A European-built probe designed to explore the hot, dense atmosphere of Venus left Earth's orbit early Wednesday and started on its five-month journey to Earth's neighbor, scientists at mission control said. The European Space Agency's Venus Express probe lifted off at 0333 GMT at the Russian-leased Baikonur cosmodrome in Kazakhstan, before heading northeast above the desert and into orbit around the earth in a successful launch. About 1 1/2 hours later it separated from its final booster, leaving orbit on a trajectory toward Venus. Scientists at European Space Agency picked up a signal from the Venus Express probe on their first try. Venus Express - Europe's first mission to Venus - was originally scheduled to go up October 26. However, the launch was postponed after checks revealed a problem with the thermal insulation in the upper section of the Soyuz-Fregat rocket. The mission aims to explore the hot and dense atmosphere around the planet, concentrating on its greenhouse effect and the permanent hurricane force winds that constantly encircle it. It should take 163 days, or roughly five months, for the $260 million probe to reach Venus. Venus Express is expected to begin its experiments in early June.