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Telescopes with aspherical mirrors, long focal length, and large aperture are usually used to acquire high spatial resolution remote sensing images of earth surface, while they are expensive and large in volume. CubeSat is one of the fastest growing sectors in space science and technology, for that it has a relative superiority over other micro and mini satellites in terms of their shorter manufacture time, lower complexity, and most importantly less cost. An optical design of an all-spherical catadioptric telescopic objective for 3 U CubeSat missions is proposed in this chapter, aiming at implementing as low cost as possible. In order to correct aberrations of an all-spherical system, two corrector groups are introduced. One is afocal lens group at the front end of the primary mirror to eliminate spherical and coma aberrations of two-mirror objective. It is composed of two lenses with opposite focal power for achromatic design. Its diameter is close to the size of the primary mirror. The other is a negative focal power group with four pieces of lenses before image plane that amplifies the focal length of the two-mirror structure and corrects astigmatism, field curvature, and distortion aberrations of the whole system. All lenses used are made from the same kind of glass material for the convenience of the athermalization design. Furthermore, in order to minimize its outer barrel length, the secondary mirror adopts a Mangin type, which greatly reduces the marginal ray height of full field of view. Based on the mentioned basic idea and structure, its primary aberration formulas are derived, and the methods for the correction of its aberrations are analyzed. Then a designed example is given. It approaches diffraction-limited imaging performance. The total length of the system is 1/6 less than its effective focal length. At last, tolerance analysis is performed for verifying its manufacturability.

With the development of unmanned airborne vehicle (UAV) remote sensing technology, miniature high-resolution imaging spectrometers are greatly needed. In order to improve remote sensing efficiency and get wider coverage, it’s urgent to design and develop fore-optics with wide field of view and waveband for imaging spectrometer. As the refractive system has no central obscuration and it’s conducive to manufacture and assemble, so it’s used for our fore-optics. The key is the correction of secondary spectrum of systems working in broad waveband and meeting the requirement of imagery telecentricity to be appropriate for linear pushbroom imaging system. Suitable glasses are selected on the Glass Map, from where each glass has an Abbe number υ d and Partial Dispersion. Based on the theory of Gaussian Optics and Seidel third-order aberration theory, the paper derives apochromatic formula, and the power of individual lenses can be calculated. Then with a required value of spherical aberration and coma, this paper derives equations to calculate the initial structure of apochromatic optical systems. Finally, optimized refractive SWIR fore-optics working in 1μm-2.5μm with effective focal length (EFFL) of 11mm is reported. Its full field and F-number are respectively 40°, F/2.8. The system has many advantages such as simple and compact structure, small size, near diffraction-limited imaging quality, small secondary spectrum and imagery telecentricity. Especially it consists of spherical surfaces that can greatly reduce the difficulty and the cost of manufacture as well as test, which is applicable for SWIR imaging spectrometer with wide field of view.