RU2730886C1 - Method of achieving diffraction limit of resolution of images of remote probing of earth for small spacecrafts - Google Patents

Abstract

FIELD: instrument engineering.SUBSTANCE: invention relates to space instrument-making of optoelectronic equipment (OEU). Method for achieving diffraction limit of resolution of Earth remote sensing images for small spacecrafts (ERS SS), wherein lens and digital detector of OEU are matched by Nyquist criterion and provide for achievement of diffraction limit of instrumental resolution of spacecraft ERS SS on terrain. To eliminate atmospheric distortions when obtaining remote ERS images, it is proposed to exclude time and frequency averaging of atmospheric distortions of light radiation, that in absence of spatial averaging {r(λ,H) > D} enables to register statistically independent diffraction-limited short-exposure images of ERS, accidentally shifted and attenuated by atmosphere. To eliminate these atmospheric distortions when processing the registered series N of "instant" low-contrast images, high-quality images M are selected among them, rejecting washed-out and noisy images, a, while shifting and accumulating selected, compensate for atmospheric shifts and attenuation of images, obtaining high-contrast and high (diffraction) resolution panchromatic image of the probed portion of the earth's surface for various ERS tasks of ultrahigh resolution and multizone thematic processing.EFFECT: technical result consists in providing the possibility of increasing contrast of ERS images in conditions of atmospheric distortions.1 cl, 5 dwg, 1 tbl

Description

The claimed invention relates to the field of optical instrumentation, and, in particular, space instrumentation of optical-electronic equipment (OEA) of small spacecraft for remote sensing of the Earth (MCA ERS), and is intended to achieve the diffraction limit of the linear resolution of the MCA ERS on the ground and increase the contrast of ERS images in conditions of atmospheric distortion.

According to the generally accepted classification, ERS spacecraft are divided according to their weight and size characteristics into large and small ones. The section boundary is declared to be a weight of –1000kg. Small spacecraft, in turn, are subdivided into:

picosatellites - less than 5kg;

nanosatellites - from 5 to 50 kg;

microsatellites - from 50 to 200 kg;

small spacecraft ERS - from 200 to 1000 kg.

Analysis of world trends in the development of equipment and technologies for constructing and using ERS means demonstrates an increased interest in the creation and use of ERS MCA constellations that provide the ability to observe "... any part of the earth's surface at any time ..." with high spatial resolution. Such constellations can consist of 50 ÷ 60 ERS small spacecraft (for example, as WorldView "Legion"), located in low circular sun-synchronous orbits. The orbital position of the small spacecraft in the constellation is selected and maintained in such a way as to ensure the minimum time of approach to the zone of interest. With the indicated number of small spacecraft, the breaks in the observation of arbitrary areas of the earth's surface can be 30–20 minutes. The OEA of such ERS small spacecraft should have a high spatial resolution with low weights and dimensions.

Each small spacecraft in the constellation must provide the maximum possible observation time for the selected area of the earth's surface with the maximum (diffraction) resolution, while the requirements for the remote sensing spacecraft in terms of its performance, determined by the size of the OEA field of view, are not imposed due to the large number of small spacecraft.

Let us consider the features of the influence of the atmosphere on Earth remote sensing systems (ERS).

The propagation medium of solar illumination reflected from the Earth in ERS tasks is the troposphere (the lower 10 km of the surface layer of the atmosphere). In foreign literature, two terms are used to characterize the atmosphere as a medium for the propagation of light radiation: “turbid”, which means “turbid”, and “turbulent”, which means “restless”.

As a turbid environment, the atmosphere leads to a weakening of the light signal and deterioration of the signal-to-noise ratio (contrast) of the remote sensing images. The reason for this is the absorption and scattering of light by molecules and aerosols in the atmosphere, which are usually taken into account by introducing the appropriate attenuation coefficients determined from the tables.

As a turbulent medium, the atmosphere leads to random changes in the parameters of the light information signal, and its presence between the probed area of the earth's surface and the ERS small spacecraft significantly limits the information capabilities of the remote sensing spacecraft. Two problems arise: the problem of "seeing" through a turbulent atmosphere and the problem of "isoplanaticity" of the atmosphere-remote sensing telescope system.

The essence of these problems is that the problem of "seeing" imposes restrictions on the minimum size of details resolved by the atmosphere-ERS telescope system on the sounded area of the earth's surface, and the problem of "isoplanaticity" limits the maximum size of the sounded area of the earth's surface, which is still spatially invariant. to atmospheric distortions, that is, this problem limits the field of view of the atmosphere-ERS telescope system.

These problems significantly depend on the observation conditions, and. in particular, on the conditions of registration of remote sensing images.

So, if the time of registration (exposure) τ _E exceeds the interval of temporal correlation of atmospheric fluctuations τ _A , called the time of "freezing" of atmospheric turbulence, then they speak of long-exposure registration, and if the registration time τ _{E is} less than τ _A , then they speak of short -exposure registration [1] (Fried DL, "Optical Resolution through a Randomly Inhomogeneous Medium for Very Long and Very Short Exposures", J. Opt. Soc. Am., 1966, v. 56, No. 10, p. 1372).

These two extreme cases differ significantly in the nature of atmospheric distortions. So, if a long-exposure image averaged over atmospheric distortions over a time τ _E > τ _A has a worse resolution than an “instant” (short-exposure) image recorded in a time τ _E <τ _A , then it is spatially invariant to atmospheric distortions in the entire field of view of the ERS atmosphere-telescope system, in contrast to the short-exposure image, which consists in this field of a number of instantaneous isoplanaticity regions that are spatially invariant to atmospheric distortions [2] (Sviridov K.N., Bakut P. A., Ustinov ND, Khomich N.Yu., "Problems of isoplanaticity of optical systems that form images through a turbulent atmosphere", Optics and Spectroscopy, 1986, vol. 60, issue 3, p. 611).

In accordance with these features of the influence of a turbulent atmosphere on images, at an early stage of the development of remote sensing technologies, the desire to work in a wide field of view (with maximum performance) stimulated the acquisition of long-exposure remote sensing images.

as in domestic ERS spacecraft:

- "Resurs-DK1" [3] (Petri G., "Russian satellite" Resurs-DK1 ": an alternative source of ultra-high resolution data", Geomatika, 2010, No. 4, p. 38) and

- "Resurs-P" [4] (Kirilin A.N. et al. "Spacecraft" Resurs-P ", Geomatika, 2010, No. 4, p. 23),

and in foreign ERS spacecraft:

- IKONOS, QuickBird, EROS, Pleiades, WorldView, GeoEye, etc. [5] (Lavrov V.V., "Ultra-high resolution space imaging systems", Geo-information portal of the GIS Association, 2010, No. 2, p. 19).

We consider these publications [3, 4, 5] here as analogs of the proposed method in terms of obtaining ERS images distorted by the atmosphere. The technology used in them for detecting time delay and accumulation (VZN [3, 4] and TDI [5]) leads to the registration of a long-exposure image averaged over atmospheric distortions.

The disadvantage of existing ERS technologies [3, 4, 5], considered by us as analogs of the proposed method in terms of image acquisition, is the lack of any processing in them that corrects atmospheric distortions of the recorded long-exposure image.

With the development of remote sensing technology, new technologies have appeared that make it possible to determine and correct atmospheric distortions. These technologies, proposed by JSC Russian Space Systems, can be conditionally classified into three classes: hardware technologies, algorithmic technologies and hardware-algorithmic technologies. Consider these analogs and a prototype of the proposed method.

. Здесь

– пространственный радиус корреляции атмосферных флуктуаций светового излучения на высоте Н космического аппарата ДЗЗ, а λ–средняя длина волны видимого диапазона длин волн

солнечного излучения подсвета земной поверхности (λ = 0,6 мкм). Эта технология, предложенная и исследованная в работе [6] (Cвиридов К.Н., «О предельном разрешении аэрокосмических систем дистанционного зондирования Земли (ДЗЗ)», Ракетно-космическое приборостроение и информационные системы, 2014, т. 1, вып. 1, с. 34), позволяет в условиях атмосферных искажений и при длинно-экспозиционной регистрации изображений ДЗЗ достигать предельного линейного разрешения КА ДЗЗ на местности, равного

(4,6 см).The first hardware technology for increasing the linear resolution of the ERS spacecraft on the ground is based on changing the lens of the ERS spacecraft telescope, namely, on replacing the glass refractor lens of domestic ERS spacecraft [3, 4] with mirror reflector lenses, as in foreign ERS spacecraft [5], and most importantly, by increasing the diameter of the receiving aperture of the telescope D to the required value

... Here

Is the spatial correlation radius of atmospheric fluctuations of light radiation at the height H of the ERS spacecraft, and λ is the average wavelength of the visible wavelength range

solar radiation illumination of the earth's surface (λ = 0.6 microns). This technology, proposed and investigated in [6] (Sviridov K.N., "On the ultimate resolution of aerospace remote sensing systems of the Earth (ERS)", Rocket and space instrument making and information systems, 2014, vol. 1, issue 1, 34), allows, in conditions of atmospheric distortion and with long-exposure registration of ERS images, to achieve the limiting linear resolution of the ERS spacecraft on the ground, equal to

(4.6 cm).

, где

– величина пространственного радиуса корреляции атмосферных флуктуаций светового излучения на верхней границе турбулентного слоя атмосферы

(

≈10км). Отсюда видно, что: при Н=350км,

оказывается равной 3,5м; при Н=500км,

, и при Н=750км, величина

оказывается равной 7,5м. А так как в соответствии с проведенными исследованиями [6] необходимо иметь

, то полученные значения для

, во-первых, объясняют требуемые величины для диаметров апертуры телескопов КА ДЗЗ: D=7м; 10м и 15м, и, во-вторых, показывают, что эти диаметры оказываются существенно большими диаметра D=1,1м существующих сегодня телескопов ДЗЗ [5]. В связи с тем, что сегодня

, атмосферные искажения светового излучения на приемной апертуре телескопа ДЗЗ представляют собой случайные наклоны волнового фронта, приводящие к случайным сдвигам дифракционно ограниченных изображений ДЗЗ (Фиг.5).The disadvantage of this analogue lies in the difficulty of its practical implementation, since it requires the creation of ERS telescopes based on aperture synthesis, and in particular, the concept of an MZT (multi-mirror telescope) with aperture diameters: D = 7m at H = 350km; D = 10m at H = 500km and D = 15m at H = 750km. Such diameters are explained by the fact that, in accordance with the studies carried out in [6], the value of r _O (λ, H) is determined by the relation

where

- the value of the spatial correlation radius of atmospheric fluctuations of light radiation at the upper boundary of the turbulent layer of the atmosphere

(

≈10 km). From this it is seen that: at H = 350 km,

turns out to be equal to 3.5m; at H = 500 km,

, and at Н = 750 km, the value

turns out to be equal to 7.5m. And since, in accordance with the studies [6], it is necessary to have

, then the obtained values for

, firstly, they explain the required values for the aperture diameters of the ERS spacecraft telescopes: D = 7m; 10m and 15m, and, secondly, show that these diameters turn out to be significantly larger than the diameter D = 1.1m of the existing Earth remote sensing telescopes [5]. Due to the fact that today

, atmospheric distortions of light radiation at the receiving aperture of the remote sensing telescope are random tilts of the wavefront, leading to random shifts of diffraction-limited remote sensing images (Fig. 5).

This circumstance led to the development of a new hardware technology for compensating for atmospheric distortions and increasing the linear resolution of an ERS spacecraft on the ground. It is based on random preddetektornoy adaptive compensation of the wavefront slopes of the "frozen" turbulent atmosphere τ _A. This technology (analogue) was proposed in [7] (Sviridov K.N., Volkov S.A., "Method for remote sensing of the Earth", Patent of the Russian Federation No. 2597144 dated 08.16.2016 for invention application No. 2015129353 dated 17.07.2015 , applicant and copyright holder
JSC "Russian Space Systems") and investigated in work [8] (Sviridov K.N., "Remote sensing of the Earth with adaptive compensation for random tilts of the wavefront", Rocket and space instrument making and information systems, 2015, vol. 2, no. 3, p. 12). This method of remote sensing with a long-exposure strategy of recording VZV images allows obtaining an average short-exposure image. Its average short-exposure optical transfer function (OTF) prevails over the average OTF of a long-exposure image in the entire range of spatial frequencies, providing a gain in the resolution of the average short-exposure ERS image as compared to the long-exposure one. Studies [8] have shown that a system with adaptive compensation for random tilts of the wavefront compared to a system without compensation provides a real gain in resolution.

The disadvantage of this analogue of the proposed method, like the previous analogue, is that, although the hardware technologies provide potentially good results in resolution, they require significant modernization, and most importantly, the complication of the equipment of the remote sensing systems.

Algorithmic technologies provide a simpler and more realistic way of achieving positive results of atmospheric distortion compensation and increasing the linear resolution of ERS spacecraft on the ground.

, до зарубежного уровня пространственного разрешения [5], равного

. As an analogue of the proposed method, we consider the algorithmic ERS technology proposed in [9] (Sviridov K.N .. "A method for obtaining and processing images distorted by a turbulent atmosphere", the decision to issue a patent for invention No. 2016100934/28 (001133) dated 12.03 .2019 on application for invention No. 2016100934 dated 14.01.2016, applicant and copyright holder of JSC Russian Space Systems). This technology does not require a change in the WZV detection strategy and is based on post-detector adaptive filtering of the recorded long-exposure ERS image, which is spatially invariant to atmospheric distortions throughout the entire field of view of the ERS atmosphere-telescope system. The studies [10] (Sviridov K.N., "Adaptive filtering of middle images distorted by a turbulent atmosphere", Rocket and space instrument making and information systems, 2015, vol. 2, issue 4, p. 40), confirmed the effectiveness of adaptive filtering long exposure image distorted by a turbulent atmosphere to improve its resolution. At the same time, it was found that the gain in resolution does not exceed 2 times, but this gain may also be sufficient to increase the level of linear resolution on the ground of domestic remote sensing data [11] (Sviridov K.N., "On the ultimate instrumental resolution of the spacecraft" Resource-P "(No. 1, 2, 3)", Rocket and space instrumentation and information systems, 2017, vol. 4, issue 2, p. 20.), equal to

, to the foreign level of spatial resolution [5], equal to

...

Note that these estimates of the linear resolution of the Earth remote sensing spacecraft on the ground are given on the basis of the domestic evaluation criterion proposed by JSC Russian Space Systems, which is free from the shortcomings and limitations of the foreign criterion for evaluating GSD, and is associated with it by the relationship RKS = 2GSD [12] ( Sviridov K.N., Tyulin A.E., “On the criteria for assessing the limiting instrumental resolution of a spacecraft for remote sensing of the Earth on the ground”, Information and Cosmos, 2018, No. 3, p. 143). The above estimates, however, are far from the diffraction limit of the instrumental resolution of the ERS spacecraft on the ground due to two reasons: the uncompensated influence of the atmosphere, and, most importantly, because of the mismatch between the lens and the digital detector OEA according to the Nyquist criterion, which is equivalent to the diaphragm setting D _{E of the} receiving aperture of the lens D ( D _E <D). The method proposed here eliminates both of these reasons and ensures the achievement of the diffraction limit of the linear resolution of the ERS small spacecraft on the ground in conditions of atmospheric distortion.

As a prototype of the proposed method, we select the hardware-algorithmic technology proposed in [13] (Sviridov K.N., "Method for remote sensing of the Earth (ERS)", Patent of the Russian Federation No. 2531024 dated 08/20/2014 on application for invention No. 2013125540 dated 03.06.2013, applicant and copyright holder of JSC Russian Space Systems). This method is based on the combined use of “instant” (short-exposure) images of the probed area of the earth's surface and the average (long-exposure) image obtained by their accumulation.

The hardware technology of the prototype consists in the formation and detection of spectrally-filtered, short-exposure images of the probed area of the earth's surface, statistically independent from each other in atmospheric distortions, but spatially non-invariant to them.

The algorithmic technology of the prototype is that according to the registered series of short-exposure images, the module of the spatial spectrum from the object is determined not distorted by the atmosphere, and from the long-exposure image obtained by their accumulation, which is spatially invariant to atmospheric distortions, the low-frequency part of the phase of the spatial spectrum from the object is determined , combining which and carrying out the Fourier transform from the synthesized spatial spectrum, restore the image of the probed area of the earth's surface improved by processing.

Studies of this method carried out in [14] (Sviridov K.N., "On a new approach to obtaining and processing ERS images distorted by a turbulent atmosphere", Rocket and space instrument making and information systems, 2014, vol. 1, issue 4 , p.28), showed that here, as a result of processing, the average short-exposure image is restored, characterized by the resolution of the average short-exposure OPF, in contrast to the previously obtained resolution [3,4,5], characterized by the average long-exposure OPF, due to the strategy of image detection — VZN.

The main disadvantage of the prototype, as well as of its analogues, is that during the design and creation of optoelectronic equipment (OEA) of the ERS spacecraft in them, the lens and the digital detector were not matched by the Nyquist criterion, which prevented the achievement of the diffraction limit of the ERS spacecraft resolution during image processing. on the ground, and the processing itself, even with such a match, did not allow reaching the diffraction limit of resolution, since it did not fully compensate for the atmospheric distortions of the reconstructed image in the region of high spatial frequencies.

To eliminate the noted shortcomings of the prototype, this method is proposed.

The proposed method, like the prototype, can be attributed to the hardware-algorithmic technology for achieving high linear resolution of the ERS small satellite on the ground.

At the same time, the hardware technology of the proposed method consists in the perfect design of the OEA, based on the matching of the telescopic lens and the digital detector OEA according to the Nyquist criterion and providing the possibility of reaching the diffraction limit of the instrumental resolution of the ERS MCA on the ground. This technology is implemented at the stage of obtaining in the panchromatic spectral filtering band of a digital detector a series of N short-exposure (τ _E ≤τ _A ) images of the probed area of the earth's surface, statistically independent in atmospheric distortions and spatially invariant to them. The introduction of photomagnifying optics between the objective and the digital detector, which matches the OEA according to the Nyquist criterion, in contrast to the use of one long-focus lens for this purpose, allows one to reduce the weight and dimensions of the OEA, which is important when creating small ERS spacecraft.

The hardware technology of short-exposure registration of “instantaneous” images allows to eliminate not only the temporal averaging of atmospheric distortions of each image in a series, but also the blur of each image. The elimination of blurring of the recorded images, in addition to a short exposure, is also facilitated by the implementation of programmed turns of the small spacecraft relative to its center of mass in order to slow down the movement of the recorded image of the probed area of the earth's surface along the receiving matrix of the digital detector.

раз, и получают контрастное дифракционно ограниченное панхроматическое изображение зондируемого участка земной поверхности, а, анализируя его через мультиспектральные узкополосные фильтры, осуществляют многозональную тематическую обработку, при которой в интересах различных потребителей отслеживают изменения состояний естественных и искусственных объектов на зондируемом участке земной поверхности.The algorithmic technology of the proposed method is implemented at the stage of processing a series of N "instantaneous", statistically independent images and is aimed at the formation of a high-contrast diffraction-limited image of the probed area of the earth's surface, for this, first, a registered series of N diffraction-limited, randomly shifted and weakened by the atmosphere images is analyzed and (select) the clearest and most contrasting images in it, rejecting blurry and noisy, then summarize the selected images and form a reference image of the probed area of the earth's surface, determine from it the characteristic features (reference points) of the probed area of the earth's surface and compare each of the M selected by selection briefly -exposure images with the reference, defining in them the characteristic features of the reference, then they shift short-exposure images, combining their characteristic features with the characteristic features standard, and at the same time compensate for the atmospheric shifts of the images, after which the shifted short-exposure images are accumulated, increasing the signal-to-noise ratio (contrast) of the resulting image in

times, and a contrast diffraction limited panchromatic image of the probed area of the earth's surface is obtained, and, analyzing it through multispectral narrow-band filters, they carry out multi-zone thematic processing, in which, in the interests of various consumers, changes in the states of natural and artificial objects on the probed area of the earth's surface are monitored.

The technical result (goal) of the proposed method is to achieve the diffraction limit of the resolution of the remote sensing images and increase their contrast by matching the OEA for obtaining the remote sensing images according to the Nyquist criterion and compensating for atmospheric distortions of the remote sensing images during their acquisition and processing.

, приравнивают ее к требуемому линейному разрешению и дифракционному пределу разрешения МКА ДЗЗ на местности

, где

_.средняя длина волны солнечного излучения подсвета в видимом диапазоне длин волн Δλ_В=(0,43÷0,73)мкм, и на основании равенства

определяют требуемый диаметр апертуры объектива проектируемой ОЭА, как D=λH/R_ЛРМ {м}, а на основании равенства

определяют фокусное расстояние объектива проектируемой ОЭА, как

{м}, затем, для оценки результатов проектирования ОЭА, формируют коэффициент совершенства проектируемой ОЭА, как отношение

, и, подставляя в него результаты проектирования: D и F, а также d и

, получают величину

, равную единице (К_С=1) при наличии согласования F_C=FK , что свидетельствует о совершенстве спроектированной ОЭА, согласованной по критерию Найквиста (

) и обеспечивающей достижение дифракционного предела инструментального разрешения МКА ДЗЗ на местности (

), далее, для реализации результатов проектирования, создают спроектированную ОЭА, содержащую выбранный цифровой детектор с пикселем d и объектив с диаметром D и фокусным расстоянием F, а для увеличения фокусного расстояния объектива до согласующей величины F_C=FK в ОЭА между объективом и цифровым детектором вводят фотоувеличительную оптику, совмещая ее оптическую ось с оптической осью объектива и размещая стандартные микро объективы (или линзы Барлоу) с увеличением М^Х=К между объективом и цифровым детектором ОЭА так, чтобы передний фокус фотоувеличительной оптики находился в фокальной плоскости объектива F, а задний фокус сборки объектива и фотоувеличительной оптики F_C находился в плоскости формируемых и детектируемых изображений, далее размещают созданную ОЭА на борту МКА ДЗЗ, выводят МКА на орбиту и осуществляют дистанционное зондирование наблюдаемых участков земной поверхности, для чего в режиме орбитальной ориентации МКА ДЗЗ производят его программные развороты вокруг центра масс в продольном направлении, и при этом, подлетая к объекту наблюдения на расстояние, равное высоте полета Н, МКА ДЗЗ наводит на него ОЭА и, препятствуя возникновению смазов изображений, удерживает ОЭА в направлении зондируемого участка до тех пор, пока не удалится от него на такое же расстояние Н, одновременно с этим на борту МКА ДЗЗ в узком поле зрения сборки объектив-фото увеличительная оптика и в широкой полосе спектральной чувствительности цифрового детектора

при

(где

, а

– дисперсия атмосферных искажений фазы θ светового излучения на апертуре D, всегда меньшая единицы в задачах ДЗЗ) регистрируют серию из N коротко-экспозиционных изображений зондируемого участка земной поверхности при τ_Э=τ_А=1мс (где τ_Э –время экспозиции регистрируемых изображений, а τ_А–интервал временной корреляции атмосферных флуктуаций), статистически независимых друг от друга по атмосферным искажениям при τ_П>τ_Д (где τ_П=6τ_К- промежуток между соседними регистрациями, τ_К – длительность кадра, а τ_Д–инерционность цифрового детектора) и передают их на землю для последующей обработки, при которой, сначала анализируют зарегистрированную серию из N дифракционно ограниченных, случайно сдвинутых и ослабленных атмосферой, малоконтрастных изображений и селектируют (отбирают) в ней М наиболее четких и контрастных изображений, отбраковывая размытые и зашумленные, затем суммируют отобранные изображения и формируют эталонное высококонтрастное изображение зондируемого участка земной поверхности, определяют по нему характерные особенности (опорные ориентиры) и сравнивают каждое из М отобранных селекцией коротко-экспозиционных изображений с эталонным, определяя в них характерные особенности эталона, далее сдвигают коротко-экспозиционные изображения, совмещая их характерные особенности с характерными особенностями эталона, и компенсируют при этом атмосферные сдвиги изображений, после чего накапливают сдвинутые дифракционно ограниченные изображения, увеличивая отношение сигнал/шум (контраст) результирующего изображения в

раз, и получают контрастное дифракционно ограниченное панхроматическое изображение зондируемого участка земной поверхности для картографирования и других задач ДЗЗ сверхвысокого разрешения, а, анализируя его через мультиспектральные узкополосные фильтры, осуществляют многозональную тематическую обработку, при которой в интересах различных потребителей отслеживают изменения состояний естественных и искусственных объектов на зондируемом участке земной поверхности.The technical result is achieved by the fact that, in order to match the lens and the digital detector of optical-electronic equipment (OEA) of the MCA ERS according to the Nyquist criterion, a digital detector with pixel d is selected, the sampling period of the digital detector 2d is determined and its projection is formed on the probed earth surface

, equate it to the required linear resolution and the diffraction limit of resolution of the MCA ERS on the ground

, Where

_...average wavelength of solar radiation illumination in the visible wavelength range Δλ_IN= (0.43 ÷ 0.73) μm, and based on the equality

determine the required diameter of the lens aperture of the projected OEA, as D = λH / R_LRM{m}, and on the basis of equality

determine the focal length of the lens of the projected OEA, as

{m}, then, to evaluate the design results of the OEA, the coefficient of perfection of the designed OEA is formed as the ratio

, and, substituting the design results into it: D and F, as well as d and

, get the value

equal to one (K_FROM= 1) in the presence of agreement F_C= FK, which indicates the perfection of the designed OEA, consistent with the Nyquist criterion (

) and ensuring the achievement of the diffraction limit of the instrumental resolution of the ERS small spacecraft on the ground (

), then, to implement the design results, create a designed OEA containing a selected digital detector with a pixel d and a lens with a diameter D and a focal length F, and to increase the focal length of the lens to a matching value F_C= FK in the OEA between the lens and the digital detector, photographic magnifying optics are introduced, aligning its optical axis with the optical axis of the lens and placing standard micro lenses (or Barlow lenses) with magnification M^X= K between the lens and the digital detector OEA so that the front focus of the magnifying optics is in the focal plane of the lens F, and the back focus of the lens assembly and the magnifying optics is F_C was in the plane of the generated and detected images, then the created OEA is placed on board the ERS spacecraft, the spacecraft is placed into orbit and remote sensing of the observed areas of the earth's surface is carried out, for which, in the orbital orientation mode, the ERS spacecraft performs programmed turns around the center of mass in the longitudinal direction, and at the same time, flying up to the object of observation at a distance equal to the flight altitude H, the ERS MCA directs the OEA at it and, preventing the appearance of image smears, keeps the OEA in the direction of the sounded area until it moves away from it at the same distance H, simultaneously with this, on board the ERS small spacecraft in a narrow field of view of the lens-photo assembly magnifying optics and in a wide spectral sensitivity band of a digital detector

at

(Where

, and

- the dispersion of atmospheric distortions of the phase θ of the light radiation at the aperture D, always less than unity in ERS problems) a series of N short-exposure images of the probed area of the earth's surface is recorded at τ_E= τ_AND= 1ms (where τ_EIs the exposure time of the recorded images, and τ_ANDIs the interval of time correlation of atmospheric fluctuations), statistically independent of each other in terms of atmospheric distortions at τ_P> τ_D (where τ_P= 6τ_TO- the interval between adjacent registrations, τ_TOIs the frame duration, and τ_D- the inertia of the digital detector) and transmit them to the ground for subsequent processing, in which, first, the registered series of N diffraction limited, randomly shifted and weakened by the atmosphere, low-contrast images is analyzed and M of the clearest and most contrasting images are selected (selected) in it, rejecting blurry and noisy, then summarize the selected images and form a reference high-contrast image of the probed area of the earth's surface, determine from it the characteristic features (reference landmarks) and compare each of the M short-exposure images selected by selection with the reference, defining the characteristic features of the reference in them, then shift shortly -exposure images, combining their characteristic features with the characteristic features of the reference, and compensate for the atmospheric shifts of the images, after which the shifted diffraction-limited images are accumulated, increasing the signal-to-noise ratio (contrast) to the cut flipping image into

times, and receive a contrast diffraction limited panchromatic image of the probed area of the earth's surface for mapping and other tasks of ultra-high resolution ERS, and analyzing it through multispectral narrow-band filters, they carry out multi-zone thematic processing, in which, in the interests of various consumers, changes in the states of natural and artificial objects are monitored probed area of the earth's surface.

The features and essence of the claimed invention are illustrated in the following detailed description, illustrated by the drawings, which shows the following:

Figure 1 shows a variant of the scheme of the practical implementation of the proposed method, which shows:

Fig. 1a - Block diagram of the ERS imaging channel, where:

1 - mirror telescopic lens with aperture diameter D and focal length F, built according to the Ritchie-Chrétien or Doll-Kirkham scheme and made entirely of silicon carbide (SiC), which ensures its small dimensions and weight required for the creation of an ERS small spacecraft;

2 - focal plane of the lens F;

3 - photomagnification optics (M ^X = K), which ensures the matching of the lens and the digital detector according to the Nyquist criterion. Standard micro-lenses or Barlow lenses can be used as photomagnification optics;

4 - focal plane of matching photo-magnifying optics (plane of formed and detected images) F _C (F _C = FK);

Fig.1b - Block diagram of the channel for detecting and registering ERS images, where:

4 - the plane of the formed and detected images F _C ;

5 - electromechanical shutter, which selects the exposure time of each recorded frame τ _E less than the time of "freezing" of atmospheric turbulence τ _A = 1 ms (τ _E ≤ τ _A ), ensuring the absence of time averaging of atmospheric distortions and possible smears of each recorded image. When registering a series of short-exposure images, it is necessary to ensure their statistical independence from each other in terms of atmospheric distortions. To do this, it is required to choose the time interval between individual short-exposure recordings in the series τ _P , exceeding the inertia of the digital detector τ _D. Due to the inertia of the digital detector 6, a charge from 4 to 5 previous frames can be retained on its target during registration of subsequent frames, which can lead to the accumulation and averaging of recorded short-exposure images. To eliminate the influence of the inertia of the detector, it is proposed to register sample frames, and not all in a row, and between registrations to clear the detector from residual charge.

The shutter 5, implementing the “sampling frame” strategy, exposes only one frame of the digital detector out of every eight.

With a 14% detection cycle performance set by the shutter, only 7 frames per second are practically recorded with a time interval between the exposed images τ _P = 6τ _K = 120 ms, where τ _K is the time of one frame, τ _K = 20 ms at a frame rate of 50 Hz for a CCD matrix. For a CMOS matrix with a frame rate of 33Hz and τ _K = 30 ms, 7 frames per second are recorded with a detection cycle rate of 21% and the same interval between registrations τ _P = 4τ _K = 120 ms. The presence of such an interval between registrations τ _P > τ _D contributes to the fact that the recorded images are independent from each other in terms of atmospheric distortions, and also free from the effects of inertia of the digital detector. Both of these facts testify to the absence of time averaging of the images initial for processing the series;

6 - digital detector {CCD matrix or CMOS matrix} (CMOS - complementary metal-oxide-semiconductor structure) with a sampling element (pixel) d is designed to detect and register a series of N short-exposure, statistically independent images. With the "sample frame" detection strategy, the digital detector 6 operates as follows:

frame 1 - the disk of the rotating light chopper (shutter 5) synchronized with the frame rate of the digital detector,

opens the photocathode for the exposure time τ _E , consistent with the time correlation interval of atmospheric fluctuations τ _A , τ _E = τ _A = 1 ms. During this exposure interval, the reading beam of the digital detector 6 is blocked by a control strobe pulse;

frame 2 - the reading beam is switched on, and the silicon surface of the target of the digital detector 6 is read into the digital video signal processing system 7;

frame 3 - the LED flashes, saturating the silicon surface of the target of the digital detector 6 and ensuring the uniformity of the subsequent erasure of the target without image residues;

frames 4, 5, 6, 7, 8 - the usual readout of the target, as in frame 2, in order to completely discharge its silicon surface, when the shutter 5 of the photocathode of the digital detector 6 is closed.

Thus, frame 1 is used to record the generated image on the target, frame 2 is used to read the image from the target and generate a video signal, and frames 3 to 8 are used to saturate and erase the target of the digital detector 6;

7 - digital video signal processing system is designed to digitize a series of N short-exposure images coming from a digital detector 6. Digitized 7 images of the probed area of the earth's surface are recorded in the buffer memory of the on-board computer 8;

8 - the on-board computer performs software turns of the ERS MCA around the center of mass to slow down the motion of the detected images along the input matrix of the digital detector and transfers the digitized images from the buffer memory to the encoder 9;

9 - the encoder compresses and encodes information for transmission to the Earth;

10 - the onboard radar transmitter transmits information from the encoder 9 via a radio link to the Earth for subsequent image processing.

The processing of a series of short-exposure, statistically independent in atmospheric distortions images of the probed area of the earth's surface, obtained on board the ERS satellite in accordance with Fig. 1a and Fig. 1b and transmitted via a radio link, is carried out on the Earth according to the scheme shown in Fig. 1c.

Here, Fig. 1c is a block diagram of the ERS image processing channel, on which:

11 - a ground-based radar receiver receives information from an on-board radar transmitter 10 via a radio link;

12 - the decoding device converts the information received in 11 to a form convenient for recording in the memory of computing means 13;

13 - computing facilities, computers, are designed to implement on the Earth the algorithm 15 for processing a series of images from the ERS small spacecraft;

14 - software (SW) of computing facilities 13 is intended for organizing the operation of computing facilities and, in particular, for the implementation of the algorithm 15 for processing ERS images;

15 - the ERS image processing algorithm represents the proposed sequence of operations over the registered series of "instantaneous" (short-exposure) images, ensuring the achievement of the maximum (diffraction) limit of the resolution of the ERS MCA on the ground and increasing the contrast of the ERS images in conditions of atmospheric distortion;

16 - the operator's workstation is designed to control the image processing process and analyze their quality (resolution and contrast) in the process of implementing the algorithm 15 for processing remote sensing images;

<1м), а также информации многозональной тематической обработки.17 - consumers of panchromatic ERS images of high contrast and ultra-high resolution (R _LRM

<1m), as well as information of multispectral processing.

Figure 2 presents the Criteria for assessing the limiting instrumental resolution of the OEA of the ERS spacecraft on the ground: a) in analogs (GSD criterion) and b) in the claimed method (RCS criterion).

Table 1 shows the OEA perfection coefficients of the existing ultra-high resolution ERS spacecraft, designed using the GSD criterion.

For all these ERS spacecraft, the perfection coefficient is more than two (K> 2), which indicates the imperfection of the designed OEA, since in a perfect OEA, agreed according to the Nyquist criterion, the perfection coefficient is equal to one (K _C = 1).

Figure 3 shows a block diagram of the implementation of the proposed method in terms of the design of the OEA based on the criterion for assessing the limiting instrumental resolution of MCA ERS on the ground - RKS (R _{2dH / F} ).

Fig. 4 presents a block diagram of the processing algorithm-15 (Fig. 1c) of the registered series of N short-exposure images of the probed area of the earth's surface.

Figure 5 shows the geometry of Earth remote sensing (ERS).

The operation of the Earth remote sensing system according to the structural diagrams shown in FIG. 1 is generally carried out as in the prototype.

The difference from the prototype here lies, firstly, in the sequence of operations of the perfect design (Fig. 3) of the optoelectronic equipment (OEA) for image acquisition (Fig. 1a), based on the determination of the required parameters (D and F) of the OEA lens and the Nyquist criterion lens OEA with the selected digital detector OEA, having a pixel d, by the required increase in the focal length of the lens to the matching value F _C = FM ^X , obtained on the basis of the RKS criterion (Fig. 2) assessing the limiting instrumental resolution of the ERS MCA on the ground and ensuring the achievement of the diffraction limit instrumental resolution of MCA ERS on the ground.

The second significant difference between the proposed method and the prototype is the sequence of processing operations for the resulting series of short-exposure images (Fig. 4).

The first technology of the proposed method (the technology of perfect design of the OEA for obtaining images) is hardware, and the second technology of the proposed method (image processing technology) is algorithmic, and only together they ensure the achievement of the diffraction limit of the linear resolution of the ERS MCA on the ground and high contrast of the ERS images in the presence of atmospheric distortion.

Let us give a rationale for the proposed method, both in terms of the perfect design of the OEA for obtaining images, matched by the Nyquist criterion with photo-magnifying optics 3 (Fig. 1a), and in terms of algorithmic support 15 (Fig. 1c) of processing the series registered in 6 (Fig. 1b) from N short-exposure remote sensing images.

Let's start with the new hardware technology of the proposed method in terms of designing the OEA for image acquisition, based on a new criterion (DCS criteria) for assessing the ultimate instrumental resolution of the Earth remote sensing spacecraft on the ground [11] and consider its implementation according to the block diagram shown in Fig. 3

It is known that the most informative and demanded by consumers ERS product is an optical image of the probed area of the earth's surface. There are various criteria for assessing the quality of optical images, however, not many of them are suitable for assessing the efficiency of observational optical systems. The studies carried out [15] (Wetserell U., Image quality assessment, ch. 6, in the book. Edited by R. Shannon, J. Wyant, Design of optical systems, 1983, M., ed. Mir.) Indicate that that the most universal criterion characterizing both the image quality of an object and the efficiency of its observation system is the resolution. The limiting value of the instrumental resolution of the ERS small spacecraft on the ground depends on the degree of agreement between the lens and the digital detector OEA according to the Nyquist criterion and can vary from some real value of the instrumental resolution limit of the ERS small spacecraft on the ground to the value of the maximum (diffraction) limit of the instrumental resolution. The choice of the criterion for evaluating the resolution determines both the correctness of determining the real limit of the instrumental resolution of the ERS spacecraft on the ground in the process of observation, and the possibility of matching the objective 1 and the digital detector 6 OEA according to the Nyquist criterion in the process of designing the OEA.

With the advent of digital detectors, new criteria for assessing the ultimate instrumental resolution of ERS spacecraft on the ground have appeared. Today, the projection of one pixel of the digital detector d onto the probed earth surface is used as the main criterion for assessing the limit of the instrumental resolution of an ERS spacecraft on the ground [5]. This limit of spatial resolution on the ground is determined by the ratio

{м},(1)

{m}, (1)

where H is the height of the ERS spacecraft above the probed earth surface.

Criterion (1) for assessing the ultimate instrumental resolution of an ERS spacecraft on the ground was adopted in ERS practice with the advent of digital detectors: first abroad, where it was named GSD [16] (Ground Sample Distance (GSD) Support (http: //support.pix4d .com / he / en-us / articles / 202559809), and later, without any justification of the legality of its use to assess the linear resolution on the ground, it was adopted in the Russian practice of remote sensing [17] (Khmelevskoy S.I., Trends in the development of digital aerial survey systems. Criteria for comparison and evaluation, Geoprofi, 2011, No. 1, p.11).

The disadvantage of the GSD criterion (1) is that it gives an optimistic but erroneous estimate of the linear resolution on the ground, leading to limitations (imperfection) of the design based on it [12].

всегда меньше реального линейного разрешения

R_ЛРМ данных ДЗЗ на местности [18] (Замшин В.В. Методы определения линейной разрешающей способности оптических и радиолокационных аэрокосмических изображений, Известия ВУЗов, Геодезия и аэрофотосъемка, 2014, №1, с.43).Experiments on the assessment of the limiting instrumental resolution of the ERS spacecraft on the ground in the optical and radio wavelength ranges indicate that in reality the size of the projection of a pixel on the Earth

always less than real linear resolution

R _LRM of remote sensing data on the ground [18] (Zamshin VV Methods for determining the linear resolution of optical and radar aerospace images, Izvestiya VUZov, Geodesy and aerial photography, 2014, No. 1, p.43).

. Существует мнение [18], что такой подход к оценке разрешения КА ДЗЗ на местности «…используется для преднамеренного завышения декларируемых технических характеристик средств ДЗЗ по сравнению с их реальными показателями, чтобы повысить коммерческую привлекательность продуктов ДЗЗ на потребительском рынке…».At present, however, contrary to the results of numerous experiments, as an estimate of the limiting value of the linear resolution of digital ERS systems on the ground, they continue to stubbornly use the projection of one pixel of a digital detector onto the probed earth surface GSD (1), that is, in practice, there is an unjustified and unjustified identification of the concepts of linear resolution on the ground R _LRM and the size of the projection of a pixel on the Earth

... There is an opinion [18] that such an approach to assessing the resolution of an ERS spacecraft on the ground "... is used to deliberately overestimate the declared technical characteristics of ERS equipment in comparison with their real performance in order to increase the commercial attractiveness of ERS products in the consumer market ...".

This discrepancy between the estimates of the GSD criterion (1) and the experimental results stimulated us to conduct research, which was the basis of the proposed method in terms of designing an OEA for obtaining remote sensing images.

R_ЛРИ определяется периодом штриховой миры, то есть суммой светлой и темной линий

, где р –размер светлой или темной линии – минимального разрешаемого элемента штриховой миры. При этом линейное разрешение на местности

аналогового изображения ДЗЗ определяется проекцией линейного разрешения в изображении

на зондируемую земную поверхность, как [21]It is known [19] (Characteristics of the image quality on the website of the STC Krasnogorsk plant named after S.A. Zverev (http://www.zenithcamera.com/qa/qa-resolution.html) that the definition of the linear resolution of analog photographic domestic and foreign practice differ at the level of standards: GOST and ISO. Indeed, the Russian standard in accordance with GOST 15114-78 [20] ("Telescopic systems for optical devices. Visual method for determining the resolution limit", Introduced 30.01.1978. M. : Publishing house of standards, 1978.6s.) Establishes that the linear resolution in the image

R _{LRI is} determined by the period of the dashed _target , that is, the sum of the light and dark lines

, where p is the size of the light or dark line - the minimum resolvable element of the dashed target. In this case, the linear resolution on the ground

analog ERS image is determined by the linear resolution projection in the image

on the sounded earth surface, as [21]

{м} (2)

{m} (2)

[21] (Kononov V., Fundamentals of the methodology for calculating the resolution and accuracy of determining the coordinates of aerial phototopographic systems. (Http://www.geomatika.kiev.ua/training/DataCapture/RemoteSensing/Chapter103.html).

In cases of digital imaging, the size of the minimum resolvable element in the image p is equal to the pixel size d of the digital detector. In this case, the formula for linear resolution on the ground (2) is transformed to the form

{м} (3)

{m} (3)

, и есть новый критерий оценки предельного инструментального разрешения КА ДЗЗ на местности, интуитивно предложенный в АО «Российские космические системы» (критерий РКС), ранее [11].The obtained expression for evaluating the linear resolution of the Earth remote sensing spacecraft on the ground, as the projection of the sampling period of the digital detector 2d onto the probed earth surface

, and there is a new criterion for assessing the limiting instrumental resolution of the ERS spacecraft on the ground, intuitively proposed at JSC Russian Space Systems (DCS criterion), earlier [11].

Here, this criterion (3) is obtained analytically on the basis that the sampling period (two pixels) of the digital detector, like its projection onto the probed earth surface, for digital ERS images, is equivalent to the period (the sum of light and dark lines) of the dashed world used for determination of linear resolution on the ground of analogue remote sensing photographs in accordance with the current Russian standard for assessing resolution [20].

At the same time, it is obvious that one pixel d in the digital image, as well as its projection onto the probed earth surface (GSD criterion), corresponds to half the period of the dashed target of the analog image, that is, the GSD is equivalent to one (light or dark) line of the dashed target and cannot evaluate the permit in accordance with Russian GOST [20].

Abroad, the introduction of the GSD criterion into ERS practice, apparently, was associated with foreign resolution standards, in accordance with which one line (light or dark) of the dashed target is taken as the value of the linear resolution in the image, as in the field. In this regard, in [19] it was noted that “... in the foreign standardized for video and digital photographic equipment (see, for example, ISO 12231, ISO 12233), the term“ pair of lines ”for a“ line ”is also considered the interval between the strokes of the world , which is physically incorrect, since in this case the spatial frequency turns out to be inverse to the half-period of the world ... ". This qualitatively testifies to the erroneousness of the GSD criterion and the design based on it. Quantitative confirmation will be given below.

Figure 2 is an illustration of the criteria for evaluating GSD and PKC.

Along with the considered criteria for assessing the spatial resolution of the ERS MCA on the ground (1) and (3), there is a diffraction limit for the instrumental resolution of the MCA ERS objective on the ground, which determines the potential OEA to achieve the maximum resolution limit of the MCA ERS on the ground in accordance with the well-known formula [ 15]

{м}(4)

{m} (4)

It should be noted that the diffraction resolution limit (4) can only be achieved when the lens and the digital detector are matched according to the Nyquist criterion [15], when at least two resolution elements fall on the diffractive lens element in the image (Airy disk) λF / D (pixel) 2d digital detector.

к дифракционному пределу разрешения R_λH/D МКА ДЗЗ на местности или , что эквивалентно , как отношение частоты отсечки объектива ОЭА f_D=D/λF к частоте Найквиста цифрового детектора ОЭА f_N=f_1/d/2=1/2dTo assess the degree of agreement between the lens and the digital detector of the projected OEA according to the Nyquist criterion, the concept of the coefficient of perfection of the OEA MCA ERS was introduced [12] as the ratio of the assessment of the RCS of the maximum instrumental resolution of the MCA ERS on the ground

to the diffraction resolution limit R _{λH / D} MCA ERS on the ground or, which is equivalent, as the ratio of the cutoff frequency of the OEA objective f _D = D / λF to the Nyquist frequency of the digital detector OEA f _N = f _{1 / d} / 2 = 1 / 2d

, (5)

, (five)

where K≥1

In the optimally designed OEA, consistent with the Nyquist criterion, the perfection coefficient is equal to one (K _C = 1) and, at the same time, from formula (5) it follows

, (6)

, (6)

,Where

,

, следует, что

, то есть, достигается дифракционный предел инструментального разрешения.which confirms the agreement of the lens and the digital detector OEA according to the Nyquist criterion, as well as, based on

, follows that

, that is, the diffraction limit of the instrumental resolution is reached.

позволяет согласовать проектируемую ОЭА по критерию Найквиста и обеспечить достижение дифракционного предела инструментального разрешения КА ДЗЗ на местности.The obtained result (6) indicates that the assessment criterion proposed by the RCC

allows matching the projected OEA according to the Nyquist criterion and ensuring the achievement of the diffraction limit of the instrumental resolution of the ERS spacecraft on the ground.

(1) к дифракционному пределу разрешения КА ДЗЗ на местности

(4) или, что эквивалентно, отношением частоты отсечки объектива ОЭА

к частоте дискретизации цифрового детектора ОЭА f_1/d=1/dTo compare the design results by the proposed method with the design results based on the GSD criterion, consider the coefficient of design excellence for the OEA prototype, denote it by K _O introduced by the GSD resolution

(1) to the diffraction limit of the ERS spacecraft resolution on the ground

(4) or, which is equivalent, the ratio of the cutoff frequency of the lens OEA

to the sampling rate of the digital detector OEA f _{1 / d} = 1 / d

, (7)

, (7)

where K _O ≥1.

The situation when K _O = 1 represents the boundary of applicability of the GSD criterion for assessing the instrumental resolution of remote sensing systems on the ground for the design of OEA, when d = λF / D, since when K _O <1, the GSD estimate becomes less than the diffraction limit, which contradicts the physical meaning.

Comparison of (5) and (7) implies that

К = 2К _О , (8)

and the limitation set by the GSD criterion on the value of K _O , namely K _O ≥1, imposes a limitation on the perfection coefficient K (5)

K ≥2 (9)

The resulting constraint (9) on the perfection of the designed OEA, due to the use of the GSD criterion, is confirmed by the real values of the OEA perfection coefficients greater than two (K> 2) for all existing foreign and domestic ultra-high resolution ERS spacecraft designed using the GSD criterion (Table 1) ...

Based on the studies carried out and the data in Table 1, it is obvious that using the GSD criterion to assess the maximum instrumental resolution of the ERS small spacecraft on the ground, it is impossible to achieve the OEA perfection factor equal to one (K _C = 1) when designing the OEA, that is, it is impossible to agree on the OEA according to the Nyquist criterion and achieve the diffraction limit of the resolution of the ERS MCA on the ground.

In fact, the coefficient K of OEA perfection, different from 1, characterizes the degree of imperfection of the designed OEA, and this applies to the entire designed OEA of the existing ultra-high resolution ERS spacecraft (Table 1).

), предложенного в работе [11] и обоснованного в работе [12]:Let us consider the proposed sequence of operations for the design of the OEA MCA ERS, based on the DCS criterion (

) proposed in [11] and substantiated in [12]:

, Н=600км, λ=0,6мкм;1) receive passport data for the remote sensing spacecraft, for example, such as:

, H = 600km, λ = 0.6μm;

2) choose a digital detector, for example, with the size of the spatial resolution element (pixel) equal to d = 4.6 μm;

, d, Н, и λ;3) determine the initial data for the design of the OEA MCA ERS, such as:

, d, H, and λ;

;4) form a projection of the sampling period of the digital detector 2d onto the probed earth surface

;

к требуемому линейному разрешению МКА ДЗЗ на местности5) equate the formed assessment

to the required linear resolution MCA ERS on the ground

(10)

(ten)

6) determine the diffraction resolution of the OEA MKA ERS lens on the ground R _{λH / D} and

7) equate it to the required linear resolution of the MCA ERS on the ground

(11)

(eleven)

8) based on the required diffraction resolution of the OEA lens on the ground (11), determine the required diameter of the lens aperture D, as

{м} (12)

{m} (12)

получают D=0,6м;and after substitution of the initial data: λ = 0.6 μm, Н = 600 km and

get D = 0.6m;

9) proceeding from equality (10), determine the focal length of the lens matching the OEA according to the Nyquist criterion, as

{м} (13)

{m} (13)

and after substitution of the initial data: d = 6mkm, H = 600km. R _LRM = 0.6 m, get F = 9.2 m;

10) to control the design results, the coefficient of perfection of the designed OEA is determined, as

(14)≡(5)

(14) ≡ (5)

11) substituting the data of the designed OEA (d = 4.6 μm, D = 0.6 m, F = 9.2 m, λ = 0.6 μm) into formula (14), the coefficient of perfection of the designed OEA is equal to one (K _C = 1 ), i.e,

, (15)

, (15)

where F _C = FK _C = 9.2m-matching focal length.

In the general case, the focal length F _C , which matches the OEA according to the Nyquist criterion, is determined as F _C = F K, (where F is the focal length of the lens in the projected OEA that is not Nyquist-matched) and for the existing ultra-high resolution ERS spacecraft F _C is presented in the right column Tables 1.

, (16), а

(17)Based on (15)

, (16), and

(17)

The resulting expression (16) is nothing more than a condition for matching the OEA MCA ERS according to the Nyquist criterion, when the diffractive lens resolution element ( _Airy disk) R _{λFс / D} in the image contains two resolution elements of the digital detector 2d .;

So, it was found that the projected OEA is perfect (K = 1) (15), matched according to the Nyquist criterion (16) and ensures the achievement of the diffraction limit of the instrumental resolution (17), while for it it was obtained:

(18)D = 0.6m, F _C = 9.2m, d = 4.6μm,

(18)

Obviously, the ERS small spacecraft at H = 600 km, λ = 0.6 μm and D = 0.6 m is located on the border of the Fresnel (near zone) and Fraunhofer (far zone) zones, defined as D ² / λ, and equal to 600 km = H ... In this case, the image plane coincides with the focal plane of the lens, and there is no defocusing of the formed ERS images. Therefore, the OEA MKA ERS does not require a control and focus control system on board, which significantly reduces its weight and dimensions (OEA).

The sequence of operations 1) ÷ 11) of the proposed OEA design method is presented in Fig. 3, and the resulting OEA design is presented in Fig. 1a and Fig. 1b.

между объективом 1 и цифровым детектором 6 вводят фотоувеличительную оптику 3 с коэффициентом увеличения

, равным коэффициенту совершенства проектируемой ОЭА, совмещая оптическую ось фотоувеличительной оптики с оптической осью объектива и размещая ее так, чтобы плоскость формируемых и детектируемых изображений 4, находилась в задней фокальной плоскости F_C сборки объектива 1 и фотоувеличительной оптики 3, а передний фокус фото увеличительной оптики 3 находился в фокальной плоскости 2(F) объектива 1. В качестве фотоувеличительной оптики можно использовать линзы Барлоу или стандартные микрообъективы, давно и успешно используемые для увеличения фокусного расстояния объектива в астрономии. Далее создают спроектированную ОЭА, размещают ее на борту МКА ДЗЗ, выводят МКА на орбиту и осуществляют дистанционное зондирование наблюдаемых участков земной поверхности, для чего в режиме орбитальной ориентации МКА ДЗЗ производят его программные развороты вокруг центра масс в продольном направлении, и при этом, подлетая к объекту наблюдения на расстояние, равное высоте полета Н, МКА ДЗЗ наводит на него ОЭА и удерживает ее в направлении зондируемого участка до тех пор, пока МКА не удалится от него на такое же расстояние Н. Это снижает скорость скольжения изображения зондируемого участка земной поверхности по приемной матрице цифрового детектора, что препятствует возникновению смаза регистрируемых изображений. Одновременно с этими разворотами, на борту МКА ДЗЗ в узком (изопланатичном) поле зрения фотоувеличительной оптики 3 получают серию из N коротко-экспозиционных (τ_Э≤τ_А) в 5,6 (Фиг.1б) изображений зондируемого участка земной поверхности, статистически независимых по атмосферным искажениям (τ_П=6τ_К) и передают их по радиолинии 10,11 (Фиг.1б,в) на Землю для последующей обработки в соответствии с алгоритмическим обеспечением 15 (Фиг1в).Here (Fig. 1a) for the required increase in the focal length of the lens F to the matching value

between objective 1 and digital detector 6, photo-magnifying optics 3 with a magnification factor

equal to the coefficient of perfection of the projected OEA, aligning the optical axis of the magnifying optics with the optical axis of the lens and placing it so that the plane of the formed and detected images 4 is in the rear focal plane F _C of the lens assembly 1 and the magnifying optics 3, and the front focus of the photo magnifying optics 3 was located in the focal plane 2 (F) of the lens 1. Barlow lenses or standard micro-lenses, which have been successfully used for a long time to increase the focal length of a lens in astronomy, can be used as a magnifying optics. Next, they create the designed OEA, place it on board the ERS spacecraft, put the spacecraft into orbit and carry out remote sensing of the observed areas of the earth's surface, for which, in the orbital orientation mode, the ERS spacecraft make its programmed turns around the center of mass in the longitudinal direction, and at the same time, flying up to to the object of observation at a distance equal to the flight altitude H, the ISA ERS directs the OEA at it and holds it in the direction of the sounded area until the ISA moves away from it at the same distance H. This reduces the sliding speed of the image of the sounded area of the earth's surface along the receiving matrix of the digital detector, which prevents blurring of the recorded images. Simultaneously with these turns, a series of N short-exposure (τ _E ≤τ _A ) 5.6 (Fig. 1b) images of the probed area of the earth's surface, statistically independent, is obtained on board the ERS in a narrow (isoplanatic) field of view of the magnifying optics 3 by atmospheric distortions (τ _P = 6τ _K ) and transmit them via radio link 10.11 (Fig. 1b, c) to the Earth for further processing in accordance with algorithmic support 15 (Fig. 1c).

Let us give a brief justification of the algorithmic technology of the proposed method in terms of the processing algorithm 15 of the resulting series of "instantaneous", statistically independent images and consider its implementation according to the block diagram shown in Fig.4.

атмосферных искажений фазы Ө волнового фронта светового излучения на приемной апертуре телескопа D, определяемая, как [22]The proposed method for compensating for atmospheric distortions is based on a probabilistic approach to achieving the diffraction resolution of an ERS MCA in conditions of atmospheric distortions. The essence of this approach is that, due to the randomness of instantaneous atmospheric distortions, there is a possibility that at some moments in time these distortions at the telescope's receiving aperture may be negligible. In this case, either the instantaneous dispersion

atmospheric distortions of the phase Ө of the wavefront of light radiation at the receiving aperture of the telescope D, defined as [22]

[рад]² (19)

[happy] ² (19)

) , либо величина мгновенного пространственного радиуса корреляции атмосферных искажений поля светового излучения

_O оказывается больше величины диаметра приемной апертуры телескопа D

>D). Коротко-экспозиционные (τ_Э<τ_А) изображения объекта, регистрируемые в эти моменты времени, при отсутствии какого-либо усреднения атмосферных искажений (Δλ<Δλ_А и τ_П=6τ_К>τ_Д), могут характеризоваться дифракционным разрешением, но только при наличии рассмотренного выше согласования ОЭА по критерию Найквиста. [22] (Greenwood D.P., Fried D.L., "Power Spectrum Requirements for Wavefront Compensative Systems", J. Opt. Soc. Am., 1976, v. 66, p. 193), turns out to be less than one (

), or the value of the instantaneous spatial correlation radius of atmospheric distortions of the light radiation field

_O turns out to be larger than the diameter of the receiving aperture of the telescope D

> D). Short exposure (τ_E<τ_AND) images of the object recorded at these times, in the absence of any averaging of atmospheric distortions (Δλ <Δλ_AND and τ_P= 6τ_TO> τ_D), can be characterized by diffraction resolution, but only in the presence of the above-considered OEA matching according to the Nyquist criterion.

_O>D) в зависимости от соотношения пространственных характеристик атмосферы и телескопа, что позволит оценить среднее число коротко-экспозиционных изображений К~1/Р(

>D), которое необходимо зарегистрировать, чтобы получить среди них хотя бы одно дифракционно ограниченное.Let us investigate the probability of such situations Р (

_O> D) depending on the ratio of the spatial characteristics of the atmosphere and the telescope, which will make it possible to estimate the average number of short-exposure images K ~ 1 / P (

> D), which must be registered in order to obtain at least one diffraction limited one among them.

подчиняется гамма - распределению вероятности Р(

).The analysis carried out in [23] (Sviridov K.N., Bakut P.A., Polskikh S.D., Khomich N.Yu., "Study of a probabilistic approach to achieving diffraction resolution of optical systems under atmospheric vision", Optics atmosphere, 1989, vol. 2, no. 1, p. 41), showed that the random variable

obeys the gamma - probability distribution P (

).

In accordance with the above-mentioned need to satisfy the inequality

, (20)

, (20)

, как [23]ensuring the achievement of diffraction resolution, it was natural to determine the probability of good vision through the gamma distribution

like [23]

(21)

(21)

, получена следующая эмпирическая формула оценки вероятности хорошего видения при D>3,5

As a result of the studies [23], the probabilities of good vision of ground-based optical systems for observing outer space, for which D>

, the following empirical formula was obtained for assessing the probability of good vision at D> 3.5

(22)

(22)

имеем

, a K=8; при

имеем

, a K=64; при

имеем

, a K=794; при

имеем

, a K=15823 и т.д. Отсюда видно, что для достижения пятикратного выигрыша в разрешении, то есть, для достижения дифракционного разрешения при (D/

)=5, необходимо в среднем зарегистрировать не менее К=64 коротко-экспозиционных изображений; при (D/

6 необходимо зарегистрировать не менее К=794 коротко-экспозиционных изображений, а при (D/

)=10 и более требуемое число регистрируемых изображений объекта становится настолько большим (К≥1,96·10⁹), что описанный вероятностный подход в астрономии и оптических системах контроля космического пространства оказывается практически нереализуемым на современных телескопах больших диаметров.Based on this formula, the probabilities of good vision from the Earth through the turbulent atmosphere of space objects were calculated, and it was obtained that:

we have

, a K = 8; at

we have

, a K = 64; at

we have

, a K = 794; at

we have

, a K = 15823, etc. Hence, it can be seen that in order to achieve a fivefold gain in resolution, that is, to achieve diffraction resolution at (D /

) = 5, it is necessary to register at least K = 64 short-exposure images on average; for (D /

6 it is necessary to register at least K = 794 short-exposure images, and at (D /

) = 10 or more, the required number of registered images of an object becomes so large (K≥1.96 · 10 ⁹ ) that the described probabilistic approach in astronomy and optical control systems of outer space is practically unrealizable on modern telescopes of large diameters.

пространственных радиусов корреляции атмосферных искажений поля светового излучения увеличивается при распространении светового излучения от турбулентного слоя атмосферы (L_А=10км) у земной поверхности до МКА ДЗЗ, находящегося на высоте Н (например, Н=600км), и определяется по формуле [6], какIn the problem of remote sensing of the Earth considered here, on the contrary, the situation with the probabilistic achievement of diffraction resolution under atmospheric vision conditions turns out to be exactly the opposite. This is due to the fact that the value of the average r _O and instantaneous

spatial radii of correlation of atmospheric distortions of the light radiation field increases with the propagation of light radiation from the turbulent layer of the atmosphere (L _A = 10 km) near the earth's surface to the ERS small spacecraft located at an altitude of H (for example, H = 600 km), and is determined by the formula [6], as

, где

(23)

where

(23)

This is because within the Fresnel zone (at H = 600 km, λ = 0.6 µm, D = 0.6 m), a diverging spherical wave propagates from each point of the probed earth surface in the direction of the ERS small spacecraft, and the wavefront distortions acquired by it in within the turbulent layer L _A , as it propagates to the height H MCA ERS spatially increase (Figure 5).

Based on (23), it is easy to verify that for L _А = 10 km and Н = 600 km, the value of r _O (λ, H) is equal to

(24)

(24)

, существенно больше диаметра апертуры объектива МКА ДЗЗ, полученного выше и равного D=0,6м. В этих условиях, когдаThis result indicates that the average value r _O (λ, H), as well as the instantaneous value

, is significantly larger than the aperture diameter of the lens MCA ERS, obtained above and equal to D = 0.6m. Under these conditions, when

, (25)

, (25)

и

, то есть, каждое зарегистрированное коротко-экспозиционное изображение в серии при отсутствии пространственного усреднения атмосферных искажений (25) оказывается дифракционно ограниченным, но случайно сдвинутым, при выполнении упомянутых выше требований: согласования ОЭА по критерию Найквиста (2d=λF_С/D) и отсутствия временного и частотного усреднения атмосферных искажений (τ_Э<τ_А, τ_П=6τ_К; Δλ<Δλ_А).atmospheric distortions at the receiving aperture of the lens OEA MCA ERS are random tilts of the wavefront (Fig. 5), leading to random shifts of short-exposure images. Moreover (25) the probability of good vision

and

, that is, each recorded short-exposure image in a series in the absence of spatial averaging of atmospheric distortions (25) turns out to be diffraction limited, but randomly shifted, when the above requirements are met: OEA matching according to the Nyquist criterion (2d = λF _С / D) and the absence time and frequency averaging of atmospheric distortions (τ _Э <τ _А , τ _П = 6τ _К ; Δλ <Δλ _А ).

Let us estimate the value of the spectral band Δλ (Δλ <Δλ_AND), ensuring the absence of frequency averaging of atmospheric distortions in ERS systems.

In accordance with previous studies [24] (Sviridov KN, Bakut PA, Belkin ND, Ustinov ND, "Statistical assessment of the spectral band of the spot interferometry method", Optics and Spectroscopy, 1983, 54, issue 5, p.890), it was found that the optimal spectral filtering band of the received light radiation Δλ, which ensures the absence of frequency averaging of atmospheric phase distortions in the generated images, should be less than the band Δλ _A , which ensures the coherence of atmospheric phase fluctuations in the received light radiation and defined as

, (26)

, (26)

определяется (19).where λ is the average wavelength of solar illumination in the band Δλ, and

is determined by (19).

Based on (19), taking into account the relation (25) characteristic of the ERS, we obtain that

<1 , (27)

<1, (27)

and at λ = 0.6 μm (6000Å), the value of Δλ _А > 6000Å, that is, in the entire visible and near-IR wavelength range of the received light radiation (Δλ _P = 4300Å ÷ 9300Å) we have Δλ _P <Δλ _А , that is, the frequency there is no averaging of atmospheric phase distortions of light radiation in ERS problems, since the condition Δλ <Δλ _{A is} always satisfied. This explains and justifies the absence of narrow-band light filters in the OEA imaging channel (Fig. 1a).

To carry out multispectral thematic processing of remote sensing data in multispectral channels of the visible and near-IR spectral ranges, it is necessary to analyze a diffraction-limited image obtained in the panchromatic spectral range {Δλ _P = (0.43 ÷ 0.93) μm} through multispectral narrow-band filters, such , for example, as: blue {Δλ _С = (0.43 ÷ 0.53) μm}, green {Δλ _З = (0.53 ÷ 0.63) μm}, red {Δλ _К = (0.63 ÷ 0 , 73) μm} and near IR {Δλ _IR = (0.73 ÷ 0.93) μm}. Multi-zone thematic processing allows you to track changes in the states of natural and artificial objects on the probed area of the earth's surface. So, for example, in the blue spectral range Δλ _С , the following is carried out: mapping of coastal waters, separation of soil and vegetation, recognition of coniferous and deciduous trees; in the green spectral range Δλ _W carry out: determination of the intensity of vegetation, assess the health of plants; in the red spectral range Δλ _K distinguish features of vegetation; in the near-IR range Δλ _{IR, the} differences in the properties of biomass and coastal zones are estimated, and in the panchromatic spectral range Δλ _P , mapping is carried out and other problems of ultra-high resolution ERS are solved.

раз. Оценим величину этого выигрыша.When accumulating a series of M short-exposure images selected from N registered images, the signal-to-noise ratio (contrast) in the resulting image increases by

time. Let's estimate the size of this gain.

=30раз.In the example considered above, the registration of images of the probed area of the earth's surface is carried out with programmed turns of the ERS small spacecraft around the center of mass to keep the OEA aimed at this area. At the same time, the ERS spacecraft travels 1200 km at a speed of 7 km / sec, and the total registration time is 170 sec. Taking into account that 7 frames per second are recorded by the “sampling frame” strategy, we find that N = 1190 short-exposure statistically independent images of the probed area of the earth's surface are recorded during an observation time of 170 sec. Rejecting during processing, for example, 25% of N registered images, we obtain M = 900 images for shifts and accumulation, and the gain in increasing the contrast of the resulting image will be

= 30 times

In accordance with the research carried out, the following sequence of operations for processing a registered series of N diffraction limited, randomly shifted and weakened by the atmosphere, low-contrast images is proposed:

1) analyze a recorded series of N diffraction limited, randomly shifted and weakened by the atmosphere, low-contrast images

, (28)

, (28)

where I _{O is the} true intensity distribution of the object (the probed area of the earth's surface), * the asterisk denotes the convolution integral, I ^j _{AT is the} instantaneous impulse response (point spread function) of the atmosphere-ERS telescope system at the j-th moment of image registration, I ^j _w - additive random noise in the j-th image, and j = 1,…, N;

2) select (select) M of the clearest and most contrasting images from N registered (28)

, (29)

, (29)

where i = 1, ..., M;

3) summarize the selected images (29) and form a reference average image of the probed area of the earth's surface

(30)

(thirty)

4) define in the reference high-contrast, but distorted by averaged shifts, image (30) characteristic features (reference points);

5) compare each of the M selected by selection 2) short-exposure images (29) with the reference and find in them the characteristic features of the reference (30);

6) shift each of the M short-exposure images (29), combining their characteristic features with the characteristic features of the reference, and compensate for the random atmospheric shifts of the recorded diffraction-limited images distorted by additive noise

,(31)

, (31)

where I _{T is the} FRT of the telescope (Airy pattern), and I ⁱ _{I is the} diffraction-limited low-contrast i-th image of the probed area of the earth's surface undistorted by random atmospheric shifts;

раз, и получают высококонтрастное высокого (дифракционного) разрешения цветное изображение зондируемого участка земной поверхности для картографирования и других задач ДЗЗ сверхвысокого разрешения7) accumulate M shifted in 6) diffraction-limited low-contrast images (31), while increasing the contrast of the resulting image in

times, and get a high-contrast high (diffraction) resolution color image of the probed area of the earth's surface for mapping and other tasks of ultra-high resolution ERS

, (32)

, (32)

–дифракционно ограниченное изображение зондируемого участка земной поверхности;Where

–Diffraction limited image of the probed area of the earth's surface;

8) analyzing a panchromatic high-contrast and high (diffraction) resolution image (32) through multispectral narrow-band filters, they carry out multispectral thematic processing, in which, in the interests of various consumers, changes in the states of natural and artificial objects on the probed area of the earth's surface are assessed.

So, as a result of the research and comparison of the proposed invention with the prototype and analogues, the following conclusion can be drawn.

) проведенного на базе критерия РКС, оптико-электронная аппаратура (ОЭА) МКА ДЗЗ согласована по критерию Найквиста (

) и обеспечивает достижение дифракционного предела инструментального разрешения МКА ДЗЗ на местности (

).As a result of the proposed perfect design (

) carried out on the basis of the DCS criterion, the optoelectronic equipment (OEA) of the ERS MCA was agreed according to the Nyquist criterion (

) and ensures the achievement of the diffraction limit of the instrumental resolution of the ERS small spacecraft on the ground (

).

To eliminate atmospheric distortions when obtaining ERS images, it was proposed to exclude the temporal (τ _E ≤τ _A , τ _P = 6τ _K > τ _D ) and frequency (Δλ <Δλ _A ) averaging of atmospheric distortions of light radiation, which, in the absence of spatial averaging characteristic of ERS {r _O (λ, H)> D}, allows you to register "instantaneous" diffraction limited images, randomly shifted and weakened by the atmosphere.

To eliminate these atmospheric distortions, when processing a registered series of N "instantaneous" images, M images of good quality are selected (selected) among them, rejecting blurry and noisy, and, by shifting and accumulating the selected images, they compensate for atmospheric shifts and weakening of the contrast of the images and thus obtain high-contrast and high (diffraction) resolution panchromatic image of the probed area of the earth's surface for various tasks of ultra-high resolution ERS and multispectral processing.

Thus, the technical result of the proposed method, namely, the achievement of the diffraction limit of the resolution of the remote sensing images and increasing their contrast by matching the OEA for obtaining the remote sensing images according to the Nyquist criterion and compensating for atmospheric distortions of the remote sensing images during their acquisition and processing, has been achieved.

List of used literature

1. Fried D.L., "Optical Resolution through a Randomly Inhomogeneous Medium for Very Long and Very Short Exposures," J. Opt. Soc. Am., 1966, v. 56, no. 10, p. 1372.

2. Sviridov KN, Bakut PA, Ustinov ND, Khomich N.Yu., "Problems of isoplanaticity of optical systems that form images through a turbulent atmosphere", Optics and Spectroscopy, 1986, vol. 60, no. .3, page 611.

3. Petri G. "Russian satellite" Resurs-DK ": an alternative source of ultra-high resolution data", Geomatika, 2010, No. 4, p.38.

4. Kirilin A.N. and others, "Spacecraft" Resource-P ", Geomatics, 2010, No. 4, p. 23.

5. Lavrov VV, Ultra-high resolution space survey systems, Geographic information portal of the GIS-Association, 2010, No. 2, p.19;

6. Sviridov K. N. "On the Ultimate Resolution of Aerospace Earth Remote Sensing Systems (ERS)", Rocket and Space Instrumentation and Information Systems, 2014, vol. 1, issue 1, p. 34.

7. Sviridov K.N., Volkov S.A., "Method for remote sensing of the Earth", Patent of the Russian Federation No. 2597144 dated 08.16.2016 for an application for invention No. 2015129353 dated 17.07.2015, applicant and copyright holder of JSC Russian Space Systems ...

8. Sviridov K.N., "Remote sensing of the Earth with adaptive compensation for random tilts of the wavefront", Rocket and space instrumentation and information systems, 2015, v.2, issue 3, p.12.

9. Sviridov K.N., "A method for obtaining and processing images distorted by a turbulent atmosphere", the decision to issue a patent for invention No. 2016100934/28 (001133) dated 12.03.2019 on application for invention No. 2016100934 dated 14.01.2016, the applicant and copyright holder of JSC Russian Space Systems.

10. Sviridov KN, "Adaptive filtering of middle images distorted by a turbulent atmosphere", Rocket and space instrumentation and information systems, 2015, v.2, issue 4, p.40.

11. Sviridov K.N., On the limiting instrumental resolution of the "Resurs-P" spacecraft (No. 1,2,3) ", Rocket and space instrument making and information systems, 2017, vol.4, issue 2, p.20 -28.

12. Sviridov K.N., Tyulin A.E., On the criteria for assessing the limiting instrumental resolution of a spacecraft for remote sensing of the Earth on the ground, scientific and technical journal "Information and Space", 2018, No. 3, pp. 143-146.

13. Sviridov K.N., "Method of remote sensing of the Earth (ERS)", Patent of the Russian Federation No. 2531024 dated 08/20/2014 for an invention application No. 2013125540 dated 06/03/2013, applicant and copyright holder of JSC Russian Space Systems.

14. Sviridov KN, “On a new approach to the acquisition and processing of remote sensing images distorted by a turbulent atmosphere”, Rocket and space instrument making and information systems, 2014, v.1, issue 4, p.28.

15. Weatherll W., Image Quality Assessment, ch. 6 in the book. ed. R. Shannon, J. Wyant, Optical Systems Design, 1983, ed. Mir, M ..

16. Ground Sample Distance (GSD) Support (http://support.pix4d.com/he/en-us/articles / 202559809);

17. Khmelevskoy SI, Trends in the development of digital aerial survey systems. Comparison and evaluation criteria, Geoprofi, 2011, No. 1, p.11);

18. Zamshin V.V., Methods for determining the linear resolution

optical and radar aerospace images, Izvestia

Universities, geodesy and aerial photography, 2014, No. 1, p.43);

19.Characteristic of image quality on the website of the STC Krasnogorsk plant named after S.A. Zverev (http://www.com/qa/qa-resolution.html);

20. GOST 15115-78, Telescopic systems for optical devices. Visual method for determining the resolution limit, State. USSR Committee for Standards, M., 1978;

21. Kononov V., Fundamentals of methods for calculating the resolution and accuracy of determining the coordinates of aerial photo-topographic systems. (http://www.geomatika.kiev.ua/training/DataCapture/RemoteSensing/Chapter103html);

22. Greenwood D.P., Fried D.L., "Power Spectrum Requirements for Wave front Compensative Systems", J. Opt. Soc. Am. 1976, v. 66, p. 193;

23. Sviridov K.N., Polskikh S.D., Bakut P.A., Khomich N.Yu., Investigation of a probabilistic approach to achieving diffraction resolution of optical systems under atmospheric vision, Optics of the atmosphere, 1989, vol. 2, no. 1, p. 41;

24. Sviridov KN, Bakut PA, Belkin ND, Ustinov ND, "Statistical estimation of the spectral band of the spot interferometry method", 1983, v.54, issue 5, p.890.

Claims (1)

The method of achieving the diffraction limit of the resolution of images of remote sensing of the Earth for small spacecraft, which consists in the fact that to match the lens and the digital detector of the optical-electronic equipment (OEA) of the ERS MCA according to the Nyquist criterion, a digital detector with a pixel d is selected, the sampling period of the digital detector 2d is determined and form its projection onto the sounded earth surface

, equate it to the required linear resolution and the diffraction limit of resolution of the MCA ERS on the ground

, where λ = 0.6 μm is the average vona length of solar illumination radiation in the visible wavelength range Δλ_IN= (0.43 ÷ 0.73) μm, and based on the equality

determine the required diameter of the lens aperture of the projected OEA, as

{m}, and on the basis of equality

determine the focal length of the lens of the projected OEA, as

{m}, then, to evaluate the design results of the OEA, the coefficient of perfection of the designed OEA is formed as the ratio

, and, substituting the design results into it: D and F, as well as d and λ, we obtain the value

equal to one in the presence of the required agreement F_C= FK, which indicates the perfection of the designed OEA, consistent with the Nyquist criterion, namely 2d = λF_C/ D, and ensuring the achievement of the diffraction limit of the instrumental resolution of the ERS spacecraft on the ground

, then, to implement the design results, create a projected OEA containing a selected digital detector with a pixel d and a lens with a diameter D and a focal length F, and to increase the focal length of the lens to a matching value F_C= FK in the OEA between the lens and the digital detector, photographic magnifying optics are introduced, aligning its optical axis with the optical axis of the lens and placing standard micro-lenses or Barlow lenses with magnification M^X= K between the lens and the digital detector OEA so that the front focus of the magnifying optics is in the focal plane of the lens F, and the back focus of the lens assembly and the magnifying optics is F_C was in the plane of the generated and detected images, then the created OEA is placed on board the ERS small spacecraft, the spacecraft is put into orbit and remote sensing of the observed areas of the earth's surface is carried out, for which, in the mode of orbital orientation, the ERS spacecraft makes its programmed turns around the center of mass in the longitudinal direction, and at the same time, flying up to the object of observation at a distance equal to the flight altitude H, the ERS MCA directs the OEA at it and, preventing the appearance of image smears, keeps the OEA in the direction of the sounded area until it moves away from it at the same distance H, simultaneously with this on board the ERS small spacecraft in a narrow field of view of the lens-photo-magnifying optics assembly and in a wide spectral sensitivity band of a digital detector

at

where

, and

- the dispersion of atmospheric fluctuations of phase Ө at the aperture D, always less than unity in ERS problems, a series of N short-exposure images of the probed area of the earth's surface is recorded at τ_E= τ_AND= 1ms. where τ_E Is the exposure time of the recorded images, and τ_AND- the interval of time correlation of atmospheric fluctuations, statistically independent from each other in atmospheric distortions at τ_P> τ_D, where τ_P= 6τ_TO- the interval between adjacent registrations, τ_TOIs the frame duration, and τ_D- the inertia of the digital detector, and transmit them to the Earth for subsequent processing, in which the recorded series of N diffraction limited, randomly shifted and weakened by the atmosphere low-contrast images is first analyzed and M of the clearest and most contrasting images are selected in it, rejecting the blurry and noisy ones, then the selected images and form a reference high-contrast image of the probed area of the earth's surface, determine the characteristic features from it and compare each of the M short-exposure images selected by selection with the reference, defining the characteristic features of the reference in them, then shift the short-exposure images, combining their characteristic features with the characteristic features of the standard, and compensate for the atmospheric shifts of the images, after which the shifted diffraction-limited images are accumulated, increasing the signal-to-noise ratio of the resulting image in

times, and receive a high-contrast and high diffraction resolution panchromatic image of the probed area of the earth's surface for mapping and other tasks of ultra-high resolution ERS, and analyzing it through multispectral narrow-band filters, they carry out multi-zone thematic processing, in which, in the interests of various consumers, changes in the states of natural and artificial objects are monitored on the probed area of the earth's surface.

Images