RU2505843C1 - Double-channel space telescope for simultaneous observation of earth and stars with image spectral spreading - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: telescope has in a first channel a main mirror, a secondary mirror, a lens corrector, a recording device mounted in the focal plane of the telescope, and in a second channel a flat slanted elliptical mirror for observing stars, which is mounted in the plane of intersection of the first and second channels. The central part of the surface of the main mirror which faces the secondary mirror and on which light from the Earth falls is coated with a green reflecting light filter. In the central area of the cross-section of the second channel there is a circular diaphragm which prevents that part of light from stars which does not fall on the flat slanted elliptical mirror from falling into the first channel. The part of the surface of the recording device facing the lens corrector is coated with a red transmitting light filter.

EFFECT: enabling detection of a sufficient number of stars while simultaneously obtaining an image of the surface of the Earth in order to reduce gridding error of said image.

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Description

The invention relates to the space field, in particular to remote sensing equipment for the Earth, and can find application on spacecraft (KA) for remote sensing of the Earth, images from which must meet stringent requirements for the coordinate reference of the images received from them. Also, this equipment can be used on a spacecraft for remote sensing of the Earth as an auxiliary tool for determining the orientation of a spacecraft during a space flight.

Currently, the widespread use of images from spacecraft (SC) of remote sensing of the Earth to solve a number of problems. To successfully solve these problems, satellite images should be tied to the earth's surface.

The error of the geographic location is most strongly affected by the error in the knowledge of the orientation of the axes of the sighting coordinate system of the space telescope.

One way to reduce the error in the knowledge of the orientation of the axes of the sighting coordinate system is to register the image of the starry sky with the space telescope itself.

In order to ensure a sufficient number of stars observed in the field simultaneously with the image of the Earth, it is necessary to separate the bright image of the Earth and the faint images of stars. In this case, it is desirable to ensure the passage of light through the same optical elements for the light of stars and the Earth. This can be achieved by separating images using reflective and transmitting interference filters in different spectral ranges.

The well-known space telescope T-170M of the spacecraft "Spectrum-UV" (edited by K. M. Pichkhadze, Space Flight NPO named after S. A. Lavochkin, M., Publishing House MAI-PRINT, 2010, pp. 94-96 )

The T-170M space telescope is designed according to the Ritchie-Chretien scheme without a lens corrector and has one entrance pupil. The telescope is adapted to image stars and record them with scientific spectrometric instruments.

The disadvantage of this telescope is the impossibility of constructing and recording a high-quality image of the earth’s surface, since the telescope is adapted to register images of stars and the focal surface of this telescope has a spherical shape, and there are no image receivers for registering images of the earth’s surface.

The Victoria Space Telescope is known for the Arkon-1 spacecraft (edited by K. M. Pichkhadze, Space Flight of the Scientific and Production Association named after S. A. Lavochkin, M, Publishing House MAI-PRINT, 2010, pp. 133-139) .

Unlike the T-170M telescope, the Victoria Space Telescope is adapted to obtain high-quality images of the earth's surface. It is made according to the classical scheme for space telescopes for remote sensing of the Earth - the Ritchie-Chretien scheme with a corrected focal surface and has one entrance pupil.

The disadvantage of this telescope is the impossibility of simultaneously recording images of stars and images of the earth's surface. The image of stars can be registered with this telescope separately from the image of the Earth provided that the telescope is reoriented from the Earth to the starry sky.

The closest analogue to the claimed invention is the space telescope of the spacecraft "Lomonosov" (edited by V.V. Nesterov et al., Space astrometric experiment "Lomonosov": Collection of scientific works / Lomonosov Moscow State University, State. Astron. Institute of P.K. Sternberg; M., Publishing House of Moscow State University, 1992, p.191).

This telescope is made according to the original optical scheme based on the Cassegrain scheme and has two entrance pupils. It is designed to perform astrometric experiments, and both of its channels are designed to build images of stars. The telescope is not designed to record the image of the Earth, however, theoretically, the image of the earth's surface can be detected by this telescope (channel for the measured star) simultaneously with the image of stars (channel for the reference star).

The disadvantage of the Lomonosov space telescope is the inability to reconstruct the image of the Earth and stars. This leads to the fact that if you simultaneously observe the earth's surface and the starry sky (channels with different entrance pupils), a bright image of the Earth and faint images of stars will be recorded simultaneously on the image receiver (CCD), which in turn will lead to a decrease the number of stars observed in the field simultaneously with the image of the Earth, which, accordingly, will lead to an increase in the error in determining the orientation of the telescope coordinate system and in an increase in the coordinate coordinate error ki obtained image earth telescope.

The technical problem solved by the invention is the ability to register a telescope with a sufficient number of stars at the same time as receiving an image of the earth's surface in order to reduce the coordinate error of this image.

This task is ensured by the fact that in the well-known two-channel space telescope for remote sensing of the Earth, containing a main mirror, a secondary mirror, a lens corrector, a recording device located in the focal plane of the telescope and a plane inclined plane installed in the second channel in series with the optical beam of the first channel an elliptical mirror for observing stars, placed in the plane of intersection of the first and second optical channel, new is that the center The main part of the surface of the main mirror facing the secondary mirror, which receives light from the Earth, is covered by a green reflective filter, and a circular diaphragm is installed in the central zone of the cross section of the second channel, which prevents the part of the world from the stars that does not get into the first channel a flat inclined elliptical mirror, while part of the surface of the recording device facing the lens corrector is closed by a red transmitting light filter.

In addition, in a two-channel space telescope, the recording device is made in the form of a CCD matrix.

Due to the fact that the central part of the surface of the main mirror facing the secondary mirror, which receives light from the Earth, is covered by a green reflective filter, and a circular diaphragm is installed in the central zone of the cross section of the second channel, which prevents stars from entering the first channel of the light, which does not fall on a flat inclined elliptical mirror, despite the fact that part of the surface of the recording device facing the lens corrector is closed by a red light transmitting ltrom increased quantity observable stars and thereby reduced the error made by gridding telescope images the surface, which leads to better quality and to increase the scope of the telescope received information.

Moreover, the execution of the recording device in the form of a CCD matrix, divided into two parts, one of which is closed by a red transmitting light filter, allows registration of images of the earth's surface and stars using one recording device without mixing these images.

The proposed space telescope with spectral dilution of the image is illustrated in the drawing, where figure 1 shows a schematic diagram of a telescope.

The space telescope (Fig. 1), made, for example, according to the Cassegrain scheme, contains a main mirror 1, partially covered with a green reflective filter in the part where light from the Earth gets, a secondary mirror 2, a lens corrector 3, a CCD matrix for observing the Earth and stars 4, a circular diaphragm 5, a flat inclined elliptical mirror for observing stars 6, a red transmission filter 7.

Figure 1 indicates: I - the entrance pupil of the channel for observing the Earth; II - the entrance pupil of the channel for observing the starry sky.

Before starting work, the telescope is oriented in the following way: the sighting axis of the channel for observing the Earth (entrance pupil I) is directed to a recorded object on the surface of the Earth, at the same time, the region of the starry sky containing stars should fall into the field of view of the channel for observing stars (entrance pupil II) .

The light from a photographic object on the Earth’s surface enters the entrance pupil I, then on the main mirror 1 (and the light from a photographic object on the Earth’s surface enters only that part of the main mirror that is covered by a green reflective filter), then the light is reflected from the main mirror to the secondary mirror 2, and from it, after passing through the lens corrector 3, it falls into the focal plane in which the CCD matrix 4 is installed, one part of which is closed by a red transmitting light filter 7. The image from the recorded object on Earth is registered iruetsya only that portion of the CCD that is not covered with the color filter, because the combination of the reflective light filter of the main mirror and the transmitting light filter of the CCD matrix gives a signal level lower than the sensitivity of the CCD matrix.

The light from the stars enters the entrance pupil II, while the circular aperture 5 cuts off the light that does not fall on the flat inclined elliptical mirror 6, thereby reducing the level of scattered light inside the telescope. A flat oblique elliptical mirror reflects the light from the stars to the main mirror (to that part of the main mirror that is not covered by the green reflective filter), then reflected from the main and secondary mirrors, the light from the stars passes through the lens corrector into the focal plane, where it is detected by both parts of the CCD matrices.

Thus, the image recorded by that part of the CCD matrix that is covered by a red transmitting light filter contains only the image of the starry sky, and the image recorded by the part of the CCD matrix without the filter contains the image of the earth's surface and the image of a certain number of the brightest stars.

The proposed design of the space telescope will increase the number of stars observed and thereby reduce the coordinate error of the telescope’s images of the earth’s surface, which leads to an improvement in the quality and scope of the information received by the telescope.

Claims (2)

1. A two-channel space telescope for remote sensing of the Earth, containing a main mirror, a secondary mirror, a lens corrector, a recording device placed in the focal plane of the telescope, and a flat oblique elliptical mirror for observing stars, installed in the second channel, sequentially installed along the optical beam of the first channel, placed in the plane of intersection of the first and second optical channel, characterized in that the Central part facing towards the secondary mirror n the surface of the main mirror, to which light from the Earth enters, is covered by a green reflective filter, and in the central zone of the cross section of the second channel there is a circular aperture that prevents the part of the light from the stars that does not fall on a flat inclined elliptical mirror from entering the first channel part of the surface of the recording device facing the lens corrector is closed by a red transmitting light filter. 2. The two-channel space telescope according to claim 1, characterized in that the recording device is made in the form of a CCD matrix.