Remote Sensing: Platforms and Sensors

Platforms

In remote sensing, the vehicle or structure that carried a sensor is called a platform (Table 1; Figure 1). Airborne or space-borne platforms are often used in remote sensing of the environment. Aircraft or balloons are some examples of airborne platforms, while satellites or space shuttles can be considered as space-borne. Balloons, considered to be the cheapest airborne platforms, are often used for academic training, experiments, and rapid damage assessment purposes. However, ground-based platforms are also in use. Towers, scaffoldings, and cars can be used as ground-based platforms to record detailed information about the surface for experiments to validate data collected from other sources.

Figure 1 Remote sensing platforms

Source: Authors.

Aircraft are commonly used platforms to collect detailed images and facilitate the collection of data about Earth's surface at desired times. Cameras mounted on aircraft have been used to monitor land use practices, locate forest fires, and produce detailed and accurate maps of Earth's surface based on aerial photographs captured with aircraft-mounted cameras. Remote sensing can be also conducted using space shuttles. The NASA Shuttle Radar Topographic Mission (SRTM) 90-m Digital Elevation Data for the entire world was one of the examples of using a space-borne platform, namely, the space shuttle. However, with the advancement of technology, satellites are becoming commonly used space-borne platforms in remote sensing.

Satellites are placed outside the atmosphere at a large distance, orbiting around the Earth at a designated time frequency. Because of their flight path, satellites permit repetitive coverage of Earth's surface on a continuing basis. The Land-sat, SPOT, RADARSAT, IKONOS, ALOS, and NOAA satellites are some examples of satellites that have been providing data about the Earth at various scales for more than four decades. The data acquired by each platform may possess specific data characteristics within the constraints imposed by the individual sensors.

Some satellite platforms are sun-synchronous, while some are geosynchronous. A sun-synchronous satellite passes over the same part of Earth at roughly the same local time each day. RADARSAT, Landsat, SPOT, and COSMOS are examples of sun-synchronous satellites. A geosynchronous satellite has an orbital track around Earth that it repeats regularly over time. For example, if a satellite's orbit lies over the equator and the orbit is circular, it is called a geostationary satellite. Geostationary meteorological satellites and NOAA satellites are examples of geosynchronous satellites.

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