemeris state vector were performed, with the tether cut simulated at various points during the mission. Additionally, updates to the onboard navigational state via ground uplinks were provided prior to the assumed loss of communication. Through these comparisons, the onboard navigation state error was determined. Alternative responses result from efforts to minimize this error during the various phases of TSS-1 deployment. These results demonstrated existing NASA flight rules could be violated by cutting the tether, and suggests reponses to a loss of communications contingency to maintain a more accurate navigational state

Simple proof of confidentiality for private quantum channels in noisy environments

Complete security proofs for quantum communication protocols can be notoriously involved, which convolutes their verification, and obfuscates the key physical insights the security finally relies on. In such cases, for the majority of the community, the utility of such proofs may be restricted. Here we provide a simple proof of confidentiality for parallel quantum channels established via entanglement distillation based on hashing, in the presence of noise, and a malicious eavesdropper who is restricted only by the laws of quantum mechanics. The direct contribution lies in improving the linear confidentiality levels of recurrence-type entanglement distillation protocols to exponential levels for hashing protocols. The proof directly exploits the security relevant physical properties: measurement-based quantum computation with resource states and the separation of Bell-pairs from an eavesdropper. The proof also holds for situations where Eve has full control over the input states, and obtains all information about the operations and noise applied by the parties. The resulting state after hashing is private, i.e., disentangled from the eavesdropper. Moreover, the noise regimes for entanglement distillation and confidentiality do not coincide: Confidentiality can be guaranteed even in situation where entanglement distillation fails. We extend our results to multiparty situations which are of special interest for secure quantum networks.Comment: 5 + 11 pages, 0 + 4 figures, A. Pirker and M. Zwerger contributed equally to this work, replaced with accepted versio

RRL: A Rich Representation Language for the Description of Agent Behaviour in NECA

In this paper, we describe the Rich Representation Language (RRL) which is used in the NECA system. The NECA system generates interactions between two or more animated characters. The RRL is a formal framework for representing the information that is exchanged at the interfaces between the various NECA system modules

User interface guidelines for the control of interactive television systems via smart phone applications

International audienceThere are a growing number of smart phone applications allowing the user to control their television, set-top box or other entertainment devices. The success of these applications is limited. Based on findings from media studies in Austria and France focusing on how people currently use their TV and iTV systems and associated devices, this article describes recommendations for the design of a smart phone application enabling users to control Internet Protocol Television (IPTV) systems including all connected entertainment devices. Recommendations include the need to allow users to control devices that are related to the IPTV experience (not only the set-top box or television set) and the focus on scenarios of usage like supporting listening to music, enjoying a movie or controlling the connected home. Based on similarities and differences found in the two samples, future smart phone applications for controlling TV will only succeed if they provide meaningful functionalities that satisfy the (varying) user needs, support personalisation and personal usage and respect the limitations of mobile phones with respect to possible parallel activities performed