• The Helios Spacecraft/Ground Telecommunications System Concept

      Hertlein, H. P.; Gesellschaft fuer Weltraumforschung (International Foundation for Telemetering, 1974-10)
      The U. S.-German joint Helios Program is briefly presented with emphasis upon the Spacecraft Telecommunications System design and Ground Tracking and Data System. The design constraints for the radio system, and some tradeoff considerations germane to the Helios radio system are discussed. The block diagram, major performance parameters and some test results are given as bases for the understanding of more detailed telecommunications system discussions.
    • A Transponder for Deep Space Probes-Design and Performance Characteristics

      Go, G. Bie; AEG-Telefunken (International Foundation for Telemetering, 1974-10)
      Deep space probes necessitate the use of coherent ranging transponders. The requirements for this class of transponder can be divided into telemetry, command and ranging requirements. Usually the telemetry requirements are rather straightforward and concern more with hardware design aspects. On the other hand, command requirements generally requires iterative computations to achieve an optimum system design. Ranging requirements are based either on a simple turn-around ranging channel, or on the complex regenerative channel. The design of this transponder is based on the former type of ranging channel. This paper shows the system design for such a transponder and a comparison with measured performance characteristics. Additionally, spurious signal analysis for the ranging operation is dealt with briefly.
    • Computer Controlled Radio Information System for Public Vehicle Operations

      Go, G. Bie; AEG-Telefunken (International Foundation for Telemetering, 1974-10)
      Radio control centers for Public vehicle operations has long been an essential instrument to control and monitor schedules and operations. However, due to the rapid development of city and urban traffic the capacity limit of the small amount of voice channels is already reached, especially during rush hours. Moreover the dispatchers are overburdened, so that adherence to schedule and safe operations cannot be guaranteed. Data communications is the means to increase the efficiency and the capacity of the existing system. AEG-TELEFUNKEN has conceived an advanced system TELETRANS utilizing computer control and radio monitoring. This system makes improved use of the existing channel capacity without infringing on current FCC regulations. Through the use of co-channel transmission, which is a special type of transmit diversity, large areas with diameters up to 40 km (25 mi.) can be covered. This system is flexible, so that requirements of small and large public transportation authorities can be fulfilled economically.
    • The Technical Characteristics of the German Telecommand Station for Deep Space

      Öttl, H.; Holl, H.; Institut für Flugfunk und Mikrowellen (International Foundation for Telemetering, 1974-10)
      The technical description of the Telecommand Station is based on the results of the final subsystem tests. Some outstanding results are illustrated by measured diagrams. The design of some station systems differs from those of the well known DSN stations. Presently, the station is equipped for command purposes only. Nevertheless, the station concept is such that a full-fledged deep space station can be achieved with a few additions, such as receiving and ranging equipment.
    • Use of Pseudo-Random PCM Tape Signatures for Telemetry Ground Station Validation

      Schoeck, K. O.; Pickett, R. B.; Vandenberg Air Force Base (International Foundation for Telemetering, 1974-10)
      This paper describes an improved tape recorder signature using pseudorandom PCM data. The use of the signature for telemetry ground station validation is discussed. Advantages over other techniques in common use are shown.
    • Comparison of Viterbi and Sequential Decoding with a Noisy Carrier Reference

      Hofman, L. B.; Lumb, D. R.; NASA Ames Research Center (International Foundation for Telemetering, 1974-10)
      Performance of convolutionally encoded telemetry systems with Viterbi decoding or sequential decoding is well understood for the additive white Gaussian noise channel with coherent detection of bi-phase-shift-keyed signals. Significant degradation from ideal performance can occur due to correlated noise resulting from low signal-to-noise ratios in the receiver carrier tracking phase-locked loop. Performance at the lower telemetry data rates on the two Pioneer Jupiter deep space probes provides examples of the effect of correlated noise on a sequential decoding system. Performance degradation needs to be quantified as a function of carrier signal-to-noise ratio (P(c)/N(o)2B(lo)) and carrier-tracking- loop-bandwidth-to-symbol-rate ratio (B(l)/R(s)) in order to provide design and analysis information on such effects. Analytical modeling is extremely difficult, particularly where B(l)/R(s) is neither very large nor very small.
    • Analysis and Test Results of a Hybrid PCM/FM-subcarrier Baseband Multiplex on an FM Carrier

      Nichols, M. H.; The Aerospace Corporation (International Foundation for Telemetering, 1974-10)
      Engineering formulae have been developed for estimating the performance of a telemetry system utilizing an NRZ PCM multiplex plus an FM/FM multiplex frequency modulating a carrier. These formulae have been checked against a laboratory simulation and the agreement is within 1 dB for the PCM and 1.8 dB for the FM/FM. About 1 dB of the 1.8 dB is tentatively accounted for on the basis of lack of symmetry of the carrier predetection (IF) filter used.
    • Some Simulation Results for Convolutional Codes Over a PCM/FM Fading Channel

      Grant, T. L.; Hofman, L.; NASA Ames Research Center (International Foundation for Telemetering, 1974-10)
      NASA is now actively planning entry probe missions for the outer planets. Such an entry probe requires a new telemetry link design. A probable modulation for this link is a continuous phase, narrow-band FSK (or PCM/FM), and this paper reports on simulations which can be used to estimate convolutional code performance with mild fading on such a channel. Simulated decoding has been performed for a range of signal-to-noise ratios on the PCM/FM channel with various fading characteristics.
    • A Markov Model for NASA's Ground Communications Facility

      Adeyemi, Oduoye (International Foundation for Telemetering, 1974-10)
      For those burst noise channels that can be mode l led by finite state Markov chains (FSMC) this paper presents a 'natural' way of constructing such models and in particular gives a five-state Markov chain as a model of errors occurring on the NASA's Ground Communications Facility (GCF). A Maximum Likelihood procedure applicable to any FSMC is developed for estimating all the model parameters starting from the data of error runs. Then we give a few of the statistics important for estimating the performance of error control strategies on the channel.
    • Volunteer Medical Engineers Can Aid Physicians and Hospitals in Telemetry Purchases and Tests

      Jackman, K. R. (International Foundation for Telemetering, 1974-10)
      Inasmuch as this 'ITC/USA/’74’ paper may be on a unique subject in the medical field, an attempt will be made to cover, with references and bibliography, sufficient background to identify some serious hospital and medical problems, with possible technical solutions. Most of these solutions involve the use of trained and experienced Medical (or Clinical) Engineers and Biomedical Equipment Technicians (BMET) in hospitals, clinics, and equipment servicing laboratories. The use of volunteer 'Med. Engrs’, as a public-service of the ACTION groups in each city, will be proposed to solve the local hospital needs for technical performance specifications in purchasing 'vital’ medical instruments, such as the 'ECG’ telemetry systems common to local hospitals. Even greater need for low-cost medical-care exists in many 'developing’ countries, such as India. The writer makes a plea, using Med. Engrs. methods developed and successfully used in Los Angeles in the last three-years, to bring graduate (medically-oriented and trained) engineers, seeking employment into hospitals in their own towns. A 'pilot’ program will be reviewed, using 'ACTION’ professional volunteers in San Diego hospitals, to set an example for 'Med.Engrs’ retrained in Madras, India, to enter their local hospitals, and thereby select techniques for use in other Indian cities.
    • The Shallow Sea-A New Challenge to Telemetry and Communication

      Werner, Edgar; Inter American University of Puerto Rico (International Foundation for Telemetering, 1974-10)
      A preliminary study of the environmental and operational parameters requisite to the design and development of low cost simplified communication and telemetry devices usable in the shallow waters of continental shelves is presented. Specific requirements peculiar to the needs of Ocean Resource Utilization Programs in underdeveloped countries lacking both economic and technological capabilities for using current off the shelf devices are outlined. The environment in which this equipment must operate is defined, first physically and then subjectively, and operational aspects of this type of endeavor are described in terms of the individuals involved. Finally, some design parameters are suggested with a general consideration of the potential market as these programs increase in scope and number. It is hoped that feedback from this paper will generate future specific designs and quantitative criteria on which to base more detailed development work.
    • An S-Band Telemetry Receiver System for Deep Space Applications

      Lampert, E.; Siemens AG (International Foundation for Telemetering, 1974-10)
      To receive the transmitted signals from the HELIOS space probe a S-band telemetry receiver system was built. Of this system the S-band telemetry receivers and the subcarrier demodulators are described. Measured values are presented. The S-band receiver includes a digitally implemented phase-locked-loop. Polarization tracking is possible in a two channel mode as well as in a single channel mode. In the subcarrier demodulator the subcarrier is demodulated before demodulating the RF-carrier. Good noise thresholds and low degradation is reached because remodulation is used in the subcarrier loop. The equipment works in a fully computer controlled station, this includes all aquisition procedures.
    • Evolution of the Douglas Flight-Test Data System

      Crowley, L. D.; Douglas Aircraft Company (International Foundation for Telemetering, 1974-10)
      The process of developing new techniques and systems for the purpose of flight-test data acquisition, communication, and processing is, in fact, an evolutionary one. It is filled with potential mutations formed when an orderly or direct path is not taken in any of supporting disciplines or when the capabilities of one link greatly exceed those of another. The rigid design philosophy that made the Douglas system so successful in support of numerous test programs has had both a negative and positive effect of limiting, or at least slowing, the future growth in flexibility. Upgrading the system with new hardware and software must be accomplished in a manner that does not degrade the existing performance and throughput capabilities while making room for the new species to evolve. Problems have been minimized by placing the development of the acquisition and processing systems under common management and, in turn, having this group accountable to the project users of the system. Constant feedback between system developers and users has ensured a degree of adaptability to the hostile environment of test program costs and schedules.
    • The Antenna System of the Helios Solar Probe

      Horwath, L.; Liesekötter, B.; Tymann, G.; Messerschmitt-Boelkow-Blohm GmbH. (International Foundation for Telemetering, 1974-10)
      For the Helios solar probe a complete antenna system was developed and manufactured which is suitable for the various mission requirements, as near earth phase varying aspect angles, close sun flyby and maximum distance of 3,0. 10⁸ km with spin axis orientation perpendicular to the ecliptic. The near earth phase requirements were covered by a low gain antenna system with an isotropic radiation pattern. After the rough orientation of the spin axis a medium gain antenna with an omnidirectional radiation pattern will be used. After final orientation of the spin axis perpendicular to the ecliptic plane a high gain antenna with a despun wire grid reflector will be used for the telemetry link. By switching devices and/or hardwire connections the antenna systems are partly redundant in order to get the required high reliability. The maximum operating temperature range of the antenna system is + 200° to - 200°C.
    • Capacity of Noncoherent MFSK Channels

      Bar-David,I.; Butman, S. A.; Klass, M. J.; Levitt, B. K.; Lyon, R. F.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1974-10)
      This article computes the capacity of a noncoherent multifrequency-shift-keying channel as a function of the number of orthogonal signals, M, and the predetection signal-to-noise ratio, ST/N₀, for three basic receiver types; these are hard decision, unquantized (optimum), and quantized (soft decision). Computational cutoff rates for sequential decoding are also computed.
    • The Future of Real Time Telemetry Systems

      LeCann, Raymond P.; Grumman Data Systems Corporation (International Foundation for Telemetering, 1974-10)
      This paper briefly outlines the development of real time data processing systems and discusses the techniques used in present systems to bring full power of computer facilities to the systems user. While discussing existing systems, future user requirements are examined and the application of recent technology to these needs is investigated. Software systems, hardware techniques and systems management are reviewed so that future systems design may be responsive to the human, as well as the technical elements of vehicle testing.
    • The Data Handling System of the Helios Probes

      Pabst, Dietrich; Digital Space Applications (International Foundation for Telemetering, 1974-10)
      The Helios probes A and B will have a maximum distance of 2AU from Earth. The typical requirements which are applicable to all deep space missions, especially decreasing link capacity, need a flexible data handling system. Taking the Helios probe as an example, it will be shown how the specific problems of data handling in deep space probes were solved from the technical standpoint. The system processes 4 selectable scientific formats at 8 to 4096 bit/sec with 320 subcommutated housekeeping channels, also to be transmitted in a separate engineering format. Simultaneously, a special format is stored cyclically with up to 16kbit in a 0.5Mbit memory, which can also be used for the storage of all the other data in an automatic sequence mode. Telemetry data are convolutional coded. Due to its flexibility and its multiplicity, the data handling system is a useful instrument for deep space missions.
    • Telemetry in Underground Mines Using Leaky Transmission Line Nets

      Hu, A. H.; New Mexico State University (International Foundation for Telemetering, 1974-10)
      A wayside underground communication system using leaky electromagnetic transmission line nets is presented in this paper. This leaky line or cable enables radio wave propagation through tunnels and out-of-sight places via combined cable and atmospheric transmission. It is also an all-purpose communication link which provides telemetry, communication, traffic control, emergency capabilities, paging, TV surveillance, fire detection, and fire control.
    • German Telecommand Station-The Dynamic Behaviour of the Steel Structure and Its Drive and Control System

      Eschenauer, H. A.; Schwarz, R. K.; Krupp Industrie- und Stahlbau; Siemens AG, Unternehmensbereich Energietechnik (International Foundation for Telemetering, 1974-10)
      The mechanical equipment and steel structure of large antennas represents a vibratory system made up of very many elastically coupled masses. Together with the drive control equipment, this complex system has to meet certain requirements with regard to pointing accuracy, turning range, turning speed, and acceleration. Prior knowledge of the dynamic behaviour of the whole control loop is essential to avoid unpleasant surprises at the commissioning stage.
    • Flexibility Objectives for Real-Time Telemetry Processing Systems

      Rymer, J. W.; Naval Air Test Center (International Foundation for Telemetering, 1974-10)
      A generalized real-time telemetry processing system model is developed in four blocks: Demod/Synchronization, Data Channel, Processing/Control and Display. Flexibility objectives are stated for each block and illustrated with respect to the Navy's existing Real-time Telemetry Processing System (RTPS). Features and tradeoffs are discussed for each block along with references to the growing and significant body of such systems already existing and currently under development.