This PDF file contains the front matter associated with SPIE Proceedings Volume 9227, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

The crosstalk effect considerably limits the capability of holography-based modal wavefront sensing (HMWS) when measuring wavefronts with large aberrations. In this contribution, we introduce a curvature-based measurement technique into HMWS to extend the dynamic range and the sensitivity of HMWS via a compact holographic design. If the input aberrations are large, the dominating aberration modes are first detected via curvature sensing and compensated using a wavefront correcting device, e.g. a membrane mirror. The system then switches to HMWS to obtain better sensitivity and accuracy with reduced aberrations. Different approaches for the reconstruction of the wavefront have been tested and extensive simulations for different aberrations have been analyzed.

Various techniques and algorithms have been developed to improve the resolution of sensor-aliased imagery captured with an under-sampled pixelated image plane. In the literature these de-aliasing algorithms are sometimes included under the broad umbrella of super-resolution. One basic approach to multiframe de-aliasing is the well-known noniterative algorithm termed variable pixel linear reconstruction (VPLR) or “drizzling.” Many modern techniques are based on iterative optimization of a forward model (objective function). Regardless, both iterative and noniterative techniques rely on estimation of frame-to-frame displacements and rotations to subpixel accuracy. Weights are then solved for and used to distribute low-resolution (LR) pixel values to a high-resolution (HR) grid. One approach used in both VPLR and iterative methods to determine weights is to calculate pixel overlap areas. Well-known spatial domain approaches based on computational geometry exist to perform such calculations. Here we present a novel approach based on exactly calculating overlap areas in the spectral domain, which we call the spectral-overlap (SO) method, and include a comparison with the geometric approach of O’Rourke. All spatial spectra in the SO method are calculated analytically once and for all, resulting in expressions devoid of quadratures. Initial studies indicate that this new algorithm executes about 20 times faster than using the O’Rourke algorithm. The speedup is partly explained by the ability to precompute many quantities involved in the SO approach and apply these quantities to the computation of many distinct spatial overlaps. Application of the algorithm to multiframe de-aliasing is demonstrated using simulated imagery.

The FITTS correlation algorithm has been widely used for over forty years in high speed video trackers. It has the advantage that it is very simply implemented in a digital computer with a small number of calculations. At each step the algorithm attempts to estimate the shift between an image of a moving target and a proto-type image. There are several well-known short comings of the FITTS algorithm. First the error in the shift estimate increases if the shift is greater than one pixel of the digital image. Second the FITTS algorithm is susceptible to errors from sensor noise if the video images have low signal to noise ratio. These errors can force a lower tracker closed loop bandwidth to maintain track loop stability. An alternative correlation tracker algorithm is known as Projection Based Phase Only Correlation. In this paper we compare the two algorithms with respect to the effect of sensor noise.

In wavefront sensor-less adaptive optics systems, wavefront sensing is often replaced with far-field detection. If the detection is inaccurate, even if the optimal performance metric is achieved, the correction quality may still be poor. In this paper we focus on the effects of improper far-field detection positions. At first we build a simple modal of a wavefront sensor-less adaptive with improper detection position. Then a series of analyses are carried out using this modal and the precision of placing far-field sensor is concluded. Finally simulations with practical systems are presented and the method for analysis are given.

Applications of stellar occultation by solar system objects have a long history for determining universal time, detecting binary stars, and providing estimates of sizes of asteroids and minor planets. More recently, extension of this last application has been proposed as a technique to provide information (if not complete shadow images) of geosynchronous satellites. Diffraction has long been recognized as a source of distortion for such occultation measurements, and models subsequently developed to compensate for this degradation. Typically these models employ a knife-edge assumption for the obscuring body. In this preliminary study, we report on the fundamental limitations of knife-edge position estimates due to shot noise in an otherwise idealized measurement. In particular, we address the statistical bounds, both Cramér- Rao and Hammersley-Chapman-Robbins, on the uncertainty in the knife-edge position measurement, as well as the performance of the maximum-likelihood estimator. Results are presented as a function of both stellar magnitude and sensor passband; the limiting case of infinite resolving power is also explored.

A novel technique is proposed for ultra-wideband imagery of space objects from distributed multi-band radar data. The complex exponential (CE) model is used for representation of ultra-wideband radar signals, where an iterative procedure is developed for optimized model parameter estimation. A subband coherent processing technique is developed which combines the de-noising cross-correlation (DNCC) algorithm with statistical method to obtain the phase and amplitude incoherent parameters (ICP) between subbands. Ultra-wideband data fusion via two-dimensional gapped-data state space approach (2-D GSSA) is then applied to multiple subband signals for supper-resolution imagery. Experiments using computational electromagnetic data from the method of moment (MoM) as well as anechoic chamber measurement data are used to validate the proposed technique and demonstrate its applications.

Rockets and other high altitude aerospace vehicles produce interesting visual and aural phenomena that can be remotely observed from long distances. This paper describes a compact, passive and covert remote sensing system that can produce high resolution sound movies at >100 km viewing distances. The telescopic high resolution camera is capable of resolving and quantifying space launch vehicle dynamics including plume formation, staging events and payload fairing jettison. Flight vehicles produce sounds and vibrations that modulate the local electromagnetic environment. These audio frequency modulations can be remotely sensed by passive optical and radio wave detectors. Acousto-optic sensing methods were primarily used but an experimental radioacoustic sensor using passive micro-Doppler radar techniques was also tested. The synchronized combination of high resolution flight vehicle imagery with the associated vehicle sounds produces a cinema like experience that that is useful in both an aerospace engineering and a Hollywood film production context. Examples of visual, aural and radar observations of the first SpaceX Falcon 9 v1.1 rocket launch are shown and discussed.

Thin observation module by bounded optics (TOMBO) is an optical system substituting a micro lens-let array with smaller apertures for a conventional large full aperture. This array allows us to capture multiple low resolution sub-images of the same scene and use them to reconstruct a high resolution image. While lost resolutions can be recovered, there has been very little work on experimentally evaluating restored resolution performance in the TOMBO system. Our work focuses on resolution comparisons among a 4×4 lens-let TOMBO and Nikon lenses in the same f number condition. Experimental results present the equivalent focal length of the experimental TOMBO system.

The down-looking synthetic aperture imaging ladar (SAIL) with electro-optic modulation was proposed. The measurement uses electrically controlled scanner to produce beams with spatial parabolic phase difference, which consists of electro-optic crystal and cylindrical lens. Due to the high modulation rate without mechanical scanning, this technique has a great potential for applications in extensive synthetic aperture imaging ladar fields. The phase mapping of electrically controlled scanner under the different applied voltage is achieved and measured by the polarized digital holographic interferometry. The phase mappings of the scanner in the down-looking SAIL with the o-polarized light and e-polarized light are obtained. The linear phase distribution and the parabolic phase distribution are observed after applying the external electric field. The corresponding analyses and discussions are proposed to explain the phenomena.

Synthetic aperture radar interferometry (InSAR) can gain three-dimensional topography with high spatial resolution and height accuracy using across track interferometry[1]. Conventional InSAR produce three-dimensional images from SAR data. But when the working wavelength transit from microwave to optical wave, the transmission antenna and receive antenna become very sensitive to platform vibration and beam quality[2]. Through differential receive antenna formation, we can relax the requirement of platform and laser using synthetic aperture imaging ladar (SAIL) concept[3]. Line-of-sight motion constraints are reduced by several orders of magnitude. We introduce two distinctive forms of antenna formation according to the position of interferogram. The first architecture can simplify the interferogram processing and phase extraction algorithm under time-division multiplex operation. The second architecture can process the 2D coordinate and height coordinate at the same time. Using optical diffraction theory, a systematic theory of side-looking SAIL is mathematically formulated and the necessary conditions for assuring a correct phase history are established[4]. Based on optical transformation and regulation of wavefront, a side-looking SAIL of two distinctive architectures is invented and the basic principle, systematic theory, design equations and necessary conditions are presented. It is shown that high height accuracy can be reached and the influences from atmospheric turbulence and unmodeled line-of-sight motion can be automatically compensated.

Down-looking synthetic aperture imaging ladar(SAIL) has overcome many difficulties in side-looking SAIL. However, it is inevitably impacted by the speckle effect. There is temporally varying speckle effect due to the angular deflecting of two coaxial polarization-orthogonal beams transmitted in the orthogonal direction of travel, and a spatial varying speckle effect in the travel direction. Under the coaxial heterodyne, phase variations caused by speckle effect are compensated, leaving the amplitude variations of speckle field. In this paper, the speckle effect in the down-looking SAIL is analyzed, expressions for two-dimensional data collection contained speckle effect are obtained and the two-dimensional image influenced by speckle effect is simulated.

Compared to synthetic aperture radar (SAR), synthetic aperture imaging ladar (SAIL) is more sensitive to the phase errors induced by atmospheric turbulence, undesirable line-of-sight translation-vibration and waveform phase error, because the light wavelength is about 3-6 orders of magnitude less than that of the radio frequency. This phase errors will deteriorate the imaging results. In this paper, an algorithm based on low-pass filtering to suppress the phase error is proposed. In this algorithm, the azimuth quadratic phase history with phase error is compensated, then the fast Fourier transform (FFT) is performed in azimuth direction, after the low-pass filtering, the inverse FFT is performed, then the image is reconstructed simultaneously in the range and azimuth direction by the two-dimensional (2D) FFT. The highfrequency phase error can be effectively eliminated hence the imaging results can be optimized by this algorithm. The mathematical analysis by virtue of data-collection equation of side-looking SAIL is presented. The theoretical modeling results are also given. In addition, based on this algorithm, a principle scheme of optical processor is proposed. The verified experiment is performed employing the data obtained from a SAIL demonstrator.