Kevin J. Quirk

Optical PPM synchronization for photon counting receivers

The performance of two signal synchronization schemes for photon counting receivers used in optical PPM communication systems operating in low-flux conditions, such as proposed deep space optical communication links, are analyzed. The pilot symbol insertion and inter-symbol guard time synchronization schemespsila performance are compared under conditions of equal throughput and equal peak or average power at representative operating points, including frequency offset due to transmit and receiver oscillator instability.

Analysis of sampling and quantization effects on the performance of PN code tracking loops

Pseudonoise (PN) code tracking loops in direct-sequence spread-spectrum systems are often implemented using digital hardware. Performance degradation due to quantization and sampling effects is not adequately characterized by the traditional analog system feedback loop analysis. A low-complexity digital PN code tracking loop with one-bit non-commensurate sampling is analyzed, and the steady-state delay error variance is derived. The results are compared with that of an equivalent analog loop.

Cooperative modulation techniques for long haul relay in sensor networks

Cooperative modulation techniques can reduce the energy requirements for the long haul transmission of data from localized sensor networks. This saving is vital in extending the battery life of power limited sensor nodes communicating over a time-limited channel. Several transmission methods, including a novel scheme that conveys information via node selection, are analyzed. The energy cost in local communications needed to support the cooperative long haul link is determined and used to make comparisons between the techniques.

A receiver for the Lunar Laser Communication Demonstration using the optical communications telescope laboratory

We discuss the design and implementation of a receiver for the Lunar Laser Communication Demonstration based on a 12-pixel array of tungsten silicide superconducting nanowire single photon detectors. The receiver was used to close a software communication link from lunar orbit at 39 and 79 Mbps.

Optical PPM Combining Loss for Photon Counting Receivers

The performance of an equal gain combining architecture for an array of photon counting receivers used in an optical PPM communication system operating in low-flux conditions is analyzed in the presence of synchronization errors. Comparisons are made to an equal gain combiner with perfect synchronization as well as to the performance of a system with timing synchronization error associated with a single large aperture. These comparisons allow one to ascertain the absolute loss due to synchronization as well as the relative loss due to independent synchronization of the elements in this optical array receiver

Palomar Receive Terminal (PRT) for the Mars Laser Communication Demonstration (MLCD) Project

Significant technological advances were made toward utilizing the Hale telescope for receiving the faint laser communication signals transmitted from an optical transceiver on a spacecraft orbiting Mars. The so-called Palomar receive terminal design, which would have supported nominal downlink data rates of 1-30 Mbps, is described. Testing to validate technologies for near-Sun (3deg from edge of solar disc) daytime operations is also discussed. Finally, a laboratory end-to-end link utilizing a 64-ary pulse-position modulated photon-counting receiver and decoder that achieved predicted near-capacity (within 1.4 dB) performance is described.

Tungsten silicide superconducting nanowire arrays for the lunar laser OCTL terminal

We have developed 12-pixel arrays of fiber-coupled tungsten silicide superconducting nanowire single photon detectors and performed end-to-end tests of a 39 Mbps pulse position modulation optical communication link with a software receiver.

Lunar topographic mapping using a new high resolution mode for the GSSR radar

Mapping the Moons topography using Earth based radar interferometric measurements by the Goldstone Solar System Radar (GSSR) has been done several times since the mid 1990s. In 2008 we reported at this conference the generation of lunar topographic maps having approximately 4 m height accuracy at a horizontal posting of 40 m. Since then GSSR radar has been improved to allow 40 MHz bandwidth imaging and consequently obtained images and interferograms with a resolution of about 4 m in range by 5 m in azimuth. The long synthetic aperture times of approximately 90 minutes in duration necessitated a migration from range/Doppler image formation techniques to spotlight mode processing and autofocusing methods. The improved resolution imagery should permit the generation of topographic maps with a factor of two better spatial resolution with about same height accuracy. Coupled the with the recent availability of new lidar topography maps of the lunar surface made by orbiting satellites of Japan and the United States the geodetic control of the radar generated maps products can be improved dramatically. This paper will discuss the hardware and software improvements made to the GSSR and present some of the new high resolution products.

An MSK Waveform for Radar Applications

We introduce a minimum shift keying (MSK) waveform developed for use in radar applications. This waveform is characterized in terms of its spectrum, autocorrelation, and ambiguity function, and is compared with the conventionally used bi-phase coded (BPC) radar signal. It is shown that the MSK waveform has several advantages when compared with the BPC waveform, and is a better candidate for deep-space radar imaging systems such as NASAs Goldstone Solar System Radar.

Deep-space optical terminals

We report on engineering trades that led to the conceptual design of a laser communications terminal for a spacecraft orbiting Mars. The flight terminal, the ground receiver and the ground transmitter subsystems are described. The designed system is capable of 0.25 Gb/s downlink data-rate, 0.3 Mb/s uplink data-rate, and ranging with a 30 cm precision when the distance to the flight terminal is the Earth-Mars close range (0.42 AU).