Phil's European probe on Wednesday was on its way to make the first comet landing in history, after separation from its carrier ship Rosette.
“Phil separated at 3:35 am ET (8:35 GMT),” said Andrea Accomazzo, director of the mission control center at the European Space Agency (ESA).
“We observe it by telemetry,” he said against the background of applause from the team members.
"Phil's lander separated from the Rosette orbiter and is on its way to becoming the first spacecraft to land on a comet," the agency’s source said.
The descent of a 100-pound (220 pounds) robot will last about seven hours.
Carrying 10 auxiliary tools on board, Phil is designed to conduct experiments on the comet Churyumov-Gerasimenko, which rushes to meet the Sun at a distance of more than 500 million kilometers (300 million miles) from Earth.
Comets are believed to be intact pieces of ice and dust, containing secrets of the origin of the solar system and, possibly, life on Earth, originated more than 4, 6 billion years ago. If everything goes well, the Earth will receive a signal at about 11:00 am EST (8:35 GMT).
“Now he descends according to the laws of physics. We are on our way to the surface,” said ESA Senior Advisor Mark McCorin. “I don't have nails, so I won't bite them,” he joked.
Fila, which descends at a speed of 3.5 kilometers per hour, will release two harpoons into the surface of the comet, which, as engineers hope, will ensure sufficient grip.
Ice screws, located in the three legs of the module, will have to enter the ground, so that the probe does not jump back into space.
“The last test revealed an obvious malfunction in the thruster, which was to provide a downward push,” said Stefan Ulamek of the German aerospace company DLR.
"So we will be completely dependent on harpoons, which can penetrate to a depth of 2.5 meters," said Ulamek.