• 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.
    • The Effects, Measurement, and Analysis of Flutter in Instrumentation Recorders

      Moore, Laurence; Micom, Inc. (International Foundation for Telemetering, 1968-10)
      As instrumentation recorders are improved to provide wider bandwidths and shorter recorded wavelengths, the effects of flutter and attendant time base distortion severely limit the potential for accurate recording and retrieval of data. The effects of flutter on typical classes of data is given and the measures necessary to determine flutter with high accuracy shown. Since the degrading effects of flutter depend upon the application and the characteristics of the flutter, means of analyzing flutter both in the time domain and in the frequency domain are necessary. A self contained instrument for accurate measurement and analysis of flutter sensitive enough for the most sophisticated transports is described, as are necessary conditions for its use.
    • Communications Between Satellite and Ballons for the Eole Mission

      Bourdeau, J. P.; Debray, P.; Namy, X.; CNES (International Foundation for Telemetering, 1968-10)
    • 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.
    • 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.
    • 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.
    • Performance Characteristics and Specification of PCM Bit Synchronizer/Signal Conditioners

      Peavey, B.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1968-10)
      The PCM BR Synchronizer/Signal Conditioner, hereafter called "synchronizer," plays a vital role in telemetry data recovery, and is perhaps the most important and complex component of telemetry data processing systems (DPS). The synchronizer, being the "front end" of the system, makes an irrevocable decision as to the binary value of each data bit, and provides the fundamental timing signal (clock) for the entire DPS. Thus, the performance characteristics of the synchronizer substantially determine the system's capabilities, and it may be said that the system is as good (or bad) as the synchronizer. This paper presents and discusses test data obtained on synchronizers available to date, and used at Goddard Space Flight Center (GSFC) and its satellite tracking and data acquisition network (STADAN) stations. Performance characteristics such as bit synchronization (bit sync), bit sync acquisition, tracking, bit error rate, and intersymbol interference have been measured with respect to split-phase (SP) and NRZ-L input signals between 500 bps and 300 Kbps, perturbed by "white" Gaussian noise plus jitter. The effect of tape recording and band limiting of these signals on synchronizer performance is also discussed. It is shown that bit error rate alone does not "tell the whole story" about synchronizers, particularly when operating with low (less than 7 dB) SNR's plus jitter. The test data indicate that there is no single synchronizer excelling in all respects. For example, a synchronizer which operates well down to SNR of -3 dB has inferior acquisition, and slippage characteristics when jitter is added to noise. Generally, the performance threshold for random jitter (defined later) is at SNR greater than 10 dB. Some synchronizers seem to perform better with SP than NRZ-L signals, and vice versa. Finally, discussed and suggested are definitions of performance parameters which would uniformly and unambiguously describe and specify synchronizers. A lack of precisely defined and measurable performance parameters and characteristics has caused misinterpretation and misunderstanding of specifications presented by both vendor and customer.
    • The Signal-to-Noise Ratio Estimation Techniques for PCM Signals

      Sos, John Y.; NASA/Goddard Space Flight Center (International Foundation for Telemetering, 1968-10)
      Reliable estimation of signal-to-noise (S/N) ratio in a demodulated PCM telemetry signal can be useful in evaluating the performance of the complete telemetry link, including its signal detection and data processing portions. This paper describes three potentially practical methods developed at Goddard Space Flight Center for estimating the S/N ratio in a PCM signal. One method referred to as "spectral null" method uses spectral characteristics of PCM' signals to estimate the S/N ratio, the other two use statistical properties of the signal, i.e., its mean value and variance. These two methods are known as "variance estimations and "null zone." The implementation of each method is discussed. The spectral null method takes the least amount of equipment, but is more difficult to calibrate and operate over a wide range of bit rates, than the other two systems. All three approaches, however, are uncomplicated enough to be included into almost any existing PCM data handling system. An analysis of the performance characteristics of each system is made. It is shown that the variance estimation method is the most versatile. It can reliably estimate the S/N ratio to within 1.5 db over a range of S/N ratios from 0 db to +10 db. (The S/N ratio is defined as the ratio of signal energy per bit/noise power density.) Under certain conditions all three methods can provide estimates to within 1 db, especially over a S/N ratio range from +3 db to +10 db.
    • Appendix A: Seventh Annual Report of the Telemetering Standards Coordination Committee

      Frost, Walter O. (International Foundation for Telemetering, 1968-10)
    • Laser Applications to Biology and Medicine

      Rounds, Donald E.; Pasadena Foundation for Medical Research (International Foundation for Telemetering, 1968-10)
      The unique physical characteristics of coherence, intensity, and monochromatically offered by laser instrumentation has placed renewed importance on studies in photochemistry and photobiology. Sufficient research experience has now been accumulated to demonstrate the potential usefulness of laser energy to fundamental cell biology, and to the diagnosis and treatment of certain pathological conditions. Current progress in laser applications to ophthalmology, oncology, and dentistry is briefly summarized.
    • Tranmission of Cardiovascular Data from Dogs

      Rader, R.; Meehan, J. P.; Henry, J. P.; Krutz, R.; Trumbo, R.; University of Southern California (International Foundation for Telemetering, 1968-10)
      Prolonged acquisition of dynamic blood pressure data from animal subjects in various experimental conditions has become a special research area in numerous institutions. To properly conduct many of these experiments, the subject must be instrumented with blood pressure sensors and a means of conveying the indicated pressure level to a remote station. Quite often data must be obtained over several weeks in which recalibration can not be conducted. Telemetry techniques are quite adaptable to these problems and in many instances are the only solution available. To illustrate the special applications of telemetry, several experiments are described along with the hardware required to conduct these experiments.
    • 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.
    • 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.
    • Performance of a Bandwidth Limited PCM/PSK/PM Telemetry System

      Miller, G. E.; Jennings, V. A.; The Boeing Company (International Foundation for Telemetering, 1968-10)
      This report investigates the use of coherent and non-coherent FM/PM detectors as applied to recovery of PCM telemetry data. Given a PCM Manchester II encoded FM carrier, a theoretically perfect bit detector was derived. A laboratory prototype was built and evaluated under simulated threshold conditions. Agreement with theory was obtained within 1.50 db, using a coherent demodulator without a limiter stage. Amplitude and phase characteristics are shown in addition to the filter circuit and component values. Several commercial demodulators are compared against the theoretical model. The results of the comparisons are discussed, and recommendations concerning deficient areas are submitted.
    • Compatibility Requirements and Considerations of Range Telemetry Tape

      Schulze, G. H.; Pan American World Airways, Inc. (International Foundation for Telemetering, 1968-10)
      Range Telemetry Tape crossplay operations may be arranged into four major classes each with unique compatibility considerations: a. Between like recorders at the same Range. b. Between unlike recorders at the same Range. c. Between unlike recorders at different Ranges. d. Between unlike recorders at Range User facilities and the Ranges. Like model recorders at the same Range are more likely compatible and capable of optimum tape crossplay than any other combination. Sometimes this very fact produces an atmosphere of complacency which can invite problems. The assumption that the recorder manufacturer has properly controlled his production for optimum crossplay or for complete conformance to IRIG1 is naive and should not be a substitute for compatibility testing at the using Range facility. With field use and equipment aging, compatibility can be gradually lost without becoming detected. Adjustment procedures at one' site may not be identical to procedures at other sites and perfectly compatible equipments can unknowingly become incompatible. The absence of adequate compatibility testing is the major cause of difficulty with this class of crossplay. Crossplay between unlike model recorders at the same Range poses unique problems but these can be controlled providing the unlike recorders have individually been strictly specified and tested to conform to IRIG Standards. Compatibility testing by the using Range is a definite requirement as manufactures may differ in their interpretation of the IRIG Document or may differ in the extent to which they conform. No manufacturer appears to be knowledgeable regarding crossplay between competitive recorders, and some appear to be just as uncertain about compatibility between complimenting recorders from their own product line. Crossplay between unlike recorders at different Ranges is being accomplished but many factors stand in the way of automatic success for this type of venture. When different equipments, different tape types, different operational procedures, and different procurement specifications all combine, the compatibility of the whole system is strained. The possibility of different tape types specified by competing equipment manufacturers should produce cautious awareness by the user and compatibility testing with both tapes should be conducted. The question "Which Range is responsible for the incompatibility?" can be difficult to answer. Currently, no central agency exercises control over Range-to-Range crossplay compatibility, and each Range conforms to IRIG Standards on an individual basis. Crossplay between unlike reproducers at Range User facilities and Range copy recorders is probably the most severe test of compatibility that exists. In this type of crossplay IRIG Standards may not have been invoked by the Range User, different bandwidth classes of systems may be involved and the fact that the User, and the Range may be virtually strangers all promote an environment unconducive to compatibility. Anything that can possibly go awry usually does. The major responsibility must lie with the Range who supplies the original or copy tapes to the Users. Ideally, the copy tapes should all be generated identically regardless of individual recipient requirements, and the IRIG Standards should be religiously followed.
    • Digital FM-Tutorial

      Salz, J.; University of Florida (International Foundation for Telemetering, 1968-10)
      A review of the state of knowledge of digital FM techniques is undertaken. The digital FM signal and its spectral properties are first discussed. We then turn to the analysis of discrimination detection and review a recently proposed phenomenological model from which the error causing mechanism can be understood. We use this model to derive estimates of error-rate as a function of pertinent system parameters. The results obtained for practically instrumented systems are then compared with the ideal. The paper concludes with a discussion of some computer-aided analysis capable of predicting the performance of digital FM systems operating over the dispersive gaussian channel.
    • Output SNR of an FM Discriminator with Non-Ideal Limiting

      Schilling, D. L.; Refi, J. J.; Polytechnic Institute of Brooklyn; Bell Telephone Laboratories (International Foundation for Telemetering, 1968-10)
      The effect of abrupt-limiting on the output of a frequency discriminator has been treated thoroughly by Middleton. This paper considers the case of smooth band-pass limiting both for the simple differentiator and for the balanced discriminator. The error function is used as a model for the smooth limiter. The idealness of the limiter is related to the quantity "μ" - the limiting hardness. The analysis reveals that for a balanced discriminator, the output signal-to-noise ratio can be made largely immune to changes in "μ". However, for the unbalanced discriminator, the signal-to-noise is not only appreciably "μ" dependent, but also a function of carrier frequency.
    • Rician Intersymbol Interference in Frequency Shift Keying

      Vencill, J. J.; McDonnell Douglas Astronautics Company (International Foundation for Telemetering, 1968-10)
      Many communications links involve a reflected signal which is Rician in nature. In troposcatter systems, this reflection constitutes the entire received signal while in communications between satellites or aircraft, such a reflection from the surface corrupts the direct signal. Other such situations involve low elevation tracking or intentional coherent jamming. This paper derives the bit error probability for a non-coherent binary FSK link in this environment for any order of diversity and any ratio of specular to diffuse reflection assuming orthogonal signalling frequencies, matched filter detection and perfect bit synchronization. The interfering signal may represent the same datum as the direct signal (Mark-Mark interference) or, for delays longer than a bit period, the interference may appear in the opposite receiver channel from the direct signal (Mark-Space interference). Results are stated in terms of the direct signal energy to noise density ratio and factors determined by the geometry of the situation; the ratio of direct signal to interfering power, the ratio of specular to diffuse reflected power and the relative carrier phases of the direct signal and the specular reflection in the Mark-Mark case. These geometric parameters are most conveniently treated separately from the modulation and detection problem.
    • A PCM-Telemetry System for Sounding Rock Payloads

      Hommel, R.; Deutsche Versuchsanstalt für Luft- und Raumfahrt e.V. (International Foundation for Telemetering, 1968-10)
      Complex sounding rocket payloads require on-board data processing and channel capacity which frequently exceed the capability of the standard FM-FM-telemetry system. To obtain the full benefit of the accuracy and information density of sounding rocket experiments a PCM-telemetry system has been developed which provides sufficient flexibility in the choice of channel number, bit rate, time resolution, and accuracy. A first version with Bo channels for scientific data, and 62 channels for technical data will be flown on board of five Black Brants from the Esrange in Kiruna.