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On September 15, NASA's ICESat-2 satellite departed Earth on the latest Delta II rocket. Fortunately, the satellite provides a successful shipment to the Delta II, as it began its important mission without incident. On Wednesday, NASA unveiled the first data transmitted: measurements of the Antarctic ice.
Like its predecessor, ICESat-2 is a laser altimeter capable of very accurately mapping surface elevations. These satellites were designed to take into account the changing altitude of surfaces, mainly the decrease of sea ice and polar ice sheets. The first edition of ICESESat had ended in 2010. Without ICESat-2, NASA has turned to similar instruments on board aircraft to collect the data it had in the meantime – an intensive project called Operation IceBridge.
Compared to some other Earth observation satellites, the principle at work here is quite simple, although the technology used to make it work is pretty much miraculous. The satellite emits a laser pulse on the Earth and measures the time necessary for its reflection. Do the math (speed of light and all that) and you have the distance between the satellite and the ground. With a precise knowledge of the position of the satellite, you can map with extreme precision the altitude of the surface of the globe.
Although ICESat-2 actually uses the same wavelength as the green laser pointer, you do not have to worry about being blinded by looking up at an unlucky moment. It is not an extremely bright laser that operates the satellite, but an extremely sensitive telescope. While billions of photons of laser light are sent to each pulse, only one dozen Or come back to the detector on the satellite – a fact that NASA has chosen to illustrate with what may be an exceedingly cute video with cartoon photons.
The delay between the disappearance of ICESat and the launch of ESESat-2 has at least led to an upgrade of the instrument. While the first satellite had a resolution of about 100 meters per pixel, ICESat-2 reduced it to just 0.7 meters, sending 10,000 pulses of laser light per second. It should also be slightly more sensitive, detecting surface elevation changes less than one centimeter per year.
ICESat-2 orbit from pole to pole by repeating measurements of each location of the Earth every 91 days. These measures track the shrinkage (or growth) of the ice sheet, as well as the thickness of the sea ice. The data can also show interesting things about unfrozen areas of the planet. The canopy height of the forest can be calculated when some photons bounce off trees and others sneak into the forest floor. One can also detect the movement of the ground surface caused by the displacement of the fault during an earthquake, as well as by changes in the level of the reservoir or lake.
According to NASA, the ICESat-2 team will spend a few weeks testing and optimizing the instrument before proceeding to official data collection. Although the European Space Agency has successfully orbited the similar CryoSat-2 (but radar-based) satellite since 2010, you can bet that glaciologists and other scientists would like to see the data from this new satellite enter. flow, eight years after the first dark ICESat.
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