Remote Sensing from Air and Space

Atmospheric Absorption, Scattering, and Turbulence (Visible Imagery) (Remote Sensing)

In the previous topic we looked at the illumination of objects by sunlight and the reflectance or scattering of light from those objects. As we follow the photons along their paths, we move in sequence from the atmosphere (in this section) through optical systems (in the next section) and then on to the detectors. There […]

Basic Geometrical Optics (Visible Imagery) (Remote Sensing)

The sequence of physical processes considered here has followed the photons from the source (generally, the sun for visible imaging) and through the atmosphere. The energy now needs to be detected by a sensor. This requires an optical system and detectors. The simplest aspects of optical systems are considered here; our primary concern is the […]

Diffraction Limits: the Rayleigh Criterion (Visible Imagery) (Remote Sensing)

In addition to geometrical issues in optics, we must consider the impact of physical principles that depend upon the wave character of light. One manifestation of this wave character is diffraction—the fact that light can diffuse around sharp boundaries. Diffraction applies equally to sound and ocean waves, which have scales of distance we’re more familiar […]

Detectors (Visible Imagery) (Remote Sensing)

Following optics, the next primary element in any sensor system is the detector. There are two primary detection techniques: film and electronic. We’ll discuss film systems briefly, and then modern solid-state electronic systems. Figure 3.24(a) The silver bromide grains of an x-ray film emulsion (2,500 diameters). Figure 3.24 (b) Cross section of the unprocessed emulsion […]

Imaging System Types (Visible Imagery) (Remote Sensing)

Remote sensing systems can be divided into a handful of basic types, depending on the form of imaging technology used. These distinctions affect the resolution and sensitivity of the system, and to a certain extent, the quality of the data. Framing systems—mostly film systems (Corona) Framing systems are those that snap an image, much like […]

Hubble: The Big Telescope (Visible Imagery) (Remote Sensing)

The science and technology of remote sensing involves the propagation of light from source to subject to sensor and relies on an understanding of the platform (or satellite bus) and the processes that transmit remotely sensed imagery to the ground. The Hubble Space Telescope serves to illustrate all these elements in the image chain. The […]

Commercial Remote Sensing—IKONOS and Quickbird (Visible Imagery)

The world of remote sensing changed dramatically on September 24, 1999, with the successful launch of the IKONOS satellite by Space Imaging Corporation. The subsequent launch of the Quickbird satellite by Digital Globe on October 18, 2001 emphasized the dramatically new world that imaging reconnaissance had become. Figure 3.39 First light image from IKONOS of […]

DMSP: Visible Sensor, Earth at Night (Visible Imagery) (Remote Sensing)

Defense Meteorological Satellite Program (DMSP) satellites are primarily intended to gather weather data for military purposes. We’ll look at the system as an example of low-light imaging. This system consists of platforms in sun-synchronous orbits with dayside equatorial crossings at 6:00 AM and 10:30 AM, local time. The purpose is to help forecasters identify and […]

Exposure Times (Visible Imagery) (Remote Sensing)

We have neglected one final, rather important point. For high-spatial-resolution systems, satellite movement becomes an issue because of motion blur, just as occurs in regular photography of rapidly moving targets. A simple calculation can estimate exposure time. CCD arrays have sensitivity not unlike regular daylight film, with a standard speed defined as ISO 100. An […]

Gravitational Force (Orbital Mechanics Interlude) (Remote Sensing)

The design and operation of remote sensing systems depends on the orbital motion of the satellites they employ, and a proper understanding of how they work and how to exploit them requires knowledge of orbital mechanics. This topic is designed to provide an understanding of orbital mechanics as it impacts remote sensing. Orbital mechanics for […]

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