This PDF file contains the front matter associated with SPIE Proceedings Volume 10288, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

An overview of the micro-nanotechnology field is presented with application toward future space systems. Specific discussions are presented on the insertion of MEMS, MOEMS and quantum effect nanoelectronic devices into both current and future space systems. Silicon satellites, based on batch-fabricated microengineered systems are also discussed.

The degradation of space photosensors and optical devices in several radiation environments is reviewed. The effects are of concern to designers of spacecraft and ground-based systems dedicated to observation, inspection and other practical tasks. Design and prediction methods can be developed which make observation systems more tolerant to radiation effects. The methods for predicting radiation effects in light sensors, phosphors and optics are common to high-radiation in space and on the ground. In all cases, the creation of defects and the trapping of charge in silicon, insulators and transparent materials and the associated hardened technologies (such as hardened silicon, hardened oxide films, hardened fibres and ultrapure scintillators) are discussed and instruments for the measurement of radiation dose and silicon defect creation in orbit are described.

While the study of radiation effects in microelectronic devices has been ongoing for many decades, it was only with the first successful space demonstration (1984) of an active optical fiber system comprised of fiber waveguides, light emitting diodes and photodetectors that the radiation effects community increased focus on the effects of space environments on photonic technologies. The intent of this critical review of radiation effects research in photonics is to historically and briefly summarize an overview of the leading research achievements of the last decade. The review also brings to focus very recent and emerging research directions using new ion microbeam methodologies for performing highly accurate radiation effects investigations on photonic and microelectronic components and systems. The bulk of the review deals with recently reported radiation induced response phenomena in: LiNb03 integrated optic structures, AlGaAs vertical cavity surface emitting laser diodes, acousto optic Bragg cells, GaN light emitting diodes, and organic spatial light modulators.

AlGaN/InGaN/GaN material system is very attractive for a large number of optoelectronic and electronic applications. In this paper, we focus on space applications and examine the material and device properties relevant to these applications. The review indicates that group-III nitrides are very attractive for fabrication of short-wavelength visible light emitters for harsh environment applications.

Present and future space-based applications such as sensors, low-weight and low-power data links for satellites, communication between electromagnetically-shielded modules, and short-distance cross-links within satellite constellations may benefit from the inclusion of small, low-power, and high-efficiency lasers such as the recently-developed Vertical Cavity Surface-Emitting Laser (VCSEL). Many factors influence the application of these devices to space. Temperature response, operational lifetime and reliability, and power consumption are all important considerations for space applications. In addition, the space radiation environments must be considered. In this work, the effects of ionizing radiation on VCSELs are studied with an emphasis on proton damage, and with comparisons to related neutron and gamma-induced phenomena. The influence of proton irradiation is studied in-depth for selected VCSEL structures by the use of an ion microbeam. The experiments indicate that VCSELs exhibit much less threshold current shift for a given radiation dose, compared to the more traditional edge-emitting semiconductor lasers, but that self-heating is a more important consideration for VCSELs. The high current densities associated with VCSELs also lead to a strong influence from forward-bias annealing. These effects are common to various VCSEL types (780 nm and 850 nm) and their magnitude at a given dose is strongly dependent on device size. This indicates that, while VCSELs appear to be very insensitive to ionizing radiation when compared with alternative technologies, there are a number of factors that must be taken into account when optimizing for the space environment.

Whenever equipment is intended for use in hostile environmental conditions or when severe reliability demands constrain its functional specifications, very specific research is required to assess the successful operation of individual devices and subsystems. This statement is certainly valid as far as both space and nuclear applications are concerned. Indeed, space and nuclear environments show several similar characteristics, among which the presence of ionizing and particle radiation as well as extreme pressure or temperature conditions. Even if the basic environmental conditions such as dose rates, total doses, particle types, pressure and temperature ranges may differ, the fundamental effects which influence or degrade the specifications of devices often remain the same. Hence, we are convinced that space and nuclear communities have to learn from each other's complementary experience. This perspective serves as a frame for the results reviewed in this paper, as they are issued from research and development efforts of (European) nuclear actors on one hand and space industry on the other. After an introductory comparison of nuclear and space radiation environments, three complementary contributions are highlighted. The first two focus on radiation testing and include radiation effects on two modem individual photonic devices as well as standard irradiation test procedure definitions for fiber-optic systems. Then we turn to a major part of this paper which describes advanced photonic systems especially designed for space applications.

A number of serious consortiums develop satellite communication networks. The objective of these communication projects is to service personal communication users almost everywhere on earth. The inter satellite links (ISL) in those project use microwave radiation as the carrier. Free space optical communication between satellites networked together can make possible high speed communication between different places on earth. The advantages of an optical communication system instead of a microwave communication system in free space are: a) smaller size and weight, b) less transmitter power, c) larger bandwidth, d) higher immunity to interference, and e) smaller transmitter beam divergence. The use of optical radiation as a carrier between the satellites creates very narrow beam divergence angles. Due to the narrow beam divergence angle and the large distance between the satellites the pointing from one satellite to another is complicated. The problem is more complicated due to vibration of the pointing system caused by two stochastic fundamental mechanisms 1) tracking noise created by the electrooptic tracker and 2) vibrations created by internal and external mechanical mechanisms. The vibrations displace the transmitted beam in the receiver plane. Such movement of the transmitted beam in the receiver plane decreases the average received signal which decreases increases the bit error rate. In this paper we review: 1) the present status of satellite networks 2) developing efforts of optical satellite communication around the world, 3) performance results of vibration effects on different kinds of optical communication satellite networks and 4) seven approaches to overcome the problems caused by transmitter pointing vibration.

Optical interconnects have long promised significant advantages over their electrical counterparts. Specific advantages include increased bandwidths at long (ten meters or more) interconnection distances, immunity to EMI effects, negligible crosstalk, reduced size, and lower weight. Optical interconnects have been developed for, and are being used in, a range of ground based and aircraft applications, however they are only now beginning to gain acceptance in spaceborne systems. In addition to the maturity demanded from components destined for ground-based applications and the wider temperature excursions characteristic of airborne applications, spaceborne components must also be able to survive the radiation environments associated with their intended applications. The additional qualification required has resulted in delayed introduction of photonic interconnects. We describe the tradeoffs involved in implementing for the first time a spaceborne fiber optic data bus with a clock speed of 1.2 Gbps. The tradeoffs include emitter, detectors, fiber, connectors and packaging. We have selected a series of commercial grade optoelectronic devices which were then qualified for use in spaceborne environments and have developed a space qualifiable packaging scheme. We have designed and implemented the optoelectronic subsystem of the data bus and have simulated its operation.

We also describe recent advances in Vertical Cavity Surface Emitting Lasers (VCSELs) for spacebourne databuses. VCSELs also offer advantages in simplicity of packaging and electronic control. We summarize available initial radiation data on these devices and project their impact on spaceborne photonic interconnects.

Optoelectronic processing provides significant advantages for space applications. These advantages include enhanced processing capability with reduced size, weight and power. Design considerations that are unique to space can have a significant impact on the development schedule. Optoelectronic processors are most efficient at operations that involve correlation, Fourier transforms, or a combination of these functions. Several application areas where these functions are used are presented along with the rationale for using optoelectronics. Two key applications include telecommunications switching and radar processing. Synthetic Aperture Radar (SAR) processing in space is discussed as a specific example.

In this paper some significant aspects of the possible and useful synergies in R and D programs and the main problems in the technology transfer process relevant to space and leading to competitiveness are presented. Guided-Wave devices and recent technological advances in optoelectronics for space are also described and discussed to highlight new directions towards innovation.

We present a review of volume holographic memory technology highlighting the most important issues for the development of commercially viable mass data storage systems. To record data using volume holographic storage, data is encoded on a laser beam with a spatial light modulator (SLM). The object beam is directed into an optically sensitive material, typically a photoreffactive crystal, and superimposed with a coherent reference beam, forming interference gratings. The material reacts to the interference pattern by spatial modulation of its optical absorption or refractive index. During data retrieval the reference beam alone illuminates the modulated region, causing diffraction of a beam that is modulated as if it were generated by the original object beam incident on the SLM; that is a duplicate of the original object beam. This beam is imaged onto a photodetector array for capture and decoding.

Because the data are stored and retrieved as a two-dimensional matrix, a volume holographic storage system is inherently parallel. Consequently, data is read many bits (conceivably in the range of megabits) at a time, so that this approach offers the potential of high data retrieval rates, on the order of tens of gigabits per second and access times of much less than a millisecond. Data recording speeds are very dependent on the choice of storage material and energy of the laser. System capacity and capability are a consequence of three major interrelated factors: (1) the time-energy requirement of the storage material and the permanence of the stored data; (2) the capacity and efficiency of the spatial light modulator; and (3) the laser’s power, physical size, and coherence properties. When compared with traditional flat surface magnetic or optical storage, volume holographic data storage has the potential of advantageous capacity, speed, weight, power, and physical size. While these are attractive attributes, they are particularly useful for space applications. This paper presents an assessment of the past, present, and future of holographic memories by consideration of the various developments since the initial concept of volume holographic data storage.

The concept of a photonic satellite where optical subsystems replace the microwave and digital electronics on-board communications spacecraft is considered very attractive for its potential to reduce the mass and volume of a payload requiring increased processing bandwidth. Use of on-board photonic subsystems could therefore render advanced Satcom systems highly cost-competitive with respect to alternative technologies. In this invited paper, the status of onboard photonic subsystems such as phased-array antenna beam forming and steering, high-speed signal distribution, control, and processing, millimeter wave (mmW) signal generation, and intersatellite link, and relevant photonic devices and technologies is reviewed. Issues of network architecture, technology feasibility, reliability, and redundancy requirements, and their impact on the mass, power, and size of the payload are discussed. Also, a time line of critical optical technology, onboard implementation issues, and the cost-benefits achievable over advanced RF subsystems are presented.

GaAs asymmetric Fabry-Perot vertical cavity modulators are useful in a wide variety of applications. Such modulators have been demonstrated in large format arrays. The majority of vertical cavity devices have employed amplitude modulation to produce optical switching. Additional uses for the pixels include detection, phase modulation, directional modulation, and light-emitting capability. When arrays of these devices are integrated with electronic circuits-most significantly silicon CMOS VLSI-at the pixel level, large, complex optical spatial light modulators, detectors, transceivers, computation devices, and emitters can be created for a wide variety of applications. These applications range from target recognition to SAR radar processing, to optical data routing, to optical interconnect systems, to optical memory access.

Continuous investigation of new technologies for avionics and space processing has led to the improvement of applications capabilities and processing for tactical platforms (commercial and government satellites, tactical asset such as the USN Reconnaissance Fighter F/A-18R, USAF Fighter F-16, various helicopters, etc.,) and surveillance platforms (commercial and government satellites, Joint Surveillance Target Attack Radar System (JSTARS), Advanced Warning and Control System (AWACS)). This paper focuses on the potential benefits of inserting optical interconnect technology into these platforms while subscribing an Open Optical Interconnect Architecture (OOIA) concept and a methodology for systems development and integration.

Space-based laser altimeters are effective in providing topographic measurements critically important to the understanding of the formation and early evolution of planetary bodies. Using laser altimetry data, topographic grids can be produced that provide significant insight into the shape, internal structure and evolution of the subject body. Prime examples of space-based altimetry efforts are the Clementine and the Near-Earth Asteroid Rendezvous (NEAR) missions. Clementine spent two months sampling the Moon, and through its altimetry data, provided a glimpse of the lunar surface previously unseen. NEAR will place a laser altimeter (NLR) in orbit at the near-Earth asteroid 433 Eros for a one year observation period. Specifications for such altimeters are driven by mission requirements and host spacecraft constraints. Mission requirements usually prioritize observation objectives associated with other payload instruments, therefore, altimeter design must readily accommodate other payload instruments. Constraints placed on altimeters include mass, power, and volume; also for deep-space missions, data rates are limited and become an issue especially when imaging instruments are part of the mission. Altimeter performance specification and modeling to meet these requirements are described and approaches to verify instrument performance during pre-launch testing are provided. Lessons provided from laser altimetry missions indicate the technological progression to the next-generation laser altimeters.