• Cause and Effect of Time Base errors in Coherent Demoudlation of a Suppressed Carrier AM Multiplex

      Nichols, M. H.; Schmitt, F. J.; White Sands Missile Range; Lockheed Electronics Company (International Foundation for Telemetering, 1968-10)
      Two types of time base error, TBE, are discussed. One type results from variations in tape speed (flutter) and the other type is the result of additive noise. Measured data on TBE from a typical tape machine are included. Quantitative effects of TBE on coherent demodulation of DSB, SSB and quadrature DSB are discussed.
    • Flight and Laboratory Testing of a Double Sideband FM Telemetry System

      Richardson, Robert B.; Harney, Paul F.; NASA Flight Research Center (International Foundation for Telemetering, 1968-10)
      This paper discusses the NASA Flight Research Center's laboratory and preliminary flight evaluation of a double sideband suppressed carrier constant-bandwidth telemetry system that will be used as an airborne high-frequency data recorder. Some practical limitations are illustrated, and laboratory and flight-test results are compared. No attempt is made to compare this system with systems using other forms of modulation. Results obtained using an RF link are compared with magnetic tape recording of data. Calibration requirements are included for each system.
    • A High-Rate Telemetry System for the Mariner 1969 Mission

      Tausworthe, R. C.; Easterline, M. F.; Spear, A. J.; California Institute of Technology (International Foundation for Telemetering, 1968-10)
      This presentation deals with a multi-mission deep-space telemetry system, its rationale, analysis, development into hardware, and its subsequent planned application to an actual spacecraft mission whose preparation is now in progress. The spacecraft system encodes raw binary data into a comma-free, bi-orthogonal code which antipodally modulates a square-wave subcarrier, which in turn phase-modulates the downlink carrier. There is no separate signal for subcarrier, word, or symbol sync; all transmitted sideband power is thus available for data transmission.
    • Multifunciton Receiver System for Integrated Tracking, Telemetry and Ranging Data Acquisition

      Shaffer, H. W.; King, E. L.; NASA/Goddard Space Flight Center; General Dynamics Corporation (International Foundation for Telemetering, 1968-10)
      The state-of-the-art for Tracking, Telemetry and Ranging data acquisition has reached a point where simultaneous performance of each of these functions is possible with one receiving system. In addition to simultaneous reception of data with one receiver, this Multifunction Receiver System was developed to be compatible with the other DOD and NASA Tracking and Data Acquisition systems besides the specific system for which it was designed, the Goddard Range and Range Rate System. NASA/Goddard Space Flight Center initiated development of this integrated receiver system in September 1967 and will have the first system operational in December 1968 at Rosma4, North Carolina. Three more systems will be installed: one each at NASA STADAN stations in Alaska, Tananarive, and Carnarvon, Australia. The receiver system was designed to cover all the currently known NASA and DOD frequency bands from VHF to 10 GHz. The data handling capability of the system is optimized for both narrowband and wideband data. AM, FM and PM data is accommodated in varying bandwidths from 10 kHz to 10 MHz. The primary objectives for developing such a system were to achieve improved mission effectiveness of NASA STADAN operations and reduce life-cycle costs in carrying out NASA Tracking and Data Acquisition responsibilities.
    • Results of the UHF Telemetry System R & D Flight Tests at White Sands Missile Range

      Chin, Ball; Hamilton, James W.; White Sands Missile Range (International Foundation for Telemetering, 1968-10)
      This paper describes results of UHF telemetry R&D tests conducted at White Sands Missile Range (WSMR), New Mexico. UHF telemetry problems, such as multipath and target scintillation, are discussed. Several recommendations which may improve the reliability of telemetry data transmission at UHF frequencies are made based on experience and data gained from many UHF telemetry tracking operations.
    • The Small Astronomy Satellite (SAS) Program

      Townsend, Marjorie R.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1968-10)
      One of NASA's newest Explorer class satellite programs, the Small Astronomy Satellite (SAS), will provide much-needed information in the most recently studied fields of astronomy, X-ray, Gamma-ray, UV and IR. This paper will describe the basic spacecraft functions with emphasis on its key feature, the SAS control system, as proposed for early sky surveys, and the changes needed in it for later flights which will require a pointing capability of one arc-minute or better. Its flexibility and versatility for application to many different types of astronomy experiments will be examined.
    • Telemetry with Unrestrained Animals

      Baldwin, Howard A.; Brumbaugh, Donald L.; Sensory Systems Laboratory (International Foundation for Telemetering, 1968-10)
      Telemetry from animals in their natural environment requires simple but efficient data coding methods. The problems common to behavioral or physiological studies with wild animals include immobilization techniques, harness design and ruggedized instrumentation development. Radio tracking experiences with the lion, elephant and buffalo and other game animals are summarized and an outline of instrumentation requirements for a study of long range goal finding ability in the green sea turtle is presented.
    • Expected Number of Spikes of Phase Locked Loop Demodulators

      Osborne, P. W.; Schilling, D. L.; Polytechnic Institute of Brooklyn (International Foundation for Telemetering, 1968-10)
      A new method is presented for finding the expected number of spikes in a phase locked loop of any order, with or without modulation. The procedure can also be employed to determine the threshold of FMFB, FM discriminators and the Maximum Likelihood Estimator. The low pass equivalent gaussian noises x(t), y(t) in the differential equation describing the system (PLL or FMFB) are replaced by the deterministic time functions (Conditional Expectations) 1) E[x(t)/x(0), ẋ(0)] 2) E[y(t)/y(0), ẏ(0)] and solved on a digital computer. The mid spike time (t=0)is taken to be the time when x(0) (quadrature noise)=0, and a surface or surfaces in ẋ(0), y(0), ẏ(0) space are determined which indicates the region A where spikes in the demodulator are obtained. From this the expected number of spikes per second is calculated. Results are presented for the first, second, and third order phase locked loops, and for an ordinary FM discriminator (which can be shown to be equivalent to a PLL of infinite gain). The second order loop used a constant plus integral filter, while the third order loop used a constant plus integral plus double integral filter.
    • High Reliability Tape Recorders for Satellite, Aircraft & Drone Applications

      Wiig, Selmer; Santee, Robert; Lucas, E. D., Jr.; Borg-Warner Controls; Best Electronics (International Foundation for Telemetering, 1968-10)
      A new series of magnetic tape recorders has been developed and flight tested, offering a much higher reliability figure and somewhat improved performance over previous design, especially in terms of long life. Featured is a transport design having only seven moving parts, as compared with three or four times that many in conventional tape recorder mechanisms. Details of this design are described indicating how it is possible to achieve an operating life of 16,000 hours of continuous service in satellite applications. A comparable electronic advance has been in digital record-reproduce techniques where Borg-Warner Controls engineers have developed bit dejittering and servo speed control circuitry that makes possible transmission of recorded PCM or other digital data at high data rates with an essentially jitter-free output from reproducer to telemetry transmitter.
    • Errors Resulting from Channel Filters and Adjacent Channel Crosstalk in DSB/SC Telemetry Systems

      Salter, W. E.; Frost, W. O.; Sperry-Rand Corporation; Marshall Space Flight Center (International Foundation for Telemetering, 1968-10)
      The waveform distortion resulting from adjacent channel crosstalk and from amplitude and phase nonlinearity in channel filters limits the minimum channel spacing, and hence the bandwidth utilization efficiency of a double sideband/suppressed carrier (DSB/SC) telemetry link. The paper presents results of an analysis defining the minimum achievable mean-square error when Butterworth filters are used in the DSB demodulator/demultiplexer. With data inputs consisting of band-limited random signals, solutions are given for various combinations of data order, filter order, channel spacing, and filter cut-off. The trade-off between waveform distortion and channel spacing is illustrated, and optimum locations for the filter cut-off are defined. The irremovable error based on Weiner optimum filter theory is presented as an interesting basis for comparison.
    • An Adaptive Airborne VHF/UHF Transmitter System

      Franke, E. B.; Trover, W. F.; Teledyne Telemetry Company (International Foundation for Telemetering, 1968-10)
      The impending 1970 change-over of telemetry RF links from VHF (215- 265 MHz) to UHF (1435-1545 and 2100-2200 MHz) requires a quantum jump in the state-of-the-art of solid-state transmitters. This problem is compounded by the fact that in certain instances, especially for spacecraft and special applications, there is still a need for transmitters at many different VHF and lower UHF frequencies between 136 MHz and 1 GHz. Therefore, the optimum RF product line is represented by a modular transmitter system composed of fundamental building blocks which will permit the assembly of transmitters capable of producing from 50 watts at 136 MHz to 1/2-watt at 5500 MHz with minimal variations in the over-all mechanical configuration. This adaptive transmitter system must also be able to provide optional features such as power-to-case ground isolation, modulation-to-power ground isolation, turn-on current limiting, either frequency of phase modulation remote turn-on capabilities, and internal telemetry functions of temperature, RF power, dc voltage. Additional design requirements for such a transmitter system are wideband frequency response and carrier deviation capabilities so that the transmitter may handle real-time video signal for use with television, radar and infra-red transmission systems. This paper describes the design alternatives and the conceptual approaches that were used in development of such an adaptive transmitter system. Performance data presented is typical of that achieved from L-band and S-band units.
    • Buoy Telemetry for Environment Prediction in Fisheries Research

      McAlister, W. Bruce; Bureau of Commercial Fisheries Biological Laboratory (International Foundation for Telemetering, 1968-10)
      A telemetering buoy has been developed for the Bureau of Commercial Fisheries to provide environmental information in support of salmon research. The buoys are designed to be free-drifting units; sensors are inductively coupled to a 200 m. single conductor cable beneath the buoy. Present sensors measure temperature, conductivity and depth. One buoy is equipped to participate in the IRLS satellite telemetry experiment. Present development includes equipment to have the buoys determine their position by use of the U.S. Navy Navigation Satellite System.
    • The Effect of Coding on Rate Equalization of Digital Channels

      Butman, S.; Jet Propulsion Laboratory (International Foundation for Telemetering, 1968-10)
      The pulse stuffing technique for rate equalization of digital channels is generalized in this article to the stuffing of a sequence of pulses (a word), which can be coded. The extra capacity needed for signaling the stuffed word decreases exponentially with the number of pulses in it, and may, in fact, be eliminated at a negligible increase in the error rate of the channel.
    • A Data Recording System for Deep Sea Logging

      Ben-Yaakov, S.; UCLA (International Foundation for Telemetering, 1968-10)
      A data recording-reproducing system has been developed in conjunction with an oceanographic in situ multi-sensor probe for measuring chemical properties. The recording unit is built around a deck of a single channel, entertainment-type miniature magnetic tape recorder. The tape speed was reduced to 0.125 ips by slightly modifying the original speed control, which results in four hours' continuous recording. The recording unit incorporates a frequency counter to convert the input frequency signal to a serial, four digits, BCD code. The code is recorded twice per frame by chopping the bits with a 250 Hz signal. The frame lasts 5 seconds after which a command is sent to the main unit advancing the multiplexer one step ahead. The reading unit consists of a second small tape recorder and a decoding circuit. The tape is played back 15 times faster than the recording speed. Synchronization and bits identification are based on counting the (original) 250 Hz chopping signal. This eliminates the problem due to wow flutter and non constancy of tape speeds. The serial BCD code is converted to a parallel code to facilitate printing or tape-to-tape transfer, for computer compatibility. The use of non-expensive tape decks as well as integrated circuit modules reduces markedly the price of the system without compromising on accuracy or reliability.
    • Bit Error Rates in the Presence of Untracked Time Base Fluctuation

      Roche, A. O.; Mallory, P.; General Dynamics; Dynatronics (International Foundation for Telemetering, 1968-10)
      This paper presents a simple four-step procedure for estimating the error probability of an NRZ PCM Synchronizer and Detector operating on an NRZ Bit Stream in the presence of a fluctuating data frequency source. The four steps are as follows. First, the bit error probability is calculated for Gaussian time base fluctuation as a function of the energy per bit to noise power density ratio. The second step is to model the synchronizer as an ordinary linear servo for small phase errors and a closed loop bandwidth, small compared to the bit rate, so that effect of the randomness of the data is averaged out. With the linear model, the time base error in tracking the input signal is calculated also utilizing this approximation as if there were no additive noise. The third step is to calculate the mean squared time base error due to the additive Gaussian noise alone. The fourth step is to combine the errors found in steps two and three as if they were independent and use the graphs found in Step 1 to determine the error rates. It is assumed that the total untracked time base fluctuation is Gaussian. The calculated error probabilities are compared with measured data. There appears to be good correspondence between the calculated and measured error probability.
    • International Telemetering Conference Proceedings, Volume 04 (1968)

      Unknown author (International Foundation for Telemetering, 1968-10)
    • Digital-Data Transition Tracking Loops

      Lindsey, W. C.; Anderson, T. O.; University of Southern California; Jet Propulsion Laboratory (International Foundation for Telemetering, 1968-10)
      This paper is devoted to the problem of tracking data-transitions in digital communication systems by means of decision-directed phase-tracking loops. Such techniques are of interest because these methods provide the receiver with a knowledge of the time instants when the modulation may change states without using the additional transmitter power. The results presented are useful in designing synchronizing circuitry for a wide variety of digital systems. One particular system mechanization plan is presented.
    • Communications for the Apollo Applications Programs

      Fordyce, Samuel W.; NASA (International Foundation for Telemetering, 1968-10)
      The Apollo Applications Program will consist of a series of extended duration manned missions in low earth orbit. The initial missions are based upon equipment and techniques proved in previous space flight programs. This is especially true of the communications systems which rely heavily on the Gemini, Saturn, and Apollo communications hardware operating with the Manned Space Flight Network. Following AAP missions may include new spacecraft developments involving television, teleprinters, satellite relays and spacecraft data management systems. These developments are described briefly, but many of them are concepts in early development stages, and it is difficult to specify the configurations that will be flown.
    • Performance of Binary PSK Communication Systems

      Oberst, J. F.; Schilling, D. L.; Polytechnic Institute of Brooklyn (International Foundation for Telemetering, 1968-10)
      The degree of RF coherence which can be established between transmitter and receiver greatly influences the performance of binary communication systems. Practical systems are partially coherent; the main classes are transmitted reference (TR) and single channel (SC). Although SC systems are potentially superior, they are difficult to analyze and have an inherent mark-space ambiguity problem. In this paper, four SC PSK systems have been studied using Monte Carlo simulation on an IBM 360/50 digital computer. Differential data encoding was used. The systems investigated include Decision Feedback (DF), Squaring (SQ), and a variation of SQ called Absolute Value (AB). In addition, a new Maximum Likelihood (ML) SC system, which is optimum in a restricted sense, is derived and simulated. The simulation results show that all of these systems yield comparable average probability of error. This is in contrast with results which have been published previously. Furthermore, the systems can all be shown to reduce to Differential PSK when the number of reference bauds is one. Finally, a method is introduced for studying the effects of various methods of data encoding on SC system operation.
    • Single RF Carrier Time-Sharing by Remote Locations

      Stadler, S. L.; United Aircraft Corporation (International Foundation for Telemetering, 1968-10)
      It is of vital national interest to know the essential real-time factors involved in the evaluation of an air attack versus a ground defense. This need led military planners to request the development of a computerized system to determine the victors and the vanquished in a war game on a par with an actual combat situation. From an engineering point of view, the evaluation system would permit all "combatants" full scope of operation and would not introduce, of itself, any "artificialities" into a complexity of split-second duels taking place over a wide geographical area. This paper discusses a unique time-division telemetry technique that was designed to resolve the data and control flow to and from remote locations, in this case, tactical aircraft. The actual system that evolved from this approach transfers all "aim and fire" events, coming from a group of aircraft engaged on a "mission", to a central communications and data processing facility. The control in the form of timing synchronization is sent from the facility to all aircraft. It should be noted that this time-sharing method could not utilize classical time-division multiplexing, e.g., PAM or PDM, since the test elements were all physically separate from one another (up to 120 miles). Preliminary test data is presented herein as an indication of the validity of this new technique. The paper concludes with a brief description of this method as applied to air and water pollution control and other posited applications.