Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “GROUND STATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Parametric analysis of RF communications and tracking systems for manned space stations

System performance, system interface compatibility, and system management and operations are analyzed for external and internal communications provided by the modular space station. Mathematical models are utilized to evaluate performances of the various communication links between the MSS and the tracking and data relay satellites, the shuttle, and the ground stations. Communication control design requirements are determined from overall MSS control design and checkout requirements are developed in a related systems study. Parallel design efforts consider equipment configurations for the external communication assembly baseband and the internal communication assembly to accommodate signal transfer and control. The recommended baseline design considers also interfaces between equipment groups and the critical functional and signal characteristics of these interfaces. The data processing assembly has direct communication circuits to the external communication assembly and the control interface is provided via a digital data bus and a remote acquisition and control unit.

Source record↗
NASA NTRS2016

Overview and Status of the Laser Communication Relay Demonstration

NASA is presently developing first all optical high data rate satellite relay system, LCRD. To be flown on commercial geosynchronous satellite, it will communicate at DPSK and PPM modulation formats up to 1.244 Gbps. LCRD flight payload is being developed by NASA's Goddard Space Flight Center. The two ground stations, one on Table Mountain in CA, developed by NASA's Jet Propulsion Laboratory and another on Hawaiian island will enable bi-directional relay operation and ground sites diversity experiments. In this paper we will report on the current state of LCRD system development, planned operational scenarios and expected system performance.

free space optical communication↗
NASA NTRSDate not supplied

200 Gbps TBIRD CubeSat Downlink: Pre-Flight Test Results

The Terabyte Infrared Delivery (TBIRD) program will establish an optical communication link from a 6Unanosatellite in low-Earth orbit to a ground station at burst rates up to 200 Gbps. The system is capable of reliable data delivery from a 2 TB storage buffer on the payload to a ground terminal in the presence of atmospheric fading. An overview of the communication architecture for TBIRD is provided as well as results from communications performance testing of the 3U lasercom payload prior to spacecraft integration. Launch is scheduled for mid-year 2022.

space communications↗
NASA NTRS2000

Automatic Weather Station (AWS) Lidar

An autonomous, low-power atmospheric lidar instrument is being developed at NASA Goddard Space Flight Center. This compact, portable lidar will operate continuously in a temperature controlled enclosure, charge its own batteries through a combination of a small rugged wind generator and solar panels, and transmit its data from remote locations to ground stations via satellite. A network of these instruments will be established by co-locating them at remote Automatic Weather Station (AWS) sites in Antarctica under the auspices of the National Science Foundation (NSF). The NSF Office of Polar Programs provides support to place the weather stations in remote areas of Antarctica in support of meteorological research and operations. The AWS meteorological data will directly benefit the analysis of the lidar data while a network of ground based atmospheric lidar will provide knowledge regarding the temporal evolution and spatial extent of Type la polar stratospheric clouds (PSC). These clouds play a crucial role in the annual austral springtime destruction of stratospheric ozone over Antarctica, i.e. the ozone hole. In addition, the lidar will monitor and record the general atmospheric conditions (transmission and backscatter) of the overlying atmosphere which will benefit the Geoscience Laser Altimeter System (GLAS). Prototype lidar instruments have been deployed to the Amundsen-Scott South Pole Station (1995-96, 2000) and to an Automated Geophysical Observatory site (AGO 1) in January 1999. We report on data acquired with these instruments, instrument performance, and anticipated performance of the AWS Lidar.

Rall, Jonathan A.R.↗
NASA NTRS2013

High Efficiency Traveling-Wave Tube Power Amplifier for Ka-Band Software Defined Radio on International Space Station-A Platform for Communications Technology Development

The design, fabrication and RF performance of the output traveling-wave tube amplifier (TWTA) for a space based Ka-band software defined radio (SDR) is presented. The TWTA, the SDR and the supporting avionics are integrated to forms a testbed, which is currently located on an exterior truss of the International Space Station (ISS). The SDR in the testbed communicates at Ka-band frequencies through a high-gain antenna directed to NASA s Tracking and Data Relay Satellite System (TDRSS), which communicates to the ground station located at White Sands Complex. The application of the testbed is for demonstrating new waveforms and software designed to enhance data delivery from scientific spacecraft and, the waveforms and software can be upgraded and reconfigured from the ground. The construction and the salient features of the Ka-band SDR are discussed. The testbed is currently undergoing on-orbit checkout and commissioning and is expected to operate for 3 to 5 years in space.

Simons, Rainee N.↗
NASA NTRS1995

Anticipated uncertainty budgets of PRARETIME and T2L2 techniques as applied to ExTRAS

The Experiment on Timing Ranging and Atmospheric Soundings, ExTRAS, was conceived jointly by the European Space Agency, ESA, and the Russian Space Agency, RSA. It is also designated the 'Hydrogen-maser in Space/Meteor-3M project'. The launch of the satellite is scheduled for early 1997. The package, to be flown on board a Russian meteorological satellite includes ultra-stable frequency and time sources, namely two active and auto-tuned hydrogen masers. Communication between the on-board hydrogen masers and the ground station clocks is effected by means of a microwave link using the modified version for time transfer of the Precise Range And Range-rate Equipment, PRARETIME, technique, and an optical link which uses the Time Transfer by Laser Link, T2L2, method. Both the PRARETIME and T2L2 techniques operate in a two-directional mode, which makes it possible to carry out accurate transmissions without precise knowledge of the satellite and station positions. Due to the exceptional quality of the on-board clocks and to the high performance of the communication techniques with the satellite, satellite clock monitoring and ground clocks synchronization are anticipated to be performed with uncertainties below 0.5 ns (1 sigma). Uncertainty budgets and related comments are presented.

Thomas, Claudine↗
NASA NTRSDate not supplied

SPRINT: Scheduling Planning Routing Intersatellite Network Tool

The Scheduling Planning Routing Intersatellite Network Tool (SPRINT) software system plans and schedules the operations (observations, inter-satellite crosslink communications, and ground communications) of Earth observation (EO) constellations of hundreds of resource-constrained small satellites to enable global, near real-time science. Historically, most CubeSats have flown radios only for direct-to-ground downlink of data; as a result, data availability is delayed by as long as it takes for the capturing satellite to pass over a ground station, typically hours. Current Planning and Scheduling (P&S) systems for constellations cannot handle data routing through a large, dynamic network topology, and all planning is handled on the ground without .the ability to autonomously prioritize important observations, or respond to unexpected changes in communication window or bandwidth. SPRINT directly handles both data routing for low latency bulk observation data downlink and replanning onboard to deal with dynamic priorities and fault response, maximizing the utility of downlinked data.

Kerri Cahoy↗
NASA NTRS2023

Flexible User Radio for Lunar Missions

NASA’s Artemis program and other lunar exploration and development programs are planning over 40 lunar missions before 2030. Lunar missions, both crewed and uncrewed, include orbiters, landers, rovers, and surface stations. All these missions require communications with Earth, either via Direct to Earth (DTE) links or through relays in lunar orbit. Multiple DTE options are available among existing and planned ground stations: Deep Space Network (DSN), European Space Agency, and others. Relay options include the planned Lunar Gateway, LunaNet compliant relays, and some lunar landers propose to launch dedicated orbiters. The dilemma for lunar system designers is to identify a communication link which meets mission requirements but does not have issues of limited access (e.g. DSN is in high demand supporting deep space missions with high priority and some with inflexible schedules), system impacts (high power Radio Frequency (RF) for DTE links), cost (dedicated relay), or operational date. To avoid this difficult decision, a Flexible Radio for Lunar Missions is proposed, which will enable system designs to proceed prior to any final decision on the communication network to be used, by enabling compatibility with any of multiple DTE or orbital relay communication systems. The Flexible Radio will support the necessary frequency, bandwidth, modulation, and power requirements to interoperate with the majority of known or planned DTE or relay systems, and can be designed into a lunar mission without prior knowledge of which link will ultimately be used. Furthermore, the link being used can be changed as needed during the mission, in near real time. The Flexible Radio design will leverage work already completed at NASA in the areas of Wideband RF, Software Defined Radio, Adaptive Coding and Modulation, and Phased Array antennas. The Flexible Radio requires sufficient bandwidth to cover the allocated frequencies for both the operation of links in cislunar space and for space-to-Earth links; the flexibility to support multiple modulations, data rates, and coding schemes; the ability to identify available relays, detect and recognize the signals of those relays, and adapt its own frequency, modulation, symbol rate, and code rate to operate with the detected relay (or DTE station); and finally, it requires appropriate software to support network configuration and interoperability with the detected network. The Flexible Radio can be designed in a sufficiently small, lightweight, and low-power package to be used in a wide variety of lunar systems. The initial implementation, as proposed, will focus on the Ka-band, supporting up to 2 GHz bandwidth around the 27 GHz frequency for return links, and 23 GHz for forward links. Other frequency bands are under consideration for future configurations. The software defined modem will support OQPSK, BPSK, and NASA-defined modulations which also support two-way ranging with data. For near-real time adaptation, the Flexible Radio will scan the sky for available relays, using a phased array antenna with Adaptive/Cognitive Communications. It will then configure for network interoperability supporting DTN and other protocol options. The Flexible Radio will support scheduled connections and on-demand use when available.

Lunar Space Communications↗
NASA NTRSDate not supplied

Flexible User Radio for Lunar Missions

NASA’s Artemis program and other lunar exploration and development programs are planning over 40 lunar missions before 2030. Lunar missions, both crewed and uncrewed, include orbiters, landers, rovers, and surface stations. All these missions require communications with Earth, either via Direct to Earth (DTE) links or through relays in lunar orbit. Multiple DTE options are available among existing and planned ground stations: Deep Space Network (DSN), European Space Agency, and others. Relay options include the planned Lunar Gateway, LunaNet compliant relays, and some lunar landers propose to launch dedicated orbiters. The dilemma for lunar system designers is to identify a communication link which meets mission requirements but does not have issues of limited access (e.g. DSN is in high demand supporting deep space missions with high priority and some with inflexible schedules), system impacts (high power Radio Frequency (RF) for DTE links), cost (dedicated relay), or operational date. To avoid this difficult decision, a Flexible Radio for Lunar Missions is proposed, which will enable system designs to proceed prior to any final decision on the communication network to be used, by enabling compatibility with any of multiple DTE or orbital relay communication systems. The Flexible Radio will support the necessary frequency, bandwidth, modulation, and power requirements to interoperate with the majority of known or planned DTE or relay systems, and can be designed into a lunar mission without prior knowledge of which link will ultimately be used. Furthermore, the link being used can be changed as needed during the mission, in near real time. The Flexible Radio design will leverage work already completed at NASA in the areas of Wideband RF, Software Defined Radio, Adaptive Coding and Modulation, and Phased Array antennas. The Flexible Radio requires sufficient bandwidth to cover the allocated frequencies for both the operation of links in cislunar space and for space-to-Earth links; the flexibility to support multiple modulations, data rates, and coding schemes; the ability to identify available relays, detect and recognize the signals of those relays, and adapt its own frequency, modulation, symbol rate, and code rate to operate with the detected relay (or DTE station); and finally, it requires appropriate software to support network configuration and interoperability with the detected network. The Flexible Radio can be designed in a sufficiently small, lightweight, and low-power package to be used in a wide variety of lunar systems. The initial implementation, as proposed, will focus on the Ka-band, supporting up to 2 GHz bandwidth around the 27 GHz frequency for return links, and 23 GHz for forward links. Other frequency bands are under consideration for future configurations. The software defined modem will support OQPSK, BPSK, and NASA-defined modulations which also support two-way ranging with data. For near-real time adaptation, the Flexible Radio will scan the sky for available relays, using a phased array antenna with Adaptive/Cognitive Communications. It will then configure for network interoperability supporting DTN and other protocol options. The Flexible Radio will support scheduled connections and on-demand use when available.

Lunar Space Communications↗
NASA NTRSDate not supplied

Space-to-Ground Optical Interface Verification for the Orion Artemis II Optical (O2O) Communications Demonstration

The Orion Artemis II Optical Communications (O2O) system will demonstrate the operational utility of laser communications for the first crewed Artemis mission scheduled to launch next year. O2O will provide an optical link with data rates up to 260 Mbps return from the moon and up to 20 Mbps forward to the moon. The optical link employs a Serially Concatenated Pulse Position Modulation (SCPPM) communications signal, compliant with the Consultative Committee for Space Data Systems (CCSDS) standard, and a modulated uplink beacon for acquisition and collaborative tracking. O2O employs optical ground stations located at the White Sands Complex (WSC) and Table Mountain Facility (TMF) to support the Earth end of the link. We describe interface testing performed between the space and ground terminals to verify the physical layer communication and beacon signals.

optical↗
NASA NTRS1973

All chain Loran-C time synchronization

A program is in progress to implement coordinated universal time (UTC) synchronization on all Loran-C transmissions. The present capability is limited to five Loran-C chains in which the tolerance is twenty-five microseconds with respect to UTC. Upon completion of the program, the transmissions of all Loran-C chains will be maintained within five microseconds of UTC. The improvement plan consists of equipping selected Loran-C transmitting stations for greater precision of frequency standard adjustment and improved monitoring capability. External time monitor stations will utilize television time transfer techniques with nearby SATCOM terminals where practicable, thus providing the requisite traceability to the Naval Observatory. The monitor equipment groups and the interrelationships with the ground station equipment are discussed. After a brief review of control doctrine, forth-coming improvements to transmitting stations and how the time monitor and navigation equipments will complement each other resulting in improved service to all users of the Loran-C system are described.

Sherman, H. T.↗
NASA NTRS1985

Geosynchronous satellite collision avoidance

The increases in the number of satellite systems, the growing dependency on these systems, and the potentially hazardous conjunctions in space, dictates careful management of satellite positions. The potential for satellite collision increases as more objects are placed in orbit. At geosynchronous altitudes active satellites maintain fixed longitudinal station-keeping control while inactive satellites and debris generally drift around the globe or oscillate about two geopotential stable points. Portions of the total objects in geosynchronous orbit are tracked by ground stations while a significant number of additional pieces of space debris regularly pass through geosynchronous orbit altitudes. The probability of an operational satellite colliding with another satellite or a piece of space debris will increase in the number of space objects, their sizes, and on-orbit lifetimes.

Fraser, W.↗
NASA NTRS2006

Reliability Block Diagram (RBD) Analysis of NASA Dryden Flight Research Center (DFRC) Flight Termination System and Power Supply

In order to perform public risk analyses for vehicles containing Flight Termination Systems (FTS), it is necessary for the analyst to know the reliability of each of the components of the FTS. These systems are typically divided into two segments; a transmitter system and associated equipment, typically in a ground station or on a support aircraft, and a receiver system and associated equipment on the target vehicle. This analysis attempts to analyze the reliability of the NASA DFRC flight termination system ground transmitter segment for use in the larger risk analysis and to compare the results against two established Department of Defense availability standards for such equipment.

Morehouse, Dennis V.↗
NASA NTRS1990

Tests Of A Differential Global Positioning System

Paper describes validation tests of global positioning system (GPS) for low-flying helicopters. Configured as differential GPS, in which components in both aircraft and ground station compute position errors relative to known location using satellite navigational data. Corrections computed from differences between computed and measured ranges to four satellites being tracked by receiver in both aircraft and ground systems. Tests conducted to determine whether equipment and computer programs of system operated correctly and consistently.

Edwards, F. G.↗
NASA NTRS1993

Simultaneous observation of the poleward expansion of substorm electrojet activity and the tailward expansion of current sheet disruption in the near-earth magnetotail

A substorm that occurred on 7 June 1985 at 2209 UT for which simultaneous measurements from ground stations and CCE are available is considered. The event occurred during a close conjunction between CCE, the EISCAT magnetometer cross, and the STARE radar, allowing a detailed comparison of satellite and ground-based data. Two discrete activations took place during the first few minutes of this substorm: the expansion phase onset at 2209 UT and an intensification at 2212 UT, corresponding to a poleward expansion of activity. The energetic particle data indicate that the active region of the magnetotail during the 2212 UT intensification was located tailward of the active region at 2209 UT. This is direct evidence for a correspondence between tailward expansion of localized activity in the near-earth magnetotail (current disruption and particle energization) and poleward expansion of activity (electrojet formation) in the ionosphere.

Lopez, R. E.↗
NASA NTRS2006

Wireless Command-and-Control of UAV-Based Imaging LANs

Dual airborne imaging system networks were operated using a wireless line-of-sight telemetry system developed as part of a 2002 unmanned aerial vehicle (UAV) imaging mission over the USA s largest coffee plantation on the Hawaiian island of Kauai. A primary mission objective was the evaluation of commercial-off-the-shelf (COTS) 802.11b wireless technology for reduction of payload telemetry costs associated with UAV remote sensing missions. Predeployment tests with a conventional aircraft demonstrated successful wireless broadband connectivity between a rapidly moving airborne imaging local area network (LAN) and a fixed ground station LAN. Subsequently, two separate LANs with imaging payloads, packaged in exterior-mounted pressure pods attached to the underwing of NASA's Pathfinder-Plus UAV, were operated wirelessly by ground-based LANs over independent Ethernet bridges. Digital images were downlinked from the solar-powered aircraft at data rates of 2-6 megabits per second (Mbps) over a range of 6.5 9.5 km. An integrated wide area network enabled payload monitoring and control through the Internet from a range of ca. 4000 km during parts of the mission. The recent advent of 802.11g technology is expected to boost the system data rate by about a factor of five.

Herwitz, Stanley↗
NASA NTRSDate not supplied

Geodetic Reference Instrument Transponder for Small Satellites (Gritss)

The accuracy of the Terrestrial Reference Frame is limited by systematic errors in tying the contributions from the different geodetic techniques. Local survey uncertainties are limited due to the inaccessibility of the instrument reference points. NASA is implementing a technology demonstration mission called Geodetic Reference Instrument Transponder for Small Satellites(GRITSS) that uses a small satellite as a space-based ref-refence point for tying together collocated geodetic stations. The technology being demonstrated uses a novel idea of upconverting the Global Positioning System (GPS) signals received at the satellite and transponding them to a VLBI Global Observing System (VGOS) antenna ground station. This approach does not require the satellite to be in view of more than one VLBI station at a time, allowing the use of Low Earth Orbits and an inexpensive CubeSat. The demonstration will initially involve only the NASA VGOS stations in Maryland, Hawaii, and Texas, but may be expanded later in the mission to include other international VGOS stations. This presentation will provide an overview of the GRITSS mission and the measurement concept.

S M Merkowitz↗