Next generation digital GPS receiver

The architecture and technology features of the next-generation (NGR) digital GPS (Global Positioning System) receiver manufactured by Collin are described. The project's objective was to develop an advanced GPS receiver chipset with high antijam capabilities. The program, initiated in 1985, has provided the technology for miniature receiver products for both unmanned and manned vehicle applications. A two-channel version of the receiver is in full-scale development for tactical missile applications. A five-channel version is being tested and evaluated as a drop-in replacement for RCVR-3A, the US Department of Defense standard high dynamic receiver. The NGR design started with the digital signal processing architecture developed for the Defense Advanced Research Project Agency (DARPA) hand-held GPS receiver. Enhancements were made to improve the antijam and signal acquisition performance. Producible, qualifiable and cost-effective silicon monolithic microwave integrated circuits and semicustom digital technologies were used to develop the core GPS chipset. A system design approach was established to permit reuse of mature and validated GPS software     

A nickel/hydrogen battery for PV systems

The nickel-hydrogen battery, developed in the early nineteen-seventies as an energy-storage subsystem for commercial communication satellites, is discussed. The advantages offered by nickel-hydrogen batteries, including long life, low maintenance and high reliability, make it very attractive for terrestrial applications such as stand-alone photovoltaic systems. The major drawback to the wider use of the nickel-hydrogen battery is its high initial cost. A 7-kWh battery has been on test since January 1988 using a flat-plate photovoltaic array for charging. The cell, battery design and test methods are briefly described, and the results of cycling and solar tests are presented. It is concluded that the battery is well suited for remote solar applications     

Reduced minimum configuration fiber optic gyro for land navigationapplications

Further cost reduction of the fiber optic gyroscope is necessary to meet the economic requirements of land navigation systems. Previous concentration was on the reduction of the number of splices and component improvements in the open-loop minimum configuration. Now non-essential components and splices are eliminated. The source-detector coupler is not part of the Sagnac interferometer, and serves solely to direct light from the interferometer into the output photodetector. Many commercial laser diodes incorporate a back-facet photodetector to monitor laser intensity. The signal returned from the Sagnac traverses the laser, and can be detected at this photodetector. The gyro signal can be distinguished from the laser signal by the bias modulation applied in the interferometer. Configuring a gyro in this manner eliminates a directional coupler and the separate photodetector, as well as up to two fiber splices in an all-fiber gyroscope. A production, open-loop fiber optic gyroscope has been modified to demonstrate this principle. The gyroscope exhibits performance comparable to the conventional minimum configuration     

Communication System Architecture for Air Traffic Management and Weather Information Dissemination

The authors present the communication system architecture for air traffic management and weather information dissemination as viewed within the context of the overall National Airspace System (NAS) and the services it provides. This presents the architecture in the 2015 time frame when the final phases of transition take place from analog voice to digital data exchange of common data via integrated networks. The results of this transition are an integrated collection of systems and procedures that efficiently use the capacity of the NAS while balancing access to all user classes and maintaining the highest levels of safety. Efficient collaboration among users is built on a foundation of common data. This information base provides common situational awareness to all participants. All users are accommodated and will receive benefits commensurate with equipage level. This architecture development provides a technical framework for decision-making, research, and analysis of communication technologies     

Organization of cytoskeleton during differentiation of gravisensitive root sites under clinorotation.

Key role in cell gravisensing is attributed to the actin cytoskeleton which acts as a mediator in signaling reactions, including graviperception. Despite of increased attention to the actin cytoskeleton, major gaps in our understanding of its functioning in plant gravisensing still remain. To fill these gaps, we propose a novel approach focused on the investigation of actin involvement in the development of columella cells and cells in the transition zone of roots submitted to clinorotation. Both statocytes and cells in the transition zone represent the postmitotic cells which take origin in root meristems and are specified into graviperceptive (root cap) and gravireacting (transition zone) root tissues. The aim of the research was to investigate and compare the microfilament arrangements in root cap statocytes and peripheral root tissues (epidermis and cortex cells) in the transition zone and to find out how the actin cytoskeleton is involved in their specification under clinostat conditions. So far, our experiments have shown that under clinorotation the cytoplasmic microfilament network in the cortex cells in the transition zone is significantly enhanced. It is suggested that more abundant cytoplasmic microfilaments could strengthen the cortical actin cytoskeleton arranged parallel with the cortical microtubules, which are found to be partially disorganized in this area. Due to microtubule disorganization, the functioning of cellulose-synthesizing machinery and proper deposition of cell wall might be affected and could cause the alterations in the growth mode. But, in our case growth of the cells in the transition zone under clinorotation was rather stable. Due to our opinion, general stability of cell growth under clinorotation is promoted by mutual functional interrelation between actin and tubulin cytoskeletons. It is suggested that a strengthened cortical actin cytoskeleton restricts the cell growth instead of disorganized microtubules.     

The observation of the galactic anticenter region by the balloon borne gamma-ray telescope Natalya-I

This paper presents the results of measurements of gamma radiation with energies above 5 MeV, from the galactic anticenter region. The balloon-borne gamma ray telescope “Natalya-I”, was launched on 6 November, 1980 from the Tata Institute of Fundamental Research's Balloon Facility (Hyderabad, India) and reached ceiling altitude of 35 km. The results on the accelerator calibration of the telescope, using a “tagged” gamma ray beam are also presented.     

INMARSAT integrity channels for global navigation satellite systems

The transmission of integrity information using a signal format compatible with the Global Positioning System (GPS) and relayed through a geostationary satellite repeater, which will be critical in achieving high integrity and availability of global navigation by satellite is discussed. The inclusion of navigation repeaters designed to fulfil this function, the next generation of INMARSAT spacecraft, INMARSAT-3 is examined. The global navigation satellite system (GNSS) integrity channel (GIC) will employ pseudorandom codes in the same family as, but distinct from, the codes reserved by GPS. The data format of the basic integrity channel is designed to convey user range error information for 24 to 40 satellites. A closed-loop timing compensation technique will be used at the uplinking Earth station, to make the signal's clock and carrier Doppler variations identical to those that would result from an onboard signal source. Therefore, the INMARSAT-3 satellites will increase the number of useful navigation satellites available to any user, and can also function as sources of precise timing. There is also a possibility that wide area differential corrections can be carried on the same signal     

The instrument IKS and its calibration

The IKS infrared spectro-photometer will fly on board the VEGA platforms. It is designed to characterize the size, temperature and emissivity of the Comet Halley nucleus, to identify the major gaseous components of the inner coma and to detect the emission of the cometary grains. This paper presents the “calibration” experiments required to reduce the raw data: (i) absolute wavelength calibration of the filter wheels; (ii) modeling of the internal signal, as a function of the temperature of the different sub-systems; (iii) absolute and spectral responsivities of each of the spectrometric and photometric channels, as a function of the wavelength and position of the source in the field of view. Finally, we shall indicate the expected S/N ratios.