It is a difficult business to design, build, successfully launch and then operate spacecraft on other worlds. Accomplishing the mission is particularly difficult for planetary probes, which go through significant atmospheres, collecting data on their way to the surface and, due to the challenges of the extreme environments associated with such destinations, often only survive for relatively brief periods once they have landed. Planetary probe missions go to places like Venus where the surface temperatures are 900° F, the pressures are 90 times that of Earth, and the largely carbon dioxide atmosphere has a significant component of sulfuric acid. Others attempt to reach giant gas balls like Saturn (only the Saturn moon Titan has been the target of a probe) or Jupiter. Jupiter's gaseous outer layer was successfully entered by the Galileo probe up to the point where the pressures were 22 times that of Earth. Such entries, unlike entering the atmosphere and landing, are more like blasting into the very stuff of the planet itself, dodging lightning strikes on the way.

NASA lost some early probe missions like Mariner 1, their first mission to Venus, and the international community has an even spottier record than the US. These missions require years of development and expensive, specialized advanced technologies like pressure chambers and thermal protection systems, not to mention specialized instrumentation. There have been a few notable successes such as the Pioneer Venus multi-probe mission, the Galileo probe and the recent European Huygens probe to Titan, which was part of the Saturn Cassini Mission. These missions, though, were either a while ago, hugely expensive, or both. The challenge for the next generation of missions is to take advantage of new technological developments, but no one wants to put unproven technologies on missions where close to $1 billion may be a stake. Yet, we need to consider some of the tasks at hand. How do you get there from here?

http://www.space.com/searchforlife/070719_seti_probing.html