• Reed-Solomon Coding as a Multipath Fading Countermeasure for PCM/FM Aeronautical Telemetry

      Rice, Michael D.; Friend, Daniel H.; Brigham Young University (International Foundation for Telemetering, 1998-10)
      This paper evaluates the use of Reed-Solomon error correcting codes as a countermeasure for the bursty errors caused by multipath fading seen in aeronautical telemetry channels. The tradeoff between code rate and interleaving depth is analyzed and an equation for predicting the code rate given a fixed burst length and interleaving depth is presented. Close agreement is found between predictions made by this equation and simulated results.
    • Acquiring PN Codes Without Serial Searches Using Modified Correlation Loops

      Yadati, Uday; Kosbar, Kurt; University of Missouri-Rolla (International Foundation for Telemetering, 1998-10)
      This paper analyzes the performance of a modified correlation, or delay-locked loop (DLL). These devices typically cross-correlate the received signal with a differentiated version of the originally transmitted signal. This paper describes some interesting properties the loop assumes when the differentiator is replaced by a Hilbert transform. The loop will still track the timing offset of the code, but it will also be able to acquire the signal when the initial offset is greater than one chip time. The new loop may also be superior to traditional DLL in low SNR environments, since it is much less likely to lose lock. Since the new loop is highly non-linear, it is studied through the use of computer simulations.

      Briggs, James R.; Youssef, Ahmed H.; Edwards Air Force Base (International Foundation for Telemetering, 1998-10)
      Optical trackers are often used at the Air Force Flight Test Center (AFFTC) and at other Department of Defense (DoD) ranges to collect video and trajectory data for real-time display and postflight processing. When optical trackers are used in remote areas, pointing data from radar is utilized to enable the trackers to initially acquire targets. To enable the trackers to use radar-pointing data, offsets to true north must first be known. This offset is taken into account given the current position of the optical tracker. During postflight processing, when determining the trajectory of the target, the offsets are also taken into account to produce an accurate trajectory solution. Current methods of determining offsets to true north are time consuming and involve a lot of guesswork. Typically, a map and a known landmark are used to determine the offsets to true north. Another method is to look for the North Star (Polaris) and input an estimated offset. This paper will describe an inexpensive, stand-alone system that utilizes the Global Positioning System (GPS) to determine these offsets. This device may be modified and integrated with other systems that may need to point accurately. For example, a gun barrel on a tank may need to point accurately to within a degree. This device may also be used to accurately position telemetry antennas.

      Mackall, Dale A.; Sakahara, Robert; Kremer, Steven E.; National Aeronautics and Space Administration; Edwards Air Force Base (International Foundation for Telemetering, 1998-10)
      Development of an extended test range, with range instrumentation providing continuous vehicle communications, is required to flight-test the X-33, a scaled version of a reusable launch vehicle. The extended test range provides vehicle communications coverage from California to landing at Montana or Utah. This paper provides an overview of the approaches used to meet X-33 program requirements, including using multiple ground stations, and methods to reduce problems caused by reentry plasma radio frequency blackout. The advances used to develop the extended test range show other hypersonic and access-to-space programs can benefit from the development of the extended test range.

      Barton, Randal L.; New Mexico State University (International Foundation for Telemetering, 1998-10)
      The Near Earth Asteroid Prospector (NEAP) has a scheduled launch date between mid- 1999 and mid-2000, and will encounter a yet to be determined near Earth asteroid (1.1 - 2.2 AU distance from Earth) some ten months later [2]. The purpose of this mission is not only to collect valuable scientific and geological data, but to also determine the value of the asteroid’s materials for possible mining and exploitation [2], [3]. The purpose of this paper is to detail frequency allocation issues and to determine possible return (space to Earth) data rates associated with deep space communications with the NEAP spacecraft.

      O’Donnell, John; AYDIN Telemetry (International Foundation for Telemetering, 1998-10)
      There are well-known advantages in using pseudo-random sequences for testing of data communication links. The sequences, also called pseudo-noise (PN) sequences, approximate random data very well, especially for sequences thousands of bits long. They are easy to generate and are widely used for bit error rate testing because it is easy to synchronize a slave pattern generator to a received PN stream for bit-by-bit comparison. There are other aspects of PN sequences, however, that are not as widely known or applied. This paper points out how some of the less familiar characteristics of PN sequences can be put to practical use in the design of a Digital Test Set and other specialbuilt test equipment used for checkout of the EOS AM-1 Space Data Receiver. The paper also shows how knowledge of these PN sequence characteristics can simplify troubleshooting the digital sections in the Space Data Receiver. Finally, the paper addresses the sufficiency of PN data testing in characterizing the performance of a receiver/data recovery system.

      Eslinger, Brian; Garza, Reynaldo; TYBRIN Corp.; Edwards Air Force Base (International Foundation for Telemetering, 1998-10)
      Communications support for the X-33 requires addressing several unique challenges to meet program and range safety requirements. As an avenue to minimize costs, the program has reduced requirements to the communications system, which lowered the cost of networking the extended range. Cost trade-offs showed that by lowering the telemetry data rate from 2 Megabits per second to 1.440 Megabits per second that significant cost avoidance could be realized. Also, by adopting standard telecommunications data rate for the uplink data stream, an efficient and integrated solution for the extended range communications could be supported. Meeting the program requirements as well as range safety requirements for this effort are critical to the success of the program. This paper describes some of the important requirements driving the design of the extended range communications support and the design of the system to meet those requirements.

      Hordeski, Theodore J.,Jr.; GDP Space Systems (International Foundation for Telemetering, 1998-10)
      The telemetry and aerospace communities require communications equipment providing various modulation and demodulation formats. One format, with application in Space Ground Link Subsystems (SGLS), utilizes a Ternary (tri-tone) Frequency Shift-Keyed (FSK) signal Amplitude Modulated (AM) by a triangle waveform. Historically, SGLS equipment has operated with a fixed tri-tone frequency set (e.g., 65 kHz, 76 kHz and 95 kHz). The need for additional transmission channels and increased bandwidth efficiency creates the requirement for equipment with the flexibility to generate and receive varied and higher frequency tone sets. Combining analog and digital techniques, GDP Space Systems has developed the FDT001. It is an FSK/AM detector which recovers a bit rate clock at one of four selectable bit rates and reproduces ternary FSK modulation data over a widely tunable range of tone frequencies. The tuning range is expanded by using two methods of digital frequency discrimination. The following paper describes the design of the FDT001.
    • International Telemetering Conference Proceedings, Volume 34 (1998)

      International Foundation for Telemetering, 1998-10

      Boulinguez, Marc; Carlier, Pierre-Marie; ENERTEC (International Foundation for Telemetering, 1998-10)
      Designed for unattended 24 hours-a-day operation in automatic system environments, the 3801 TT&C Digital Processor Unit is the key communication unit for ground stations operating spacecraft, from integration to positioning phase and in-orbit operation. Its architecture and technology concept combine high performance, compactness and modularity. The 3801 TT&C Digital Processor Unit supports multiple formats in a single stand-alone chassis, and incorporates extensive interfacing and functional provisions to maximize effectiveness, reliability and dependability. It supports a number of configurations for satellite control applications and performs :* • Telemetry IF demodulation and transmission of data to a high-level communication interface, with time tagging and display of decommutated parameters, • Command generation, with FSK or PSK and FM or PM modulation at 70 MHz, • Ranging measurements and calibration using ESA, INTELSAT and major standards (tones and codes). In addition, the 3801 TT&C Digital Processor supports a Synchronous Command Generator for spinning satellite in a single stand-alone chassis and includes : • FM signal discrimination, for satellite spin reference information coming from the Telemetry Reception channel, • Synchronization Controller for providing the reference « top » for the transmission of the synchronous tones, • Tones Generation of frequency tones towards the PM/FM Modulator.

      De Leon, Phillip L.; Scaife, Bradley J.; New Mexico State University (International Foundation for Telemetering, 1998-10)
      In any satellite communication, the Doppler shift associated with the satellite’s position and velocity must be calculated in order to determine the carrier frequency. If the satellite state vector is unknown then some estimate must be formed of the Doppler-shifted carrier frequency. One elementary technique is to examine the signal spectrum and base the estimate on the dominant spectral component. If, however, the carrier is spread (as in most satellite communications) this technique may fail unless the chip rate-to-data rate ratio (processing gain) associated with the carrier is small. In this case, there may be enough spectral energy to allow peak detection against a noise background. In this paper, we present a method to estimate the frequency (without knowledge of the Doppler shift) of a spread-spectrum carrier assuming a small processing gain and binary-phase shift keying (BPSK) modulation. Our method relies on a simple, averaged discrete Fourier transform along with peak detection. We provide simulation results indicating the accuracy of this method. In addition, we will describe an all-digital hardware design based around a Motorola DSP56303 and high-speed A/D which implements this technique in real-time. The hardware design is to be used in NMSU’s implementation of NASA’s demand assignment, multiple access (DAMA) service.

      Berg, Dale E.; Robertson, Perry J.; Sandia National Laboratories (International Foundation for Telemetering, 1998-10)
      Researchers at the National Wind Technology Center have identified a need to acquire data on the rotor of an operating wind turbine at precisely the same time as other data is acquired on the ground or a non-rotating part of the wind turbine. The researchers will analyze that combined data with statistical and correlation techniques to clearly establish phase information and loading paths and insights into the structural loading of wind turbines. A data acquisition unit has been developed to acquire the data from the rotating system at precise universal times specified by the user. The unit utilizes commercial data acquisition hardware, spread-spectrum radio modems, and a Global Positioning System receiver; and a custom-built programmable logic device. A prototype of the system is now operational, and initial field deployment is anticipated this summer.

      Willis, James; L-3 Communications (International Foundation for Telemetering, 1998-10)
      Universal acceptance of the Windows NT operating system has made utilization of the personal computer (PC) platform for critical space operations a reality. The software attributes of the operating system allow PC products to attain the reliability necessary for secure control of on-orbit assets. Not only is the software more reliable, it supports better networking interfaces at higher speeds. The software upgrades that the Microsoft Corporation generates on a regular basis allow PCs to offer capabilities previously available only with UNIX-based solutions. As technology matures, PCs will operate faster, offer more graphical user interfaces, and give customers a lower cost versus performance choice. These reasons, and others to be discussed further, clearly demonstrate that PCs will soon take their place at the forefront of mission-critical ground station applications.

      Voudouris, Thanos; NASA (International Foundation for Telemetering, 1998-10)
      This paper discusses the evolution of the ground satellite communication systems and the efforts made by the Goddard Space Flight Center's (GSFC) Advanced Architectures and Automation (AAA) branch, Code 588 to bring satellite scientific data to the user’s desktop. Primarily, it describes the next generation desktop system, its architecture and processing capabilities, which provide autonomous high-performance telemetry acquisition at the lowest possible cost. It also discusses the planning processes and the applicability of new technologies for communication needs in the next century. The paper is presented in terms simple for those not very familiar with current space programs to understand.

      Tonello, E.; Monica, G. Della; ALCATEL (International Foundation for Telemetering, 1998-10)
      Presentation for ITC 98 of Alcatel Espace last studies and developments regarding TTC Products This document lays on 3 parts: · a technical point of view · a technology/design description · a synthesis showing main performance and results

      Abbott, Laird; 49th Test Squadron (Air Combat Command) (International Foundation for Telemetering, 1998-10)
      Airborne instrumentation used during flight tests is being installed and maintained in a unique way by operational bomber testers from the Air Force’s 53d Wing. The ability of the flight test community to test on operational aircraft has always been somewhat curtailed by the need for advanced forms of instrumentation. Operational fighter flight test squadrons have aircraft assigned to them, which they modify on as needed basis, much the same as developmental testers. However, bomber operational test units must use operational aircraft to accomplish their mission as there are no bombers in the Air Force’s Air Combat Command (ACC) specifically set aside for operational tests. During test missions, these units borrow aircraft from operational bomb wings, and then return them to service with the bomb wing after testing is complete. Yet, the requirement for instrumentation on these test missions is not much different than that of developmental testers. The weapon system engineer’s typically require Mil-Std-1553, video, telemetry, and Global Positioning System (GPS) Time-Space-Position-Information airborne receiver recordings. In addition, this data must be synchronized with an IRIG-B time code source, and recorded with the same precision as the data gathered during development test and evaluation (DT&E). As a result, several techniques have been developed, and instrumentation systems designed for these operational test units to incorporate instrumentation on operational aircraft. Several factors hamper the usual modification process in place at bases such as Edwards AFB and Eglin AFB. Primary among these is the requirement to maintain the aircraft in an operational configuration, and still meet all of the modification design safety criteria placed on the design team by the aircraft’s single manager. Secondary to the list of restrictions is modification time. Aircraft resources are stretched quite thin when one considers all of the bomb wing’s operational commitments. When they must release an aircraft for test missions, the testers must insure that schedule impacts are minimal. Therefore, these systems must install and de-install within one to two days and be completely portable. Placing holes in existing structures or adding new permanent structure is unacceptable. In addition, these aircraft must be capable of returning to combat ready status at any time. This paper centers on the B-52 bomber, and the active aircraft temporary modifications under control of the 49th Test Squadron (49 TESTS) at Barksdale AFB in Louisiana. The B-52 presents unique design challenges all its own, in addition to the general restrictions already mentioned. This paper will present the options that the 49 TESTS has successfully used to overcome the aforementioned restrictions, and provide an appropriate level of specialized instrumentation for its data collection requirements.

      Reighter, Greg; Whiteman Air Force Base (International Foundation for Telemetering, 1998-10)
      Instrumenting the operational B-2 Strategic Bomber presents some unique problems. For example, the requirement to remain operational dictates that the aircraft must retain its stealth characteristics. This means traditional antennas cannot simply be attached to the airframe. A solution to this problem is an antenna designed with stealth, or Low Observable (LO), attributes. Stealth is not an absolute; it is relative. Therefore, antenna design becomes a balancing act between the LO relativity, antenna directivity, and antenna gain. Weapons testing is an additional concern, where instrumented ordinances transmit data that must be monitored real-time prior to launch. Stealth vehicles must carry weapons internally, restricting the Radio Frequency (RF) transmission of telemetered data from the weapon. With the development of future stealthy conveyances, such as the F-22, Joint Strike Fighter (JSF), ground, and ocean-going craft, these concerns will become even more prevalent.
    • A Narrowband Model For Aeronautical Telemetry Channels

      Rice, Michael; Welling, Kenneth; Brigham Young University (International Foundation for Telemetering, 1998-10)
      This paper presents a narrowband channel model appropriate for modeling multipath interference in aeronautical telemetry applications. This model uses a simplified version of Bello’s aeronautical fading channel model [1] with the following three parameters: the specular to direct power ratio T, the direct to diffuse power ratio K and the relative Doppler shift of the specular component. Data taken from Patuxent River NAWC, Edwards AFB and White Sands Missile Range demonstrate that the model is a reasonably accurate statistical representation of the envelope (and power) fluctuations observed in the data. The model works well for those cases where a dominate line-of-sight signal component exists, as well as for those cases where the power in the specular reflections is on the order of the power in the line-of-sight component.
    • Calendars and Current Calendar Issues: Year 2000 and GPS 1999 Week Number Roll Over

      Claflin, Ray, III; Claflin Associates (International Foundation for Telemetering, 1998-10)
      This paper will present a selected overview of calendars and calendar development from antiquity to the current Gregorian calendar. The current hot topics of the GPS 1999 Rollover and the Year 2000 Millennium Rollover will be explained.

      Jones, Charles H.; Gardner, Lee S.; Edwards Air Force Base (International Foundation for Telemetering, 1998-10)
      “The radio frequency spectrum is a limited natural resource; therefore, efficient use of available spectrum is mandatory.” IRIG Standard 106-96 [4] As the availability of the frequency spectrum decreases and demands for bandwidth from users increases, the telemetry community will have to find ways to use spectrum efficiently. This paper is an overview of the major areas of research that promise potential increases in the efficient use of the telemetry spectrum. The discussion is summarized in a matrix that compares potential gains with overall costs for each research area using relative values of high, medium, and low.