Voyager 2 pipes up again
Discussion
Voyager (as well as a number of spacecraft) uses the decay of Plutonium as a heat source to generate electricity. It has on board a Radioactive Thermal Generator (RTG) which is, in effect, a nuclear battery.
RTGs are used on spacecraft in situations when other, more common power sources such as chemical batteries, fuel cells or solar cells are not sufficient for the job.
When Voyager was being designed in the late 1960s, its original mission was a fly by of Jupiter. Jupiter is 500 million miles from the sun and power of sunlight at that distance is only 1/25 what it is at earth (93 million miles from the sun). Because of the low light levels, it was decided early on in the mission planning that solar cells would not be able to provide sufficient power so the decision was made to go for the RTG option. This decision also opened up the possibility of follow on flybys of further planets - which were eventually incorporated into the mission.
Other space missions have used RTGs too, notably the Viking Mars landers, the experiment packages left on the moon by later Apollo missions, the Galileo probe to Jupiter, the Cassini probe to Saturn, and the New Horizons probe to Pluto.
At the moment, orbiting Jupiter is the Juno probe. Juno DOES use solar panels to provide power even though it is 500 million miles from the sun. This is because, in the half century since Voyager was designed, solar panels have become much more efficient so it was deemed a practical proposal for Juno. The Juno solar panels are very large, being 30 feet long (there are three of them).
RTG is only ever installed on a spacecraft if there is no other option because there is a small but definite risk attached to their use, particularly during launch. If a launch vehicle is lost (it does happen every now and then) with an RTG powered spacecraft on board, the RTG cannister will end up back on earth, possibly damaged and possibly leaking. As most RTG launches have been from Cape Canaveral, the RTG cannister would end up in the Atlantic.
RTGs are used on spacecraft in situations when other, more common power sources such as chemical batteries, fuel cells or solar cells are not sufficient for the job.
When Voyager was being designed in the late 1960s, its original mission was a fly by of Jupiter. Jupiter is 500 million miles from the sun and power of sunlight at that distance is only 1/25 what it is at earth (93 million miles from the sun). Because of the low light levels, it was decided early on in the mission planning that solar cells would not be able to provide sufficient power so the decision was made to go for the RTG option. This decision also opened up the possibility of follow on flybys of further planets - which were eventually incorporated into the mission.
Other space missions have used RTGs too, notably the Viking Mars landers, the experiment packages left on the moon by later Apollo missions, the Galileo probe to Jupiter, the Cassini probe to Saturn, and the New Horizons probe to Pluto.
At the moment, orbiting Jupiter is the Juno probe. Juno DOES use solar panels to provide power even though it is 500 million miles from the sun. This is because, in the half century since Voyager was designed, solar panels have become much more efficient so it was deemed a practical proposal for Juno. The Juno solar panels are very large, being 30 feet long (there are three of them).
RTG is only ever installed on a spacecraft if there is no other option because there is a small but definite risk attached to their use, particularly during launch. If a launch vehicle is lost (it does happen every now and then) with an RTG powered spacecraft on board, the RTG cannister will end up back on earth, possibly damaged and possibly leaking. As most RTG launches have been from Cape Canaveral, the RTG cannister would end up in the Atlantic.
nealeh1875 said:
It's unbelievable especially considering this..
Of no real relevance. They were programmed to carry out certain tasks, which they did wonderfully well. Indeed, they exceeded expectations. And they were updated and improved whilst in space from time to time by uplinking new code.Article said:
they have 200,000 times less memory than a smartphone
At the moment they aren't doing much at all apart from basically sending out a signal to tell us that they are still powered up. Nearly all the experiments (cameras, ultra violet sensors, electric motors etc) were turned off many years ago. The only experiment package still functioning is the magnetometer which measures fluctuations in the sun's magnetic field. This was left operating as they can use the data from this to help determine the boundaries of the solar system through measuring the sun's interaction with intergalactic space.
Eric Mc said:
nealeh1875 said:
It's unbelievable especially considering this..
Of no real relevance. They were programmed to carry out certain tasks, which they did wonderfully well. Indeed, they exceeded expectations. And they were updated and improved whilst in space from time to time by uplinking new code.Article said:
they have 200,000 times less memory than a smartphone
At the moment they aren't doing much at all apart from basically sending out a signal to tell us that they are still powered up. Nearly all the experiments (cameras, ultra violet sensors, electric motors etc) were turned off many years ago. The only experiment package still functioning is the magnetometer which measures fluctuations in the sun's magnetic field. This was left operating as they can use the data from this to help determine the boundaries of the solar system through measuring the sun's interaction with intergalactic space.
Depends on how powerful the radio signal is and the sensitivity of the receiving equipment. Some of the furthest objects in the universe (13 BILLION light years away) can ONLY be detected by their radio signals.
Obviously, a spacecraft the size of a Transit Van is not going to have the radio power of a galaxy so the signal from something like Voyager is exceedingly weak. However, the ground equipment on earth is very sensitive and it can still pick up these very weak signals. In fact, Voyage will most likely run out of power generating juice before its signal becomes too weak to be picked up on earth (don't forget that there are two of these Voyagers and both are still in contact with earth).
Obviously, a spacecraft the size of a Transit Van is not going to have the radio power of a galaxy so the signal from something like Voyager is exceedingly weak. However, the ground equipment on earth is very sensitive and it can still pick up these very weak signals. In fact, Voyage will most likely run out of power generating juice before its signal becomes too weak to be picked up on earth (don't forget that there are two of these Voyagers and both are still in contact with earth).
Taita said:
Are those other sensors turned off to save power or similar? eg the plutonium slowly drops its output over the years?
They were. Once Voyager 2 had passed by Neptune (in 1989) there was nothing for its camera to look at so the camera was turned off to save power. Famously, before it did this, Carl Sagan requested that it take one last shot as it faced back along its trajectory from the inner Solar System - the famous Blue Dot picture.
Other sensors were turned off too for the same reason.
tight fart said:
Gameface said:
It's the TWELVE BILLION miles that gets me.
I get the hump when I have to drive from London to Cambridge!
How long would it take for light to travel 12 billion miles?I get the hump when I have to drive from London to Cambridge!
(My guess around a day?)
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