Eye On The Space

i was reading Time.com's Eye On Science and found this interesting NASA mission that they have put up in the skies above us.... Its called GRACE aka. Gravity Recovery And Climate Experiment.

The GRACE mission will have two identical spacecrafts flying about 220 kilometers apart in a polar orbit 500 kilometers above the Earth. it will map the Earth's gravity fields by making accurate measurements of the distance between the two satellites, using GPS and a microwave ranging system. The gravity variations that GRACE will study include: changes due to surface and deep currents in the ocean; runoff and ground water storage on land masses; exchanges between ice sheets or glaciers and the oceans; and variations of mass within the Earth... (This will be crucial when you will consider the mass difference that will happen due to the speeding up of melting of the polar ice caps.. such information will provide an undeniable evidence to the rejectionists that Global Warming is for real.... )

GRACE will obtain a gravity field map by looking at how the Earth's mass varies from place to place on the surface as the twin satellites pass over.Since the Earth has varied topographic features such as mountains, valleys, and underground caverns, the mass is not evenly distributed around the globe and different physical features can be distinguished. The lumps observed in the Earth's gravity field result from this uneven distribution of mass on the Earth's surface and GRACE will map these perturbations with unprecedented accuracy.Here's an example of how it works. The two GRACE satellites are traveling in space, both 500 kilometers above the earth. As the front satellite approaches an area of higher gravity, it will be pulled toward the area of higher gravity and speed up. This increases the distance betweenthe two satellites. As the satellites straddle the area of higher gravity, the front satellite will slow down and the trailing satellite will speed up. As the trailing satellite passes the area of higher gravity, it will slow down and the lead satellite will not be affected. As the satellites move around the Earth, the speeding up and slowing down of the satellites will allow scientists to measure the distance between the two satellites, and, therefore, map the earth's gravity field.

You can read full artice relating to GRACE MISSION and its objectives at the GRACE webpage

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