Browsing International Telemetering Conference Proceedings, Volume 22 (1986) by Issue Date
Now showing items 1-20 of 93
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DPSK MODULATION AND DEMODULATION USING BULK ACOUSTIC WAVE (BAW) DELAY ELEMENTSDPSK modulation and demodulation are usually based on logical selection of the difference phase before modulation and the recovery sum phase after detection. Here, we describe an analogue procedure done directly on the PSK’d I-F. BAW delay elements are used in arrangements of feed-forward for difference modulation and of feedback for demodulation. Characteristics are described, and results of laboratory implementation tests for data rate and carrier frequency variations are given. An I-F of 60 MHz and a bit rate of 200 kHz were used as nominal values. Robust performance is indicated.
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ON-BOARD DATA ACQUISITION AND PROCESSING SYSTEMThis paper describes an on-board PCM data acquisition and processing system using standard PCM units and commercial micro-computer equipments. A special interface, which was developed in order to allow a direct connection to PCM encoders, is also presented. It performs data buffering and decommutation prior to the data acquisition process. This approach facilitated the independent conduction of flight tests away from the users’ ground stations using a minimal investment. It helped to provide test results in flight or immediately after flights, thus shortening the flight test processing turn around time and contributing to expedite the overall flight test program.
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SIGNAL-TO-NOISE RATIO PERFORMANCE OF THE SAWTOOTH PHASE DETECTOR WHEN DEMODULATING PM SUBCARRIERSThe noise performance of the sawtooth phase detector when demodulating a sinusoidal subcarrier plus direct data modulation is studied. At predetection signal-to-noise ratio (SNR) levels of about 10 dB or more, significant improvements in the postdetection SNR of the subcarrier can be obtained using the sawtooth detector rather than a linear multiplier. Below predetection SNR levels of about 10 dB, significant improvements can still be obtained; however, a threshold occurs and the performance degrades until leveling off at 3.2 dB worse than that of a linear multiplier. The predetection SNR level where the sawtooth detector performance becomes worse than that of a linear multiplier depends upon the subcarrier and direct data modulation indices. Performance curves are given between predetection SNR levels of -20 dB and +20 dB for various values of subcarrier modulation index and direct data modulation index.
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A UNIVERSAL RANGE TIMING SYSTEM USING NAVSTAR GPSThe NAVSTAR Global Positioning System (GPS) allows extremely accurate global determination of time as well as position and velocity. Currently, the DoD test and training ranges of the United States are working towards using GPS to obtain position and velocity information and recently attention has been given to using GPS for precise range timing. This paper provides background information, discusses the advantages of using GPS for range timing, and describes two timing system configurations using Tri-Service GPS range equipment.
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REVIEW OF LASER AND RF SYSTEMS FOR SPACE PROXIMITY OPERATIONSThis paper presents a review of the ranging and tracking systems/techniques used in the past NASA programs. A review of the anticipated requirements for future rendezvous and docking operations is also presented as rationale for further development of the technology in this area. The first American rendezvous in space was between Gemini VI-A and Gemini VII and took place on December 15, 1965. The Gemini vehicles were equipped with a noncoherent pulse radar. The target vehicle carried a transponder to assist the radar in target acquisition. Angle tracking was accomplished by the phase-comparison monopulse technique. In the Gemini, Apollo, and Skylab programs, the rendezvous and/or docking were manual operations supported by radar measurements and visual observations. The Shuttle rendezvous radar is a Ku-band, pulse-Doppler radar which doubles as a communications transceiver. This radar is not accurate enough to support close-in stationkeeping or docking. An automatic soft-docking capability has been established as a requirement for future space operations. Millimeter wave and laser radar systems have shown promise in satisfying the needed accuracy requirements and size constraints (for space applications) compared to the microwave systems for proximity attitude, position and velocity measurements. A review of these systems and their capabilities is presented in this paper. Rather than developing a separate sensor to satisfy the requirements of each new spacecraft, a hybrid design is proposed for a versatile system which can satisfy the needs for different spacecrafts and missions.
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DATA ACQUISITION SYSTEM FOR AIRCRAFT QUALIFICATIONThe Boeing Commercial Airplane Company presently uses an Airborne Data Analysis and Monitor System (ADAMS) to support extensive qualification testing on new and modified commercial aircraft. The ADAMS system consists of subsystems controlled by independent processors which preprocess serial PCM data, perform application-specific processing, provide graphic display of data, and manage mass storage resources. Setup and control information is passed between processors using the Ethernet protocol on a fiber optic network. Tagged data is passed between processors using a data bus with networking characteristics. During qualification tests, data are dynamically selected, analyses performed, and results recorded. Decisions to proceed or repeat tests are made in real time on the aircraft. Instrumentation in present aircraft includes up to 3700 sensors, with projections for 5750 sensors in the next generation. Concurrently, data throughput rates are increasing, and data preprocessing requirements are becoming more complex. Fairchild Weston Systems, Inc., under contract to Boeing, has developed an Acquisition Interface Assembly (AIA) which accepts multiple streams of PCM data, controls recording and playback on analog tape, performs high speed data preprocessing, and distributes the data to the other ADAMS subsystems. The AIA processes one to three streams in any of the standard IRIG PCM formats using programmable bit, frame and subframe synchronizers. Data from ARINC buses with embedded measurement labels, bus ID’s, and time tags may also be processed by the AIA. Preprocessing is accomplished by two high-performance Distributed Processing Units (DPU) operating in either pipeline or parallel environments. The DPU’s perform concatenation functions, number system conversions, engineering unit conversions, and data tagging for distribution to the ADAMS system. Time information, from either a time code generator or tape playback, may be merged with data with a 0.1 msec resolution. Control and status functions are coordinated by an embedded processor, and are accessible to other ADAMS processors via both the Ethernet interface and a local operator’s terminal. Because the AIA assembly is used in aircraft, the entire functional capability has been packaged in a 14-inch high, rack-mountable chassis with EMI shielding. The unit has been designed for high temperature, high altitude, vibrating environments. The AIA will be a key element in aircraft qualification testing at Boeing well into the next generation of airframes, and specification, design, development, and implementation of the AIA has been carried out with the significance of that fact in mind.
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COMPARISON OF GPS PSEUDORANGE AND BIASED DOPPLER RANGE MEASUREMENTS TO DEMONSTRATE SIGNAL MULTIPATH EFFECTSThe TI 4100 Geodetic Global Positioning System (GPS) Receiver has been field tested in several environments. These include collocation rooftop tests near reflective equipment, isolated desert positioning tests, and shipboard survey tests. The receiver data consisted of pseudorange (code) and biased Doppler range (phase) measurements on both L1 and L2 frequency channels. This paper compares differences between ionospherically corrected pseudorange and biased Doppler range measurements to demonstrate the significant effects of signal multipath on the pseudorange measurements. That is, pseudorange signal multipath effects can be isolated, detected, and statistically modeled using only the above measurements. Examples are given for various receiver antenna locations. Day-to-day comparisons are made to demonstrate the repeated multipath effects due to repeated satellite-to-antenna geometries. The results can be used to analyze and statistically model pseudorange multipath effects for possible improved positioning and GPS satellite orbit determination accuracy.
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DOUBLE DENSITY ANALOG MAGNETIC RECORDINGThis paper discusses measured performance of double density recording. Tests were conducted using different recorders, playback machines, and magnetic tapes. The main topics discussed are slot signal-to-noise ratio (SNR) and high density digital bit error rate (BER).
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THE CLEANING AND TESTING OF MAGNETIC TAPESDescription of various off-line magnetic tape cleaning techniques and testing process to measure defects of tape before using it for tape recording applications. Discussions are made on the type of cleaning methods and also the ways and means to achieve better evaluation results.
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HIGH SPEED DOUBLE DENSITY RECORDINGThe Western Space and Missile Center has requirements to record high bit rate PCM telemetry data in both predetection and post-detection formats. Recording time is inadequate using standard wideband instrumentation magnetic tape recorder/reproducers. Using double density recording technology, recording time can be doubled, but results in some degradation in recorder performance. This paper discusses the effects of double density recording on recorder performance and on the quality of high bit rate telemetry data.
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THE PACIFIC MISSILE TEST CENTER’S AIRBORNE TELEMETRY COLLECTION CAPABILITYProviding realtime telemetry collection to the Pacific Missile Test Center’s (PMTC) range users presents some unique problems. Operations are staged in an open sea environment with participants often at very low altitude and/or far from land based collection instrumentation. This paper will present an overview of the airborne telemetry collection instrumentation that has been developed at PMTC to overcome these problems and will discuss some of the operational problems encountered in its use.
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EFFECTS OF BASEBAND PULSE SHAPE AND DEVIATION RATIO SELECTIONS ON THE SPECTRUM OCCUPANCY OF M-ARY PCM/FMPower spectra of M-ary, or multi-level, PCM/FM are calculated for a limited selection of baseband pulse shapes and deviation ratios. Parameter values, such as number levels, symbol rates, and deviation ratios, are determined for those cases in which the corresponding spectra fit into 1, 3, and 10 MHz bandwidth channels. The IRIG specifications are used to produce the spectrum occupancy values from the normailized power spectra densities.
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APPLICATION OF VLSI/VHSIC TECHNOLOGY FOR SATELLITE/PLATFORM ONBOARD PROCESSINGWith the advent of higher and higher data rates and signal processing requirements for onboard satellite processing, the need for a faster computational capability has grown well beyond the capabilities of existing space-qualified computers. This has become a major technical issue in the design of next-generation satellite systems for commercial and military use. As a matter of fact, it is becoming a major issue in the Strategic Defense Initiative (SDI), the development of the MILSTAR Satellite System, and in future infrared (IR) and radar satellites/platforms. Future platforms will require larger onboard processing systems than are currently in use in order to satisfy their data processing and commandand-control communications requirements. The platforms of tomorrow will be very sophisticated and therefore expensive. For such systems to have acceptable life-cycle costs, they must be produced from highly reliable hardware that will operate in space for system design lifetimes of up to 10 years. This paper will summarize the processing needs of onboard systems and present a specific example of the design of a VLSI/VHSIC processor for an onboard satellite controller in an airborne platform.
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AN UNCOMPROMISING DUAL FREQUENCY ANTENNA FOR TELEMETRY TRACKING APPLICATIONSCurrently, the majority of telemetry tracking systems in use throughout the world operate in the S-Band frequency range. While this frequency band serves as an adequate vehicle for most applications, some require an additional higher frequency for high bit-rate data. This requirement necessitates use of a dual frequency antenna and, more often than not, suffering an attendant performance compromise at both frequencies which is typically realized in such a device. One agency had such a requirement but was unwilling to accept the usual compromise in the S-band and X-band down-links used in aircraft testing. The design implemented by EMP Inc. satisfied the S-band requirements with the reputable, EMP developed, RADSCAN conical scan feed positioned at the focal plane of an eight foot paraboloidal reflector. The RADSCAN feed radome was redesigned, shaping the frontal surface to form a hyperboloidal dichroic subreflector for the X-band Cassegrain antenna. The subreflector was transparent to S-band while presenting a highly reflective surface to X-band energy. The hyperboloid was fed by a profiled corrugated horn mounted at the vertex of the paraboloidal reflector. The X-band Cassegrainian system produced optimum performance with no degradation whatsoever from the S-band Newtonian antenna. The degradation of the S-band system was less than 0.15 dB. The system provided simultaneous reception of both bands with collimated beams. The S-band system also included a side lobe comparison antenna which precludes acquisition of a target vehicle on a side lobe.
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International Telemetering Conference Proceedings, Volume 22 (1986)International Foundation for Telemetering, 1986-10
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USAF SATELLITE CONTROL FACILITY NETWORK DEVELOPMENTThis paper presents an architectural overview of the Air Force Satellite Control Facility (AFSCF) with emphasis on the on-going development effort of the AF Satellite Control Network (AFSCN). The AFSCF originated twenty-seven years ago, and has evolved into a global satellite service network. This worldwide network is composed of twelve RTSs, located at seven geographically dispersed locations, and a Satellite Test Center (STC) at Sunnyvale, California. The AFSCF provides real-time telemetry, tracking, and commanding (TT&C) service to Department of Defense (DoD) spacecraft and launch vehicles. To cope with the projected operational workload and to reduce life cycle costs, the AFSCF began a major effort several years ago to modernize the Network. The two programs, (Data Systems Modernization and Automated Remote Tracking Station) in this effort will bring about major changes in the Network’s current configuration and operations concept. Another program, the development of the Consolidated Space Operations Center (CSOC), also introduces major changes to the network architecture. Additionally the formation of the USAF Space Command has profound impacts on the AFSCN and its development effort. With these changes, brought about in response to changing DoD space support requirements, the AFSCF network has grown through expansion and modernization of its tracking, data processing, and communication capabilities. This paper discusses the past, the present, and the impending changes to the AFSCN as it continues to evolve in support of the DoD space programs.
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THE EFFECTS OF INCREASED SATELLITE POWER FLUX DENSITY ON NWC TELEMETRY OPERATIONSThis paper presents an analysis of the proposed increase in satellite power flux density as it would affect present, currently proposed, and possible future telemetry operations at NWC and other ranges and multi-range operations. Also included are proposed methods for mitigation of interference if flux density is raised anyway.
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FLIGHT INSTRUMENTATION TELEMETRY FOR AEROSPACE APPLICATIONIn Aerospace missions it is often required to have a flexible telemetry system for carrying out flight test on aircraft, in which the bit rate, sampling rate and the number of channels can be programmed. This enables the pilot of the aircraft to reconfigure the telemetry system to suit any particular test missions. An L-Band PCM/FM Telemetry System containing a Stored Programme Multiplexer, 12 bit ADC and other digital interfaces for carrying out the measurements on Speed, Events, etc has been developed as a flight instrumentation telemetry for HAL, India. This paper not only presents complete details of the system, which was qualified to meet MIL-5422 levels but also the performance of the system during actual aircraft missions.
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TEST AND EVALUATION RESULTS FOR THE AIRBORNE INSTRUMENTATION STATION TELEMETRY SYSTEMAn airborne multibeam telemetry system has been acquired and accepted by the Pacific Missile Test Center. Major system capabilities are to receive, record, and retransmit telemetry data from five tracked objects in widely dispersed directions within the twodimensional planer array field of view. A system description, performance characteristics, test methods, and test results will be presented.
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SELECTING THE OPTIMUM TELEMETRY TRACKING ANTENNA FOR RECEIVING TRANSLATED GPS SIGNALSPerformance data taken on three candidate telemetry tracking antennas which employ significantly different beam scanning principles are presented. Measurements of antenna feed-induced phase noise were made at S-Band and compared.