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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The effects of Viterbi decoder node synchronization losses on the telemetry receiving system

The Viterbi decoders currently used by the Deep space Network (DSN) use an algorithm for maintaining node synchronization that breaks down at bit signal-to-noise ratios (SNRs) of about 2.0 dB. It is shown that this can become an important consideration when the effects of noisy carrier referencing are combined with the lower SNRs that are expected at Voyager 2 Uranus and Neptune encounters. Depending on the available carrier power, node synchronization losses of between 0.85 and 1.25 dB can be expected in addition to the radio loss.

Deutsch, L. J.↗
NASA NTRS1984

Implementation of Large Antennas for Deep Space Mission Support

The large antennas of the DSN support reception of low power telemetry signals from spacecraft (S/C), transmission of high power commands to S/C, and navigation of S/C by precision radiometric data. The specification and design of antennas were driven by the requirement to support those functions with high reliability. The number of antennas required in the DSN is determined by the number of S/C to be supported and their level of activity. A given size antenna aperture can be realized with a single element or by arraying smaller elements with the same total area. That approach can be applied to meeting many DSN requirements. There is a cost vs capability trade-off in arrayed vs single element designs. The operating microwave frequency is an important parameter for the antenna. Major radio astronomy antennas can be arrayed with DSN antennas to increase reception capability. The specification, design, and development of DSN antennas are examined.

Stevens, R.↗
NASA NTRS2012

CASSIUS: The Cassini Uplink Scheduler

The Cassini Uplink Scheduler (CASSIUS) is cross-platform software used to generate a radiation sequence plan for commands being sent to the Cassini spacecraft. Because signals must travel through varying amounts of Earth's atmosphere, several different modes of constant telemetry rates have been devised. These modes guarantee that the spacecraft and the Deep Space Network agree with respect to the data transmission rate. However, the memory readout of a command will be lost if it occurs on a telemetry mode boundary. Given a list of spacecraft message files as well as the available telemetry modes, CASSIUS can find an uplink sequence that ensures safe transmission of each file. In addition, it can predict when the two on-board solid state recorders will swap. CASSIUS prevents data corruption by making sure that commands are not planned for memory readout during telemetry rate changes or a solid state recorder swap.

Cassini mission↗
NASA NTRS1986

ICE encounter operations

The operations encompassing the International Cometary Explorer's (ICE) encounter with the Comet Giacobini-Zinner on September 11, 1985 are documented. The ICE mission presented new challenges for the Deep Space Network (DSN) 64 meter subnetwork. Because of poor telemetry link margin predicted for Giacobini-Zinner (GZ) encounter, supplemental support by the Japanese Institute for Space and Astronautical Sciences 64-meter antenna at Usuda, Japan and the 305-meter Arecibo Radio Observatory in Puerto Rico was required. To improve the 64 meter subnetwork telemetry performance the following were also implemented: (1) Real time antenna array of 64 meter and 34 meter at a single complex and the required performance testing; and (2) Nonreal time antenna array of two complexes was implemented as a backup in the event of ground or spacecraft failure.

Fanelli, N.↗
NASA NTRS1986

Antenna arraying of Voyager telemetry signals by symbol stream combining

Telemetry signals received from the Voyager 2 spacecraft at Deep Space Stations at Parkes and Canberra, Australia, on February 6, 1986, were combined by the method of symbol stream combining. This second demonstration of symbol stream combining followed the International Cometary Explorer (ICE) demonstration at Giacobini-Zinner encounter in September 1985. The Voyager demonstration was at a symbol rate of 43.2 ksymb/s, compared to 2 ksymb/s for ICE. Recording, playback, and combining at this higher rate were demonstrated. The average symbol signal-to-noise ratio (SNR) of the combined data was 2.84 dB, or 0.23 dB less than the sum of the SNRs of the two imput symbol streams. This 0.23 loss from ideal combining was due to use of 4-bit quantization of the input symbol stream and imperfect scaling. A practical implementation with 8-bit quantization could achieve combining losses of under 0.05 dB over a wide dynamic range of input signal levels.

Hurd, W. J.↗
NASA NTRS2007

High-Capacity Communications from Martian Distances

High capacity communications from Martian distances, required for the envisioned human exploration and desirable for data-intensive science missions, is challenging. NASA s Deep Space Network currently requires large antennas to close RF telemetry links operating at kilobit-per-second data rates. To accommodate higher rate communications, NASA is considering means to achieve greater effective aperture at its ground stations. This report, focusing on the return link from Mars to Earth, demonstrates that without excessive research and development expenditure, operational Mars-to-Earth RF communications systems can achieve data rates up to 1 Gbps by 2020 using technology that today is at technology readiness level (TRL) 4-5. Advanced technology to achieve the needed increase in spacecraft power and transmit aperture is feasible at an only moderate increase in spacecraft mass and technology risk. In addition, both power-efficient, near-capacity coding and modulation and greater aperture from the DSN array will be required. In accord with these results and conclusions, investment in the following technologies is recommended:(1) lightweight (1 kg/sq m density) spacecraft antenna systems; (2) a Ka-band receive ground array consisting of relatively small (10-15 m) antennas; (3) coding and modulation technology that reduces spacecraft power by at least 3 dB; and (4) efficient generation of kilowatt-level spacecraft RF power.

Williams, W. Dan↗
NASA NTRS2011

An Analysis of Database Replication Technologies with Regard to Deep Space Network Application Requirements

The Deep Space Network (DSN) has three communication facilities which handle telemetry, commands, and other data relating to spacecraft missions. The network requires these three sites to share data with each other and with the Jet Propulsion Laboratory for processing and distribution. Many database management systems have replication capabilities built in, which means that data updates made at one location will be automatically propagated to other locations. This project examines multiple replication solutions, looking for stability, automation, flexibility, performance, and cost. After comparing these features, Oracle Streams is chosen for closer analysis. Two Streams environments are configured - one with a Master/Slave architecture, in which a single server is the source for all data updates, and the second with a Multi-Master architecture, in which updates originating from any of the servers will be propagated to all of the others. These environments are tested for data type support, conflict resolution, performance, changes to the data structure, and behavior during and after network or server outages. Through this experimentation, it is determined which requirements of the DSN can be met by Oracle Streams and which cannot.

Oracle Database File System↗
NASA NTRS1983

Antennas

Reception of the exceedingly small signals from spacecraft typical of deep space communication requires antennas of enormous size, complexity, and precision. The two Voyager spacecraft each have 20-watt X-band transmitters; and at their Saturn encounter distances from Earth of approximately 1.5 billion kilometers, the power density received on the Earth was less than 10 to the minus 19th power watts per square meters. The thrust in deep-space communications improvement was in the areas of ground and spacecraft antenna size and performance increases, spacecraft transmitter power increase, ground receiving system design, and telemetry information coding. Ground antenna theory, design, and performance as related to the particular problem of receiving spacecraft signals using the Deep Space Network (DSN) is described.

Slobin, S. D.↗
NASA NTRS1987

32 GHz deep space communications

The present analysis of the use of a 32-GHz (Ka-band) downlink for deep space communications notes significant benefits over current standard 8.4-GHz downlinks; the consequences of the 8-dB telemetry performance gain thus obtained is presently evaluated for the case of the Cassini and Mars Sample Return missions. This potential can only be realized, however, with upgradings of both the ground stations in the Deep Space Network and the spacecraft communications subsystem. Proposals are made for the use of a Ka-band beacon on the Mars observer spacecraft, as well as the demonstration of such a system aboard the CRAF.

Hansen, D. M.↗
NASA NTRS1990

Interagency telemetry arraying for Voyager-Neptune encounter

The reception capability of the Deep Space Network (DSN) has been improved over the years by increasing both the size and number of antennas at each complex to meet spacecraft-support requirements. However, even more aperture was required for the final planetary encounters of the Voyager 2 spacecraft. This need was met by arraying one radio astronomy observatory with the DSN complex in the United States and another with the complex in Australia. Following a review of augmentation for the Uranus encounter, both the preparation at the National Radio Astronomy (NRAO) Very Large Array (VLA) and the Neptune encounter results for the Parkes-Canberra and VLA-Goldstone arrays are presented.

Brown, D. W.↗
NASA NTRS1982

Mark 4-A DSCC telemetry system description

The DSN is undertaking a major modification of the Mark 3. The modified network described is the Mark 4-A. The DSCC portion of the DSN telemetry system is changed in two major ways as a result of the Mark 4-A DSN implementation. Two 34 meter antennas are added to each deep space communications complex (DSCC). The arraying of those antennas with the existing 64 and 34 meter antennas will provide the equivalent of two separate 64 meter antennas or two 64 meter antennas arrayed together. To accomplish this, the DSCC is modified to provide baseband combining of three 34 meter antennas and one 64 meter antenna. The telemetry system is configured to support either two deep space missions and one highly elliptical orbiter or two highly elliptical orbiters and one deep space mission. Highly elliptical orbiter missions have data rates up to 202 ksps modulated directly on the carrier.

Burt, R.↗
NASA NTRS1986

Utilization of the Usuda Deep Space Center for the United States International Cometary Explorer (ICE)

The Usuda Deep Space Center, which supported the ICE mission by enhancing the telemetry capability, is described. An outline of the comet Giacobini-Zinner observation project is provided. Usuda performance with one receiver channel was comparable to, if not better than, that of the Goldstone 64-m antenna with the two channels combined. The Usuda beam waveguide system is analyzed and found to have many advantages over conventional waveguide systems. It is concluded that this experience with the Usuda beam waveguide will become an integral part of future DSN decision making processes.

Fanelli, N. A.↗
NASA NTRS1980

Deep Space Station (DSS-13) automation demonstration

The data base collected during a six month demonstration of an automated Deep Space Station (DSS 13) run unattended and remotely controlled is summarized. During this period, DSS 13 received spacecraft telemetry data from Voyager, Pioneers 10 and 11, and Helios projects. Corrective and preventive maintenance are reported by subsystem including the traditional subsystems and those subsystems added for the automation demonstration. Operations and maintenance data for a comparable manned Deep Space Station (DSS 11) are also presented for comparison. The data suggests that unattended operations may reduce maintenance manhours in addition to reducing operator manhours. Corrective maintenance for the unmanned station was about one third of the manned station, and preventive maintenance was about one half.

Remer, D. S.↗
NASA NTRS2006

Asynchronous Message Service for Deep Space Mission Operations

While the CCSDS (Consultative Committee for Space Data Systems) File Delivery Protocol (CFDP) provides internationally standardized file transfer functionality that can offer significant benefits for deep space mission operations, not all spacecraft communication requirements are necessarily best met by file transfer. In particular, continuous event-driven asynchronous message exchange may also be useful for communications with, among, and aboard spacecraft. CCSDS has therefore undertaken the development of a new Asynchronous Message Service (AMS) standard, designed to provide common functionality over a wide variety of underlying transport services, ranging from shared memory message queues to CCSDS telemetry systems. The present paper discusses the design concepts of AMS, their applicability to deep space mission operations problems, and the results of preliminary performance testing obtained from exercise of a prototype implementation.

asynchronous message exchanges↗
NASA NTRS1996

Sequence-of-events-driven automation of the deep space network

In February 1995, sequence-of-events (SOE)-driven automation technology was demonstrated for a Voyager telemetry downlink track at DSS 13. This demonstration entailed automated generation of an operations procedure (in the form of a temporal dependency network) from project SOE information using artificial intelligence planning technology and automated execution of the temporal dependency network using the link monitor and control operator assistant system. This article describes the overall approach to SOE-driven automation that was demonstrated, identifies gaps in SOE definitions and project profiles that hamper automation, and provides detailed measurements of the knowledge engineering effort required for automation.

Hill, R., Jr.↗
NASA NTRS1996

Sequence-of-Events-Driven Automation of the Deep Space Network

In February 1995, sequence-of-events (SOE)-driven automation technology was demonstrated for a Voyager telemetry downlink track at DSS 13. This demonstration entailed automated generation of an operations procedure (in the form of a temporal dependency network) from project SOE information using artificial intelligence planning technology and automated execution of the temporal dependency network using the link monitor and control operator assistant system. This article describes the overall approach to SOE-driven automation that was demonstrated, identifies gaps in SOE definitions and project profiles that hamper automation, and provides detailed measurements of the knowledge engineering effort required for automation.

Hill, R., Jr.↗