Browsing International Telemetering Conference Proceedings, Volume 27 (1991) by Issue Date
Now showing items 1-20 of 100
-
RECENT ADVANCES IN LOSSLESS CODING TECHNIQUESLossless data compression systems allow an exact replica of the original data to be reproduced at the receiver. Lossless compression has found a wide range of applications in such diverse fields as: compression of computer data, still images (e.g., medical or graphical images) and video (usually, in the form of entropy coding of the output of intra/inter-frame lossy schemes). It has been studied for over forty years and new compression algorithms are still continuously developed. This paper is a survey of current lossless techniques with results quoted for both sequential data files and still images.
-
REAL-TIME TELEMETRY DATA PROCESSING and LARGE SCALE PROCESSORSReal-time data processing of telemetry data has evolved from a highly centralized single large scale computer system to multiple mini-computers or super mini-computers tied together in a loosely coupled distributed network. Each mini-computer or super mini-computer essentially performing a single function in the real-time processing sequence of events. The reasons in the past for this evolution are many and varied. This paper will review some of the more significant factors in that evolution and will present some alternatives to a fully distributed mini-computer network that appear to offer significant real-time data processing advantages.
-
THE REAL/STAR 2000: A HIGH PERFORMANCE MULTIPROCESSOR COMPUTER FOR TELEMETRY APPLICATIONSIn this paper we describe the design of the REAL/STAR 2000 system, a highperformance real-time computer for telemetry applications. The REAL/STAR 2000 is a symmetric, tightly-coupled multiprocessor, optimized for real-time processing. The system provides a high level of scalability and flexibility by supporting three configurations: single, dual, and quad processor configurations, based on Motorola 88100 RISC processors. The system runs the multiprocessor REAL/IX operating system, a real-time implementation of the AT&T UNIX System V. It compiles with BCS and OCS standards, meets the POSIX 1003.1 standard, and has the current functionality of the emerging POSIX 1003.4 real-time standard. The REAL/STAR 2000 promotes an open system approach to real-time computing by supporting major industry standards. Benchmark results are also presented in the paper.
-
CARRIER PHASE MODULATION USING DIRECT DIGITAL SYNTHESIS FOR AN S-BAND UPLINKPhase modulation has traditionally been performed in analog hardware. A new product will be described that implements this function using a phase-modulating NCO IC. The modulating signal is sampled and added digitally to the phase of the carrier generated by the NCO. This method produces an output spectrum with highly accurate modulation control, low spur levels and minimal distortion. The effects of generating sampled phase-modulated signals will be described. The selection of the clock and output frequencies are critical to ensuring a clean spectrum. Resulting output spectra are shown.
-
A GENERIC OBJECT-ORIENTED DESIGN FOR A RADIO FREQUENCY SIMULATION IN A SPACE TELEMETRY AND COMMAND ENVIRONMENTIn a generic telemetry simulation the overall fidelity of the simulation is largely based on the simulated vehicle’s On-Board-Systems (OBS) engineering models that drive the generation of the telemetry. Also, the actual transfer of data between the simulated vehicle and control center depends on the ability of the Radio Frequency (RF) OBS to acquire and process the RF links thus resulting in a Acquisition of Signal or Loss of Signal (AOS/LOS) determination. The simulated RF links are a function of the communications OBS models, and the communications environment models. The communications OBS models are responsible for propagating the RF signal. Since the RF link analysis is highly integrated into the characteristics of the communications equipment and environment models, RF link software needs to be constantly redeveloped as communications equipment models change, fidelity is added, or multiple links are created. However, by using a generic objectoriented design, RF link software can process any number of differing links based on the RF characteristics of the propagated wave. As a result, the communications equipment model software can be changed to reflect possible design changes without having to rewrite the RF link software thus allowing reuse of existing code.
-
PCM BIT SYNCHRONIZATION TO AN Eb/No THRESHOLD OF -20 dBThis paper presents an overview of a digital PCM adaptive bit synchronizer capable of bit synchronization down to an Eb/No of -20 dB where Eb/No is the energy contrast ratio. The topics addressed include: 1. Functional block diagrams. 2. Loop bandwidth as a function of synchronization threshold. 3. Accuracy, resolution and stability requirements of the Numerically Controlled Oscillator (NCO) and Loop Filter (LF). 4. Performance data. The purpose of this paper is to highlight the major components of a unit capable of performing this task based on an actual development program.
-
ADVANCED TELEMETRY TRACKING SERVO SYSTEMThe primary objective of the Advanced Telemetry Tracking System Integration and Development program at WSMR was the development and evaluation of an advanced, almost totally digital servo tracking and control system. This was satisfied by replacing the aging analog servo tracking and control system in one of WSMR’s seven Transportable Telemetry Acquisition Systems (TTAS) with a Digital Control Unit (DCU), an Antenna Control Unit (ACU), and other related equipment, and then evaluating the performance of the resultant digital tracking system, referred to as the Advanced TTAS (TTAS-A). The ACU is the primary interface between the operator and the DCU. Through the ACU, the TTAS-A operator has independent control over each pedestal axis (elevation and azimuth) involving the selection of tracking mode and servo bandwidth. The DCU reports various servo system status and warning conditions back to the operator through the ACU. In this paper, a discussion of the TTAS-A servo system, with emphasis upon hardware external to the DCU, is presented. This includes the operation of servo position and rate loops, system status and warning conditions, and a description of the operator-to-system interface via the ACU display and control functions.
-
MISSILE FLIGHT SAFETY AND TELEMETRY AT WHITE SANDS MISSILE RANGEMissile Flight Test Safety Managers (MFTSM) and other flight safety personnel at White Sands Missile Range (WSMR) constantly monitor the realtime space position of missile and airborne target vehicles and the telemetered missile and target vehicle performance parameters during the test flight to determine if these are about to leave Range boundaries or if erratic vehicle performance might endanger Range personnel, Range support assets or the nearby civilian population. WSMR flight safety personnel rely on the vehicle telemetry system to observe the Flight Termination System (FTS) parameters. A realtime closed loop that involves the ground command-destruct transmitter, the vehicle command-destruct receiver (CDR), other FTS components, the missile S-band telemetry transmitter, and the ground telemetry acquisition/ demultiplex system is active when the vehicle is in flight. The FTS engineer relies upon telemetry to provide read-back status of the flight termination system aboard the vehicle. WSMR flight safety personnel use the telemetry system to assess realtime airborne vehicle systems performance and advise the MFTSM. The MFTSM uses this information, in conjunction with space position information provided by an Interactive Graphics Display System (IGDS), to make realtime destruct decisions about missiles and targets in flight. This paper will aid the missile or target developer in understanding the type of vehicle performance data and FTS parameters WSMR flight safety personnel are concerned with, in realtime missile test operations.
-
A PC-Based Telemetry System for Acquiring and Reducing Data from Multiple PCM StreamsThe Solar Energy Research Institute’s (SERI) Wind Research Program is using Pulse Code Modulation (PCM) telemetry data-acquisition systems to study horizontal-axis wind turbines. Many PCM systems are combined for use in test installations that require accurate measurements from a variety of different locations. SERI has found them ideal for data-acquisition from multiple wind turbines and meteorological towers in wind parks. A major problem has been in providing the capability to quickly combine and examine incoming data from multiple PCM sources in the field. To solve this problem, SERI has developed a low-cost PC-based PCM telemetry data-reduction system to facilitate quick, in-the-field multiple-channel data analysis. Called the “PC-PCM System,” it consists of two basic components. First, PC-compatible hardware boards are used to decode and combine multiple PCM data streams. Up to four hardware boards can be installed in a single PC, which provides the capability to combine data from four PCM streams directly to PC disk or memory. Each stream can have up to 62 data channels. Second, a software package written for use under DOS was developed to simplify data-acquisition control and management. The software provides a quick, easy-to-use interface between the PC and multiple PCM data streams. Called the “Quick-Look Data Management Program,” it is a comprehensive menu-driven package used to organize, acquire, process, and display information from incoming PCM data streams. This paper describes both hardware and software aspects of the SERI PC-PCM system, concentrating on features that make it useful in an experiment test environment to quickly examine and verify incoming data from multiple PCM streams. Also discussed are problems and techniques associated with PC-based telemetry data-acquisition, processing, and real-time display.
-
HIGH SPEED FIBER OPTIC TELEMETRY SYSTEM FOR AN UNMANNED, TETHERED, UNDERWATER VEHICLEThe Naval Ocean Systems Center (NOSC) has developed the Advanced Tethered Vehicle (ATV) that can perform a variety of tasks at ocean depths to 20,000 feet. The ATV employs a bidirectional, fiber optic telemetry system. The design of the telemetry was validated by at-sea testing and its reliability contributed to the ATV’s successful deep ocean operations. The telemetry system transmits commands to the vehicle, and two videos and sensor data to the surface over a single optical fiber. Design requirements, descriptions, and implementation of a high speed 200 Megabits-per-second (Mbps) uplink and a 5 Mbps downlink Time Division Multiplexed telemetry system are discussed in this paper.
-
OPEN ARCHITECTURE SYSTEM FOR REAL TIME TELEMETRY DATA PROCESSINGThere have been many recent technological advances in small computers, graphics stations, and system networks. This has made it possible to build highly advanced distributed processing systems for telemetry data acquisition and processing. Presently there is a plethora of vendors marketing powerful new network workstation hardware and software products. Computer vendors are rapidly developing new products as new technology continues to emerge. It is becoming difficult to procure and install a new computer system before it has been made obsolete by a competitor or even the same vendor. If one purchases the best hardware and software products individually, the system can end up being composed of incompatible components from different vendors that do not operate as one integrated homogeneous system. If one uses only hardware and software from one vendor in order to simplify system integration, the system will be limited to only those products that the vendor chooses to develop. To truly take advantage of the rapidly advancing computer technology, today’s telemetry systems should be designed for an open systems environment. This paper defines an optimum open architecture system designed around industry wide standards for both hardware and software. This will allow for different vendor’s computers to operate in the same distributed networked system, and will allow software to be portable to the various computers and workstations in the system while maintaining the same user interface. The open architecture system allows for new products to be added as they become available to increase system performance and capability in a truly heterogeneous system environment.
-
DESIGN OF A DATA ACQUISITION SYSTEM BASED ON THE DECOMMUTATION OF AN EMBEDDED ASYNCHRONOUS DATA STREAM WITHOUT PRIMARY AND SECONDARY FRAME SYNCHRONIZATIONThe use of embedded asynchronous data streams is becoming a popular means of expanding existing telemetry systems and acquiring subsystem data. In such systems, synchronization between the primary and secondary system(s) clocks is usually considered a prerequisite. The Phillips Laboratory has developed a software/hardware approach to the problem of decommutating an embedded asynchronous data stream without primary and secondary frame and clock synchronization. The methodology employed is easily implemented and adapted to many system configurations, and represents a low-cost option in the acquisition of subsystem data. More importantly, the use of such a system greatly reduces the amount of systems integration effort required to incorporate multiple subsystems into a host telemetry system.
-
USING DATAFLOW ARCHITECTURE TO SOLVE THE TRANSPORT LAG PROBLEM WHEN INTERFACING WITH AN ENGINEERING MODEL FLIGHT COMPUTER IN A TELEMETRY SIMULATIONOne of the most challenging technical problems in the development of a spacecraft telemetry simulation is the interface with a flight computer running real-world flight software. The ability of the simulation to satisfy flight software requests for telemetry data, and to load, mode, and control the flight software along with the simulation, can be constrained or degraded using conventional interface solutions. Telemetry dataflow architecture systems can be utilized to solve the interface problems with less constraints. This is an especially attractive solution in a telemetry simulation where the telemetry system can also be used to format and serialize spacecraft telemetry, and receive and preprocess commands. This paper discusses the concepts developed for such a system for a training simulation of the Orbital Maneuvering Vehicle for NASA at Johnson Space Center.
-
FREQUENCY DOMAIN EFFECTS OF LOW RESOLUTION DIGITIZATIONThere is a requirement to digitize certain wide-band analog signals in telemetry applications. Typically, an analog-to-digital converter (ADC) with eight or more bits of resolution is used. The resulting signal requires a much larger transmission bandwidth than the original analog signal. The frequency domain information is of primary interest for many applications. In these cases, there are several methods for minimizing the transmitted bandwidth. One method is to perform fast fourier transforms (FFTs) on the signals and only transmit information about the largest signals. The disadvantages of this approach include: relatively long time delay before transmission, resolution bandwidth fixed when FFT performed (unless phase information is also transmitted), and extra complexity in the telemeter. This paper will discuss some effects of minimizing the transmitted bandwidth by quantizing to a small number of bits. The performance will also be compared with analog frequency modulation (FM). Measured performance will be presented for four different input signals and one-, three-, and eight-bit quantization. These signals are amplitude modulation, angle modulation, sum of sine waves, and frequency sweep. The test setup is shown in figure 1. The analyses presented in this paper were performed using either fast fourier transforms (FFTs) or a Kay DSP Sonagraph. The FFT length was 1024 points and a Hann (cosine) window was used. The analysis hardware used for these tests has an analog input, therefore, all digitized signals were converted to analog signals before analysis. The signals were low pass filtered before analysis to minimize aliasing in the analysis and display process.
-
A PRECISION TRANSPORTABLE TRACKING TELEMETRY SYSTEMChanging mission requirements have forced NASA to procure a new generation of tracking telemetry system with performance and features greatly exceeding existing system capabilities in many areas. These requirements and the system that was designed to meet them are discussed. Initial results of system testing are presented.
-
International Telemetering Conference Proceedings, Volume 27 (1991)International Foundation for Telemetering, 1991-11
-
HIGH “G” MICROWAVE TELEMETRY SYSTEMThe high “G” microwave telemetry system is a microwavemetre wave compatible telemetry system and a telemetry system of time division-frequency division hybrid. The so-called “hybrid” means by adding a microwave programcontrolled receiving antenna and a microwave frequency converter to the front-end of metre wave telemetry system, the microwave telemetry system shall be made up, by removing the additional front-end microwave head and connecting to metre wave receiving antenna instead, the metre wave telemetry system shall be made up. The so-called high “G” means that the microwave projectile-borne equipment can stand the high acceleration shock overloading and the high-speed rotation of the gunshot. This system is compact in structure, flexible in forming ground equipment and unique in high-strength design for projectile-borne equipment, the system meets the requirements of small-size, all-purpose and economization for range telemetry, therefore it is the necessary equipment for the range.
-
REMOTE TELEMETRY CONCEPTSA Remote Telemetry Station (RTS) was developed to support Boeing’s requirement to relocate its flight test telemetry range away from Seattle, Wa. As requirements to relocate the test range were investigated high level requirements were documented and various approaches were evaluated. The end result of the analysis and requirements definition was the procurement of the Remote Telemetry Station (RTS). The RTS is capable of supporting many sites, tracking and receiving up to 1024 Kbits/sec of telemetry data, providing fully redundant two-way radio communication in the UHF and VHF bands, linking all the data back to Seattle and appearing transparent to the users. The RTS was designed and developed by a Boeing/Veda Incorporated team. The end result of this joint design and development effort is a system that meets all Boeing requirements in a highly integrated, extremely efficient, and very flexible package providing for growth through the year 2000.
-
ADVANCED DIGITAL DATA ACQUISITION SYSTEMAn ARINC 429 data acquisition system has been developed by Flight Test Engineering for the Boeing Commercial Airplane Group. Traditionally, acquired ARINC 429 data is stored in the acquisition system and periodically sampled for recording. This paper describes a system which acquires data from many different ARINC 429 digital data buses and records that data as soon as it is has been transmitted on the bus.
-
INTERNATIONALIZATION OF TELEMETRY SYSTEMSThe international market for telemetry systems is growing, and U.S. companies offer technology that cannot be matched. Foreign customers increasingly require local language user interfaces on delivered systems. Emerging software standards allow these requirements to be addressed.