BERLIN, Germany (AP) -- Scientists were counting down Tuesday for the blast off of a Russian booster rocket carrying a European-built probe aimed at exploring the hot, dense atmosphere around Venus.The launch of the European Space Agency's Venus Express probe is planned for 0333 GMT Wednesday at the Russian-leased Baikonur cosmodrome in Kazakhstan.Venus Express was originally scheduled to go up on October 26, but the launch was postponed after checks revealed problems with the thermal insulation in the upper stage of the Soyuz-Fregat rocket. Once it separates from the rocket, scientists at ESA's mission control in Darmstadt, south of Frankfurt, plan to make contact with the probe."We've just had the pre-launch briefing and everything is in the green zone," said ESA spokeswoman Jocelyne Landeau. "Everything is ready for go."The mission, Europe's first to Venus, will concentrate on the greenhouse effect around the planet and the permanent hurricane force winds that constantly encircle it.In addition, instruments on the probe will try to find an indication as to whether Venus' many volcanoes are active."Venus is still a big mystery," Gerhard Schwehm, head of the planetary missions at ESA said Monday.The probe will take 155 days, or roughly five months, to reach Venus. It is expected to begin its experiments in early June.Copyright 2005 The Associated Press. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.