• Autonomous Control and Data Acquisition for Advanced Satellite Systems

      Turner, Tim; Gulton Industries, Inc. (International Foundation for Telemetering, 1985-10)
      Autonomous operation is rapidly becoming a requirement for most new spacecraft systems. An autonomous spacecraft greatly simplifies the ground station processing and monitoring requirements, freeing ground station capabilities for other important tasks. The T2C2 (Telemetry, Timing, Command and Control) System has been conceived and architected to facilitate spacecraft autonomy. The T2C2 architecture is ideally suited for onboard closed-loop control, redundancy management, housekeeping and other autonomous functions. This paper provides an overview of the T2C2 architecture and its applications in the design and implementation of an autonomous spacecraft.

      Mohanty, Nirode C.; The Aerospace Corporation (International Foundation for Telemetering, 1985-10)
      A demand access Satellite Communication System for multiple users has been analyzed. A number of channels, m 1, of each satellites are necessary to coordinate the self-served users to allow access to a satellite having s channels. m depends upon traffic intensity and number of top priority users. A waiting time period for a Poisson arrival and exponential holding time M/M/s system for “preemptive resume” discipline has been derived. There is a significant reduction in waiting time in accessing the channel and in transmission time over other access schemes. There is no waiting time for a top priority user, either in accessing the channel or in transmitting its messages, when the appropriate number of order wires is used.

      Vorce, Richard G.; Fairchild Weston Systems Inc. (International Foundation for Telemetering, 1985-10)
      The unit to be described differs from present tunable discriminator products chiefly because it is designed to simultaneously demodulate all the subcarrier channels in a frequency division multiplex. In addition the demodulated output data is presented in digital format that is compatible for direct computer entry. The discriminator implementation techniques will be discussed at the block diagram level. Particular emphasis will be given to the use of “Finite Impulse Response” filters and also to the internal tape speed compensation process.

      Wickham, M. E.; COMSAT Laboratories (International Foundation for Telemetering, 1985-10)
      An advanced microwave power leveling loop (MPLL) was conceived, designed, fabricated, tested, and used during spacecraft in-orbit testing. The primary function of the MPLL is to maintain constant RF power transmitted from an earth station antenna during spacecraft in-orbit transponder testing. The MPLL utilizes nonlinear analog electronics with flexible signal path routing under microprocessor control. It achieves a power control dynamic range of greater than 50 dB with better than 0.1 dB of control resolution. Power level step changes of 20 dB can be accomplished in under 10 ms. The MPLL is IEEE-488 bus controllable and is designed for use in automated in-orbit test systems to facilitate the measurement process and produce more repeatable results than have previously been possible. Measurements performed with the aid of the MPLL include transponder frequency response, group delay, gain, and saturation level. The system can also be operated in a manual mode, and utilizes state-ofthe-art human interfacing techniques such as a display/entry panel and a rotary encoder control knob. This paper describes the MPLL design process, including computer simulation work and breadboard testing. Performance and temperature chamber test results are presented for breadboard and manufactured units.

      Jones, Samuel C.; May, Charles; The Johns Hopkins University Applied Physics Laboratory (International Foundation for Telemetering, 1985-10)
      Radar altimetry data for the Navy GEOSAT-1 Mission are acquired by a single ground station that also archives, preprocesses, and distributes the data. The ground station, located at the Applied Physics Laboratory in central Maryland, commands and controls the spacecraft and monitors its health and status. Because satellite altimetry data transmitted during any pass over the ground station are unique in terms of ocean surface coverage, there is a program requirement for a 24-hour-per-day operational station with a high degree of reliability and maintainability. The spacecraft command and health monitoring functions are free from single point failures, and automation is used to reduce operator error. Store and forward techniques are used extensively to minimize altimetry data loss and to facilitate recovery from failures.

      Zhou, R.; Mavretic, A.; Boston University College of Engineering (International Foundation for Telemetering, 1985-10)
      This paper will describe the design of a quaternary memory cell and a quaternary shift register. The concept used here is based on multiple-valued logic algebra, which can be extended to a design of other high radix memory cells and high radix shift registers. A comparison of the quaternary memory cell and quaternary shift register with its binary counterpart will be discussed. The reduction of device counts and interconnections in quaternary systems promisses a good future in digital signal processing and communication network design realized by VLSI technology.

      Moore, Willard; Grahame, Bill; Loral Data Systems (International Foundation for Telemetering, 1985-10)
      Previous solid rocket motor instrumentation was inadequate to correlate motor performance with analysis. This is particularly obvious when flight failures occur. The addition of instrumentation, both externally and internally, to the rocket motor has helped solve this problem. External instrumentation has been implemented quite easily with existing technology. However, internal instrumentation has been very difficult to implement. This has been mainly due to the complexity of breaching the motor case. A system was developed that transmits power through the case structure to a unique encoder/signal conditioner which then transmits the data back across the case structure for analysis. This was accomplished by magnetic coupling avoiding any disruption of the case structure. A detailed discussion of the magnetic coupling, signal conditioning and encoding functions will be presented.

      Shituan, Shen; Li, Zhou; Qishan, Zhang; Beijing Institute of Astronautics and Astronautics (International Foundation for Telemetering, 1985-10)
      In this paper a Haar telemetry system is introduced. There are two key points for construction of the Haar telemetry system: to generate Haar function waveforms and to design a multivalue logic multiplier. First, we discuss the way of building the Haar function generator. There are several ways to solve this problem. One of them will be introduced in some detail. Secondly, the multivalue logic multiplier is described. The multiplier consists of three parts: operational amplifier, switching element and its control circuit. Thirdly, according to the relationship between Haar waveforms and switching control wignal, we combine the multiplier with the generator as a whole which is called Harr function modulator. The function of the modulator is the same as Haar function generator plus a number of multipliers, but the circuit of which is greatly simplified. The experimental results show that the new system is effective and as compared with Walsh system the Haar one seems to be a little better.

      Shituan, Shen; Li, Zhou; BEIJING INSTITUTE OF AERONAUTICS AND ASTRONAUTICS (International Foundation for Telemetering, 1985-10)
      The mathematical basis which can form a telemetry system is orthogonal functions. The Haar function set forms a complete set of orthogonal functions. Assording to the princeples of orthogonal multiplexing, a new telemetry system can be formed with Haar functions. Haar functions assume the values +1, 0 and -1, multiplied by powers of o2 &. In this paper we first make a modification to the Haar functions. The functions are so modified that it is suitable for computer to simulate and it also can be easily realized by hardware. The orthogonality of the orthogonality of the modified Haar functions is unchanged. Then,the simulation of Haar telemetry system with microcomputer is given by software. Finally, we have proved that the design of Haar telemetry system is workable.

      Martini, Willy; Telemetering and Systems Department (International Foundation for Telemetering, 1985-10)
      After a brief glimpse of the composition of a modern airborne transmitter, a reminder is given of how the choice of a servoed carrier scheme after frequency division on a quartz crystal reference, favoring transmissions at high data speed, has opened up the way to a whole generation of frequency synthesis transmitters covering the 2.1 - 2.7 GHz band in sub-bands of 150 MHz with a pitch of 0.5 MHz. The advantages of frequency synthesis from the quadruple aspect of maintenance, availability “on the shelf”, flexible use in a congested frequency plan and discretion, are then commented on. Finally, in a last section - more theoretical than the previous ones - the technical difficulties which arise from the “spirit” of frequency synthesis are referred to.

      NOBLE, R.J.; GANDY, W.W.; BAHR, H.A.; SNYDER, W.J.; LOWERY, F.B.; Headquarters, U.S. Army Training and Doctrine Command (TRADOC) (International Foundation for Telemetering, 1985-10)
      In early 1978, as part of on-going organizational and resource assessments at Headquarters, U.S. Army Training and Doctrine Command (TRADOC), one important factor evaluated was the most efficient and effective way to support current and future TRADOC sponsored user tests and how to maximize TRADOC support to the Operational Test and Evaluation Agency (OTEA) and joint testers within existing and anticipated resource limitations. It was concluded that existing test and evaluation instrumentation was: a. Not mobile which caused test scheduling conflicts at fixed test sites. b. Not adequate to support current and future Army user and joint test requirements for large scale realistic scenarios and c. Obsolete and becoming uneconomical to operate and maintain; particularly at the TRADOC Combined Arms Test Activity (TCATA). In May 1978, TCATA, in conjunction with the Combat Developments Experimentation Center (CDEC), was directed to develop TRADOC requirements and a concept for an instrumentation system that would meet the goals indicated in Figure 1. Some of the key goals indicated in this tasking are commonality and interoperability of test and training range instrumentation and the capability of instrumenting field exercises. The concept developed as a result of this directive is the Mobile Automated Field Instrumentation System (MAFIS) development program. The purpose of this presentation is to provide a MAFIS system overview and discuss the implementation of the various MAFIS subsystems and how the chosen implementation supports the goals identified by the TRADOC Commander.

      Su, Yu T.; Choi, Hyung J.; LinCom Corporation (International Foundation for Telemetering, 1985-10)
      This paper presents a method of noncoherent demodulation of the PSK signal for signal distortion analysis at the RF interface. The received RF signal is downconverted and noncoherently sampled for further off-line processing. Any mismatch in phase and frequency is then compensated for by the software using the estimation techniques to extract the baseband waveform, which is needed in measuring various signal parameters. In this way, various kinds of modulated signals can be treated uniformly, independent of modulation format, and additional distortions introduced by the receiver or the hardware measurement instruments can thus be eliminated. Quantization errors incurred by digital sampling and ensuing software manipulations are analyzed and related numerical results are presented also.

      Hedeman, Walter R., Jr.; Aerospace Corporation (International Foundation for Telemetering, 1985-10)
      A novel source of noise is identified and described in this study. If a continuous recording medium is less than perfectly uniform, a given quantity may be recorded differently at different locations in the medium. Inadvertent “encoding” occurs, embedding noise in the signal. Symmetrical sideband noise power results from amplitude and phase modulation of the signal stream by the nonuniform recording medium. “Write noise”, so-called because writing is required, is correlated in amplitude with signal amplitude, and its mean frequency is the signal frequency. It is the dominant noise source for the current generation of recorders and tapes; its power spectrum is almost the same as the power spectrum of the signal. The ratio of standard deviation to mean value of the signal envelope when recording cw signals is an absolute measure of tape quality independent of record level, tape speed, and track width, and establishes an available signal-to-noise ratio which cannot be exceeded. It is assumed that the recorder output has a normal amplitude distribution about its mean value. Theory is confirmed by experiment, within experimental error, for cw and digital recording.

      Skelton, Michael T.; The BDM Corporation (International Foundation for Telemetering, 1985-10)
      An integrated ground data acquisition and reduction facility for monitoring rocket motor testing is being implemented for a large commercial client at their northern Utah test site. This system is capable of recording and processing in near real time large amounts of data from varied types of instrumentation. The system was developed as a stand alone data gathering and processing center and consists of one-of-a-kind integrating hardware, commercial off-the-shelf hardware and a DEC VAX 11-750 based computer system for data processing. This paper discusses the design of the system, the real time acquisition of data, and user friendly data reduction system.
    • ROTATING AERODYNAMIC- EXCITERS for in-flight flutter testing

      PENNACHIONI, M.; Istres Aircraft Testing Base (International Foundation for Telemetering, 1985-10)
      Telemetering, as used in in-flight testing, has several advantages including that of allowing what is known as real-time utilization; and thereby, in certain specific cases, the continuation of the flight programme in terms of the results obtained therein. This feature is especially attractive during the opening of the aircraft’s flutter envelope. It then becomes a matter of experimentally determining the aircraft’s aeroelastic stability throughout its flight envelope, and specifically at high speeds. In this connection, it’s common knowledge that in excess of a certain so-called critical speed, two or more vibratory modes of the structure can become coupled via the aerodynamic forces they respectively generate; and can lead to diverging oscillation liable to cause vibration failure. It’s easy to see that such a critical speed must be well within the permitted aircraft operation envelope and that approaching it during in-flight testing should only be considered with a certain amount of prudence and subject to strict monitoring of the structure’s behaviour. The most widely used monitoring system is to measure the transfer function relating an alternating force applied to the aircraft structure in flight to the displacements it causes at different points of that structure (figure 1). Progress in the flight envelope is made in speed steps, any variations in this transfer function being monitored between steps, and usually being reflected in terms of vibration frequencies and damping. Using telemetering, as in conducting these tests, is beneficial in several respects (figure 2). First it allows instant visual monitoring of the structure’s behaviour at its most significant points (rudders, bearing surface ends) by a team conveniently arranged on the ground. Then, further to a preliminary processing operation occurring in real-time, the test can be validated by merely observing the spectrums and the coherence functions existing between the forces applied and the structure’s response; a poor quality test, either due to a mismatched excitation or to the unexpected effect of an atmospheric turbulence, can be rerun without waiting for the aircraft to land. Finally, if adequate computing facilities are available, a comprehensive utilization of the values measured and their identification with a theoretical model lets the structure’s general behaviour be compared with the estimated figures, and thereby lets the aircraft resume the same test sequence at a higher speed or Mach number. The accuracy of the result and the speed at which it is obtained, so essential to the safe resumption of the flight, primarily depend on the extent and on the adequacy of the available information on the artificially applied forces. The design of “exciters” capable of creating controlled and measurable forces of an adequate level is thus the most vital constraint of the flutter testing facility.

      Wolting, Duane; Hewlett-Packard Company (International Foundation for Telemetering, 1985-10)
      In many engineering applications, a systems analysis is performed to study the effects of random error propagation throughout a system. Often these errors are not independent, and have joint behavior characterized by arbitrary covariance structure. The multivariate nature of such problems is compounded in complex systems, where overall system performance is described by a q-dimensional random vector. To address this problem, a computer program was developed which generates Taylor series approximations for multivariate system performance in the presence of random component variablilty. A summary of an application of this approach is given in which an analysis was performed to assess simultaneous design margins and to ensure optimal component selection.

      Grebe, David L.; General Data Products, Inc. (International Foundation for Telemetering, 1985-10)
      This paper is concerned with the concept and development of cost effective methods for determining sensor-to-user system performance under simulated real world conditions. Many system elements involved in the digital pre- and post- processing functions found in telemetry systems are designed to operate primarily on error free data. The presence of bit errors drastically alters the performance of these elements: data compressors pass noise, E.U. converters produce subtle and wild data variations, and embedded voice channels become overly noisy. This paper identifies the digital areas affected by noise in modern systems, categorizes their susceptability, and suggests laboratory simulation techniques that may identify problems prior to mission data flow.

      NIFONG, R. L.; PACIFIC MISSILE TEST CENTER (International Foundation for Telemetering, 1985-10)
      For the past 30 years, the Pacific Missile Test Center (PMTC) has provided test and evaluation for Navy weapon systems in the sea test range, which extends from Point Mugu approximately 60 miles seaward to San Nicolas Island. The requirement for larger missile footprints in T&E and also encroachment from oil exploration, commercial shipping and recreational boating has made it necessary to develop instrumentation to cover an area expanded to 250 miles beyond San Nicolas Island. This instrumentation development effort is known as the Extended Area Test System (EATS). The primary functions of EATS include participant tracking, telemetry data collection, UHF communications relay and target control relay. Participant tracking for EATS has been accomplished by development of a transponder called a Relay, Reporter, Responder (R3) which is installed aboard all participants. This R3 Unit, which is also installed at numerous surveyed ground stations and carried in airborne stations, permits a continuous multilateration solution in a Master Operations Control Station (MOCS) at Point Mugu, for participant tracking. Telemetry data collection will be accomplished by an airborne phased array antenna system on a P-3A aircraft with the capability to record onboard or retransmit in real time to the Range Operations Control Center. The P-3A aircraft will also provide a UHF communications relay capability, a target control relay capability, as well as providing another airborne R3 reference station for multilateration tracking. The multilateration tracking capability has been operational for over a year. Additional R3 Units are under procurement to increase the number of participants in an operation. The installation of the Phased Array Telemetry Antenna System in the EATS P-3A aircraft has recently been completed. It is presently undergoing operational integration into the PMTC Range system. Three additional Phased Array Aircraft are programmed over the next four years.

      Crossley, David; Drexler, Morrie; Waterman, Al; New Mexico State University (International Foundation for Telemetering, 1985-10)
      PSL is developing a telemetry antenna intended to avoid the mechanical complexity of traditional parabolic passive monopulse trackers. For a considerable range of reception scenarios, a stationary non-tracking antenna will fill the reception requirement while greatly simplyfing the antenna hardware as compared to mechanical passive trackers. A single, phi-symmetric, shaped-beam antenna provides proper coverage of the test range for multiple airborne targets. This system is not time shared and requires no acquisition time. Approximate azimuth to the target is displayed on a CRT. This paper examines the applicable test scenario and the resulting hardware.

      HANEY, J. L.; HILGARTH, C. O.; McDONNELL AIRCRAFT COMPANY (International Foundation for Telemetering, 1985-10)
      McDonnell Aircraft Company recently completed installation of a telemetry tracking system at their Edwards Air Force Base, CA flight test facility. A discussion of the planning, specifications, acquisition, installation, operation, as well as observations and comments about the system is presented from a user’s perspective.