Frame synchronization for pulsed jammed satellite telecommand links

A new issue of the satellite telecommand synchronization and channel coding sublayer protocol 1 includes LDPC coded communication link transmission units (CLTU) that contain a 64-bit start sequence. The novel data structures allow operation at lower signal-to-noise ratios than before, and offer improved protection against jamming attacks. This paper considers the corresponding CLTU frame synchronization process. We derive practical algorithms to locate the start sequence in the presence of high noise levels and pulsed jamming. The different algorithms are compared in terms of implementation complexity and performance under various jamming conditions. It is shown that among the considered frame synchronizers, those involving a full search over the entire observation window provide the desired accuracy, i.e., they guarantee a frame synchronization error probability that is significantly smaller than the codeword error rate, for codeword error rates near a target value of 10−4 . Among these synchronizers, the full-search hard-decision-directed correlation-based algorithm has the lowest complexity

Towards improved satellite telecommand link availability

Compliant with the Consultative Committee for Space Data Systems (CCSDS) set of protocols, we explore enhancing the availability service for space links. In particular, we consider specific improved defences against jamming attacks affecting symbol synchronization. More robust adaptive closed-loop symbol synchronizers are designated with a view to the planned update of the CCSDS standard for the telecommand synchronization and channel coding sublayer of the data link layer. It is shown that adaptive schemes exploiting instantaneous jammer state information are recommended to counter destructive attacks that may harm the availability

Performance of advanced telecommand frame synchronizer under pulsed jamming conditions

This paper studies frame synchronization for use with the advanced communication link transmission unit format that was recently proposed for updating the telecommand synchronization and channel coding standard for space applications. With a view to improving the robustness against jamming, future satellite telecommand systems are planning to adopt direct-sequence spread spectrum modulation and advanced channel coding. Compared to the frame synchronization algorithm specified in the current Consultative Committee for Space Data Systems (CCSDS) recommendation, we consider a longer start sequence and relax the condition for declaring synchronization. We investigate the performance of this algorithm in the presence of jamming, and show that the frame synchronizer can be designed such that the overall system’s robustness against pulsed jamming is limited by the robustness of the code rather than the synchronizer

Universal-SBAS: A worldwide multimodal standard

This paper describes a generalisation of the aeronautical GNSS Space Based Augmentation System (SBAS) air interface, in a true worldwide multimodal standard named Universal S-BAS. Examples of usages of this multifrequency future standard are presented in the area of science and precise positioning, timing, security, robust positioning, maritime and reflectometry applications

A Multi-Band Far-Infrared Survey with a Balloon-Borne Telescope

Nine additional radiation sources, above a 3-sigma confidence level of 1300 Jy, were identified at 100 microns by far infrared photometry of the galactic plane using a 0.4 meter aperture, liquid helium cooled, multichannel far infrared balloon-borne telescope. The instrument is described, including its electronics, pointing and suspension systems, and ground support equipment. Testing procedures and flight staging are discussed along with the reduction and analysis of the data acquired. The history of infrared astronomy is reviewed. General infrared techniques and the concerns of balloon astronomers are explored

Far-Infrared Photometry with an 0.4-Meter Liquid Helium Cooled Balloon-Borne Telescope

A 0.4-meter aperture, liquid helium cooled multichannel far-infrared balloon-borne telescope was constructed to survey the galactic plane. Nine new sources, above a 3-sigma confidence level of 1300 Jy, were identified. Although two-thirds of the scanned area was more than 10 degrees from the galactic plane, no sources were detected in that region; all nine fell within 10 degrees and eight of those within 4 degrees of the galactic equator. Correlations with visible, compact H lines associated with radio continuum and with sources displaying spectra steeply rising between 11 and 20 microns were noted, while stellar objects were not detected

Proceedings of the Eleventh Annual Precise Time and Time Interval (PTTI) Application and Planning Meeting

Thirty eight papers are presented addressing various aspects of precise time and time interval applications. Areas discussed include: past accomplishments; state of the art systems; new and useful applications, procedures, and techniques; and fruitful directions for research efforts

Proceedings of the 40th Aerospace Mechanisms Symposium

The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, responsibility for hosting the AMS is shared by the National Aeronautics and Space Administration and Lockheed Martin Space Systems Company (LMSSC). Now in its 40th symposium, the AMS continues to be well attended, attracting participants from both the U.S. and abroad. The 40th AMS, hosted by the Kennedy Space Center (KSC) in Cocoa Beach, Florida, was held May 12, 13 and 14, 2010. During these three days, 38 papers were presented. Topics included gimbals and positioning mechanisms, CubeSats, actuators, Mars rovers, and Space Station mechanisms. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components. The use of trade names of manufacturers in this publication does not constitute an official endorsement of such products or manufacturers, either expressed or implied, by the National Aeronautics and Space Administratio

Space station systems: A bibliography with indexes (supplement 9)

This bibliography lists 1,313 reports, articles, and other documents introduced into the NASA scientific and technical information system between January 1, 1989 and June 30, 1989. Its purpose is to provide helpful information to researchers, designers and managers engaged in Space Station technology development and mission design. Coverage includes documents that define major systems and subsystems related to structures and dynamic control, electronics and power supplies, propulsion, and payload integration. In addition, orbital construction methods, servicing and support requirements, procedures and operations, and missions for the current and future Space Station are included