Communications

Design for Improving the Flatness of Solar Sails

An optically flat solar sail could be useful in optical communication and solar energy applications. NASA’s Jet Propulsion Laboratory, Pasadena, California This work describes a discontinuous or segmented mirror whose overall flatness is less dependent on the limited tension that can be supplied by the booms. A solar sail is a large, nominally flat sheet of extremely thin reflectorized film rigidly attached to a spacecraft, enabling propulsion via solar radiation pressure. Rip-stop fibers embedded in the backside of the film — with diameters ≈100× the thickness of the film — are commonly used to arrest tear propagation, which can easily occur in the handling and/or deployment of these gossamer-thin structures. Typically, the thin film or membrane that is the sail is systematically folded to enable both volumetrically compact transportation to space and mechanized deployment. It is the aggressive folding and creasing of the thin film that limits the ultimate flatness that can be achieved.

Posted in: Briefs, TSP, Solar Power

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Army Equips Stryker Unit With New Communications Technology

The Army's Stryker vehicle, designed to quickly move soldiers into a combat zone, is swift and mobile. Now its communications equipment will be, too.

Posted in: News, Wireless

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Frame Synchronization Without Attached Sync Markers

A means has been developed to detect the positions of code words directly. NASA’s Jet Propulsion Laboratory, Pasadena, California In communications systems, there must be a method to identify the beginning of a message at the receiving end, to know when the data stream of a specified structure begins. This is conventionally done by inserting attached sync markers (ASMs) between codewords, and looking for these ASMs in the transmitted data. Instead, a means has been developed to detect the positions of codewords directly, using the decoder to partially process a decoder attempt at each candidate synchronization position. A short decoding operation can successfully synchronize codewords in about two seconds in software.

Posted in: Briefs, TSP, Electronics & Computers

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Serial Communication Cards

ACCES I/O Products, San Diego, CA, announced mPCIe-ICM Series PCI Express Mini Card isolated serial communication cards that measure 30 × 51 mm and feature a selection of four or two ports of isolated RS-232 serial communications. Features include 1.5kV isolation provided port-to-computer and 500V isolation port-to-port on all signals at the I/O connectors. The cards provide ±15kV ESD protection on all signal pins, and use 128-byte transmit/receive FIFO buffers to decrease CPU loading and protect against lost data in multitasking systems.

Posted in: Products, Electronic Components

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Method for Performing GPS L1 C/A Measurements in Wideband Jamming and Interference

John F. Kennedy Space Center, Florida For effective range safety, global positioning system (GPS) metric tracking must be robust to interference with, and jamming of, GPS signals. The conventional approach to mitigating interference and jamming is to use a Controlled Reception Pattern Antenna (CRPA). These few-element phased arrays are used to steer nulls in the directions of interference sources, and/or to point beams in the directions of GPS satellites. The use of CRPAs is limited by their cost and size, as well as the difficulties of integrating the array into a platform. The problems are compounded for a launch vehicle, which must acquire and track GPS signals at high speed and acceleration, and undergo vibration and temperature conditions not common to CRPA use.

Posted in: Articles, Briefs, TSP

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Energy Harvesting Could Help Power Spacecraft of the Future

A consortium is working on a project to maximize energy harvesting on a spacecraft of the future. The initiative seeks to find energy-saving and -maximizing solutions to enable eco-friendly aircraft to stay in space for long periods of time without the need to return to Earth to re-fuel, or to avoid carrying vast amounts of heavy fuel on long-stay journeys.

Posted in: News, Aviation, Energy Efficiency, Energy Harvesting

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Automatic Dependent Surveillance Broadcast System for Traffic Situational Awareness

Armstrong Flight Research Center, Edwards, California An integrated communications and control system for unmanned aircraft systems (UAS) utilizes automatic dependent surveillance broadcast (ADS-B) technology. The prime objective of this system is to address safety concerns related to UAS sharing airspace with traditional aircraft. This system is capable of real-time traffic and weather updates in three-dimensional trajectories, and can be re-engineered for specific missions and applications.

Posted in: Articles, Briefs, TSP

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