Search NASA⌕ Search

SEARCH · Search NASA

Results for “Free Space Optical”

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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Monitoring Spacecraft Telemetry Via Optical or RF Link

A patent disclosure document discusses a photonic method for connecting a spacecraft with a launch vehicle upper-stage telemetry system as a means for monitoring a spacecraft fs health and status during and right after separation and deployment. This method also provides an efficient opto-coupled capability for prelaunch built-in-test (BIT) on the ground to enable more efficient and timely integration, preflight checkout, and a means to obviate any local EMI (electromagnetic interference) during integration and test. Additional utility can be envisioned for BIT on other platforms, such as the International Space Station (ISS). The photonic telemetry system implements an optical free-space link with a divergent laser transmitter beam spoiled over a significant cone angle to accommodate changes in spacecraft position without having to angle track it during deployment. Since the spacecraft may lose attitude control and tumble during deployment, the transmitted laser beam interrogates any one of several low-profile meso-scale retro-reflective spatial light modulators (SLMs) deployed over the surface of the spacecraft. The return signal beam, modulated by the SLMs, contains health, status, and attitude information received back at the launch vehicle. Very compact low-power opto-coupler technology already exists for the received signal (requiring relatively low bandwidths, e.g., .200 kbps) to enable transfer to a forward pass RF relay from the launch vehicle to TDRSS (Tracking and Data Relay Satellite System) or another recipient. The link would be active during separation and post-separation to monitor spacecraft health, status, attitude, or other data inventories until attitude recovery and ground control can be re-established. An optical link would not interfere with the existing upper stage telemetry and beacon systems, thus meeting launch vehicle EMI environmental constraints.

Fielhauer, K. B.↗
NASA NTRS2012

Quantum Limits of Space-to-Ground Optical Communications

Quantum limiting factors contributed by the transmitter, the optical channel, and the receiver of a space-to-ground optical communications link are described. Approaches to move toward the ultimate quantum limit are discussed.

free space optical communications↗
NASA NTRS1993

Optical communications and a comparison of optical technologies for a high data rate return link from Mars

The important principles of direct- and heterodyne-detection optical free-space communications are reviewed. Signal-to-noise-ratio (SNR) and bit-error-rate (BER) expressions are derived for both the direct-detection and heterodyne-detection optical receivers. For the heterodyne system, performance degradation resulting from received-signal and local oscillator-beam misalignment and laser phase noise is analyzed. Determination of interfering background power from local and extended background sources is discussed. The BER performance of direct- and heterodyne-detection optical links in the presence of Rayleigh-distributed random pointing and tracking errors is described. Finally, several optical systems employing Nd:YAG, GaAs, and CO2 laser sources are evaluated and compared to assess their feasibility in providing high-data-rate (10- to 1000-Mbps) Mars-to-Earth communications. It is shown that the root mean square (rms) pointing and tracking accuracy is a critical factor in defining the system transmitting laser-power requirements and telescope size and that, for a given rms error, there is an optimum telescope aperture size that minimizes the required power. The results of the analysis conducted indicate that, barring the achievement of extremely small rms pointing and tracking errors (less than 0.2 microrad), the two most promising types of optical systems are those that use an Nd:YAG laser (lambda = 1.064 microns) and high-order pulse position modulator (PPM) and direct detection, and those that use a CO2 laser (lambda = 10.6 microns) and phase shifting keying homodyne modulation and coherent detection. For example, for a PPM order of M = 64 and an rms pointing accuracy of 0.4 microrad, an Nd:YAG system can be used to implement a 100-Mbps Mars link with a 40-cm transmitting telescope, a 20-W laser, and a 10-m receiving photon bucket. Under the same conditions, a CO2 system would require 3-m transmitting and receiving telescopes and a 32-W laser to implement such a link. Other types of optical systems, such as a semiconductor laser systems, are impractical in the presence of large rms pointing errors because of the high power requirements of the 100-Mbps Mars link, even when optimal-size telescopes are used.

Spence, Rodney L.↗
NASA NTRS1990

Free-space laser communication technologies II; Proceedings of the Meeting, Los Angeles, CA, Jan. 15-17, 1990

Various papers on free-space laser communication technologies are presented. Individual topics addressed include: optical intersatellite link experiment between the earth station and ETS-VI, the Goddard optical communications program, technologies and techniques for lasercom terminal size, weight, and cost reduction, laser beam acquisition and tracking system for ETS-VI laser communication equipment, analog dividers for acquisition and tracking signal normalization, fine pointing mechanism using multilayered piezoelectric actuator for optical ISL system, analysis of SILEX tracking sensor performance, new telescope concept for space communication, telescope considered as a very high gain antenna, design of compact transceiver optical systems for optical intersatellite links, ultralightweight optics for laser communications, highly sensitive measurement method for stray light and retroreflected light, depolarization effects on free space laser transceiver communication systems, in-orbit measurements of microaccelerations of ESA's communication satellite Olympus, high-performance laser diode transmitter for optical free space communication, diode-pumped Nd:host laser transmitter for intersatellite optical communications, single-frequency diode-pumped laser for free-space communication.

Begley, David L.↗
NASA NTRS2013

The Architecture of the Laser Communications Relay Demonstration Ground Stations: An Overview

NASA's Laser Communication Relay Demonstration (LCRD) will be NASA's first long-duration demonstration of laser communications (lasercom) in space, providing geosynchronous-satellite-hosted bidirectional relay services between two Earth ground stations. LCRD will leverage and enhance existing ground stations. Ground Station 1 (GS-1) will leverage the Optical Communications Telescope Laboratory (OCTL) built by JPL, while Ground Station 2 (GS-2) will leverage the Lunar Laser Communications Demonstration (LLCD) Ground Terminal (LLGT) built by MIT Lincoln Laboratory. While each ground system has unique telescopes and integrated optics, many of the backend subsystems (e.g., communications, environmental monitoring, control, user simulators) will be common to both terminals. Here we provide an overview of the architecture of the LCRD ground stations, and the planned enhancements to the existing facilities.

deformable mirror↗
NASA NTRS2011

Deep-Space Optical Terminals

We eport on engineering trades that led to the conceptual design of a laser communications terminal for spacecraft probing Mars. The flight terminal, the ground receiver and the ground transmitter subsystems are described. The flight terminal point design has 0.25 Gb/s downlink data-rate capability from the Mars close distance (0.42 AU). Capability for uplink data-rate of 0.3 Mb/s and ranging with 30 cm precision are also addressed.

laser communications↗
NASA NTRS2009

Robust Short-Pulse, High-Peak-Power Laser Transmitter for Optical Communications

We report on a pulsed fiber based master oscillator power amplifier laser at 1550 nm to support moderate data rates with high peak powers in a compact package suitable for interplanetary optical communications. To accommodate pulse position modulation, the polarization maintaining laser transmitter generates pulses from 0.1 to 1 ns with variable duty cycle over a pulse repetition frequency range of 10 to 100 MHz.

fiber amplifier↗
NASA NTRS2012

Overview and Status of the Lunar Laser Communication Demonstration

The Lunar Laser Communication Demonstration (LLCD), a project being undertaken by MIT Lincoln Laboratory, NASA's Goddard Space Flight Center, and the Jet Propulsion Laboratory, will be NASA's first attempt to demonstrate optical communications between a lunar orbiting spacecraft and Earth-based ground receivers. The LLCD space terminal will be flown on the Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft, presently scheduled to launch in 2013. LLCD will demonstrate downlink optical communications at rates up to 620 Mbps, uplink optical communications at rates up to 20 Mbps, and two-way time-of-flight measurements with the potential to perform ranging with sub-centimeter accuracy. We describe the objectives of the LLCD program, key technologies employed in the space and ground terminals, and show the status of development of the several systems.

deep space communications↗
NASA NTRS2022

S-band Network Analysis and Strategies for LEO Multi-CubeSat Science Missions

This paper presents the network architecture utilized at NASA’s Goddard Space Flight Center (GSFC) to support a mission set of five 6U CubeSats. These five CubeSats employ a multi-waveform Software Defined Radio (SDR) platform developed by Vulcan Wireless for use with NASA’s Space Relay (SR) and Direct to Earth (DTE) networks. The performance testing of the SDR is discussed via a comprehensive S-band and communication link analysis. The tested capabilities of the SDR and antenna components are reviewed in terms of the mission requirements for each CubeSat. Size Weight and Power (SWaP), required availability, and access times are discussed. The measured data from experimental compatibility testing is incorporated into detailed simulations of the CubeSat mission set to verify desired performance over the mission lifetime. The model is also used to investigate the impact of potential adverse effects on the communication links such as interference and weather conditions. This paper also reviews potential improvements from future technological advances and commercial partnerships. A collaborative investigation between GSFC and Oklahoma State University is presented in which a qualitative analysis of Hybrid RF/Optical communication strategies is performed. The data rate improvements of optical communication techniques are weighed against attitude control and science mission requirements for CubeSats, and network architectures/switching strategies are discussed. A separate analysis reviews the potential benefits of ground station partnerships, which aligns with NASA’s future goal to include commercial partners in its Earth and space network architectures, e.g. LunaNet.

Space networks↗
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↗