Back in Monday's post about the return of the Soviet Union's Cosmos 482 lander originally intended to land on Venus looking to come back to the ground on Earth, the window it would re-enter in was originally cited as "May 10, plus/minus 2.2 days."
A good rule of thumb in these situations is the closer we get to the launch
window, the less the uncertainty.
As of 3:00 PM ET, the latest prediction from the European Space Agency
is: "2:37 a.m. ET (0637 GMT) on May 10 +/- 3.28 hours." Since 0.28
hours is 16.8 minutes, I'll just call it 17 minutes and add/subtract 3 hours 17 minutes to get both ends of the window - which is just about 6:34 (hrs: mins) long. The uncertainty therefore covers 0320 to 0954
GMT. They also provide this graphic of the orbits that cover that
range. Notice over on the west coast of Australia, there's a red dot
noted as COW 0637, or Center of Window 0637 GMT. The uncertainty combines to cover 9:54 PM Friday
night to 5:20 AM Saturday morning.
A 'ground track' map showing the latest predictions on where the Kosmos 482
Venus probe could fall to Earth on May 9 or May 10. (Image credit: ESA/ESOC
Space Debris Office)
The main thing to bear in mind that things like getting affected by reentering space junk is so unlikely that it makes winning the Lotto seem like an absolute certainty. The Earth's surface is 71% water and an area of just under 197 million square miles. Both the target and the satellite are a couple/few square feet out of those millions of square miles. I dove into this a year ago in a story about a guy in Naples, (southwest Florida) who is either the luckiest or unluckiest guy on the planet because a piece of a battery pack from the International Space Station hit his house.
That's also assuming that the vehicle doesn't 'catch air' and skate around during reentry. Then there's the boost from internal parts turning gaseous and 'jetting' the vehicle.
ReplyDeleteAnd, dammit, the swish of doom in the above photo includes Florida. So far. Pretty much.
Fingers crossed.
Please, allow me to highlight my ignorance. Why does the path make a wavy line?
ReplyDeleteThe ground track is the projection of the satellite’s elliptic orbit onto the prolate spheroidal earth, and then mangled with the map-maker’s projection of that prolate spheroid onto the flat surface of a map. Geometry is fun!
DeleteIt makes a wavy line because the orbit is not in the plane of the earth's equator, it is inclined by 52° (where it ended up after a failed boost into Venus transfer orbit). Because the earth is spinning underneath the orbit (which is an ellipse) the ground trace of the satellite is the wavy line plotted. The space between the different orbit tracks is essentially how far the earth rotates during the time of one orbit (the lower the satellite, the less time an orbit takes). There are a lot of complications if you want to get precise, but this is the simple explanation for us non-rocket scientists .
DeleteART
Thanks, Rob, thanks Anon..I think it makes sense now.
DeleteYears ago, I watched a Chinese satellite de-orbit early one morning. At first, it appeared as a bolide near the horizon. Then it looked more like a fireworks mortar before it explodes. Soon, it was a conglomeration of bits and pieces burning up like meteors overhead. I could even hear very faint sonic booms. As I watched it pass overhead, I suddenly realized I was standing in the middle of a parking lot at work, there was nothing to even slow down anything that fell to the ground, and made a quick dash into the shop.
ReplyDeleteI think I'll go outside for awhile, and gaze at the stars. One of orbital paths is over my area, and a good light show will be interesting to watch.
That's a pretty large area, lots of land for a planet mostly water.
ReplyDeleteJonathan
Got to watch a satellite or a meteor burn up one night while star watching, it was when I was a kid in the BoyScouts, started out just above the horizon, dull red, quickly went up thru the color scale to white hot, lit up the ledge we where sitting on bright as day, quickly whatever it was went back down to dull red before it went behind a mountain, from high orange to white lot of streamers and sparks shot out of it. Strangest thing was there wasn't any noises, watching this totally spectacular event in silence. It left afterimages in our eyes. And fast, that thing was blistering fast, maybe 4 seconds horizon to almost horizon with a mountain blocking the last bit of its trajectory. We tried to find mention of what it was, but back in 1968 news was a might slower than now. Fantastic thing to be fortunate enough, right time right place. Happened seconds from 1:30am too. You really must see it with your eyes to appreciate the intensity and incredible speed it had burning up.
ReplyDeleteMSG Grumpy got my hopes up on your prior post by recalling the Six Million Dollar Man battling a fallen Russian Venus probe.
ReplyDeleteRT Russia posted it has landed in the Indian Ocean.
ReplyDelete