Remote Sensing and Geosynchronous
Satellites, since their
inception, have been one of the greatest boons to mankind. Hundreds of
satellites circle the earth, all with very different missions. A satellite’s
mission determines a great deal about it, its orbit for example. The correct
positioning of a satellite in space is paramount for mission success. A
geosynchronous orbit is an example of where one might place a satellite to
achieve a specific goal. This orbit was popularized by Arthur Clarke in 1945,
it revolutionized how satellites are positioned to better collect and
distribute data. While Clarke focused on this orbit for communications it is
also useful for remote sensing.
is Remote Sensing?
Remote sensing is
gathering information without making physical contact with that object.
Detecting the energy reflected from Earth is how most sensors gather
information. Aircraft and satellites are the main vehicles used to conduct
remote sensing. There are two types of remote sensors: active and passive.
Active sensors will project something, such as a laser, onto the earth and then
record how much time it takes to return to the sensor. A passive sensor will
collect data based on outside stimuli, such as radiation from the sun. Remote
sensing is used for many reasons: terrain mapping, tracking weather, observing
patterns in wildlife, monitoring land use, and many other types of observation.1
Most remote sensing
satellites reside in geosynchronous orbit also called GEO orbit. This orbit is
ideal for telecommunications, monitoring weather patterns, and continuous
observation over a given area. To achieve geosynchronous orbit a satellite will
orbit the earth at a distance of 35,786 kilometers and have a speed of about
three kilometers per second. At this altitude and speed its orbit will take 24
hours to complete matching that of the earth’s rotation making the satellite
appear to be stationary.2 A geosynchronous orbit is
advantageous for a number of reasons. One reason is the amount of ground
coverage achieved; over 40 percent of the equatorial plane is covered by one
satellite. This means that only three satellites are needed to provide full
coverage of the planet, with the exception of the poles. Ground stations
benefit from this orbit as well; not having to track a moving object reduces
costs. Currently, 402 satellites reside in geosynchronous orbit, a testament to
how useful this orbit for different satellite operations.3
One satellite that utilizes GEO is the
Geostationary Operational Environmental Satellite Program (GOES). GOES is a
constellation of satellites used by NASA and the NOAA for the remote sensing of
weather patterns. GOES sensors provide worldwide coverage to aid meteorologists
in predicting local weather such as: hurricanes, tornadoes, dust storms,
volcanoes and many other weather phenomena. GOES can monitor solar activity as
well, enabling scientists to predict space weather as well as terrestrial.
While the GEO orbit is incredibly useful for remote sensing it can greatly
improve communications as well.4
satellites are used for common daily activities such as television and radio or
they can be used for military purposes. If the military wants to observe an
area of the world a satellite in GEO can take constant pictures and collect
other data on a particular region, or be used for global communications.
Wideband Global SATCOM (WGS-5) is one example of a communications
satellite used to benefit the military. WGS-5 launched in 2013, it is the fifth
satellite in a constellation that provides the military a protected wideband
communication network. These five satellites in GEO allow the military to have
focused coverage of a particular region of the world; WGS-1 covers the Pacific,
WGS-2 covers the Middle East, 3 covers Europe and Africa, 4 looks at Southeast
Asia, and 5 will be used to cover the United States. The WGS constellation is
just one example of a satellite based in GEO that benefits us.5
Using geosynchronous orbit
for communications and remote sensing has benefited all of mankind. This orbit changed
the way we focus satellites for data collection and distribution. The way we predict
weather and map the surface of the Earth has been revolutionized by remote sensing
GEO satellites. Arthur Clarke made an observation that changed how we position satellites
in space to maximize their capabilities. Satellites continue to be launched into
GEO, some for communications, others for remote sensing, making it one of Earth’s
most popular orbits.
James B., and Randolph H. Wynne. Introduction to Remote Sensing. New York,
NY: Guilford Press, 2011
“Basics of satellite communications .” January 18, 2010. Accessed
January 20, 2018. https://edge.apus.edu/access/content/group/science-and-technology-common/SPST/SPST501/Week%203/JISC_SatCom_Reading.pdf
Howell, Elizabeth. “What is Geosynchronous Orbit.” Space.com. April
24, 2015. Accessed January 20, 2018. https://www.space.com/29222-geosynchronous-orbit.html.
Jenner, Lynn. “GOES Overview and History.” NASA.gov. August 3, 2017.
Accessed January 20, 2018.
Ray, Justin. “Powerful New US Military Satellite Launches Into
Orbit.” Space.com. May 25, 2013. Accessed January 20, 2018. https://www.space.com/21316-night-rocket-launch-military-satellite.html.