University Microsatellites Equipped with an Optical System for Space Debris Monitoring

The paper considers the principles of construction and application strategies of the ground optical system for space debris monitoring protected by the patent of the Russian Federation for the invention. The aim of this invention was to increase the diffraction resolution of the formed images of a small space object and improve the accuracy of restoration of the module undistorted by the atmosphere and phase of its spatial spectrum. To achieve this goal, formation of atmospherically distorted images of a space object is carried out by a coherent matrix of M moving telescopes of the diameter D in the process of space-time aperture synthesis, which directs the combined subbeams from moving telescopes along the tracks to the center of the matrix, where the stationary base is placed, which performs both coherent combination of subbeams and detection of formed series of N images with their subsequent registration and processing. During statistical processing of moduli and phases of spatial spectra of registered images, the island nature of the optical transfer function (OTF) of matrix along the ellipses of coherence and its semi-island in the radial direction extending from the center of the spatial frequency domain to the cutoff frequency of the synthesized aperture of the diameter Dэ is taken into account. The positive effect of using this invention is that the coherent operation of the matrix provides a gain in the diffraction resolution of Dэ/D times (Dэ/D 1), and an increase of D/r0 times, where r0 is the atmospheric fluctuations correlation radius, the accuracy of restoration of the undistorted by the atmosphere module and phase of the space spectrum from the object by the proposed smoothing procedure allows reducing by the same factor (D/r0 1) the required number of N registrations in series reducing the total monitoring time.

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Ground-based observing optical system for remote sensing of space debris

10.1117/12.326751 ◽

1998 ◽

Author(s):

Konstantin N. Sviridov ◽

Nicolay D. Belkin ◽

Galina Y. Sviridova

Keyword(s):

Remote Sensing ◽

Optical System ◽

Space Debris

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A Field Emission System For Transmission Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071934 ◽

1973 ◽

Vol 31 ◽

pp. 298-299

Author(s):

Michel Troyonal ◽

Huei Pei Kuoal ◽

Benjamin M. Siegelal

Keyword(s):

Electron Microscope ◽

Field Emission ◽

Optical System ◽

High Vacuum ◽

Ultra High Vacuum ◽

Objective Lens ◽

Electron Optical System ◽

Cross Sectional ◽

Transmission Electron ◽

Emission System

A field emission system for our experimental ultra high vacuum electron microscope has been designed, constructed and tested. The electron optical system is based on the prototype whose performance has already been reported. A cross-sectional schematic illustrating the field emission source, preaccelerator lens and accelerator is given in Fig. 1. This field emission system is designed to be used with an electron microscope operated at 100-150kV in the conventional transmission mode. The electron optical system used to control the imaging of the field emission beam on the specimen consists of a weak condenser lens and the pre-field of a strong objective lens. The pre-accelerator lens is an einzel lens and is operated together with the accelerator in the constant angular magnification mode (CAM).

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Information and estimation in image processing

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100125142 ◽

1987 ◽

Vol 45 ◽

pp. 14-17

Author(s):

B. Roy Frieden

Keyword(s):

Image Processing ◽

Optical System ◽

Large Amplitude ◽

Communication Theory ◽

Image Data ◽

Direct Approach ◽

Ill Posed

Despite the skill and determination of electro-optical system designers, the images acquired using their best designs often suffer from blur and noise. The aim of an “image enhancer” such as myself is to improve these poor images, usually by digital means, such that they better resemble the true, “optical object,” input to the system. This problem is notoriously “ill-posed,” i.e. any direct approach at inversion of the image data suffers strongly from the presence of even a small amount of noise in the data. In fact, the fluctuations engendered in neighboring output values tend to be strongly negative-correlated, so that the output spatially oscillates up and down, with large amplitude, about the true object. What can be done about this situation? As we shall see, various concepts taken from statistical communication theory have proven to be of real use in attacking this problem. We offer below a brief summary of these concepts.

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Atomic Resolution in Crystal Aperture Stem

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179932 ◽

1990 ◽

Vol 48 (1) ◽

pp. 236-237

Author(s):

J T Fourie

Keyword(s):

Optical System ◽

Spherical Aberration ◽

Three Dimensional ◽

Transmission Function ◽

Optical Systems ◽

Bragg Angle ◽

Electron Optical System ◽

Intimate Contact ◽

Diffraction Effects ◽

Design Aspect

The attempts at improvement of electron optical systems to date, have largely been directed towards the design aspect of magnetic lenses and towards the establishment of ideal lens combinations. In the present work the emphasis has been placed on the utilization of a unique three-dimensional crystal objective aperture within a standard electron optical system with the aim to reduce the spherical aberration without introducing diffraction effects. A brief summary of this work together with a description of results obtained recently, will be given.The concept of utilizing a crystal as aperture in an electron optical system was introduced by Fourie who employed a {111} crystal foil as a collector aperture, by mounting the sample directly on top of the foil and in intimate contact with the foil. In the present work the sample was mounted on the bottom of the foil so that the crystal would function as an objective or probe forming aperture. The transmission function of such a crystal aperture depends on the thickness, t, and the orientation of the foil. The expression for calculating the transmission function was derived by Hashimoto, Howie and Whelan on the basis of the electron equivalent of the Borrmann anomalous absorption effect in crystals. In Fig. 1 the functions for a g220 diffraction vector and t = 0.53 and 1.0 μm are shown. Here n= Θ‒ΘB, where Θ is the angle between the incident ray and the (hkl) planes, and ΘB is the Bragg angle.

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STEM and ELS Observation of Early Oxide Formation on the Surface of Cr Thin Films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001768 ◽

1980 ◽

Vol 38 ◽

pp. 412-413

Author(s):

Fumio Watari ◽

J. M. Cowley

Keyword(s):

Thin Films ◽

Optical System ◽

Room Temperature ◽

Oxide Formation ◽

Initial Nucleation ◽

Diffraction Patterns ◽

Relationship Of ◽

Multiple Twinning ◽

Moderately High Temperature

STEM coupled with the optical system was used for the investigation of the early oxidation on the surface of Cr. Cr thin films (30 – 1000Å) were prepared by evaporation onto the polished or air-cleaved NaCl substrates at room temperature and 45°C in a vacuum of 10−6 Torr with an evaporation speed 0.3Å/sec. Rather thick specimens (200 – 1000Å) with various preferred orientations were used for the investigation of the oxidation at moderately high temperature (600 − 1100°C). Selected area diffraction patterns in these specimens are usually very much complicated by the existence of the different kinds of oxides and their multiple twinning. The determination of the epitaxial orientation relationship of the oxides formed on the Cr surface was made possible by intensive use of the optical system and microdiffraction techniques. Prior to the formation of the known rhombohedral Cr2O3, a thin spinel oxide, probably analogous to γ -Al203 or γ -Fe203, was formed. Fig. 1a shows the distinct epitaxial growth of the spinel (001) as well as the rhombohedral (125) on the well-oriented Cr(001) surface. In the case of the Cr specimen with the (001) preferred orientation (Fig. 1b), the rings explainable by spinel structure appeared as well as the well defined epitaxial spots of the spinel (001). The microdif fraction from 20A areas (Fig. 2a) clearly shows the same pattern as Fig. Ia with the weaker oxide spots among the more intense Cr spots, indicating that the thickness of the oxide is much less than that of Cr. The rhombohedral Cr2O3 was nucleated preferably at the Cr(011) sites provided by the polycrystalline nature of the present specimens with the relation Cr2O3 (001)//Cr(011), and by further oxidation it grew into full coverage of the rest of the Cr surface with the orientation determined by the initial nucleation.

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