The polar regions offer a unique perspective on interactions between the solid earth, cryosphere, hydrosphere, and atmosphere. The polar regions are directly linked to the global climate system and dynamically reflect changes happening around the world.
It wasn't until relatively recently that Global Positioning System (GPS) technology available to science became capable of measuring the tiny, millimeter-scale displacements that characterize solid-earth motions and sophisticated enough to enable long-term observations in harsh, polar environments.
GPS technology was made possible by a combination of scientific and engineering advances, particularly the development of the world's most accurate timepieces: atomic clocks that are precise to within a billionth of a second. What began as a classified military operation has since expanded into a global tool that provides uniquely detailed and accurate measurements of our planet.
MAJOR ADVANCEMENTS IN GPS TECHNOLOGY:
Dr. Ivan Getting, graduate of MIT and Rhodes Scholar from Oxford, puts his PhD in astrophysics to use at Raytheon, developing a 3-D position-finding system based on time difference interval for the U.S. Air Force. His system ultimately becomes the basis for the future of GPS.
The Soviet Union launches a satellite (Sputnik) into space. MIT researchers notice that radio signals from this satellite, or "artificial star" could determine distinct positions on the ground.
The U.S. Navy's TRANSIT navigation system is developed, relying on 6 satellites and designed originally for use by submarines. More than 10 satellites were eventually launched, though ground units had to wait up to several hours to pick up a signal.
The U.S. Department of Defense launches NAVSTAR (Navigation System with Timing and Ranging), strictly for military use.
The first Block I satellite launches and in order to monitor the Soviet Union's compliance with the 1963 agreement with the United States to refrain from nuclear testing.
GPS ceases being restricted to military purposes and is made available for public use. President Ronald Reagan declassifies the system in response to a Soviet interceptor aircraft shooting down civilian airliner KAL 007 that strayed into prohibited airspace due to navigational errors, killing all 269 people on board.
The Gulf War temporarily deactivates public use of GPS because the military is in need of more receivers.
Public use of GPS returns with the decision that it will be available free of charge to the entire world.
Full Operational Capacity was declared by NAVSTAR with the placement and activation of the last of the 24 satellites. (This number had increased from the original 11 that were planned). The satellites orbit 12,000 miles high, weighing 2,000 pounds each, and circle the globe every 12 hours.
More satellites have been put into orbit, increasing availability and accuracy. As the world's dependence on GPS grows, the Government Accountability Office (GAO) has plans for continually updating the system.
A BRIEF HISTORY OF SEISMOLOGY
Empirical observations of the effects of earthquakes were rare until 1750, when England was uncharacteristically rocked by a series of five strong earthquakes. These earthquakes were followed on Sunday, November 1, 1755, by a cataclysmic shock and tsunami that killed an estimated 70,000 people, leveling the city of Lisbon, Portugal, while many of its residents were in church. This event marks the beginning of the modern era of seismology, prompting numerous studies into the effects, locations, and timing of earthquakes.
As access to and communication between various parts of the world became more common, earthquake observations from around the world could be combined.