Is there some good reason we can’t put permanently orbitting probes around every planet in the solar system? It seems like every few years we send out a probe that does a few weeks work when it gets wherever it’s going, and then crashes or dies. Why don’t we just put satellites around every planet and be done with it?
After a while they lose power and/or get mucked up by radiation.
The planned crash-landing allows the engineers to control its fate - so they can, for instance, have it plunge into Jupiter rather than eventually crash into a Jovian moon which just might have some sort of microbial life that would get contaminated.
Each probe we launch carries new telemetry equipment and other measuring devices to allow new and better information to be gathered. What advantage do you imagine there would be in having a satellite going round Mars or Venus today with 1970s technology on board?
The long distance probes took advantage of unusual planetary arrangements to make the trip from place to place to the edge of the solar system with only one launch. I don’t believe there’s any technical reason why we couldn’t send a bunch of probes out, one per planet, but there wouldn’t necessarily be any benefit in keeping them there permenantly.
Right–even Earth satellites have a fairly limited lifespan. Hubble’s only scheduled to last until 2010 (20 years total), and that’s a satellite that’s had hands-on human intervention from time to time (granted, those were to correct manufacturing errors, but you get the idea–if it’s on its own, things go even worse for a satellite).
Besides which, maintaining control of a satellite/probe, monitoring its progress and health, correcting errors, analyzing data it returns, blocking radio receiver time to get that data, etc., all take money, which is always limited.
There have been some long-term observations. The Magellan probe orbited Venus for 4 years and was only switched off when funding for its operation was cut off. The Galileo spacecraft arrived at Jupiter in 1995 and is still operational. I can’t remember if we have an operational satellite around Mars - there should have been, but there have been several failures.
Saturn, Uranus, Neptune and Pluto are very far away. It’s hard enough to get there and do a flyby, but to get there and stop - that’s even harder. You have to take the fuel necessary to brake and go into orbit. The Cassini probe is on its way to Saturn right now, and it will be the first probe to orbit that planet. We haven’t even done a flyby of Pluto yet.
There are currently two functional orbiters at Mars, Mars Global Surveyor and Mars Odyssey. MO has and future orbiters are planned to have longer operational lifetimes because they will be used as communications relays for rover missions.
I think the reason is more that if it crashes into the moon you won’t get any useful information out of the crash. But, if you crash into something interesting, maybe you’ll get some interesting data out of it. You might not, but then you’ve already gotten pretty much everything you designed the machine for (hopefully) so if you can take the chance and get something useful you might as well go for it.
It’s like hey, we’ve got all these neat pictures from orbit, and if we smash this thing straight down we’ll get some really detailed pictures of one area, but only once! So, once we’ve gotten all of our pics from orbit let’s pick an interesting area and head down towards it. Maybe you won’t see anything interesting, maybe you’ll see small martian grave stones that wouldn’t show up from orbit. Who knows. But it beats being guaranteed to see nothing more from orbit.
Nope, sorry engineer_comp_geek, the reason Galileo will be crashed into Jupiter is to avoid the miniscule chance of contaiminating an ecosystem on one of the moons. In a world without “planetary protection”, we’d probably let the thing limp around until it finally suffered a mission-ending malfunction or the money ran out.
I don’t know if there will be any opportunities to get supercloseups as it descends into Jupiter. The ability to do this will be limited by the fact that Galileo doesn’t transmit data continuously. It saves data on tape drives and then dumps it to Earth when the geometry is good.
True, you can learn things by crashing it into something interesting, but Bup is absolutely on the money as far as Galileo/Europa goes:
http://astrobiology.arc.nasa.gov/news/expandnews.cfm?id=392
Good article on NEAR/Eros crash landing, too: