How do space probes navigate large distances with such accuracy?
538789
The fact that there's pretty much nothing random in orbital mechanics is very helpful along with the fact that we know pretty much everything about what affect all the objects in the solar system have on the spacecraft, that way they can just run the simulations using computers to high precision and take account of pretty much everything.\n\nIt is of course common to use mid-course correction burns to correct for any errors when the craft was first sent off into space.
51985
We can view quite a distance away (measured in light years) from our own solar system using the latest generation of telescopes and probes but we have not even yet begun to exit from our own solar system. Even the distance needed to escape our own galaxy, the Milky Way, is beyond our capability as of yet. We do not even know most of the fundamental questions pertaining the formation and existance of the galaxy such as dark matter. Our knowledge of the outer solar system stems from mostly interpretations of photos sent back by probes such as Voyager and the Hubble Telescope as well as the never generation of scanning tools but that is all for now. Other phenomenons we can speculate and conjecture using maths such as the existance of black holes. Maybe one day we may venture farther away but with problems even for a manned flight reaching Mars, that time will be long away indeed and it may never be possible to ever reach the outer limit of what we know as space for it is light years away and even now conjecture is whether there really is an outer limit to our universe as it is still expanding. As for other galaxies there are many abound ours is only one of millions, there are examples like the Crab Nebula etc.
455827
Because of the great distances involved, the most reliable way we have to look for aliens is to search the sky for the different forms of electromagnetic radiation that a technologically advanced society might generate, such as radio waves.  SETI (Search for Extra Terrestrial Intelligence) does just this, looking for anything that might be interpreted as signs of intelligence in the background noise that otherwise permeates the universe.  Nothing conclusive so far, but absence of evidence is not evidence of absence.  With the universe as unimaginably large as it is, odds are something is out there.
581211
Astronomers determined the size and shape of our galaxy and measured distances to other stars using the “parallax method” (and eventually other methods using the star’s light spectrum).  Unfortunately, these methods do little to help us find out the exact distance to our very own star, the Sun.  Surprisingly, to get the distance to the sun, astronomers first had to determine the exact distance to Venus!\n\nWith the invention of radar, scientists were able to measure the distance to Venus very precisely.  By timing how long it took the radar beam to travel at the speed of light to Venus and back, the total distance to the object can be determined from the equation:\n\nDistance = (Speed of Light) X (Total Time)/2\n\nThe reason the total time is divided by two is to get just the distance from the Earth to the object.\nEarth-Sun Distance = (Earth-Venus Distance) / (Cos q)\n\nUsing trigonometry, astronomers now know that the “Astronomical Unit” = 92,955,820.5 miles (149,597,892 kilometers).  This incredible degree of accuracy is possible because the speed of light is known very precisely and extremely accurate clocks are used to time the radar reflection.  Radar can’t be used to determine the distance to the Sun directly because the Sun doesn’t have a solid surface to reflect the radar efficiently.
354744
This is a great question, actually, and one that bothered astronomers for centuries.  In short, there’s no simple way to measure the distances to planets—at least not without really good telescopes (and a bit of luck).\n\nIn the early 17th Century, Kepler devised his Third Law, which releated the distance of a planet from the Sun and the time it took to revolve around the Sun.  So if you know one interplanetary distance, you can figure out the rest.  Which is all well and good, except that there were no good distances at the time.  (A rough sense of the distance between the Sun and Earth constrained the numbers somewhat, but the estimates were pretty far off—Kepler thought the Solar Syatem was about one seventh its actual size.)\n\nThe first accurate means of determining the distances was by observing transits of Venus across the face of the Sun.  Through relatively simple trigonometry, one can calculate the actual distances between the Sun, Venus, and Earth.  Unfortunately, transits don’t occur very frequently, so it was only in the 19th Century that reasonable results were achieved.\n\nNowadays, the distances to planets are determined by bouncing radar off them.  Because we know how fast light travels, we can simply measure the time between emitting a radio pulse and its return back to Earth, which gives us the distance!  Easy as pie…\n\n(In the case of the Moon, we actually bounce lasers off a reflector left there by Apollo astronauts.  Because of the phase information of the laser light, we can get extremely accurate distances to our nearest neighbor.  That’s how we confirmed that the Moon is moving away from us at the rate of about 3.8 centimters per year.)\n\n\nRyan Wyatt\nRose Center for Earth & Space\nNew York, New York
303494
Geodetic Traverse Surveying
138361
Hmm...the Hubble has surely helped with that, for one. The observories here on Earth are incredibly sophisticated, with high-powered lenses. When a probe drifts into space, I suupose it can still take distant pictures if it has battery power left.
105792
This site should explain them for you:\n\nhttp://www-istp.gsfc.nasa.gov/stargaze/Slatlong.htm
229729
Same reason we don't go looking for aliens in the millions of other galaxies.  Space travel isn't something that's fast.  It takes years and years to get somewhere that you can see in a telescope, let alone trying to go to somewhere that you can't.
408419
Perry (the first man to reach the pole) used dead reckoning and solar navigation.  Because the sun never sets during the summer, you can't navigate by the stars in polar regions unless you go during the winter, which is a bad idea.\n\nAnywhere north of the tropics, at noon, your shadow points due north.  Perry used this as the basis for his navigation. Once you know which way north is, you can adjust your compasses appropriately. (The magnetic north pole is hundreds of miles or so from the real north pole, so compasses point in the wrong direction, but don't spin wildly, near the north pole.)\n\nThese navigation techniques left some room for doubt, and there have been long controversies as to how close to the pole many of those explorers got.  The source below is a really interesting article on one of those stories.
670510
GPS is not accurate enough? If I'm not wrong, GPS have the potential to measure to accuracy up to few cm. And you only need feet accuracy, it won't be problem with GPS. (Well, you had to dig your pocket deeper for a prime quality GPS though)\n\nPerhaps you can use a radio frequency device, but make sure you buy one that uses frequency that is high enough or you'll get the wrong reading. I don't know if there is any sold in the market that is specifically made for calculating distance though. And I'm doubting that a radio frequency reading is accurate too if your line of sight is not clear.\n\nPerhaps you should use a ladder or climb the bushes there and uses laser.\n\nOh yeah, I forgot, if you know the coordinate of the two points you're measuring (use GPS for this), perhaps you can use Google Earth (http://earth.google.com/ ) to plot the points there and use the distance measuring device provided there. Google Earth can measure up to cm accuracy (provided the correct coordinate)
902786
Imagine how hard it is to try to teach High Schoolers anything about the planets when one of them has a name like this! But anyway, go to NASA's website. There is a place there where you can find anything worth seeing at any location. It will even tell you when stuff like the Space Station will fly overhead. And most telescopes come with locating software if you ever get that involved. I hope you will. It seems like we never learn much about space, but it has taken a long time to get as far as we are now.
682254
The determination of angles and distance are essentially separate actions. One aims the telescope with great care first; this is the part of the process with real potential for human error. When the telescope has been aimed, the angles are determined. Only then does one initiate the reading of the distance to the target by the EDM. That takes only a few seconds; the calculations are performed immediately. \n\nThe total station is mounted on a tripod and leveled before use. Meanwhile, the prism is mounted on a pole of known height; the mounting bracket includes aids for aiming the instrument. The prism is mounted so that its reflection point is aligned with the center of the pole on which it has been mounted. Although the tip of the pole is placed on the point to be surveyed, the instrument must be aimed at the prism. So it will calculate the position of the prism, not the point to be surveyed. Since the prism is directly above the tip, the height of the pole may be subtracted to determine the location of the point. That may be done automatically. (The pole must be held upright, and a bubble level is attached to give the worker holding the pole a check. It is not as easy as one might expect to hold the pole upright, particularly if there is any wind; as a result, multiple readings may be required. Because of that problem, the sighting method chosen at Pompeii was, if possible, not to begin by sighting on the prism itself but on the tip of the pole where it touched the ground. The angle from north would then be fixed and unaffected by the movement of the pole. Then the aim of the telescope could be raised to the level of the prism, adjusting only the angle of inclination.) \n\nIn Pompeii a Topcon total station was used,* and we quickly learned a few features of the equipment. (Mr. Eiteljorg had driven to Charlottesville to learn the idiosyncrasies of the instrument in May, but a malfunctioning battery cut the session short, and a few "simple" or "trivial" processes turned out to be neither simple nor trivial without practice.) For instance, leveling the total station is more difficult than we had realized (and spongy soil is devastating, since the instrument is naturally unstable if its support is), and it depends upon accurate adjustment of the bubble level built into the instrument. We also learned that datum points were more difficult to select than expected, since they had to be repeatable; that is, we had to be able to find them again and again with absolute accuracy - this year and next. \n\nWhen the instrument is set up and turned on, it sets itself to be pointing to zero degrees (north) when power is first supplied. The user must then re-set the instrument to zero degrees when it is actually pointing north; we learned that there is no secondary battery for back-up. When the battery dies, the instrument must be re-set for zero degrees. \n\nFortunately, these lessons came in the first day or two, and we had no more surprises. (One problem was on-going, however. There are two adjustment knobs for rotating within the horizontal plane. One rotates the telescope to make a sighting, with the readout of angles displaying changes. The other, however, permits the user to rotate the entire instrument and to keep the current angle unchanged during the process. That effectively re-orients the zero or north setting. That can be very helpful when setting up or re-setting the instrument, but, of course, it can be devastating if one makes that adjustment by mistake and thereby changes the north setting. This particular instrument was designed in such a way that it was too easy to re-set the instrument when one only wanted to make a sighting.) \n\nSince we were dealing with standing architecture, the prism pole was often inadequate for our work. The pole is designed to be placed on the survey point in a vertical position; it cannot be placed on a point on the face of a wall. In fact, a prism pole can rarely be placed a
874946
Hi. This is how NASA does it : http://science.nasa.gov/headlines/y2000/ast02nov_1.htm
99926
In some cases, it uses small manuvering thrusters to steer it, but mostly uses it gyroscopes to steer in and keep it 'locked' on to the portion of the sky it is studying.
464463
Just set your reference point by yourself. Everywhere can be North in space.
201708
Several different ways depending on the distances involved.\n\nFor close stars, we look at where the star appears to be in the sky at times about half a year apart. Think of looking at your outstretched thumb through your left eye, and then your right eye. The thumb appears to be in a different position with respect to a distant building. In the same way, a star will appear to be in a slightly different position when we look at it from different ends of the earth's orbit. The amount of shift depends on the distance to the star and that allows us to figure out the distance. This method is called paralax.\n\nFor slightly more distant stars, we look at clusters of stars and measure their apparent motion across the sky over a course of *years*. Just as train tracks appear to converge at the horizon, the motions of the star will appear to converge. The rate of convergence is related to how far away the cluster is.\n\nWith these methods, we get enough stars to do statistical analyses of the brightness of the stars versus their chemical composition and other aspects of their spectrum. With this knowledge, we can estimate the distances to further stars by just comparing their spectrum to that of already measured stars. Scientific models of stars are used at this stage.\n\nFarther away than this, we look for 'standard candles', that is, stars of known brightness. By comparing the brightness they appear to be versus their actual brightness, we can estimate their distances. A particular type of 'standard candles' are the Cepheid variables. Their actual brightness depends on how fast they vibrate. Since we can see these stars in other galaxies, we can use them to determine the distances to those galaxies.\n\nFinally, after we know the ditances to some galaxies, we can measure the rate at which they move apart as a function of distance. By measure red-shift (hence speed) of more distant galaxies, we can determine their distances.