An overview of the AFMC Phillips Laboratory Space and Missiles Technology Directorate mission is presented. The development of pervasive technologies for space and missile applications is discussed. Specific areas of ongoing research and development within the five Directorate Divisions and two program offices are delineated. Examples are given of dual-use technologies and techniques being developed in the areas of microelectronics, photonics, communication systems, sensors, and other pertinent space hardware.

The steady evolution of and increased requirement for using photonic technologies within the commercial market coupled with decreased defense spending has brought forth new national philosophies regarding widespread use of the technology in both military and commercial sectors. Many commercially available photonic components (i.e., optical fibers, laser diodes, semiconductor detectors, detector arrays, spatial light modulators, integrated optic circuitry and other similar optoelectronic and electro-optic devices are being scrutinized for utility, cost effectiveness and dual-use in a variety of applications. One important area of application is space. This paper will discuss the current state-of-the-art and utility of qualifying and using several mature photonic component technologies in commercial and defense application areas.

The effect of ionizing radiation on various fiber parameters has been examined. It was demonstrated that when the real refractive index increases, the V number increases as does the numerical aperture. The percentage of power propagating in the cladding decreases with increasing real refractive index. Small changes in the refractive index will induce additional modes to form. The effect of radiation on fiber dispersion was reasoned to be negligible for short lengths of fibers (< 2 km).

Evaluation of threshold-shift damage factors versus non-ionizing energy deposition for GaAs-based, quantum-well, laser diodes and light-emitting diodes demonstrates that they obey the relation between damage factors and non-ionizing energy loss established for GaAs-based electronic devices.

The concept of an all-fiber, IC-based sensor network is presented. Fundamental issues including topology tradeoffs, power budget, and power distribution subsystem are analyzed. Some potential applications of such sensor networks are discussed.

Earth horizon sensors utilizing pyroelectric detectors are finding increasing use in infrared horizon sensing systems. These detectors, like the earlier thermistor bolometer sensors, observe the Earth's carbon-dioxide emission in the 15 micron wavelength band. This paper describes the design, construction and performance of a pyroelectric detector suitable for use in horizon scanner systems. The procedures being developed to ensure the space qualification of this detector will be described. The design of more advanced staring arrays which have been developed will also be discussed.

Optical space communication will use clouds as part of communication channels. Propagation of optical pulses through clouds causes widening and deformation in the time domain and attenuation of the pulse radiant power. These effects decrease the received signal and limit the information bandwidth of the communication system. This work defines typical characteristics of optical pulse propagation through clouds. Characteristics of the optical pulses are calculated using Monte-Carlo simulation. Based on these characteristics a model for optimum performance of digital optical communication through clouds is presented. Examples for practical communication systems are given. An adaptive method to improve and in some cases to make possible communication is suggested. Comparison and analysis of two models of communication systems in cloud channels are presented: (1) adaptive transmitter and standard receiver (semi-adaptive system) and (2) adaptive transmitter and receiver (adaptive system). An improvement of more than eight orders of magnitude in bit error rate under certain conditions is possible with the new adaptive system model.

A new and simple mathematical model for describing radiation-induced absorption in optical fibers is presented. It treats the radiation-induced defect-generation and the decay process as a series of superposable infinitesimal growth and decay events. Unlike the existing power law growth equation, the new equation is non-empirical, dose-rate dependent, and describes the growth and decay of the induced defect at the same time. It is capable of predicting long-exposure, low-dose-rate induced fiber loss normally taking place in a space mission, using short-exposure, high-dose-rate results produced in a ground-based laboratory. Numerically, the derived equation is also capable of simulating those effects caused by irregular radiation events such as solar-flare radiation burst. In the case of constant dose rate, the general equation reduces to a simple analytical form which agrees reasonably well with the experiment.

The strength of volume holographic grating being uniform throughout material depth, the efficiency of such a grating as a function of angle or wavelength has several side-maxima with magnitude comparable to that of main maximum. The side-maxima can be the origin of noises and lack of selectivity of holographic optical elements and devices such as demultiplexers, filters, etc.

As spacecraft begin to unlock the potential of fiber optic systems for spaceflight applications, system level bit error rates (BER) become of great concern to the system designer. Fiber optic data busses running up to 1 Gbps data rates require an uncorrected BER to meet system specifications. With emerging high speed and low power devices such as 3 V CMOS and GaAs ICs being utilized in the system design to interface the electronic subsystems to the fiber optics, the BER contribution of these emerging technology devices in the space Single Event Effect (SEE) arena may outweigh that of the fiber optic components. We present data on several emerging technology devices and the implication of their usage in fiber optic systems in the space SEE environment.

We will describe research being conducted in the following areas: high-speed, 50 ohm, phased-matched modulators and their applications to digital links; promising new research on flat-panel displays that will be full color, fast response, very thin, and have a very high resolution; all optical switches that are extremely fast, integrable and do not have the latency problems that exist with current optical switches; semiconductor optical amplifiers that are monolithically integrable, more flexible and less expensive than existing fiber amplifiers; novel, semiconductor waveguide devices; and automated packaging techniques that will lower the cost of photonics components.

We consider space radiation effects in components and subsystems for fiber based satellite data links and busses. These busses are designed for telemetry and command as well as payload applications spanning data rates from Mbps to Gbps. We emphasize measurements of single particle transient effects in optoelectronic components as they impact the bit error ratio. Test data are analyzed to demonstrate the bit error rate dependence on the particle energy and particle flux as well as receiver electrical characteristics. We conclude that the many advantages of fiber based data links and busses will soon be made available for emerging satellite requirements to transmit data reliability at rates from a few Kbps into the Gbps regime.

A dual rate 1773 fiber optic transceiver chip for space applications is presented. The transceiver will work with either 1 Mbps, or 20 Mbps Manchester data. The receiver features first bit capture with no preamble for 1 Mbps data, and clock recovery for 20 Mbps data. Single event effects in the photo diode are considered in the receiver design. A transmitter switch is included on the chip for driving an LED. The chip will be fabricated in a radiation hard CMOS process.

A sensitized photooxidation has been studied in polymer systems based on polymethacrylates and polyimides with anthracene nuclei chemically attached to or include into main chains. Using thermostable polyimide compositions the possibility of reversible photooxidation due to thermal decomposition of bisphenylanthracene was shown.

This paper presents a fiber optic packaging technique using qualifiable materials and processes that has been developed for space applications. The technique is consistent with a Multi Chip Module implementation. This packaging technique allows multiple fiber optic interfaces to be combined with high density electronics within a single easily integrable package and can be used wherever fiber optics are incorporated into spaceborne systems, including the Fiber Optic Data Bus, the Space Station FDDI interface, any upgrades of the Space Station Local Bus from 1553 to 1773, and various Dual Rate 1773 applications.

We report on the results of experiments performed in areas of technology required to develop gigabit optical interconnects for communication at 1.3 micrometers wavelength. The goal of this work was to develop interconnects not only with very high bandwidth, but with serve to multiple channels having multiple access and simple processing algorithms so as not to rely on high bandwidth electronics, as well. Optical correlation switches (i.e. optical `AND' gates) for use in time-division optical interconnects achieve these goals.

Boeing is in the second phase of a program to develop a common usage fiber- optic data bus for space applications. Phase 1 of the STAR-FODB program included preliminary design and feasibility studies while the goal of the second phase, now in progress, is to develop a working demonstration systems with hardware that is qualifiable for future spacecraft applications.

A radiometric calibration of the space imaging spectrometers especially with a wide field of view is performed with a help on an integrating sphere as a radiance source. Spectral radiance of the integrating sphere is defined by a comparison with the absolute diffuse source. As a diffuse source for a calibration of the integrating sphere in units of radiance may be used a halon target irradiated by a halogen lamp. The absolute diffuse source based on the halon target/four halogen lamps configuration with a good radiance homogeneity is described. The diffuse screen with a diameter 180 mm, which is made of polytetrafluoroethylene (PTFE), is irradiated by 4 symmetrically located halogen lamps. The type of the lamp is KGM 24-150. The angle of incidence on the diffuse screen is 34°. Viewing is carried out through the output window along the direction, which is normal in relation to the diffuse screen. The diameter of the output window is 140 mm. A facility for relative radiance graduation and calibration of this diffuse source against a standard lamp traceable to All-Russian Research Institute of Optical and Physical Measurements (VNIIOFI) and the results of the absolute diffuse source radiometric calibration in the spectral range from 400 nm till 2500 nm are described. A spatial inhomogeneity not more than 2.5% along the whole output aperture. A level of radiance at 900 rim is 1.6.108W/m3sr. Described absolute diffuse source was created in according to a contract with the Space Research Institute of the Russian Academy of Sciences for the radiometric calibration of imaging cameras and spectrometer in stereo-spectralimaging system ARGUS for Mars 94/96 missions.

In this paper some developments of optical techniques for space communication and space-based SAR are discussed. More specifically, the development of an optical-based frequency synthesizer is presented. In addition, the advantages of optical fiber technology for phased array systems with regard to signal distribution, beamforming/steering and multifrequency operations will be described. An optical neural net processor for pattern recognition application will also be presented.

High-reliability, high-performance microwave electro-optic (EO) modulators, low crosstalk EO switches, polarization-insensitive fiber optic isolators, tunable filters, variable attenuators, couplers, endless polarization controllers, and optical amplifier modules for aerospace, terrestrial and undersea applications are presented in this paper. Component structures, performance results, and reliability data will also be discussed.

Application of photonics in beam forming and steering for phased-array antennas is addressed in this paper. Several photonic beam forming and steering network (BFN) architectures are assessed for their capability and technology feasibility, including the mass, prime power, and volume of the payload feeding a multibeam multi-element phased-array antenna. Trade-off issues in BFN architecture and technology selection processes and critical long lead time technical areas that must be developed before its successful deployment on-board communications satellite have been identified. Results of already demonstrated proof-of-concept schemes are also presented.

Use of optical carriers to distribute RF and microwave signals can significantly reduce the size and weight of spacecraft communication systems. Optical carriers can accommodate several RF signals per fiber while permitting noise requirements for communications systems to be met. We previously reported the development of a space-qualified fiber-optic intra-satellite link that meets the requirements on single-side-band phase noise for precision RF signals. The radar altimeter radar chirp signals distributed by these links also meet system requirements. This paper reports our progress in designing a fiber-optic link that transmits RF signals in both directions on the same fiber. Tests at 5, 15, and 80 MHz showed that, for radar altimeter system applications onboard spacecraft, the bidirectional link meets the altimeter RF section's requirements on single-side-band phase noise. However, the severe attenuation requires that the modulated signals be amplified, which may increase the noise levels in the receiver section. Further work is needed to optimize the link for phase noise performance and to address power losses.

The principles of operation and the results of performance measurements are reported of a new type of coherent optical receiver that used a dynamic volume index of refraction grating formed inside a photorefractive material to coherently combine signal and local oscillator light prior to photodetection.

Free-Space optical communications has been a subject of research interest nearly since the advent of the laser. Space applications have long been the elusive destiny for this technology. This paper discusses some of the flight experiment history dating back to 1965 and the issues which have delayed widespread adoption. The general benefits and some shortcomings of optical communications over RF alternatives are described. Technological status against today's and future requirements is assessed. Various future applications, notably those in Japan and Europe, are discussed.

A new space-qualifiable, radiation-hard, ultra-lightweight, high-performance, and hermetic microwave optical link receiver has been developed to meet the demanding requirements of communications spacecraft payload interconnects. This microwave optical link receiver incorporates a small, simple package with space flight proven assembly processes and electro-optical components to provide a lightweight (2.6 grams) interconnect package. Device requirements and hardware development results are presented.