Earth Observation/Remote Sensing Satellites
NASA operates or participates in more than a dozen remote sensing satellites and international programs. The Jason satellite, a joint mission between France and the United States that follows the highly successful TOPEX/Poseidon altimeter mission, has measured an increasing rate of sea level rise. Data from the Ice, Cloud, and land Elevation Satellite (ICESat) and Gravity Recovery and Climate Experiment (GRACE) satellites have shown rapid changes in the Earth’s ice sheets.
Spacecraft are used to provide detailed images of the Earth and measure ocean temperature, vegetation coverage, pollution levels, and other phenomena. These remote sensing satellites are used for civil, scientific, and military applications. They make it possible to do everything from viewing an individual’s house on Google Earth and forecasting the path of potential hurricanes to providing key data for first responders in areas affected by natural disasters.
In 2008, there were ## remote sensing satellites launched on behalf of ## countries. Of particular note, in August, the German RapidEye constellation of ## remote sensing satellites was launched. The ## RapidEye satellites travel along the same orbital plane and feature identical sensors, allowing large amounts of imagery to be collected, up to ## million square kilometers (## million square miles) per day. ## satellites in the same orbital plane allow for a higher number of multiple imaging passes over the same spot and quick revisit times. With these capabilities, the RapidEye constellation is capable of imaging any point on Earth every day.
LEO spacecraft are also used to provide images of the Earth for civil, scientific, and military applications. In 2008 the U.S. National Oceanic and Atmospheric Administration’s (NOAA) Advisory Committee on Commercial Remote Sensing reported that there were ## satellites in use or in development for this purpose, operated by ## different countries. The U.S. has been the leader in the commercialization of electro-optical remote sensing technology, but recent years have seen other countries begin to excel in the development of synthetic aperture radar (SAR) systems.
AGI designates remote sensing satellites as surveillance/military satellites. Exhibit 3p (below) provides the number of these satellites by country. AGI reports ## active U.S. surveillance/military satellites that it designates as having “unavailable” orbital parameters. In addition, the line between some remote sensing and Earth science satellite classifications is not always clear-cut.
Remote sensing satellites provide images of the Earth for civil, scientific, military, and intelligence applications using a number of different technologies.
From Sidebar — “Satellite imagery sales were helped along by increasing tensions in Afghanistan and then Iraq. In time, foreign purchases and major contracts for data (ClearView and NextView) from the U.S. National Geospatial-Intelligence Agency (NGA) brought growth and a measure of stability to the data market. The acquisition of Space Imaging by ORBIMAGE [now known as GeoEye] has also further stabilized the industry.”
The DoD and national security agencies could also use a variety of Earth observation satellites, like Space Based Infrared System (SBIRS) under development, Fast On-orbit Recording of Transient Events (FORTÉ), and the Multispectral Thermal Imager (MTI) that provide intelligence through a variety of sensors, including multi-spectral imagery, thermal images and event classification, radio burst detectors, and radar imaging.
Different wavelengths of light are ideal for different sensing activities. For example, radar technology, which uses microwave frequencies, can observe clouds, aerosols, volcanic plumes, sea-surface temperatures, ocean color, vegetation, land cover, snow, ice, fires, and many other phenomena. Visible light and near infrared portions of the spectrum can perceive fine detail and can be used for mineral and soil mapping, precision agriculture, and forestry.