This paper proposes an optical system of the telescope for space research. The system comprises a segmented spherical mirror with a diameter of 10 m and a secondary aspherical mirror. The focal length of the telescope is equal to the radius of a spherical primary mirror. The paraxial focal point of the spherical mirror is aligned with the focal point of the whole system. The closest analog of the proposed optical system is the optical system of the Millimetron space observatory (Spektr-M). The physical aperture ratio of the proposed system is ten times that of the Millimetron telescope with the same overall dimensions. The proposed system rigorously satisfies the Abbe sine condition. The focal length of the system is 7070 mm, and the numerical aperture is 0.7071. The Airy disk diameter of the proposed system is more than ten times smaller than the diffraction circle of the Millimetron telescope. The angular field of the system is determined by the selected image quality criteria and specific wavelength.