Optical Beam Control

Chapter 7Imaging Satellites

7.1 Introduction

Telescopes are optical instruments designed to gather and magnify light, allowing us to observe distant objects. Space telescopes used in imaging satellites are specifically designed for observations outside Earth’s atmosphere, which eliminates atmospheric distortions and allows for clearer and more detailed observations. There are two commonly used types of telescopes: reflecting telescopes and refracting telescopes. Reflecting telescopes’ primary mirror reflects light to a focus point, where it can be observed or directed to instruments. Refracting telescopes have a primary lens that gathers and refracts light. The eyepiece is used to magnify the focused image. Reflecting telescopes do not suffer from chromatic aberration, a distortion caused by different colors of light focusing on different points. Mirrors reflect all colors equally. Refracting telescopes can suffer from chromatic aberration, where different colors of light focus on slightly different points. This can affect image quality and is mitigated using extra lenses or lens coatings. Reflecting telescopes are easier to manufacture and maintain. Mirrors can be coated to improve reflectivity, and adjustments are often simpler. Refracting telescopes are more complex to manufacture and maintain. Lenses require precise shaping and coating, and misalignment can be more challenging to correct. Reflecting telescopes can be more compact and lighter for a given aperture size. ...