Optical: systems and elements – Mirror – Including specified control or retention of the shape of a...
Patent
1989-07-18
1992-10-20
Arnold, Bruce Y.
Optical: systems and elements
Mirror
Including specified control or retention of the shape of a...
359851, 2502011, G02B 508, G02B 718
Patent
active
051575566
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a primary reflector for a reflector telescope, comprising a plurality of individual polygonal reflector bodies and positioning and adjusting elements assigned to said reflector bodies the positioning and adjustment elements are arranged below the reflector bodies and the reflector surface of the reflector bodies cooperate to form a full circular surface which is joined radially at inner and outer boarders of various polygonal reflector bodies.
BACKGROUND OF THE INVENTION
A reflector telescope of this kind is known as Mauna Kea reflector telescope with 10 m reflector diameter being still in the planning stage (Sterne und Weltraum, 1984/August-September, p. 412, Appl. Optics, No. 14, 2631-2641).
In this reflector telescope, the primary reflector is formed of 36 hexagonal reflector bodies forming, in a honey-comb structure, the reflector surface, in the center of which a reflector body being omitted for observation purposes in the Cassegrain focus. Manufacture of the individual hexagonal reflector bodies themselves is very problematic. They are off-axis segments of a paraboloid to be cut in hexagon shape (Appl. Optics, vol. 19(1980), No. 14, 2332-2340).
When manufacturing, as part to be fashioned, a circular part is selected to be deformed by accurately defined shearing and bending forces acting on the borders. Into the deformed blank, a spherical shape is ground. Then, the forces exerted are removed. As far as the forces have been selected properly, each reflector body accepts the desired shape of a paraboloid segment of the primary reflector after unloading. It has been found out, however, that faults occur when cutting to hexagonal shape.
Furthermore, depending on the position of the primary reflector of the reflector telescope, on thrusts due to wind and on temperature variations, the positions of the individual very thin-walled hexagonal reflector bodies have to be readjusted. For this purpose, the support points of each reflector segment are connected with three position controllers to refocus the the reflector body and to adjust it in two inclination directions. At the edges of the reflector bodies, sensors are provided measuring the displacements of adjacent reflector bodies with respect to each other. Together with three inclination sensors measuring the total curvature of the reflector body, they provide information to be processed in a computer system controlling the in total 108 position controllers. With a total 168 different sensors, redundancy is large enough that failure of individual sensors can be tolerated. In this arrangement, however, the front sides of the reflector bodies are left free from disturbing monitoring systems. Occasionally, only, a readjustment has to be performed by means of a constellation, such that even infrared observations will be possible by day. Sensors and position controllers must operate with an accuracy of at least 50 nm.
In theoretical investigations of the primary reflector of the reflector telescope described in DE patent 35 38 208, the reflector bodies of which are circular-disk shaped, such that between the individual reflector bodies, free spaces for the support of the reflector bodies and for the supporting bars structure or its shadow areas are formed, it has been found out that the free spaces put into question the infrared suitability of the primary reflector. The metal components in the area of the free spaces of the support structure of the primary reflector transmit thermal radiations to the detector arranged in the focus of the primary reflector and disturb the signal to be received from space.
Infrared suitability of the primary reflector is necessary to detect dark bodies in space, being present as weight, or mass but not visible to the human eye by means of the primary reflector. Theoretically, the phenomenon of own infrared thermal radiation of the free spaces can be excluded by technical counter-measures. They are, however, extremely expensive.
The investigations performed because of the theore
REFERENCES:
patent: 4776684 (1988-10-01), Schmidt-Kaler
patent: 4822156 (1989-04-01), Hugenell
patent: 4825062 (1989-04-01), Rather et al.
patent: 4944580 (1990-07-01), MacDonald et al.
Morrison; "Development Problems of the Primary Mirror for Large Space Telescopes"; S.P.I.E. Journal; May 1970; vol. 8 pp. 107-118.
Angstenberger Karl F.
Arnold Bruce Y.
Shafer R. D.
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