Jamie W. Burnside

Design of an inertially stabilized telescope for the LLCD

The Lunar Laser Communication Demonstration (LLCD) program will demonstrate the first high-bandwidth optical communication payload on a NASA space mission. The inertially stabilized 108 mm aperture telescope will fly on NASAs LADEE spacecraft and is fabricated nearly entirely of beryllium, providing a high stiffness-to-weight ratio. The telescope consists of a two-axis fine positioning stage using inertial sensors and coarse and fine optical tracking. The stabilized telescope uses a two-axis coarse positioning gimbal to provide a large field-of-regard. Inertial stabilization provides local disturbance rejection while allowing modest optical uplink power to provide an absolute pointing reference. The telescope is a three-wavelength design providing separate uplink acquisition and communication wavelengths, and a downlink communication wavelength. Acquisition and coarse tracking of the uplink beacon is via a photodiode quadrant detector, while fine tracking is via nutation tracking and piezoelectric actuation of the receive fiber. Control of the downlink point-ahead angle is via piezoelectric actuation of the transmit fiber. The telescope is thermally stabilized during normal operations. The transmit and receive beams are fiber-coupled to a separate optoelectronic module and the telescope line-of-sight will be stabilized to better than 2.5 microradians during normal operations. Provision for self-test and boresighting during on-orbit operations is provided.

A Hybrid Stabilization Approach for Deep-Space Optical Communications Terminals

Near-Earth laser communication system designs typically use the near-symmetric power levels in duplex links as bright sources upon which to base active beam stabilization. In deep space, it may be difficult to provide a constant, high-power laser beacon as a stabilization reference. We describe here several means, aimed at different frequency ranges of control, for generating a combined pointing reference and for actively controlling beam position. Such a blended approach gives a highly flexible system for performing beam stabilization in deep space, where distances, conditions, and power levels can vary widely.

Artificial neural network classification of Drosophila courtship song mutants

Courtship songs produced by Drosophila males — wild-type, plus the cacophony and dissonance behavioral mutants — were examined with the aid of newly developed strategies for adaptive acoustic analysis and classification. This system used several techniques involving artificial neural networks (a.k.a. parallel distributed processing), including learned vector quantization of signals and non-linear adaption (back-propagation) of data analysis. “Pulse” song from several individual wild-type and mutant males were first vector-quantized according to their frequency spectra. The accumulated quantized data of this kind, for a given song, were then used to “teach” or adapt a multiple-layered feedforward artificial neural network, which classified that song according to its original genotype. Results are presented on the performance of the final adapted system when faced with novel test data and on acoustic features the system decides upon for predicting the song-mutant genotype in question. The potential applications and extensions of this new system are discussed, including how it could be used to screen for courtship mutants, search novel behavior patterns or cause-and-effect relationships associated with reproduction, compress these kinds of data for digital storage, and analyze Drosophila behavior beyond the case of courtship song.

The NASA Lunar Laser Communication Demonstration—Successful High-Rate Laser Communications To and From the Moon

The Lunar Laser Communication Demonstration (LLCD) is NASA’s first demonstration of the use of free-space optical communications for high-rate duplex communications between a lunar spacecraft and an Earth ground station. The LLCD system comprised a space terminal on the Lunar Atmosphere and Dust Environment Exploration (LADEE) spacecraft and three ground terminals developed by NASA and the European Space Agency. The primary mission occurred during the fall of 2013 and successfully demonstrated reliable data delivery over optical data links operating at rates as high as 20 Mbps on the uplink and 622 Mbps on the downlink.

The Mars lasercom terminal

We present the Mars lasercom terminal preliminary design that demonstrates high-rate optical communications from Mars and provide NASA with the experience necessary to develop future operational deep-space optical communication systems.

Design of a very small inertially stabilized optical space terminal

The potential of lasercom could often be much more attractive to system designers if the terminals could be made very small. In particular, in systems where one end of the link is allowed to be somewhat more capable than the other, the lesser of the two terminals could take advantage of the asymmetry and shrink as much as possible. We have investigated how such asymmetry factors into the requirements for a small terminal and have designed a terminal with a very small aperture (35-75 mm) and an inertial stabilization scheme. The space-worthy terminal has applicability to Moon-to-Earth as well as near-Earth lasercom missions.

The effect of uplink fading on the pointing and tracking system of the Mars lasercom terminal

We study the effect of atmospheric fading on the pointing and tracking system of the Mars lasercom terminal. We show system performance with varying atmospheric turbulence. Algorithms to mitigate errors caused by fading are demonstrated.

Laser communications for human space exploration in cislunar space: ILLUMA-T and O2O

In recent years, NASA has been developing a scalable, modular space terminal architecture to provide low-cost laser communications for a wide range of near-Earth applications. This development forms the basis for two upcoming demonstration missions. The Integrated Low-Earth Orbit Laser Communications Relay Demonstration User Modem and Amplifier Optical Communications Terminal (ILLUMA-T) will develop a user terminal for platforms in low-Earth orbit which will be installed on the International Space Station and demonstrate relay laser communications via NASA’s Laser Communication Relay Demonstration (LCRD) in geo-synchronous orbit. The Orion EM-2 Optical Communication Demonstration (O2O) will develop a terminal which will be installed on the first manned launch of the Orion Crew Exploration Vehicle and provide direct-to-Earth laser communications from lunar ranges. We describe the objectives and link architectures of these two missions which aim to demonstrate the operational utility of laser communications for manned exploration in cislunar space.

TeraByte InfraRed Delivery (TBIRD): a demonstration of large-volume direct-to-Earth data transfer from low-Earth orbit

Delivery of large volumes of data from low-Earth orbit to ground is challenging due to the short link durations associated with direct-to-Earth links. The short ranges that are typical for such links enable high data rates with small terminals. While the data rate for radio-frequency links is typically limited by available spectrum, optical links do not have such limitations. However, to date, demonstrations of optical links from low-Earth orbit to ground have been limited to ~10 to ~1000 Mbps. We describe plans for NASA’s TeraByte InfraRed Delivery (TBIRD) system, which will demonstrate a direct-to-Earth optical communication link from a CubeSat in low-Earth orbit at burst rates up to 200 Gbps. Such a link is capable of delivering >50 Terabytes per day from a small spacecraft to a single small ground terminal.

Model for testing various CO sensor technologies performance within a tunnel ventilation system

This document presents the CO concentration simulator design. It may be used to study the performance of sensors with ventilation and traffic control systems. The model is general enough to be used with one way or two way tunnel networks. Sensor locations and performance can be varied and the resulting changes in driver exposure can be measured.