This Pdf file contains the Front Matter associated with SPIE Proceedings Volume 7691, including Title page, Copyright information, Table of Contents, Conference Committee listing, and Introduction, if any.

After the launch of NASA's SeaWinds radar scatterometer on the QuikSCAT satellite in 1999, a radiometer function, known as the QuikSCAT Radiometer - QRad, was implemented in the Science Ground Data Processing Systems to allow the measurement of the earth's microwave brightness temperature (Tb) using the radar system noise temperature [1, 2]. This paper will describe an inter-satellite radiometric calibration technique to validate the QRad brightness temperature algorithm and the QuikSCAT L2A Tb product. This approach allows the inter-comparison of two satellite sensors (radiometers) that have significant differences in their designs. To assess the quality of the QRad instrument, we compare its Tb measurements with the near simultaneous and collocated ocean brightness temperature observations from WindSat on the Coriolis Satellite, which serves as the brightness temperature calibration standard. Since the QRad and WindSat instruments were of different designs, brightness temperature normalizations were made for WindSat before comparison to account for expected differences in Tb because of incidence angle and channel frequency differences. Brightness temperatures for nine months during 2005 and 2006 were spatially collocated for rainfree homogeneous ocean scenes (match-ups) within 1° latitude x longitude boxes and within a ± 60 minute window. To ensure high quality comparison, these collocations were quality controlled and edited to remove non-homogenous ocean scenes and/or transient environmental conditions, including rain contamination. WindSat and QRad Tb's were averaged within 1° boxes and were used for the radiometric inter-calibration analysis on a monthly basis. Results show that QRad radiometric calibration is stable in the mean over the yearly seasonal cycle.

Current surveillance systems operate in a highly dynamic environment in which large numbers of sensors on board multiple platforms must cooperate in order to achieve overall mission success. In an attempt to maximize sensor performance, today's sensors employ rudimentary or, in some cases, inflexible sensor tasking schemes. These approaches are highly tuned to a specific scenario and geometry and are inflexible to changes in the mission, environmental conditions, heterogeneous sensors, and different system architectures. As the complexity of the problem space increases and new sensors become available, it is critical to have a sensor management scheme that is capable of incorporating new environmental knowledge, new sensors and different systems approaches with minimal computational impact on the overall system. Each system should develop an autonomous sensor tasking capability which factors in global concerns within the complete distributed network of platforms and sensors. Moreover, tasking efficiency can be improved by a highly developed understanding of sensor performance at each point in time. This can be achieved by incorporating the impact of problem geometry - sensor location, track object type and view angle - and weather phenomena, such as clouds, aerosols, turbulence and sun glint. This paper describes our approach for simultaneously optimizing sensor resource management, surveillance objectives, and atmospheric transmission of signals while minimizing sensor and environmental noise. Our approach uses a genetic algorithm to evolve a population of sensor tasking assignments through constantly-updating track locations, weather conditions, and lighting conditions. Preliminary studies demonstrate encouraging improvements in sensor management performance. We will present results from our preliminary studies and discuss a path forward for our technology.

Optical instruments for space missions work in hostile environment, it's thus necessary to accurately study the effects of ambient parameters variations on the equipment performance. In particular, optical instruments are very sensitive to ambient conditions, especially temperature. This variable can cause dilatation and misalignment of the optical elements, and can also lead to rise of dangerous stresses in the optics. Optical elements displacements and surface deformations degrade the quality of the sampled images. In this work a method for simulating and studying the effects of the thermal deformations, particularly the impact on the expected optical performance, is presented. Optical elements and their mountings are modelled and processed by a thermo-mechanical Finite Element Model (FEM) analysis, reproducing expected operative conditions. The FEM output is elaborated into a MATLAB optimisation code; a non-linear least square algorithm is used to determine the equation of the best fitting n^th degree polynomial, or the spherical surface of the deformed lenses and mirrors; model accuracy is 10^-8 m. The obtained mathematical surface representations are then directly imported into ZEMAX raytracing software for sequential raytrace analysis. The results are spot diagrams, chief ray coordinates on the detector, MTF curves and Diffraction Encircled Energy variations due to simulated thermal loads. This analysis helps to design and compare different optical housing systems for finding a feasible mounting solution. The described method has been applied successfully to the optics and mountings of a stereo-camera for the BepiColombo mission. Different types of lenses and prisms constraints have been designed and analysed. The results show the preferable use of kinematic constraints, instead of using glue, to correctly maintain the instrument focus in orbit around Mercury considering an operative temperature range between -20°C and +30°C.

The need to efficiently identify the changing inertial properties of on-orbit spacecraft is becoming more critical as satellite on-orbit services, such as refueling and repairing, become increasingly aggressive and complex. This need stems from the fact that a spacecraft's control system relies on the knowledge of the spacecraft's inertia parameters. However, the inertia parameters may change during flight for reasons such as fuel usage, payload deployment or retrieval, and docking/capturing operations. New Mexico State University's Dynamics, Controls, and Robotics Research Group has proposed a robotics-based method of identifying unknown spacecraft inertia properties¹. Previous methods require firing known thrusts then measuring the thrust, and the velocity and acceleration changes. The new method utilizes the concept of momentum conservation, while employing a robotic device powered by renewable energy to excite the state of the satellite. Thus, it requires no fuel usage or force and acceleration measurements. The method has been well studied in theory and demonstrated by simulation. However its experimental validation is challenging because a 6- degree-of-freedom motion in a zero-gravity condition is required. This paper presents an on-going effort to test the inertia identification method onboard the NASA zero-G aircraft. The design and capability of the test unit will be discussed in addition to the flight data. This paper also introduces the design and development of an airbearing based test used to partially validate the method, in addition to the approach used to obtain reference value for the test system's inertia parameters that can be used for comparison with the algorithm results.

The fast development of nitrides has given the opportunity to investigate AlGaN as a material for ultraviolet detection. Camera based on this alloy present an intrinsic spectral selectivity and an extremely low dark current at room temperature. We present here an extension from near UV (360 nm-260 nm) to deep UV (10 nm-200 nm) in a packaging common to the SWIR supply chain. It concern both readout circuit and camera electronics. Such camera are now available for on UV optical budget evaluation. The vacuum UV wavelengths are a very difficult range for detection due to the strong interaction of light with materials. Nevertheless, such wavelengths are of prime importance for solar observation. We present a prototype of focal plane arrays to extend the range of detection from near UV to deep UV. It is based on 320 x 256 pixels of Schottky photodiodes with a pitch of 30 μm. AlGaN is grown on a silicon substrate instead of sapphire substrate only transparent down to 200 nm. After a flip-chip hybridization, silicon substrate is thinned and removed by dry etching. The use of a honeycomb structure straightens the membrane after hybridization and allows the membrane integrity. The results show that the dry etching process doesn't affect the readout circuit properties. The dark current is negligible and the measured noise is the readout noise due to the large capacitance of the photodiode. The spectral responsivity of this focal plane array presents a quantum efficiency from 10% to 20% from 50 nm to 290 nm after the removing of the highly doped contact layer.

Nanosatellites, in particular the sub-class of CubeSATs, will provide an ability to place multiple small satellites in space more efficiently than larger satellites, with the eventual expectation that they will compete against some of the roles played by traditional large satellites that are expensive to launch. In order to do this, it is necessary to decrease the weight and volume without decreasing the capabilities. At the same time, it is desirable to create systems extremely rapidly, less than a week from concept to orbit. The Air Force has been working on a concept termed "CubeFlow" which will be a web-based design flow for rapidly constructible CubeSAT systems. In CubeFlow, distributed suppliers create offerings (modules, software functions, for satellite bus and payloads) meeting standard size and interface specifications, which are registered as a living catalog to a design community within the web-based CubeFlow environment. The idea of allowing any interested parties to make circuits and sensors that simply and compatibly connect to a modular satellite carrier is going to change how satellites are developed and launched, promoting creative exploitation and reduced development time and costs. We extend the power of the CubeFlow framework by a concept we call "print-and-play." "Print-and-play" enriches the CubeFlow concept dramatically. Whereas the CubeFlow system is oriented to the brokering of pre-created offerings from a "plug-and-play" vendor community, the idea of "print-andplay" allows similar offerings to be created "from scratch," using web-based plug-ins to capture design requirements, which are communicated to rapid prototyping tools.

The paper presents a set of new demodulation algorithms for use in satellite systems to receive Automatic Identification System (AIS) signals, with the potential presence of other interfering signals. The combined differential demodulation scheme, referred to as CDD-n, combines n single differential demodulation schemes with appropriately selected weights. Simulation results indicate that the gain under the proposed demodulation scheme is up to 10 dB over several existing non-coherent, single differential demodulation schemes. The impact of the combination coefficients/weights, the number of single differential detectors used, the low pass filter used, the interference and phase shift on the performance are evaluated through simulation, respectively. The proposed demodulation schemes are simple and easy to implement in satellite receivers in current and future satellite networks.

In this paper, we propose a solution to the cooperative path planning with limited communication problem in two phases. In the first (offline) phase, a Pareto-optimal path problem is formulated to find a reference path and the graph cuts minimization method is used to speedily calculate the optimal solution. In the second (online) phase, a foraging algorithm is used to dynamically refine the reference path to meet the dynamic constraints of unmanned aerial vehicle (UAVs), during which an open-loop feedback optimal (OLFO) controller is used to estimate the states which may be unavailable due to infrequent battlefield information updates. Furthermore, an adaptive Markov decision process is proposed to deal with intermittent asynchronous information flow. The method is demonstrated in a simulation for a swarm of Unmanned Air Vehicle (UAV) teams with various communication ranges.

The University of Hawaii and NASA Langley Research Center are developing small, compact, and portable remote Raman systems with pulsed lasers for planetary exploration under the Mars Instrument Development Program. The remote Raman instruments developed previously utilized small telescopes with clear apertures of 125 mm and 100 mm diameters and were able to detect water, ice, water bearing minerals, carbon in carbonate form in calcite, magnesite, dolomite, and siderite from a distance of 10 to 50 m under daytime and nighttime conditions. Recently, we significantly reduced the size of our time-resolved (TR) remote Raman system in order to build a compact system suitable for future space missions. This compact time-resolved Raman system was developed by utilizing (i) a regular 85 mm Nikon (F/1.8) lens with a clear aperture of 50 mm as a collection optic, and (ii) a miniature Raman spectrograph that is 1/14^th in volume in comparison to the commercial spectrograph used in our previous work. In this paper, we present the TR remote Raman spectra obtained during daytime from various hydrous and anhydrous minerals, water, water-ice, and CO₂-ice using this new compact remote Raman system to 50 m radial distance.

We are presenting the concept, design and construction of an optical receiver of the space segment for the time transfer ground to space using optical pulses and photon counting detection. Laser time transfer link is under construction for the European Space Agency (ESA) for its application in the experiment Atomic Clock Ensemble in Space (ACES). The device is expected to be launched toward the International Space Station in 2013. The objective of this laser time transfer is the synchronization of the ground based clocks and the clock on board the station with precision of the order of units of picoseconds and the accuracy of 50 picoseconds. The photon counting approach has been selected for on-board optical detection in order to reduce the systematic biases as much as possible. However, the background photon flux of the solar light scattered by the Earth atmosphere and the Earth surface with wide field of view is a challenge in the optical detector design. The optical receiver concept and the first experiment results of indoor tests are presented.

The idea that Linear Covariance techniques can be used to predict the accuracy of attitude determination systems and assist in their design is investigated. By using the sensor's estimated parameter accuracy, one could calculate the total standard deviation of the attitude determination that is resulting from these uncertainties by simple Root- Sum-Square of the attitude standard deviation resulting from the respective uncertainties. Generalized Matrix Laboratory (MATLAB) M-functions using this technique are written in order to provide a tool for estimating the attitude determination accuracy of a small spacecraft and to identify major contributions to the attitude determination uncertainty. This tool is applied to a satellite dynamics truth model developed in order to quantify the effects of sensor uncertainties on this particular spacecraft's attitude determination accuracy. The result of this study determines the standard deviation of the attitude determination as a function of the sensor uncertainties.

This paper is concerned with the nonlinear filtering problem for tracking a space object with possibly delayed measurements. In a distributed dynamic sensing environment, due to limited communication bandwidth and long distances between the earth and the satellites, it is possible for sensor reports to be delayed when the tracking filter receives them. Such delays can be complete (the full observation vector is delayed) or partial (part of the observation vector is delayed), and with deterministic or random time lag. We propose an approximate approach to incorporate delayed measurements without reprocessing the old measurements at the tracking filter. We describe the optimal and suboptimal algorithms for filter update with delayed measurements in an orbital trajectory estimation problem without clutter. Then we extend the work to a single object tracking under clutter where probabilistic data association filter (PDAF) is used to replace the recursive linear minimum means square error (LMMSE) filter and delayed measurements with arbitrary lags are be handled without reprocessing the old measurements. Finally, we demonstrate the proposed algorithms in realistic space object tracking scenarios using the NASA General Mission Analysis Tool (GMAT).

The Canary instrument is a miniature electrostatic analyzer designed to detect positively charged ions in the energy range 0-1500 eV. The Canary concept began with the development of a Micro-Electro-Mechanical (MEMS) Flat Plasma Spectrometer (FlaPS), which, integrated with electronics onto FalconSAT-3, reduced the size and mass of an ion plasma spectrometer to about 10x10x10 cm³ and 250 g. The successor to FlaPS was the Wafer Integrated Spectrometer (WISPERS), expanding the same instrument to seven sensors all with uniquely optimized energy ranges and azimuth/elevation look angles. WISPERS is due to fly on the USAF Academy's FalconSAT-5 satellite scheduled for launch in Spring 2010. FlaPS and WISPERS created a paradigm shift in the use of such instruments in a highly capable but small, low power package. The third generation, Canary (named after the "canary in the coal mine" - an earlier technology used to provide low-cost, effective warning of danger to operators), will be flown on the International Space Station (ISS) and used to investigate the interaction of approaching spacecraft with the background plasma environment around the ISS.

Orbital collisions pose a hazard to space operations. Using a high performance computer modeling and simulation environment for space situational awareness, we explore a new paradigm for improving satellite conjunction analysis by obtaining more precise orbital information only for those objects that pose a collision risk greater than a defined threshold to a specific set of satellites during a specified time interval. In particular, we assess the improvement in the quality of the conjunction analysis that can be achieved using a distributed network of ground-based telescopes.

In order to achieve continuous attitude information of the spacecrafts or the telescopes, the star-sensors and the gyros are usually integrated to form navigation systems, which measure and determine the attitude-angles synthetically. The space combinations of the measure-vectors of the star-sensors and the gyros are analyzed to find out the influences of the combination modes on the determination precision of the attitude-angles, and the influence trends are summarized. Furthermore, the optimum space combinations of the measure-vectors are proposed for improvement the determination precision of the attitude-angles and the redundancy/complement of star-sensors and gyros. The optimum space combinations of the measure-vectors are benefit for designing optimum integrated star/gyro systems to achieve high determination precision of the attitude-angles, even any of the star-sensors or the gyros works with poor measurement precision, so as to improve the reliability of the navigation systems.