• On-Board Spacecraft Time-Keeping Mission System Design and Verification

      Wickham, Mark E.; Fairchild Space & Defense (International Foundation for Telemetering, 1994-10)
      Spacecraft on-board time keeping, to an accuracy better than 1 millisecond, is a requirement for many satellite missions. Scientific satellites must precisely "time tag" their data to allow it to be correlated with data produced by a network of ground and space based observatories. Multiple vehicle satellite missions, and satellite networks, sometimes require several spacecraft to execute tasks in time phased fashion with respect to absolute time. In all cases, mission systems designed to provide a high accuracy on-board clock must necessarily include mechanisms for the determination and correction of spacecraft clock error. In addition, an approach to on-orbit verification of these mechanisms may be required. Achieving this accuracy however need not introduce significant mission cost if the task of maintaining this accuracy is appropriately distributed across both the space and ground mission segments. This paper presents the mission systems approaches taken by two spacecraft programs to provide high accuracy on-board spacecraft clocks at minimum cost. The first, NASA Goddard Space Flight Center's (GSFC) Extreme Ultraviolet Explorer (EUVE) program demonstrated the ability to use the NASA Tracking and Data Relay Satellite System (TDRSS) mission environment to maintain an on-board spacecraft clock to within 100 microseconds of Naval Observatory Standard (NOS) Time. The second approach utilizes an on-board spacecraft Global Positioning System (GPS) receiver as a time reference for spacecraft clock tracking which is facilitated through the use of Fairchild's Telemetry and Command Processor (TCP) spacecraft Command & Data Handling Subsystem Unit. This approach was designed for a future Shuttle mission requiring the precise coordination of events among multiple space-vehicles.

      Morimoto, Todd A.; Nowitzky, Thomas E.; Grippando, Steven A.; Space & Missile Systems Center; Loral Space & Range Systems (International Foundation for Telemetering, 1994-10)
      An increasing number of satellite users and manufacturers are looking to lightweight, inexpensive satellites as substitutes to traditional large, expensive satellites with multiple payloads. Neither the Department of Defense nor the commercial sector can bear the financial or reputational consequences associated with massive program failures. With the low cost and weight of these new satellites, users can achieve mission success without great risk. One example of this new class of inexpensive spacecraft is the RADCAL (RADar CALibration) satellite. Detachment 2, Space & Missile Systems Center at Sunnyvale, CA operates the satellite. RADCAL is a 200-pound polar orbiting satellite with an average altitude of 450 miles. It is primarily used by 77 worldwide radars to calibrate their systems to within five meter accuracy. Also flying on board RADCAL is a communication payload for remote field users with small radios. The RADCAL program has satisfied all mission requirements. However, with the limited size and cost come certain challenges, both in the satellite and on the ground. Pre-launch testing was not as comprehensive as with more expensive programs; anomalies have arisen that require extensive workarounds. Data management is not a straightforward task, and it is sometimes difficult and inexact to track satellite performance. These challenges are presented with their solutions in the following discussion; this paper addresses the functional, operational, and testing aspects associated with the RADCAL satellite.
    • Optimum Symbol Synchronization

      James, Calvin L.; AlliedSignal Technical Services Corporation (International Foundation for Telemetering, 1994-10)
      Although most closed-loop synchronizers employ maximum likelihood estimators for symbol value decisions, in general, their symbol timing estimates are not optimum. It would seem only natural that an optimum timing estimator would choose interval partitions based on maximizing the observed sample signal-to-noise ratio. The symbol synchronizer described below achieves optimum performance when decisions on present symbol values are based on current and previously-received symbol samples. This procedure attempts to reestablish the interval independence criterion, thereby reducing timing estimator variance. The realization presented is motivated by an open-loop maximum a posteriori (MAP) structure analysis.

      Hui, Yang; Shanzhong, Li; Qishan, Zhang; Beijing University of Aeronautics and Astronautics (International Foundation for Telemetering, 1994-10)
      In this paper, a PCM telemetry system based on Personal computer is presented and some important methods that are used to realize the system will be introduced, such as a new kind of all digital PLL bit synchronizer and a way to solve the problem of high-rate data storage. The main idea of ours is to make the basic parts of PCM telemetry system (except receiver) in the form of PC cards compatible with EISA Bus, which forms a telemetry station with resource of PC computer. Finally, a laboratory prototype with rate up to 3.2Mbps is built.
    • Planned Evolution of Range Telemetry and Communications into the Public Data Network

      Erdahl, Mike; Loral Test & Information Systems (International Foundation for Telemetering, 1994-10)
      The area of range telemetry and communications has been under budget constraints and interoperability enhancement requirements for some time. The near-term onslaught of multimedia communications offerings by telephony and communications companies is certain to cause range engineering personnel to conduct extensive research and possibly make numerous decisions on procurements and technologies before standards are finalized. This paper will address a low-risk migration path for range telemetry to the new multimedia communications for ranges based on current capabilities. This migration path has an end goal of positioning the ranges to take advantage of future multimedia communications as they become available, while leveraging off of current products and procurements, without a major investment.
    • Portable Airborne Digital Data System Recorder

      Harris, Kevin E.; Veda Incorporated (International Foundation for Telemetering, 1994-10)
      Veda Incorporated has developed an airborne instrumentation recorder for a major commercial aircraft manufacturer. The recorder was developed for use in the aircraft company's Portable Airborne Digital Data System (PADDS), a small scale data acquisition and monitor system used for flight testing. The recorder is designed around an off-the-shelf 8mm tape drive, the Exabyte 8505. It records asynchronous, variable-rate data in a proprietary 24-bit recording format, and allows the data to be played back in real time. Its RS-422 control interface is designed to imitate the recorder used in the company's large scale data acquisition system, the Ampex DCRSi-II. Special provisions allow it to withstand the environment of an airplane's EE bay.

      Reinsmith, Lee V.; TYBRIN Corporation (International Foundation for Telemetering, 1994-10)
      This paper describes the application software used in the Message Processing System at the Air Force Development Test Center (AFDTC), Eglin AFB. The focus is on the Alpha AXP application software designed and developed to log, process, and reformat IRIG Chapter 8 1553 data. The main data reduction and editing capabilities of the processing phase are explained: message output selection, message output sampling, message translation, error identification, and IRIG Chapter 8 time editing. The design of and methods used to produce the output files, the BBNProbe STD file, and the 1553 message summary report are described. This software’s flexibility and comprehensiveness in processing, reducing, and re-formatting 1553 message data will enable AFDTC to satisfy current and future post-mission processing requirements.
    • Probability of Bit Error on a Standard IRIG Telemetry Channel Using the Aeronautical Fading Channel Model

      Nelson, N. Thomas; Brigham Young University (International Foundation for Telemetering, 1994-10)
      This paper analyzes the probability of bit error for PCM-FM over a standard IRIG channel subject to multipath interference modeled by the aeronautical fading channel. The aeronautical channel model assumes a mobile transmitter and a stationary receiver and specifies the correlation of the fading component. This model describes fading which is typical of that encountered at military test ranges. An expression for the bit error rate on the fading channel with a delay line demodulator is derived and compared with the error rate for the Gaussian channel. The increase in bit error rate over that of the Gaussian channel is determined along with the power penalty caused by the fading. In addition, the effects of several channel parameters on the probability of bit error are determined.
    • Processing Real-Time Telemetry with Multiple Embedded Processors

      BenDor, Jonathan; Baker, J. D.; Dovetail Systems Corporation; SEMCO (International Foundation for Telemetering, 1994-10)
      This paper describes a system in which multiple embedded processors are used for real-time processing of telemetry streams from satellites and radars. Embedded EPC-5 modules are plugged into VME slots in a Loral System 550. Telemetry streams are acquired and decommutated by the System 550, and selected parameters are packetized and appended to a mailbox which resides in VME memory. A Windows-based program continuously fetches packets from the mailbox, processes the data, writes to log files, displays processing results on screen, and sends messages via a modem connected to a serial port.
    • RadarMap: A Multi-Platformed Range Display Utility

      Rivero, Juan J.; Rarick, Michael J. (International Foundation for Telemetering, 1994-10)
      RadarMap is designed to take PCM-encoded radar data and process it to display the trace of radar targets on a map of the Eglin Test Range. Written in C, X Window, and OSF/Motif, RadarMap runs on a DECStation 5000/240 and utilizes the Loral Data Gathers C functions library to directly access PCM parameters from a Loral System 500 telemetry rack. X Window (a hardware-independent bitmapped graphics display system), OSF/Motif, and the Data Gathers libraries allow portability to other operating systems that support a C compiler and these libraries.

      O'Brien, R. Michael; Loral Test & Information Systems (International Foundation for Telemetering, 1994-10)
      With today's telemetry systems, an hour-long analog test tape can be digitized in one hour or less. However, the digitized data produced by today's telemetry systems is usually not in a format that can be directly analyzed by the test engineer's analysis tools. The digitized data must be formatted before analysis can begin. The data formatting process can take from one to eight hours depending on the amount of data, the power of the system's host computer, and the complexity of the analysis software's data format. If more than one analysis package is used by the test engineer, the data has to be formatted separately for each package. Using today's high-speed RISC processors and large memory technology, a real-time Flexible Data Formatter can be added to the Telemetry Front End to perform this formatting function. The Flexible Data Formatter (FDF) allows the telemetry user to program the front-end hardware to output the telemetry test data in a format compatible with the user's analysis software. The FDF can also output multiple data files, each in a different format for supporting multiple analysis packages. This eliminates the file formatting step, thus reducing the time to process the data from each test by a factor of two to nine.
    • A Real-Time Telemetry Data Processing System with Open System Architecture

      Jun, Zhang; MeiPing, Feng; Yanbo, Zhu; Bin, He; Qishan, Zhang; Beijing University of Aeronautics and Astronautics (International Foundation for Telemetering, 1994-10)
      In face of the characteristics of multiple data streams, high bit rate, variable data formats, complicated frame structure and changeable application environment, the programmable PCM telemetry system needs a new data processing system with advanced telemetry system architecture. This paper fully considers the characteristics of real-time telemetry data processing, analyzes the design of open system architecture for real-time telemetry data processing system(TDPS), presents an open system architecture scheme and design of real-time TDPS, gives the structure model of distributed network system, and develops the interface between network database and telemetry database, as well as telemetry processing software with man-machine interface. Finally, a practical and multi-functional real-time TDPS with open system architecture has been built, which based on UNIX operating system, supporting TCP/IP protocol and using Oracle relational database management system. This scheme and design have already proved to be efficient for real-time processing, high speed, mass storage and multi-user operation.
    • Recovery of Telemetered Data by Vertical Merging Algorithms

      Hoag, Joseph E.; Kalibjian, Jeffrey R.; Shih, Dwight; Toy, Edward J.; Lawrence Livermore National Laboratory; EL and Associates, Inc. (International Foundation for Telemetering, 1994-10)
      A long standing problem in telemetry applications is the recovery of data which has been damaged during downlink. Data recovery can be significantly improved by telemetering information in a packet format which employs redundant mechanisms for data encapsulation. A simple statistical algorithm (known as a "merge" algorithm) can be run on the captured data to derive a "least damaged" data set.

      Humpherys, Brian; Brigham Young University (International Foundation for Telemetering, 1994-10)
      This paper describes a method for determining high resolution time, space, and position information for a test range flight vehicle using four tracking receivers. Equipped with GPS time systems, each receiver records the exact time at which a time marker embedded in the transmitted TM data stream is received. With this information, the time difference of arrival for the time markers at three of the receivers can be calculated referenced to the fourth. Using this time difference, the position of the transmitter can be determined. The accuracy with which the received signal time delay can be calculated depends on the accuracy of the GPS time system at each receiver. The effect of time accuracy on positional resolution is evaluated.

      Jin, Minglu; Zhang, Qishan; Shenyang Institute of Aeronautical Engineering; Beijing University of Aero. & Astr. (International Foundation for Telemetering, 1994-10)
      In this paper, by using computer simulations, the interference of channel data in the SDM telemetry system is investigated, the performance of the copy demultiplexing is examined, and finally the selection rule of Walsh functions is recommended.

      Horan, Stephen; Minnix, Timothy; New Mexico State University (International Foundation for Telemetering, 1994-10)
      Small satellites have been perceived as having limited access to NASA's Space Network consisting of the TDR satellites and associated ground terminals. This paper presents the potential for access of the space network using basic small satellite design constraints and a simple helical antenna for the communications links. From the analysis derived through simulation of the orbit of both satellites, small satellites can be shown to have up to 30 minutes per orbit of single-TDRS access. Data rates on the order of 100 kbps are possible in this configuration with total daily data volumes in excess of 100 Mbits being achievable. Design parameters are given for a variety of orbital inclination angles and spacecraft transmission powers to illustrate the expected available contact time for such small satellites to the Space Network. This is compared with typical access time through a fixed ground station.
    • A Software Architecture for Client-Server Telemetry Data Analysis

      Brockett, Douglas M.; Aramaki, Nancy J.; BBN Systems & Technologies (International Foundation for Telemetering, 1994-10)
      An increasing need among telemetry data analysts for new mechanisms for efficient access to high-speed data in distributed environments has led BBN to develop a new architecture for data analysis. The data sets of concern can be from either real-time or post-test sources. This architecture consists of an expandable suite of tools based upon a data distribution software "backbone" which allows the interchange of high volume data streams among server processes and client workstations. One benefit of this architecture is that it allows one to assemble software systems from a set of off-the-shelf, interoperable software modules. This modularity and interoperability allows these systems to be configurable and customizable, while requiring little applications programming by the system integrator.
    • Space Tracking Systems/ Options Study

      Grelck, John; Ehrsam, Eldon; Means, James A. (International Foundation for Telemetering, 1994-10)
      This paper presents the findings of the Space Tracking Systems/Options Study (STS/OS) and indicates its impact on the telemetering community. The STS/OS was commissioned by Air Force Test & Evaluation (AF/TE) to develop a long range plan (vision and roadmap) for the AF Test & Evaluation (T&E) community to ensure affordable capabilities (telemetry, tracking and commanding) for the future (2003-2008). The study was conducted by the Air Force Materiel Command (AFMC), Space & Missile Systems Center (SMC), Detachment 9, at Vandenberg AFB (VAFB), with support from the primary AFMC T&E centers, the Air Force Operational Test & Evaluation Command (AFOTEC), and the Air Force Space Command (AFSPC). Both "open air" aeronautical and astronautical test needs were considered. The study solicited requirements for existing and future programs, extrapolated existing and planned test capabilities out into the future, then compared the two to identify future shortfalls in capabilities and specific actions that are necessary to insure that the future program needs can be met. Three critical types of testing were identified that cannot be satisfied with existing or planned instrumentation. These are: large area testing (LAT), over the horizon testing (OTH), and space weapons testing (SWT). A major deficiency was also uncovered in end game scoring for air and space intercepts, where inadequate capability exists to perform the required vector miss-distance measurement. This paper is important to the telemetering community because it identifies the Global Positioning System (GPS) as the primary time space position information (TSPI) system for all future open air testing. GPS provides a passive capability that permits each vehicle to determine its own precise TSPI. Means must be provided, however, for the vehicle to relay its position to the appropriate range control center. The paper shows that the problems with down linking telemetry, aircraft buss data, digital audio, digital video, and TSPI collectively represent the need for a very capable datalink. Likewise, the need to uplink commands, synthetic targets, synthetic backgrounds, and target control information also represents the need for a very capable datalink. With its extensive expertise in RF linkages, the telemetering community is ideally suited to address this need for a robust datalink for the future of T&E.
    • Sub-Optimum Receiver Filters

      Osborne, William P.; Gutierrez, Alberto; New Mexico State University (International Foundation for Telemetering, 1994-10)
      This paper presents a method for analyzing the performance of a digital receiver when using standard analog filters in place of the ideal matched filter. Expressions are developed for the probability of error and performance loss of the sub-optimum receiver as functions of the minimum eye value and noise bandwidth of the suboptimum receiver filter. A method is developed for choosing the best sub-optimum filter in the sense of minimizing the probability of error. The best sub-optimum Bessel filter of order less than or equal to 6 is specified in terms of 3-dB bandwidth and filter order for a system with a rectangular transmit pulse. This method is applicable to other transmit pulse shapes and can be applied to channels with limited bandwidth. The optimum 3-dB bandwidth obtained here can be scaled relative to the symbol rate to correspond to any practical system.

      Cardinal, Robert; Loral Test & Information Systems (International Foundation for Telemetering, 1994-10)
      The success of the client/server paradigm for modern networked telemetry systems continues to stress the LAN that carries data generated from the acquisition front ends to the display workstations and the file servers on the LAN. As the number of LAN-attached devices such as Loral's System 500 Model 550 (Loral 550) telemetry front end, workstations, and file servers grows beyond two, the Ethernet LAN collision rates increase and the throughput slows down. At what point the network performance declines is a function of the specific application bandwidth demands required. This paper describes a new method for boosting LAN performance by providing Ethernet switching and protocol filtering. The performance of the LAN is critical to the performance of the complete telemetry enterprise architecture.