The European Space Agency probe Venus Express lifted off on a Russian rocket at 3.33am GMT on Wednesday, from which it wad due to separate from two hours later.
Its journey to Venus is expected to take 163 days.
“I’m extremely happy”, European Space Agency (ESA) scientific program director David Southwood said 10 minutes after the launch, when all systems were normal.
Ninety minutes into its journey, mission controllers said it had left the Earth’s orbit and was on its way to Venus, and later received the first signal from the craft confirming all had gone to plan.
The probe was originally scheduled to launch on October 26, but was delayed due to “contamination” detected inside the fairing — the bullet-shaped hood that covers the payload on the top of the rocket — in final checks at Baikonur.
Venus Express is the ESA’s first probe to the planet closest to Earth, and will explore its unusual stormy atmosphere and runaway global warming in the hope of better understanding our own greenhouse-gas problem and climate change.
Venus, the second planet from the Sun, is similar in size, mass and age to Earth but has a vastly different and ferociously hot weather system.
It is also known as the Evening Star because of the bright light it reflects from the sun.
Venus is blanketed by thick clouds of suffocating gas, mostly carbon dioxide, which traps incoming solar radiation and is driven by often hurricane-force winds to heat the planet’s surface to an average temperature of 467 Celsius, the hottest in the solar system.
Surface pressure is about 90 times that on Earth.
The planet’s clouds reflect back 80 percent of the Sun’s radiation and absorb another 10 percent, leaving just 10 percent to filter down to the surface.
“Venus has no surface water, a toxic, heavy atmosphere made up almost entirely of carbon dioxide (CO2) with clouds of sulphuric acid, and at the surface the atmospheric pressure is over 90 times that of Earth at sea-level,” the ESA notes.
After its long journey, the craft is scheduled to arrive off Venus in April, when it will be placed in an elliptical orbit, swooping to as low as 250 kilometres above the surface to a height of 66,000 kilometres.