Transforming the Deep Space Network into the Interplanetary Network
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long range plan↗
Engineering topics
Lesh, James R.
Publications and source records attributed to Lesh, James R..
Transforming the Deep Space Network into the Interplanetary Network
Space exploration missions are undergoing a significant transformation as are the expectations of their scientific investigators and the public who participate in these great voyages of exploration.
DSN↗
Optical Communication Subsystem for the X200 Series of Planetary Missions
NASA has started a major new Advanced Deep Space System Development (a.k.a x2000) Program at JPL. The objective of this program is to develop and space-qualify (in a total system environment) advanced, cutting-edge technologies for the next generation of deep-space exploration missions.
Optical Communication Planetary Missions Fire and ↗
Extreme Deep Space Communications
Recent work in deep space telecommunication systems has been performed in support of NASA's Mission to the Solar System planning activity. The results show that high bandwidth communications (higher thatn 1 Mbps) are feasible with communication infrastructure investments at targets of high exploration activity. These targets include Mars, Jupiter, and Neptune. Infrastructure improvements must also be made at Earth.
space telecommunications Mission to the Solar Syst↗
LaserCom System Architecture With Reduced Complexity
Spatial acquisition and precision beam pointing functions are critical to spaceborne laser communication systems. In the present invention a single high bandwidth CCD detector is used to perform both spatial acquisition and tracking functions. Compared to previous lasercom hardware design, the array tracking concept offers reduced system complexity by reducing the number of optical elements in the design. Specifically, the design requires only one detector and one beam steering mechanism. It also provides means to optically close the point-ahead control loop. The technology required for high bandwidth array tracking was examined and shown to be consistent with current state of the art. The single detector design can lead to a significantly reduced system complexity and a lower system cost.
Lesh, James R.↗
Image Processing In Laser-Beam-Steering Subsystem
Conceptual design of image-processing circuitry developed for proposed tracking apparatus described in "Beam-Steering Subsystem For Laser Communication" (NPO-19069). In proposed system, desired frame rate achieved by "windowed" readout scheme in which only pixels containing and surrounding two spots read out and others skipped without being read. Image data processed rapidly and efficiently to achieve high frequency response.
Lesh, James R.↗
More About Beam-Steering Subsystem For Laser Communication
Two reports present additional information about developmental beam-steering subsystem of laser-communication system. Aspects of this subsystem described previously in "Beam-Steering Subsystem for Laser Communication" (NPO-19069) and "Digital Controller for Laser-Beam-Steering Subsystem" (NPO-19193). Reports reiterate basic principles of operation of beam-steering subsystem and of laser-communication system as whole. Also presents some of details of optical and mechanical design of prototype of subsystem, called Optical Communication Demonstrator.
Page, Norman A.↗
Beam-Steering Subsystem For Laser Communication
Proposed free-space laser communication system contains fewer optical and mechanical components. Involves novel fast beam-steering subsystem stabilizing only angle between transmitting and receiving beams instead of stabilizing both transmitting and receiving lines of sight individually. Received and transmitted beams of light both imaged onto CCD array at focal plane. Relative angular positions of beams computed from centroids of their images.
Lesh, James R.↗
Impact of Laser Communications on Future NASA Missions and Ground
NASA's past missions used RF communications to relay scientific data from.
Lesh, James R.↗
Overview of NASA R+D in Optical Communications
We review the current applications base for the use of free-space optical communications
Optical↗
(abstract) Space Communications Technologies for Interstellar Missions
This paper will examine candidate communications architectures for potential interstellar missions in an effort to determine feasibility for such links and to identify likely technology advances that will be needed to support such endeavors. Examination of this challenging and futuristic communications problem may serve to guide the direction and advancement of space telecommunications technologies useful for other nearer-term applications.
architectures interstellar communications Daedalus↗
Lasercom system architecture with reduced complexity
Spatial acquisition and precision beam pointing functions are critical to spaceborne laser communication systems. In the present invention, a single high bandwidth CCD detector is used to perform both spatial acquisition and tracking functions. Compared to previous lasercom hardware design, the array tracking concept offers reduced system complexity by reducing the number of optical elements in the design. Specifically, the design requires only one detector and one beam steering mechanism. It also provides the means to optically close the point-ahead control loop. The technology required for high bandwidth array tracking was examined and shown to be consistent with current state of the art. The single detector design can lead to a significantly reduced system complexity and a lower system cost.
Lesh, James R.↗
Progress and Plans for the Optical Communications Program at JPL
Recent accomplishments and programmatic changes in direction of the NASA-funded optical communcations program at JPL are discussed. The applications for the technology are first described. The systems and technologies for both the spapcecraft optical communications terminals and the supporting optical reception infrastructure are covered.
Optical↗
Laser Transmitter Aims At Laser Beacon
Transmitter part of developmental optical communication system. Compact, lightweight, partially-self-aiming laser transmitter built to verify some capabilities of developmental free-space optical communication system. Design capable of providing 0.5 Mbps data return over range equal to Moon-Earth distance. Breadboard of transmitting terminal constructed and tested in laboratory. Prototype transmitter includes receiving circuitry that keeps it aimed at beacon, once brought into initial alignment within about 1.7 degrees of line of sight to beacon.
Hemmati, Hamid↗
Diode-Pumped, Q-Switched, Frequency-Doubling Laser
Experimental Q-switched, diode-pumped, intracavity-frequency-doubling laser generates pulses of radiation at wavelength of 532 nm from excitation at 810 nm. Principal innovative feature distinguishing laser from others of its type: pulsed operation of laser at pulse-repetition frequencies higher than reported previously. Folded resonator keeps most of second-harmonic radiation away from Q-switcher, laser crystal, and laser diodes. Folding mirror highly reflective at fundamental laser wavelength and highly transmissive at second-harmonic laser wavelength. By virtue of difference of about 0.6 percent between reflectivities in two polarizations at fundamental wavelength, folding mirror favors polarized oscillation at fundamental wavelength. This characteristic desirable for doubling of frequency in some intracavity crystals.
Hemmati, Hamid↗
Precision Beam Pointing for Laser Communication System Using a CCD-based Tracker
Spatial acquisition and precision beam pointing functions are critical to spaceborne laser communication systems. A recent system study indicated that a single high bandwidth CCD detector can be used to perform both spatial acquisition and tracking functions. Compared to previous lasercom hardware design, the arrray tracking cocept offers reduced system complexity by reducing the number of optical elements in the design.
Laser↗
Eliminating Bias In Acousto-Optical Spectrum Analysis
Scheme for digital processing of video signals in acousto-optical spectrum analyzer provides real-time correction for signal-dependent spectral bias. Spectrum analyzer described in "Two-Dimensional Acousto-Optical Spectrum Analyzer" (NPO-18092), related apparatus described in "Three-Dimensional Acousto-Optical Spectrum Analyzer" (NPO-18122). Essence of correction is to average over digitized outputs of pixels in each CCD row and to subtract this from the digitized output of each pixel in row. Signal processed electro-optically with reference-function signals to form two-dimensional spectral image in CCD camera.
Ansari, Homayoon↗
Optical Phase-Locked Loop For Optical Communication
Experimental apparatus includes two diode-pumped solid-state lasers of non-planar-ring-oscillator type, one represents the transmitting oscillator, other local oscillator in receiver. Output of transmitting oscillator is amplitude-modulated with pulse-position-modulated data stream. Phase-error variance of less than 0.05 mrad(Sup 2) achieved with relatively-narrow-band loop. Applications include free-space and fiber-optic communications, navigation, and scientific instrumentation in which receivers are required to track phases of transmitted signals.
Win, Moe Z.↗