• DATA PROCESSING FOR THE EOLE PROJECT

      Dargent, A.; Centre National d’Etudes Spatiales (International Foundation for Telemetering, 1972-10)
      The EOLE project, either known as Cooperative Application Satellite-A (CAS/A) consists of a meteorological data collection experiment. It has been lead by CNES (Centre National d’Etudes Spatiales-FRANCE) and NASA, since 1965, and the experiment has been running from last days of August 1971 through June 1972.
    • IMPLANTABLE TELEMETRY IN THE CHIMPANZEE

      Stone, H. L.; Sandler, Harold; Fryer, Tom; Marine Biomedical Institute; NASA Ames Research Center (International Foundation for Telemetering, 1972-10)
      The chimpanzee has been proposed as a possible human analogue for a myriad of human disease states. The lack of knowledge about the cardiovascular system in this animal or the cardiovascular response to stress is understandable because of the cost and handling problems with the chimpanzee. Part of this difficulty, namely handling, can be overcome with the proper selection of cardiovascular instrumentation. Implantable telemetry systems have the advantage that the animal does not have to be handled for any reason. Several animals have been successfully used with implantable telemetry units in the chest. A vigorous antibiotic therapy program must be used for the first few days after surgery, but there have not been any complications after this period of time. The life of the implanted unit has been prolonged by the use of a power switch which also allows remote collection of data. At the present time there is one such unit still functioning 14 months after implantation. The ease with which these units can be used makes them ideally suited for use in the chimpanzee. Examples of the various types of data collected are given and described briefly.
    • A SINGLE CHANNEL COMMAND DETECTOR FOR DEEP SPACE MISSIONS

      Knapp, Siegbert; AEG-TELEFUNKEN Laboratories (International Foundation for Telemetering, 1972-10)
      AEG-TELEFUNKEN has developed a Single Channel Command Detector which will be used in the solar probe HELIOS. This command detector demodulates command data, PSK-modulated on a subcarrier with a symbol error-probability of less than 1x10^-5 at an input signal to noise ratio of 13,2 db per symbol-length. The command detector consists of two succeessive second-order phase locked loops and a matched filter. The subcarrier synchronizer loop tracks the 512 Hz subcarrier, the bitsynchronizer loop performs data-synchronisation and in contrast to former space concepts, requires no additional power. The matched filter correlates the input signal and its estimate, generated by the subcarrier synchronizer-loop. The integration over exact dataperiods is dumped by the bitsyncpulse. This command detector enables the HELIOS Receiver chain to demodulate command data with less than 1 error in 100 000 symbols over a distance of ~ 300 mill. km. Due to sophisticated digital decoding of the HELIOS Decoder, this error-probability results in 1 false command being executed in 64 years.
    • LONG LIFE 100 W TRIODE FOR ATC AND TELEMETRY TRANSPONDERS

      Kellerer, J.; Schneider, W.; Siemens AG (International Foundation for Telemetering, 1972-10)
      Further development of the Siemens planar triode type RH7C-c used in the Mariner IV S-Band transponder resulted in the conduction-cooled type YD 1380 and air-cooled version YD 1381. These metal ceramic tubes produce a CW output power of 100 W in L/S-Band with a high efficiency around 40%. Small signal gain is 17 dB, and a large signal gain of 14 dB with a 20 MHz bandwidth is achieved. Life of selected sample tubes exceeds 25,000 hours, three times higher than the figure specified for the Mariner IV tube. These tubes incorporate an osmiated metal. dispenser cathode to achieve long life with stable performance. This type of cathode is exceptionally resistant to bombardment by electrons turned back to the cathode as a result of transit-time effects in the cathode-grid space. In transponder applications this allows long intervals between maintenance to be specified for the output stages. Because of the rugged tube design and low weight of the complete amplifier, the YD 1380/81 is also suited for spacecraft applications. An air-cooled, 100 W CW amplifier for 1.6 GHz has a diameter of only 74 mm and length of 175 mm. The laboratory prototype including triode YD 1381 weighs 900 gms, but this weight can be halved if necessary. Fig. 1 shows the tubes YD 1380 and YD 1381. The main applications for these new tubes are in ATC systems, telemetry, L-band communication UHF and L-band TV (ETV) and SSB microwave link equipment.
    • OUTPUT SNR FOR A LIMITING RANDOM ACCESS REPEATER

      Nesenbergs, M.; Peterson, R. G.; Institute for Telecommunication Sciences (International Foundation for Telemetering, 1972-10)
      The acquisition delectability parameter, also known as output signal-to-noise ratio, has been computed for unrestricted random access through an ideal hard-limiter. The method is straightforward but long - it involves multi-dimensional Fourier series and numerical integration. The results depend on many parameters, such as the number of active users, the total number of users, the input signal-to-noise ratio, the length of the address code, the cross-correlation properties of this code, and so forth. The effects and tradeoffs for these parameters are shown in a number of graphs. By and large, the conclusions compare with those of other workers and, with minor exceptions, can be deduced from the well-known linear repeater characteristics. The method given provides a tool for synthesis of random access networks, be they satellite repeaters for land, sea, or air-borne transmitters, or be they mobile radio relays concerned with accidental or intentional interference.
    • FIBER OPTICS COMMUNICATIONS

      Somekh, S.; Yariv, A.; California Institute of Technology (International Foundation for Telemetering, 1972-10)
      The transfer of information in the form of light waves via an optical fiber waveguide is discussed. Small size and weight together with high information rate capability make the fibers attractive for various types of communications systems. Description of channel characteristics such as attenuation and bandwidth is given, and possible input and output devices are examined.
    • IMPACT OF SOLAR CALIBRATION ON TELEMETRY SYSTEM TESTING AND CHECKOUT

      Crane, Williams S.; Pickett, Robert B.; ITT-Federal Electric Corporation (International Foundation for Telemetering, 1972-10)
      The advent of solar calibration techniques has resulted in a drim--tic reduction in the time required to conduct telemetry antenna system measurements. Solar calibration provides a rapid, simple and accurate means of determining antenna system performance in the field environment. A program of solar calibration was instituted two years ago at the SAMTEC Western Test Range (WTR) as a basis for calibration,.trouble shooting, operational planning and determining premission “Go/No-go” status. Solar testing has assisted the site personnel in decreasing the time required for system performance tests, preventative maintenance, premission checkout and trouble isolation. The results obtained are more accurate than the laboratory or antenna field measurements for the determination of either gain or system noise temperature independently. In most cases, measurements provide absolute values within ±1 db accuracy. The Figure of Merit (M = G/T(s)) is now a required data item for some missions and is requested by the range user to assist in his data evaluation.
    • A DISTRIBUTION CONTROL UNIT FOR SATELLITE-SWITCHED COMMUNICATIONS

      Cooperman, R.; Dobyns, T.; Communications Satellite Corporation (International Foundation for Telemetering, 1972-10)
      Traffic estimates for the next generation of commercial communications satellites strongly indicate the desirability of using highly directive multibeam antennas to increase channel capacity. This antenna configuration allows multiple access via space division and frequency sharing through the isolation inherent in the directive multibeam antenna. Coupling this technique with a satellite-borne programmable communications distribution subsystem results in a highly efficient system. The distribution subsystem, consisting of a distribution control unit (DCU) and microwave switch matrix (MSM), is introduced into the satellite communications equipment prior to the output amplifiers and enables interconnection between all earth terminals accessing the satellite. Data on the traffic flow allocation required to provide service is stored in an onboard memory and is used to directly control MSM operation.. Flexibility to adapt to changes in traffic flow patterns is achieved through ground command of the onboard memory contents. A detailed description of the DCU and a general discussion of the space segment are provided.
    • U.S. AIR FORCE TELEMETRY IN THE 1970’S

      Hargrove, W. W.; Norton Air Force Base (International Foundation for Telemetering, 1972-10)
      The telemetry systems used by the U.S. Air Force in the ‘70’s must be highly reliable, flexible, possess growth potential and meet the requirements of operational realism, An attempt must he made to provision the basic weapon system design for the required telemetry hardware in order to prevent the tested version from incurring a penalty due to its subsequent incorporation. The components associated with future U.S. Air Force telemetry systems will be lighter, smaller, consume less power, withstand more severe environments, and cost much less than those of the past.
    • DIGITALLY IMPLEMENTED CLOCK ACQUISITION LOOPS FOR LOW SNR DATA SIGNALS

      Schoolcraft, R. W.; Magnavox Research Laboratories (International Foundation for Telemetering, 1972-10)
      The development of powerful error correction codes for binary data channels has generated a requirement for high performance clock acquisition loops. These loops must provide clean estimates of the data clock at very low data SNR in order to prevent dissipation of the coding gain through noise in the data recovery timing. The key element in high performance clock loops is the method of extracting clock information from the received data stream. Three loops are described which illustrate several extraction concepts and which can be used as design guides. The first loop extracts clock information by use of the function D(t)•D(t+ T/2). The extractor is implemented almost entirely with digital logic elements and is very compact. The third loop is extremely efficient due to the use of a time window which is open for only a short time around the transitions of the data. Its implementation is heavily analog. The second loop is a hybrid of the first and the third falls between them in both performance and complexity. Performance curves are presented for the three loops in terms of data SNR degradation as a function of data SNR and loop bandwidth. Experimental data is presented for the first loop.
    • STATISTICAL DYNAMICS OF A FIRST-ORDER PHASE-LOCKED LOOP

      Mengali, U.; Univerità di Pisa (International Foundation for Telemetering, 1972-10)
      The paper deals with a procedure for studying the transient behavior of a first-order phase-locked loop in the presence of noise. This procedure requires the numerical solution of an ordinary differential equation. Excellent agreement has been found between theoretical results and those obtained via computer simulation.
    • AIRBORNE VISIBLE LASER OPTICAL COMMUNICATION EXPERIMENT

      Randall, J. L.; Marshall Space Flight Center (International Foundation for Telemetering, 1972-10)
      A series of optical communication experiments between a high altitude aircraft at 18.3 km (60,000 ft) and a ground station are planned by NASA in the summer of 1972. The basic concept is that an optical tracker and transmitter will be located in each terminal. The aircraft transceiver consists of a 5-mW HeNe laser transmitter with a 30-megabit (Mbit) modulator. The ground station beacon is an argon laser operating at 488 mn. A separate pulsed laser radar is used for initial acquisition. The objective of the experiment is to obtain engineering data on the precision tracking and communication system performance at both terminals. Atmospheric effects on the system performance are of prime importance.
    • FEEDBACK DECODERS FOR NAVAL APPLICATIONS

      Heller, J. A.; Peterson, R. D.; LINKABIT Corporation; Naval Electronics Laboratory Center (International Foundation for Telemetering, 1972-10)
      Feedback decoding is a simple technique for obtaining a significant improvement in performance on a wide range of binary channels. Code interleaving for burst error correction is particularly simple to implement with feedback decoding. A flexible feedback decoder built by LINKABIT Corporation was tested on a simulated shipboard satellite communication channel. The channel was characterized as being additive Gaussian with a superimposed 5% duty factor periodic burst during which the channel error rate is close to .5. The precise radar induced error burst locations are assumed unknown to the decoder. The simple feedback decoder, operated with the error bursts,provided performance equivalent to t at of an uncoded system operating against additive Gaussian noise alone.
    • A REAL TIME MULTIPROGRAMMED TELEMETRY SYSTEM

      Muse, G. B. (International Foundation for Telemetering, 1972-10)
      A study of several Telemetry Data Reduction Systems has revealed some common problems which reduce the effectiveness of these systems. The problems include: The high cost of real-time computer analysis programs, lengthy turnaround for data product modification, lack of testing flexibility, and reduced hardware system utilization. A computer system, 11TELFILE11, has been implemented to improve upon these problem areas. This system is operational at the Space and Missile Test Center (SAMTEC), Vandenberg Air Force Base, for support of the Minuteman III Weapons Systems.
    • SOLID STATE POWER AMPLIFIERS AT L- AND S-BAND

      Schmidt, B.; Deutsche Forschungs-und Versuchsanstalt fur Luft-und Raumfahrt (International Foundation for Telemetering, 1972-10)
      Efficient solid state amplifiers in the L- and Sband have been accomplished with transistors and varactors. Power outputs of 10 W and more have been realized in microstrip technique with efficiencies of 40 % in the L-band and 30 % in the S-band.
    • RECORDER PARAMETERS AFFECTING BIT ERROR RATE

      McKelvey, G. R.; ITT-Federal Electric Corporation (International Foundation for Telemetering, 1972-10)
      Instrumentation magnetic tape is the primary storage medium employed to store PCM telemetry data representing billions of dollars of expended effort. Considerable data are lost in the recording and playback processes which could be retrieved through proper equipment alignments. The major contributors to the data losses are discussed, and the test methods used to determine the resultant loss for each factor are explained. It is shown that equipment alignment becomes critical as PCM bit rates approach one megabit.
    • HOW DO YOU DEFINE BANDWIDTH?

      Scholtz, R. A. (International Foundation for Telemetering, 1972-10)
      All definitions of bandwidth have certain basic properties which make them true measures of "width". In this paper we show that different bandwidth measures are not interchangable, and note that bandwidth can be viewed as a measure of the number of dimensions added to the signal space per unit time. Methods of computing the transmitted power spectral density in a digital communication system are given and the dependence of the spectral density on the statistical structure of the information source is indicated by example. The paper closes with bandwidth comparison s for three common sets of binary telemetry signals.
    • PHYSIOLOGICAL CONSIDERATIONS IN IMPLANTABLE UNDERWATER TELEMETRY

      Adey, W. R.; Zweizig, J. R. (International Foundation for Telemetering, 1972-10)
      Monitoring the internal environment of marine organisms as well as that of man in the oceanic milieu presents unique problems to the physiologist as signals used for data telemetry may have clear behavioral effects. The question of a tolerable level using different transmission modes is found to be species specific, but general guidelines are drawn on the basis of filtering and detection theory, the properties of the transmission media and the excitability characteristics of biological tissue. Transmission through water is surveyed and attenuation characteristics are presented. Experimental findings indicate that waves propagated through water and tissues are time dispersive and thus at sufficiently high frequencies the received signal process must be carefully evaluated with regard to optimal demodulation. Frequencies up to 1 MHz appear to be within the immediately usable range for distances of 1 meter or less. This bandwidth may be used for frequency-division multiplexed subcarriers or appropriately coded PCM transmission. Successful underwater transmission of physiological signals has been accomplished using frequency modulation of carriers transmitted by return-current-density methods, as part of an external biotelemetry system. Experimental evidence shows that implanted devices operating at high frequencies and at levels far below stimulation threshold can be used for transmission to the external transponder where adequate power is available for transmission to an underwater habitat or through data buoys to remote recording centers.
    • ON SYNCHRONIZATION TECHNIQUES FOR DIGITAL COMMUNICATIONS SYSTEMS

      Chang, R. W.; Bell Telephone Laboratories, Incorporated (International Foundation for Telemetering, 1972-10)
      This talk considers the transient response and the steady-state behavior of some digital phase-locked loops. When these loops are used to synchronize the transmission rate of digital communication stations, the system is capable of operating in two modes: (1) In master-to-slave mode when the communication stations are connected by digital transmission facilities, and (2) In slave-to-slave mode when these stations are connected by analog transmission facilities.
    • DEMODULATION OF FM SIGNALS BY A DISCRETE PHASE LOCKED LOOP

      Reddy, C. P.; Gupta, S. C.; SMU Institute of Technology (International Foundation for Telemetering, 1972-10)
      This paper discusses the discrete-phase locked loop for demodulation of an incoming frequency modulated analog signal imbedded in white noise. The discrete samples admitted into the system adoptively, represent an estimate of the message at the discrete instants of time which can be improved further with a correction factor. The work is in two parts: (1) even without the noise, perfect demodulation is not possible. To arrive at the best estimate, requirements are specified regarding the ratio of carrier frequency to maximum frequency deviation, taking into consideration the lock range and the Nyquist sample rate. A simulation study is performed to specify the bounds for the estimate to be accurate enough. (2) With the above considerations, the receiver is analyzed with noise. For high carrier to noise ratio, it is shown that the performance is at least as good as an analog discriminator. The only requirement being that the condition specified in (1) is more stringent. Digital computer solutions of the system check the above and provide a qualitative picture of the threshold behavior comparable to analog feedback discriminators.