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Durrani, S. H.

Publications and source records attributed to Durrani, S. H..

17 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Space activities - A review and a look ahead

The paper reviews the progress made in manned and unmanned space programs during the last 25 years and names several major accomplishments. The ingredients of success are identified as good engineering, good technology, and good management of a very complex enterprise. An argument is made that the pace of progress will be governed not by technological advances, which can be very rapid, but rather by future institutional arrangements, which are much slower to evolve. It is predicted that the most likely space activities for the next 20 years will be those relating to space commercialization, and several examples are cited. A hope is expressed that policy makers and entrepreneurs will match the spirit of adventure and risk-taking exhibited by engineers in exploring uncharted territory.

Durrani, S. H.↗
NASA NTRS1980

The NASA communications R & D program

About two years ago, NASA decided to reactivate its communications R&D Program, which had been phased down in 1973. The new program focuses on three major areas: (1) technology development in the 30 and 20 GHz bands for wideband communications; (2) system definition for an integrated terrestrial and satellite-aided system for land mobile communications in the 860 MHz band; and (3) development of system concepts and pilot networks for applications data services. The paper summarizes the new activities in the three areas and describes their status and plans.

Durrani, S. H.↗
NASA NTRS1979

Narrowband system activities in the NASA communications program

The objective of NASA's narrowband system activities is to identify, develop, and test the technology needed for future commercial satellite-aided mobile communications systems. Desired characteristics include low service cost, efficient spectrum utilization, and compatibility with terrestrial systems. Ongoing effort includes system concept definition and market analysis. A typical system would need a large spaceborne antenna with 50 to 100 beams, each 0.5 to 0.7 degree wide, onboard switching and processing, linear solid-state amplifiers, and low-cost user terminals. The paper describes current studies and discusses future NASA plans in this field.

Durrani, S. H.↗
NASA NTRS1978

A communications satellite system concept based on the AMPA experiment

This paper describes a system employing sophisticated satellites with steerable high gain, multibeam phased array antennas, which serve small low-cost user terminals. Adaptive techniques are used to form, point, and shape the beams. Pseudonoise signaling achieves user access/distress without requiring dedicated access/emergency channels. The L-band array has 32 elements, 34-dB gain; the user terminal has 15W transmitter, 3-dB gain antenna. The pseudonoise code and message structures are described. Approximately 100 users can be simultaneously acquired with success-probability exceeding 99%; system capacity can be increased by providing additional beams. System implementation is feasible in the Shuttle era.

Durrani, S. H.↗
NASA NTRS1976

Automatic vehicle monitoring

Automatic vehicle monitoring systems are discussed. In a baseline system for highway applications, each vehicle obtains position information through a Loran-C receiver in rural areas and through a 'signpost' or 'proximity' type sensor in urban areas; the vehicle transmits this information to a central station via a communication link. In an advance system, the vehicle carries a receiver for signals emitted by satellites in the Global Positioning System and uses a satellite-aided communication link to the central station. An advanced railroad car monitoring system uses car-mounted labels and sensors for car identification and cargo status; the information is collected by electronic interrogators mounted along the track and transmitted to a central station. It is concluded that automatic vehicle monitoring systems are technically feasible but not economically feasible unless a large market develops.

Bravman, J. S.↗
NASA NTRS1975

Modular bus and payload designs for the Shuttle era

The Space Shuttle, in combination with the Interim Upper Stage, will provide an economical means of placing payloads in geostationary orbit in the 1980s. This paper summarizes a recent study of multidiscipline applications payloads for Shuttle-IUS launch. Various concepts for modular 'bus' spacecraft structures and payload groupings based on equipment commonality are considered. Several bus and payload configurations, ranging from 160 to 1600 kg, are developed. A typical payload is described in some detail. The payload consists of equipment at 400 MHz for search and rescue and data collection, at 1.5 and 15 GHz for aeronautical, maritime, and land mobile communications, at 40 and 90 GHz for millimeter wave communications, and at other bands for meteorological radiometry, electromagnetic environment measurements, and interferometry.

Durrani, S. H.↗
NASA NTRS1974

A baseline maritime satellite communication system

This paper describes a baseline system for maritime communications via satellite during the 1980s. The system model employs three geostationary satellites with global coverage antennas. Access to the system is controlled by a master station; user access is based on time-ordered polling or random access. Each Thor-Delta launched satellite has an RF power of 100 W (spinner) or 250 W (three-axis stabilized), and provides 10 equivalent duplex voice channels for up to 1500 ships with average waiting times of approximately 2.5 minutes. The satellite capacity is bounded by the available bandwidth to 50 such channels, which can serve up to 10,000 ships with an average waiting time of 5 minutes. The ships must have peak antenna gains of approximately 15.5 dB or 22.5 dB for the two cases (10 or 50 voice channels) when a spinner satellite is used; the required gains are 4 dB lower if a three-axis stabilized satellite is used. The ship antenna requirements can be reduced by 8 to 10 dB by employing a high-gain multi-beam phased array antenna on the satellite.

Durrani, S. H.↗