ABSTRACT
In many of the missions, the primary objective is unrelated to space imagery or remote sensing. This chapter focuses on those missions and spacecraft in which the acquisition of digital imagery was a fundamental objective, although rarely the only one. It explores the technology and instrumentation of two particular missions that have played a prominent role: the Landsat remote sensing program and the Hubble telescope. A classification of missions and spacecraft based solely on their image acquisition function is a difficult task. In relation to Landsat-like projects, it is common to speak of earth-oriented missions; National Aeronautics and Space Administration calls one of its programs a Mission to Planet Earth and the satellites in this program are referred to as Earth Observing Systems. Maneuvers and housekeeping functions include re-aiming the telescope to acquire a new target, switching between the different communications antennas, changing data transmission modes, receiving commands and downlinking data, and calibrating the instruments.
