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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

A laser communication experiment utilizing the ACT satellite and an airborne laser transceiver

The Advanced Communications Technology Satellite (ACTS) will carry a laser communications transmitter package in order to attempt the experimental reception of signals transmitted from earth orbit. The ACTS laser package includes both a heterodyne transmitter and a direct-detection transmitter. The laser receiver will be installed in an aircraft that is fitted with the requisite signal window. The anticipated capability of this signal detector is noted.

Provencher, C.↗
NASA NTRS1990

A unique multi-access laser communications transceiver system

A 'many points in one point' multiaccess laser system has been examined, and results are reported which indicating the feasibility of optical communications multiaccess communications is feasible and that the resultant terminal size and with savings are very substantial compared to the dedicated optical terminals or RF multiaccess approaches. A preliminary design has been accomplished of a package that can weigh less than 150 pounds and which uses a 10-in. effective diameter fixed telescope and requires less than 100 W of regulated power and less than 8 cu ft of space.

Ross, Monte↗
NASA NTRS1991

Space Station Laser Communication Transceiver

NASA/Goddard Space Flight Center (GSFC) has initiated the development of experimental optical communication system which will be installed on Space Station Freedom. This system is part of the Space Station Attached a Payloads Program and is currently scheduled for a 1997 launch. The system is being designed to carry out comprehensive set of tests to evaluate and demonstrate the capabilities of this relatively new technology. Communication tests at rates up to 1200 mbps will be conducted over the space-to-ground link using an existing tracking facility at the GSFC. GaAlAs semiconductor lasers will be intensity modulated using 4 slot pulse position modulation format. Direct detection receivers using silicon avalanche photodiodes will be utilized, and 1 microradian accuracy pointing will be achieved with 2 cascaded pointing stages. Successful completion of this in-orbit test program should demonstrate both the technical maturity and readiness of this technology for follow-up operational missions.

Mitzmaurice, Michael↗
NASA NTRS1993

Performance of low-cost commercial fiber-optic transceivers for reference frequency distribution

Precision time and frequency reference signals were effectively disseminated using high-quality intricate fiber-optic distribution systems. The quality of signals distributed by such systems is excellent, but the cost of these systems makes them unavailable to many potential users. A study of signal quality maintained using inexpensive commercial transmitter/receiver pairs is undertaken. Seven different transmitter/receiver pairs obtained from four different manufacturers were thoroughly tested using a 5 MHz sinusoid derived from a precision, temperature controlled, crystal-controlled oscillator. The electrical signal output from each fiber-optic receiver was tested for spectral purity, single-sideband phase noise, and AM noise, and the results are tabulated and discussed without identification of the manufacturer or the equipment model number.

Dragonette, Richard↗
NASA NTRS2003

Cost and Performance Comparison of an Earth-Orbiting Optical Communication Relay Transceiver and a Ground-Based Optical Receiver Subnet

Optical communications can provide high-data-rate telemetry from deep-space probes with subsystems that have lower mass, consume less power, and are smaller than their radio frequency (RF) counterparts. However, because optical communication is more a.ected by weather than is RF communication, it requires groundstation site diversity to mitigate the adverse e.ects of inclement weather on the link. An optical relay satellite is not a.ected by weather and can provide 24-hour coverage of deep-space probes. Using such a relay satellite for the deep-space link and an 8.4-GHz (X-band) link to a ground station would support high-data-rate links from small deep-space probes with very little link loss due to inclement weather. We have reviewed past JPL-funded work on RF and optical relay satellites, and on proposed clustered and linearly dispersed optical subnets. Cost comparisons show that the life cycle costs of a 7-m optical relay station based on the heritage of the Next Generation Space Telescope is comparable to that of an 8-station subnet of 10- m optical ground stations. This makes the relay link an attractive option vis- a-vis a ground-station network.

Wilson, K. E.↗
NASA NTRS2007

Compact and Rugged Transceiver for Coherent Doppler Wind Lidar Applications in Space

High-accuracy, vertical profiles of the horizontal vector wind in earth s atmosphere, with the global coverage of an orbiting sensor, are a highly desired measurement of NASA, NOAA, and many other agencies and countries. It is the consensus of NASA and NOAA that the most cost effective, lowest risk measurement method with the earliest achievable mission date is the hybrid Doppler lidar method which utilizes both coherent- and direct-detection Doppler lidars to obtain the desired profiles. NASA Langley Research Center (LaRC) has advanced the 2-micron pulsed solid-state laser greatly over the past 15 years and has recently demonstrated 1.2 J of pulse energy whereas the requirement for a 400-km hybrid Doppler lidar mission is only 0.25 J. The IIP project reported here is an effort to increase the ruggedness and to compactly package the LaRC state-of-the-art laser technology.

Kavaya, Michael J.↗
NASA NTRS2006

Advanced Ka-Band Transceiver With Monopulse Tracking

A proposed Ka-band transmitting/ receiving system would embody a unique combination of established and semi-proven design features. The proposed system (see figure) would include a monopulse receiving feedback loop and a mirror that could be moved by piezoelectric actuators in the feedback loop to adjust the aim of the transmitted and received radio beams. Unlike in a phased-array tracking system, phase shifters (which can be complex and expensive) would not be needed in this monopulse tracking system. Moreover, the monopulse-tracking loop could be combined with other subsystems used in established subreflector and antenna designs. The final transmitter power amplifier in the proposed system would be a quasi-optical power amplifier (QOPA) -- a combination of a planar array of 25 amplifiers and corresponding planar arrays of antenna elements, such that free-space power combining would take place at the output.

Khan, Abdur↗
NASA NTRS2004

Signal Design for Improved Ranging Among Multiple Transceivers

"Ultra-BOC" (where "BOC" signifies "binary offset carrier") is the name of an improved generic design of microwave signals to be used by a group of spacecraft flying in formation to measure ranges and bearings among themselves and to exchange telemetry needed for these measurements. Ultra-BOC could also be applied on Earth for diverse purposes -- for example, measuring relative positions of vehicles on highways for traffic-control purposes and determining the relative alignments of machines operating in mines and of construction machines and structures at construction sites. Ultra-BOC provides for rapid and robust acquisition of signals, even when signal-to-noise ratios are low. The design further provides that each spacecraft or other platform constantly strives to acquire and track the signals from the other platforms while simultaneously transmitting signals that provide full range, bearing, and telemetry service to the other platforms. In Ultra-BOC, unlike in other signal designs that have been considered for the same purposes, it is not necessary to maneuver the spacecraft or other platforms to obtain the data needed for resolving integer-carrier-cycle phase ambiguities.

Young, Lawrence↗
NASA NTRS2014

Expanding CubeSat Capabilities with a Low Cost Transceiver

CubeSats have developed rapidly over the past decade with the advent of a containerized deployer system and ever increasing launch opportunities. These satellites have moved from an educational tool to teach students about engineering challenges associated with satellite design, to systems that are conducting cutting edge earth, space and solar science. Early variants of the CubeSat had limited functionality and lacked sophisticated attitude control, deployable solar arrays and propulsion. This is no longer the case and as CubeSats mature, such systems are becoming commercially available. The result is a small satellite with sufficient power and pointing capabilities to support a high rate communication system. Communications systems have matured along with other CubeSat subsystems. Originally developed from amateur radio systems, CubeSats have generally operated in the VHF and UHF bands at data rates below 10 kbps (kilobits per second). More recently higher rate UHF systems have been developed, however these systems require a large collecting area on the ground to close the communications link at 3 Mbps (megabits per second). Efforts to develop systems that operate with similar throughput at S-Band (2-4 GHz (gigaherz)) and C-Band (4-8 GHz (gigaherz)) have also recently evolved. In this paper we outline an effort to develop a high rate CubeSat communication system that is compatible with the NASA Near Earth Network and can be accommodated by a CubeSat. The system will include a 200 kbps (kilobits per second) S-Band receiver and a 12.5 Mbps (megabits per second).X-Band transmitter. This paper will focus on our design approach and initial results associated with the 12.5 Mbps (megabits per second) X-band transmitter.

Avionics↗