Venus is probably the most peculiar planet that we have in our solar system. If you were observing it from far away you’d probably think that it was a twin of Earth, and for the most part you’d be right, but we know that it’s nothing like the place we call home. It’s atmosphere is a testament to the devastation that can be wrought by global warming with the surface temperature exceeding 400 degrees. Venus is also the only planet that spins in the opposite (retrograde) direction to every other planet, a mystery that still remains unsolved. Still for all we know about our celestial sister there’s always more to be learned and that’s where the Venus Express comes in.
Launched back in 2005 the Venus Express mission took the platform developed for the Mars Express mission and tweaked it for observational use around Venus. The Venus Express’ primary mission was the long term observation of Venus’ atmosphere as well as some limited study of its surface (a rather difficult task considering Venu’s dense atmosphere). It arrived at Venus back in early 2006 and has been sending data back ever since with its primary mission being extended several times since then. However the on board fuel resources are beginning to run low so the scientists controlling the craft proposed a daring idea: do a controlled deep dive into the atmosphere to gather even more detailed information about Venus’ atmosphere.
Typically the Venus Express orbits around 250KM above Venus’ surface, a pretty typical height for observational activities. The proposed dive however had the craft diving down to below 150KM, an incredibly low altitude for any craft to attempt. To put it in perspective the “boundary of space” (referred to as the Karman line) is about 100KM above Earth’s surface, putting this craft not too far off that boundary. Considering that Venus’ atmosphere is far more dense than Earth’s the risks you run by diving down that low are increased dramatically as the drag you’ll experience at that height will be far greater. Still, even with all those risks, the proposed dive went ahead last week.
The amazing thing about it? The craft survived.
The dive brought the craft down to a staggering 130KM above Venus’ surface during which it saw some drastic changes in its operating environment. The atmospheric density increased a thousandfold between the 160KM and 130KM, significantly increasing the drag on the spacecraft. This in turn led to the solar panels experiencing heating over 100 degrees, enough to boil water on them. It’s spent about a month at various low altitudes before the mission team brought it back up out of the cloudy depths, where its orbit will now slowly degrade over time before it re-enters the atmosphere one last time.
It’s stuff like this that gets me excited about space and the science we can do in it. I mean we’ve got an almost decade old craft orbiting another planet and we purposefully plunged it down, just in the hopes that we’d get some better data. Not only did it manage to do that but it came back out the other side, still ready and raring to go. If that isn’t a testament to our talents in engineering and orbital mechanics prowess then I don’t know what is.