ESA’S ROSETTA MISSION POISED TO ‘HARPOON’ A COMET
By James Rice
On Wednesday, Nov. 12, after a journey of nearly 11 years and an estimated 4 billion miles – scientists will attempt its first-ever landing upon a comet. This double-lobed icy body has been named 67P/Churyumov-Gerasimenko and it is about 2.5 miles across. If all goes according to plan, it will be one of the largest space-related events of the year – and certainly a pivotal one for the European Space Agency (ESA ).
ESA Rosetta spacecraft, which has been orbiting the comet since August 6, 2014, will deploy its box, shaped 220 lb lander called Philae for a 19-mile long descent to the surface which will take 7 hours. Landing is scheduled for 8:03 a.m. PST. The comet will be between the orbits of Jupiter and Mars (315 million miles from Earth) at landing and hurtling in toward its orbital swing around the sun, which it completes every 6.6 years.
The surface of this comet is complex and varied. Rosetta images from orbit reveal a landscape that could have easily come from a science fiction movie.
The surface of 67P/Churyumov-Gerasimenko is covered with smooth plains, depressions, boulders (some larger than a house), grooves, ridges, layered cliffs hundreds of feet high, steep slopes, pits, and regions that are shooting out spectacular but hazardous jets of gas and dust akin to a spouting whale.
The landing site is called Agilkia and it appears to be comprised of some fairly smooth plains/depressions with small scarps surrounding them. Some minor concentrations of boulders are also present. It should be noted that this site was chosen after 3 months of analysis from a set of candidates and this site was deemed the safest. This landing will be very risky, it is not a slam dunk by any means.
Because of the comet’s extreme low gravity and unknown surface conditions and properties, the Philae lander has two harpoons it will fire to anchor it to the surface. Then after reeling the harpoon lines in the lander will touchdown and use its ice screws located at the bottom of each of the three feet to anchor itself onto the surface.
After landing Philae will commence its science operations by taking a panorama and surface property measurements. Descent and landing images are expected to be returned as soon as possible. Philae has the unique capability to drill into the subsurface for samples which will be analyzed by its suite of instruments to determine what the comet is made of and to see if any organic molecules are present.
The prime science mission is only supposed to last about 2.5 days and it will be on primary battery power. However, Philae has a second science phase planned that could last up to 3 months, which will be conducted using backup batteries that can be recharged by solar panels.