Have any probes been launched (or has it been considered) directly “north” or “south” of the solar system with the intent of getting bird’s-eye imagery of, initially, the solar system and eventually the Milky Way?
Ulysses, which studied the sun
It was launched in the ecliptic, but swung by Jupiter to knock it out by about 80 degrees relative to the ecliptic. It didn’t leave the solar system, but wanted to study the sun from all angles.
Voyager 1 was ejected significantly out of the plane of the solar system, and took the famous Family portrait of the solar system. It was ejected out of plane by Saturn.
Launching directly from Earth significantly out of the plane would be extremely costly.
Getting a bird’s-eye view of the galaxy isn’t really possible with current technology. The spacecraft would have to travel for much too long. The milky way is really, really big.
An interesting thing I just learned, the plane of the solar system is at a pretty good angle with respect to the plane of the galaxy. I guess there’s no reason for that not to be the case, but I hadn’t really thought about it before.
I understand that it would be expensive and impractical, and would not be taking advantage of the earth’s rotation. But it would be an interesting, long term project.
No. The energy required to make a direct 90° change in the orbital inclination (angle between the ecliptic of the solar system and the orbit) is on the order of 900 MJ/kg. By comparison, it costs about 10 MJ/kg to send a vehicle directly from Low Earth orbit to Mars orbit on a pseudo-minimum energy transfer. (We have yet to send vehicles directly to outer planets; all interplanetary missions to the outer planets have been done using planetary swingbys of Venus, Mars, or back around Earth, sometimes multiple times; this solution isn’t feasible for highly elliptic transfers for obvious reasons.) Performing this maneuver would require some kind of breakthrough high energy propulsion system with an I[SUB]sp[/SUB] >10,000 s (greater than nuclear thermal, in the range of fission fragment, nuclear pulse propulsion, or fusion).
It isn’t necessary to send a probe to solar north or south to go out of the plane of our galaxy, as the solar system lies at a 60° inclination to the galactic ecliptic, so being able to incline an escape trajectory at ~30° going the correct direction would be sufficient. This would require a total energy of ~120 MJ/kg, plus another 880 MJ/kg to escape from the solar system; so basically 1 GJ/kg. Mind you, this is at the minimum speed to escape Sol’s sphere of influence; just getting above the stellar disk requires travelling about 10,000 lyr, which at the speed that the Voyager 1 spacecraft is going would take about 177 million years, by which time even the Republicans and Democrats won’t care about arguing over whose Congressional district NASA appropriations should go to. (The Solar system will also be on the other side of the galaxy at that point.) To actually get sufficiently above the galatic disk so that most of the stars are not occluded by dust will take another, or, three quarters of a billion years or so. Since we couldn’t possible expect a probe to function for anything remotely like that duration nor transmit data across such vast distances, it isn’t a priority at the moment.
Stranger
It’s not just expensive and impractical. The pyramids were expensive, impractical, interesting long-term projects. The galaxy is about 100,000 light years across, and 2,000 light years thick. So how far out of the galactic plane do you have to get to get a good photo? Say you want to get out 5000 light years. That means that the signal alone would take 5000 years to reach back to earth. We don’t have ways of making electronics last 5000 years. Your spacecraft’s not going to be going the speed of light. Say you use something crazy, probably nukes, and get it going to 10% the speed of light. That means it will take 50,000 years to get that point. 50,000 years ago humans were barely a species.
It’s like interstellar travel, which could conceivably be considered an expensive, interesting long term project, but 1000 times harder.
I forgot about Ulysses, which did have an inclined and highly elliptic orbit, but was assuming that the o.p. was considering spacecraft in a more or less circular orbit at Earth orbital distance. My error.
Stranger
Several spacecraft have been launched on direct trajectories to Jupiter, and one spacecraft, New Horizons, was launched directly into an escape trajectory. It did make a gravity assist off Jupiter, but it didn’t need to in order to reach Pluto (making the gravity assist did shorten the amount of time it will take to get to Pluto).
I believe the pioneer probes 10 and 11 could be said to have done this however it was just the after effect of the way it got to the planets. Pioneer H, never launched, was planned to do exactly what the OP asked.
http://omniweb.gsfc.nasa.gov/coho/helios/book2/b2_12.html
Pioneer 11, sort of. Pioneer 10 stayed almost perfectly in the ecliptic.
Pioneer H was planned to swing by Jupiter and intentionally be swung out of the ecliptic. It eventually sort of turned into the Ulysses mission, which did just that.
Huh. I didn’t know that either. Thank you for pointing that out. I have missed it in the site you linked to, but is the Northern Hemisphere looking out at the arm and the Southern Hemisphere looking into the centre? I think I read that somewhere else on the dope.
If you look at that ‘family portrait’ of the solar system you’ll see it’s, ah, less than spectacular. It’s the constant problem of to us planets are huge but to each other they are incredibly far away. To have more than one in a photo together each will always be nothing more than a pin prick of light (if even that).
As far as a photo of the whole galaxy, even if we could send a probe through a Star Trek-like wormhole and have it instantly appear at a far enough distance from the Milky Way to fit the whole thing in its field of view, it would be so far away that even at the speed of light it would take tens of thousands of years for the transmitted picture to reach Earth.