Improvement of Spatial Resolution with Staggered Arrays As Used in The Airborne Optical Sensor Ads40

Using pushbroom sensors onboard aircrafts or satellites requires, especially for photogrammetric applications, wide image swaths with a high geometric resolution. One approach to satisfy both demands is to use staggered line arrays, which are constructed from two identical CCD lines shifted against each other by half a picel in line direction. Practical applications of such arrays in remote sensing include SPOT, and in the commercial environment the Airborne Digital Sensor, or ADS40, from Leica Geosystems. Theoretically, the usefulness of staggered arrays depends from spatial reslution, which is defined by the total point spread function of the imaging system and Shannon's sampling theorem. Due to the two shifted sensor lines staggering results in a double number of sampling points perpendicular to the flight direction. In order to simultaneously double the sample number in the flight direction, the line readout rate, or integration time, has to produce half a pixel spacing on ground. Staggering in combination with a high-resolution optical system can be used to fulfil the sampling condition, which means that no spectral components above the critical spatial frequency 2/D are present. Theoretically, the resolution is as good for a non-staggered line with half pixel size D/2, but radiometric dynamics should be twice as high. In practice, the slightly different viewing angle of both lines of a staggered array can result in a deteration of image quality due to aircraft motion, attitude fluctuations or terrain undulation. Fulfilling the sampling condition further means that no aliasing occurs. This is essential for the image quality in quasiperiodical textured image areas and for photogrammetric sub-pixel accuracy. Furthermore, image restoration methods for enhancing the image quality can be applied more efficently. The panchromatic resolution of the ADS40 opties is optimised for image collection by a staggered array. This means, it transfers spatial frequencies of twice the Nyquist frequency of its 12k sensors. First experiments, which were carried out some years ago, indicated alrady a spatial resolution improvement by using image restitution the ADS 40 staggered 12k pairs. The results of the restitution algorithm, which is integrated in the ADS image processing flow, has now been analysed quantitatively. This paper presents the theory of high resolution image restitution from staggered lines and practical results with ADS40 high resolution panchromatic images and high resolution colour images, created by sharpening 12k colour images with high resolution pan-chromatic ones

OAST space research and technology applications: Technology transfer successes

The ultimate measure of success in the Space Research and Technology Program is the incorporation of a technology into an operational mission. Charts are presented that describe technology products which OAST has helped support that (1) have been used in a space mission, (2) have been incorporated into the baseline design of a flight system in the development phase, or (3) have been picked up by a commercial or other non-NASA user. We hope that these examples will demonstrate the value of investment in technology. Pictured on the charts are illustrations of the technology product, the mission or user which has incorporated the technology, and where appropriate, results from the mission itself

Project Tech Top study of lunar, planetary and solar topography Final report

Data acquisition techniques for information on lunar, planetary, and solar topograph

Sensory information processing (1 January 1976 - 30 June 1976)

technical reportThe removal of the effects of atmospheric turbulence from optical images is a significant problem of long standing. Recent investigations by Knox and Thompson have led to the development of a restoration procedure which shows considerable promise. This procedure has not been successfully applied to real data as yet, however, nor has it been sufficiently well analyzed and simulated to provide a thorough quantitative understanding of their properties. Furthermore, these procedures will very likely require modification before they can be practically applied to large quantities of real data. We have begun an investigation of Knox's method aimed at finding suitable ways to apply it to real data

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 309)

This bibliography lists 136 reports, articles and other documents introduced into the NASA scientific and technical information system in February, 1988

Restoring the full velocity field in the gaseous disk ofthe spiral galaxy NGC 157

We analyse the line-of-sight velocity field of ionized gas in the spiral galaxy NGC 157 which has been obtained in the H\alpha emission at the 6m telescope of SAO RAS. The existence of systematic deviations of the observed gas velocities from pure circular motion is shown. A detailed investigation of these deviations is undertaken by applying a Fourier analysis of the azimuthal distributions of the line-of-sight velocities at different distances from the galactic center. As a result of the analysis, all the main parameters of the wave spiral pattern are determined: the corotation radius, the amplitudes and phases of the gas velocity perturbations at different radii, and the velocity of circular rotation of the disk corrected for the velocity perturbations due to spiral arms. At a high confidence level, the presence of the two giant anticyclones in the reference frame rotating with the spiral pattern is shown; their sizes and the localization of their centers are consistent with the results of the analytic theory and of numerical simulations. Besides the anticyclones, the existence of cyclones in residual velocity fields of spiral galaxies is predicted. In the reference frame rotating with the spiral pattern these cyclones have to reveal themselves in galaxies where a radial gradient of azimuthal residual velocity is steeper than that of the rotation velocity (abridged).Comment: 23 pages including 25 eps-figures. Accepted for publication in A&

What is limiting near-infrared astrometry in the Galactic Center?

We systematically investigate the error sources for high-precision astrometry from adaptive optics based near-infrared imaging data. We focus on the application in the crowded stellar field in the Galactic Center. We show that at the level of <=100 micro-arcseconds a number of effects are limiting the accuracy. Most important are the imperfectly subtracted seeing halos of neighboring stars, residual image distortions and unrecognized confusion of the target source with fainter sources in the background. Further contributors to the error budget are the uncertainty in estimating the point spread function, the signal-to-noise ratio induced statistical uncertainty, coordinate transformation errors, the chromaticity of refraction in Earth's atmosphere, the post adaptive optics differential tilt jitter and anisoplanatism. For stars as bright as mK=14, residual image distortions limit the astrometry, for fainter stars the limitation is set by the seeing halos of the surrounding stars. In order to improve the astrometry substantially at the current generation of telescopes, an adaptive optics system with high performance and weak seeing halos over a relatively small field (r<=3") is suited best. Furthermore, techniques to estimate or reconstruct the seeing halo could be promising.Comment: accepted by MNRAS, 13 pages, 14 figure