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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Preliminary error budget for an optical ranging system: Range, range rate, and differenced range observables

Future missions to the outer solar system or human exploration of Mars may use telemetry systems based on optical rather than radio transmitters. Pulsed laser transmission can be used to deliver telemetry rates of about 100 kbits/sec with an efficiency of several bits for each detected photon. Navigational observables that can be derived from timing pulsed laser signals are discussed. Error budgets are presented based on nominal ground stations and spacecraft-transceiver designs. Assuming a pulsed optical uplink signal, two-way range accuracy may approach the few centimeter level imposed by the troposphere uncertainty. Angular information can be achieved from differenced one-way range using two ground stations with the accuracy limited by the length of the available baseline and by clock synchronization and troposphere errors. A method of synchronizing the ground station clocks using optical ranging measurements is presented. This could allow differenced range accuracy to reach the few centimeter troposphere limit.

Folkner, W. M.↗
NASA NTRS1972

Telemetry in animal and human biometeorology

Radio transmitters swallowed, surgically implanted, or carried externally make it possible to study a subject with minimum disturbance to normal patterns of activity. The radio frequency of transmission chosen will depend on the application, and will generally fall in the range from 50 kHz to 300 MHz. A number of specific experiments are reported, including the case of a snake which has swallowed a mouse containing a transmitter of pressure and temperature. Questions of monitoring are explored. Satellite Doppler tracking considerations are discussed together with the attachment of the transmitter package in the case of a study of birds.

Mackay, R. S.↗
NASA NTRS1993

An in-depth analysis and modelling of the Shuttle to MILA S-band telemetry link

The S-Band radio frequency (RF) link between the Merritt Island (MILA) Tracking Station and the Space Shuttle launch pads is a critical communication path for prelaunch and launch operations. The proposed siting of the Center for Space Education (CSE) at the Visitor Center required a study to avoid RF line-of-sight blockage and reflection paths. The study revealed the trees near MILA's 9-meter (9-M) antennas are obstructing the optical line-of-sight. The studies found diffraction is the main propagation mechanism. This paper describes a link model based on the Geometric Theory of Diffraction.

Caroglanian, Armen↗
NASA NTRS2016

Telemetry Ranging - Concept Paper Summary

Background - Previous CCSDS meetings: Spring 2015: Telemetry ranging technique was described; Fall 2015: A comparison to GMSK (Gaussian Minimum Shift Keying) plus PN (Pseudo-random Noise) ranging was made. -How telemetry ranging works: The spacecraft tracks the phase of the uplink PN ranging signal; Receive-time of downlink telemetry frame provides timing information; No downlink ranging signal is used. - This presentation: Summarizes the telemetry ranging concept paper. - Purpose: The purpose of the concept paper is to propose that the RFM (Radio Frequency Multiplier) Working Group consider telemetry ranging for inclusion as a recommended method for two-way ranging in the 401.0-B Blue Book.

Hamkins, Jon↗
NASA NTRS1988

Phasing the antennas of the Very Large Array (VLA) for reception of telemetry from Voyager 2 at Neptune encounter

The Very Large Array (VLA) radio telescope is being instrumented at 8.4 GHz to receive telemetry from Voyager 2 during its encounter with Neptune in 1989. The procedure in which the 27 antennas have their phases adjusted in near real time so that the signals from the individual elements of the array can be added coherently is examined. Calculations of the expected signal to noise ratio, tests of the autophasing process at the VLA, and off-line simulations of that process are all presented. Various possible procedures for adjusting the phases are considered. It is shown that the signal to noise ratio at the VLA is adequate for summing the signals from the individual antennas with less than 0.1 dB of loss caused by imperfect coherence among the antennas. Tropospheric variations during the summer of 1989 could cause enough loss of coherence to make the losses higher than 0.1 dB. Experiments show that the losses caused by the troposphere can probably be kept below 0.2 dB if the time delay inherent in the phase adjustment process is no longer than approx. 5 secs. This relatively small combining loss meets the goal estabished to minimize the bit error rate in the Voyager telemetry and implies adequate autophasing of the VLA.

Ulvestad, J. S.↗
NASA NTRS2014

High Speed, Low Cost Telemetry Access from Space Development Update on Programmable Ultra Lightweight System Adaptable Radio (PULSAR)

Software Defined Radio (SDR) technology has been proven in the commercial sector since the early 1990's. Today's rapid advancement in mobile telephone reliability and power management capabilities exemplifies the effectiveness of the SDR technology for the modern communications market. In contrast, the foundations of transponder technology presently qualified for satellite applications were developed during the early space program of the 1960's. Conventional transponders are built to a specific platform and must be redesigned for every new bus while the SDR is adaptive in nature and can fit numerous applications with no hardware modifications. A SDR uses a minimum amount of analog / Radio Frequency (RF) components to up/down-convert the RF signal to/from a digital format. Once the signal is digitized, all processing is performed using hardware or software logic. Typical SDR digital processes include; filtering, modulation, up/down converting and demodulation. NASA Marshall Space Flight Center (MSFC) Programmable Ultra Lightweight System Adaptable Radio (PULSAR) leverages existing MSFC SDR designs and commercial sector enhanced capabilities to provide a path to a radiation tolerant SDR transponder. These innovations (1) reduce the cost of NASA Low Earth Orbit (LEO) and Deep Space standard transponders, (2) decrease power requirements, and (3) commensurately reduce volume. A second pay-off is the increased SDR flexibility by allowing the same hardware to implement multiple transponder types simply by altering hardware logic - no change of hardware is required - all of which will ultimately be accomplished in orbit. Development of SDR technology for space applications will provide a highly capable, low cost transponder to programs of all sizes. The MSFC PULSAR Project results in a Technology Readiness Level (TRL) 7 low-cost telemetry system available to Smallsat and CubeSat missions, as well as other platforms. This paper documents the continued development and verification/validation of the MSFC SDR, called PULSAR, which contributes to advancing the state-of-the-art in transponder design - directly applicable to the SmallSat and CubeSat communities. This paper focuses on lessons learned on the first sub-orbital flight (high altitude balloon) and the follow-on steps taken to validate PULSAR. A sounding rocket launch, currently planned for 03/2015, will further expose PULSAR to the high dynamics of sub-orbital flights. Future opportunities for orbiting satellite incorporation reside in the small satellite missions (FASTSat, CubeSat. etc.).

Simms, William Herbert, III↗
NASA NTRS1968

Telemetry with unrestrained animals.

Telemetry with unrestrained animals, discussing radio tracking of game animals and instrumentation requirements for studying green sea turtle goal finding ability

Baldwin, H. A.↗
NASA NTRS1975

Orbit and attitude state recoveries from Landmark data

The navigation of earth-referenced satellites with imaging data rather than, or in addition to, conventional radio tracking and attitude sensor telemetry is gaining increased popularity. Driving forces include a trend towards spacecraft autonomy, a need for timely and highly accurate griding information, and a growing awareness of the presence of high quality navigation information contained in such data. This paper describes the techniques used and the results obtained in an experiment to determine the orbit and attitude state of the geosynchronous SMS-1 spacecraft from Landmark observations extracted from earth images generated by the on-board Visible and Infrared Spin-Scan Radiometer (VISSR).

Fuchs, A. F.↗
NASA NTRS1975

Orbit and attitude state recoveries from Landmark data

The navigation of earth-referenced satellites with imaging data rather than, or in addition to, conventional radio tracking and attitude sensor telemetry is gaining increased popularity. Driving forces include a trend towards spacecraft autonomy, a need for timely and highly accurate gridding information, and a growing awareness of the presence of high quality navigation information contained in such data. This paper describes the techniques used and the results obtained in an experiment to determine the orbit and attitude state of the geosynchronous SMS-1 spacecraft from Landmark observations extracted from earth images generated by the on-board Visible and Infrared Spin-Scan Radiometer (VISSR).

Fuchs, A. F.↗
NASA NTRS1984

Goldstone R/D High Speed Data Acquisition System

A digital data acquisition system that meets the requirements of several users (initially the planetary radar program) is planned for general use at Deep Space Station 14 (DSS 14). The system, now partially complete, is controlled by VAX 11/780 computer that is programmed in high level languages. A DEC Data Controller is included for moderate-speed data acquisition, low speed data display, and for a digital interface to special user-provided devices. The high-speed data acquisition is performed in devices that are being designed and built at JPL. Analog IF signals are converted to a digitized 50 MHz real signal. This signal is filtered and mixed digitally to baseband after which its phase code (a PN sequence in the case of planetary radar) is removed. It may then be accumulated (or averaged) and fed into the VAX through an FPS 5210 array processor. Further data processing before entering the VAX is thus possible (computation and accumulation of the power spectra, for example). The system is to be located in the research and development pedestal at DSS 14 for easy access by researchers in radio astronomy as well as telemetry processing and antenna arraying.

Deutsch, L. J.↗
NASA NTRS1986

The Vega balloon experiment - Initial results from the global radio tracking

A unique global array of 20 radio telescopes provided 24-h telemetry acquisition of meteorological data from the Vega balloons and differential VLBI measurements of their trajectories. Initial Doppler-tracking analysis indicates mean zonal wind velocities of 69 + or - 1 and 66 + or - 1 m/sec at the Vega 1 and Vega 2 float heights, and discloses an anomaly in the Vega 2 trajectory above the mountains in Aphrodite Terra.

Preston, R. A.↗
NASA NTRS1992

Computing Modulation Losses In A Communication System

Improved method accelerates computation of means and variances of modulation losses in radio communication system where telecommand, telemetry, and turnaround ranging signals transmitted between two stations via phase modulation with residual carrier signal. Method based on uplink and downlink signals conforming to standard promulgated by Consultative Committee for Space Data Systems. Completes computations three times as fast as "brute-force" method. Modified for application to any system involving one-way and/or two-way transmission, including retransmission.

Nguyen, Tien M.↗
NASA NTRS1992

On-orbit deployment anamolies: What can be done?

Modern communications satellites rely heavily upon deployable appendage (i.e., solar arrays, communications antennas, etc.) to perform vital functions that enable the spacecraft to effectively conduct mission objectives. Communications and telemetry antennas provide the radio-frequency link between the spacecraft and the earth ground station, permitting data to be transmitted and received from the satellite. Solar arrays serve as the principle source of electrical energy to the satellite, and re-charge internal batteries during operation. However, since satellites cannot carry back-up systems, if a solar array fails to deploy, the mission is lost. The subject of on-orbit anomalies related to the deployment of spacecraft appendage, and possible causes of such failures are examined. Topics discussed include mechanical launch loading, on-orbit thermal and solar concerns, reliability of spacecraft pyrotechnics, and practical limitations of ground-based deployment testing. Of particular significance, the article features an in-depth look at the lessons learned from the successful recovery of the Telesat Canada Anik-E2 satellite in 1991.

Freeman, Michael↗
NASA NTRS1978

Medical Telemetry

Telemetry is the process whereby physiological or other data is acquired by instruments, translated into radio signals and j sent to a receiving station where the signals are decoded and recorded. Extensively used in I space operations, it is finding new Earth applications, among them transmission of medical data between emergency vehicles and hospitals. For example, transmission of an electrocardiogram from an ambulance to a hospital enables a physician to read the telemetered EKG and advise ambulance attendants on emergency procedures. Central Medical Emergency Dispatch (CMED) operates as a regional emergency medical communications center for Cleveland, Ohio and Cuyahoga County. The CMED system includes radio and telephone communications from hospital-to-hospital and from ambulance-to-hospital, but for improved emergency life support CMED sought to add a county-wide telemetry capability. The problem was that there were only eight radio frequencies available for telemetry and there were more than 30 potential users in Cleveland alone. NASA's Lewis Research Center volunteered its expert assistance. The Center's engineers studied the systems of other telemetry using cities, surveyed area hospitals to assure compatibility of telemetry equipment, and advised what types of equipment would be needed in emergency vehicles and at the various hospitals. The Lewis plan suggested that CMED be designated the central coordinating agency for the Cuyahoga County system, monitoring all telemetry frequencies and, when requested, assigning one not in use or one to be used at a sufficient distance that it would create no interference problem.

Source record↗
NASA NTRS1991

Refraction effects on the Galileo probe telemetry carrier frequency

As the Galileo probe relay radio link (RRL) signal propagates outward through the Jovian atmosphere, the atmosphere will manifest itself in two ways. First, the geometric path length of the signal is increased, resulting in a small change of the RRL signal departure angle from the proble (transmitter). Secondly, the velocity of the signal is decreased. For a spherical, static atmosphere with a known profile of refractivity versus altitude the effects of refraction on the RRL frequency can be found using a variation of standard ray-tracing techniques, whereby the ray departure angle is found by an iterative process. From the dispersive characteristics of a mixture of hydrogen and helium with trace amounts of methane and ammonia a simple model of the Jovian atmosphere is constructed assuming spherical symmetry and uniform mixing. The contribution to the RRL Doppler frequency arising from refraction is calculated, and its effect on the Doppler wind measurements is discussed.

Atkinson, D. H.↗
NASA NTRS2012

Low-Cost Telemetry System for Small/Micro Satellites

A Software Defined Radio (SDR) concept uses a minimum amount of analog/radio frequency components to up/downconvert the RF signal to/from a digital format. Once in the digital domain, all other processing (filtering, modulation, demodulation, etc.) is done in software. The project will leverage existing designs and enhance capabilities in the commercial sector to provide a path to a radiation-hardened SDR transponder. The SDR transponder would incorporate baseline technologies dealing with improved Forward Error Correcting (FEC) codes to be deployed to all Near Earth Network (NEN) ground stations. By incorporating this FEC, at least a tenfold increase in data throughput can be achieved. A family of transponder products can be implemented using common platform architecture, allowing new products to be more quickly introduced into the market. Software can be reused across products, reducing software/hardware costs dramatically. New features and capabilities, such as encoding and decoding algorithms, filters, and bit synchronizers, can be added to the existing infrastructure without requiring major new capital expenditures, allowing implementation of advanced features in the communication systems. As new telecommunication technologies emerge, incorporating them into the SDR fabric will be easily accomplished with little or no requirements for new hardware. There are no preferred flight platforms for the SDR technology, so it can be used on any type of orbital or sub-orbital platform, all within a fully radiation hardened design.

Sims, William↗