Page 69 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 1 essentials of Geography 33
(a) Geostationary Orbit 35790 km altitude
(b) Polar Orbit 200–1000 km altitude
part of the National Polar-orbiting Partnership (NPP), the next generation of satellites that will replace NASA’s aging Earth Observation satellite fleet. Many of the beautiful NASA “Blue Marble” Earth composite images are from the Suomi satellite (Figure 1.30).
Active Remote Sensing Active remote-sensing sys- tems direct a beam of energy at a surface and analyze the energy reflected back. An example is radar (radio detection and ranging). A radar transmitter emits short bursts of energy that have relatively long wavelengths (0.3 to 10 cm) toward the subject terrain, penetrating clouds and darkness. Energy reflected back to a radar receiver for analysis is known as backscatter. Several important radar satellites are in orbit at this time, such as QuikSCAT, ERS-1 and -2, CloudSat, and Canada’s RADARSAT-1 and -2. Radar images collected in a time se- ries allow scientists to make pixel-by-pixel comparisons to detect Earth movement, such as elevation changes along earthquake faults (images and discussion in Chapter 13).
Another active remote-sensing technology is air- borne LiDAR, or light detection and ranging. LiDAR sys- tems collect highly detailed and accurate data for surface terrain using a laser scanner, with up to 150000 pulses per second, 8 pulses or more per square metre, provid- ing 15-m resolution. GPS and navigation systems onboard the aircraft determine the location of each pulse. LiDAR datasets are often shared between private, public, and scientific users for multiple applications. Scientists have used LiDAR to forecast zones of flooding caused by storm surges and rising sea level in Charlottetown, Prince Edward Island.
For more on remote-sensing platforms, see the “Re- mote-Sensing Status Report” on the Mastering Geogra- phy website, or go the Canada Centre for Remote Sensing tutorial at www.nrcan.gc.ca/earth-sciences/geomatics/satellite- imagery-air-photos/satellite-imagery-products/educational- resources/9309.
Geographic Information Systems
Techniques such as remote sensing acquire large vol- umes of spatial data that must be stored, processed, and retrieved in useful ways. A geographic information system (GIS) is a computer-based data-processing tool for gathering, manipulating, and analyzing geographic in- formation. Today’s sophisticated computer systems allow the integration of geographic information from direct surveys (on-the-ground mapping) and remote sensing
▲Figure 1.28 Three satellite orbital paths.
eyes are passive remote sensors, as was the Apollo 17 astronaut camera that made the film photograph of Earth on the back cover of this book.
A number of satellites carry passive remote sensors for weather forecasting. The Geostationary Operational Environmental Satellites, known as GOES, became op- erational in 1994 and provide the images you see on television weather reports. GOES-12, -13, and -15 are op- erational; GOES-12 sits at 60° W longitude to monitor the Caribbean and South America. Think of these satellites as hovering over these meridians for continuous cover- age, using visual wavelengths for daylight hours and infrared for nighttime views. GOES-14, parked in orbit since 2009, replaced GOES-13 in 2012 when that satellite experienced technical problems.
Landsat satellites, which began imaging Earth in the 1970s, are used extensively for comparison of changing Earth landscapes over time, among other applications (Figure 1.29; more images of changing Earth systems at earthobservatory.nasa.gov). Landsat-5 was retired in 2012 after 29 years, the longest-running Earth-observing mis- sion in history; Landsat-7 remains operational as part of NASA’s ongoing Landsat Data Continuity Mission. Landsat-8 was launched in 2013, beginning the new Landsat program managed by the U.S. Geological Survey.
Although the Landsat satellites far surpassed their predicted lifespans, most satellites are removed from orbit after 3 to 5 years. Launched in 2011, Suomi NPP is
(c) Sun-Synchronous Orbit 600–800 km altitude
Georeport 1.7 Polar-Orbiting Satellites Predict Hurricane Sandy’s Path
Scientists at the european Centre for Medium-Range Weather Forecasts report that polar-orbiting satellites, such as the National Oceanic and Atmospheric Administration (NOAA) Suomi NPP satellite, were critical for predicting Hurricane
Sandy’s track. Without data from these satellites, predictions for Hurricane Sandy would have been off by hundreds of miles, showing the storm heading out to sea rather than turning toward the New Jersey coast. Suomi orbits earth about 14 times each day, collecting data from nearly the entire planet (find out more at npp.gsfc.nasa.gov/).