Europe is set to launch two satellites with missions: one will track environmental damage to Earth, while the other will test one of Einstein's physics theories.
They will be hoisted from Europe's launch pad in Kourou, French Guiana, at 2102 GMT Friday on a Russian built Soyuz rocket.
EU's satellite launch
What is the Microscope satellite?
The Microscope satellite was designed by French scientists to test the "equivalence principle" proposed by Albert Einstein, which says that a feather in a vacuum should fall at the same speed as a lead ball.
The experiment will compare the motion of two different objects "in almost perfect and permanent free fall."
If any difference in motion is observed, the principle would be disproven.
How relevant is Microscope's research?
According to France's CNES space agency, which financed 90 percent of the project, if any difference in motion between the two objects is observed, the equivalence principle would collapse—"an event that would shake the foundations of physics."
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What is the Copernicus Project?
Six satellites will be built and launched under the Copernicus project, a joint undertaking of ESA and the European Union (EU).
Sentinel 1A and 1B would involve macro monitoring of environmental changes.
Sentinel-2 will deliver high-resolution optical images of forests and land use.
Sentinel-3 provides ocean and land data while Sentinels 4 and 5 will monitor Earth's atmospheric composition for changes.
What is the Sentinel satellite?
Sentinel-1A and 1B are twin satellites, part of the 3.8-billion-euro Copernicus project.
Sentinel 1A was launched in April 2014 equipped to scan the Earth with cloud-penetrating radar.
With the launch of 1B, the twin satellites will be able to take a picture of anywhere on Earth from an altitude of 700km.
They will be used to spot icebergs, oil spills, illegal logging and landslides.
Copernicus has far reaching applications
The European Space Agency says that the Copernicus project "will provide accurate, timely and easily accessible information to improve the management of the environment, understand and mitigate the effects of climate change and ensure civil security."
29 Apr 2016
EU Sentinel radar satellite takes first image
EU's Earth observation satellite, Sentinel-1b, has returned its first radar imagery of a 250km swathe of the Arctic that includes Svalbard, the Norwegian archipelago.
The data from Sentinel 1a and 1b, approximately 5 terabits per day, will be totally free and open for anyone to use.
Scientists hailed the first image as a "massive success that bodes well for the future of the program."