Polar was launched on February 24, 1996 by NASA in the Global Geospace Science project. It is the second satellite to be launched in that project. Polar is an atmospheric studies satellite in polar orbit with an orbital period of 18 hours. The Polar satellite's mission is expected to last 1.5 years.
Polar carries several different instruments, and has many different scientific studies to perform.
One purpose of Polar is to gather information that will help scientists protect future satellites from radiation and other atmospheric dangers. Since the satellite is flying in the upper atmosphere, there is some concern that the satellite's instruments may be affected in some way or damaged by the sun's harmful radiation.
One of the main atmospheric studies experiments on board the Polar satellite is called the TIDE/PSI investigation. It is designed to observe ions in the Earth's atmosphere, especially in the polar regions. These observations include measurements of the partial pressure, wind velocity, and temperature of the ions. These ions include hydrogen, helium, nitrogen, oxygen, and molecules of these species and their compounds. These ionized gases make up what scientists call the plasma environment. An example of a plasma is the extremely hot atmosphere of the Sun. That is, it is a gas consisting of charged particles (mostly electrons and protons). The plasma being studied by Polar is made up of ionized gases in the magnetosphere. Relatively low energy/high density ionospheric plasmas and the higher energy/lower density plasmas are associated with geomagnetic activity. This geomagnetic activity causes storm-like conditions in space that can be dangerous to spacecraft. Polar's job, therefore, is to collect data that will help engineers design future spacecraft that will be able to withstand the electromagnetic activity in space.
Polar's most notable recent achievement occurred when physicist Dr. Louis Frank of the University of Iowa used images collected by Polar to support a theory that "comet-like objects" of about 10 meters in diameter are hitting the Earth's atmosphere and releasing nearly pure water as they break apart into larger clouds. These "comet-like-objects", if they exist, will be the focus of much further study regarding their chemical make-up. These "objects" could possibly have an effect on science's understanding of the sources of water on the Earth, and the water cycle of the atmosphere. Many scientists have recently joined Dr. Frank in encouraging NASA to launch a satellite dedicated specifically to studying this phenomenon.