How is it possible that Voyage 2 can transmit info back to us over some 7.8 billion miles?

Question

I just don't understand how it can still send data from so far away! Seems impossible that it would reach us...anyone care to explain?

Answer 1

there is nothing in space to stop the transmissions of radio waves it just takes a long time to reach us. thats all.

Answer 2

Very sensitive receivers with big dishes to capture

very weak signals.

(There's nothing to block the signal, it just disburses,

so we get less of it as the probe recedes.)

Answer 3

There are two reasons; First Voyager was nuclear batteries using nuclear decay to power it. These will last for a long time. Second is the NASA's Deep Space Network. This is a world wide network of radio telescopes which trace all kinds of space missions through out the solar system. You can check it out below.

As far as the Voyager missions go, they are so far out, we receive little more than weak radio signals from them just letting us know they are still there. The distortions in these radio signals can tell us about conditions in the outer solar system.  Both space craft are in good health and should continue to function for many more years

Answer 4

Distance is no barrier to radio waves, it is just a matter of time.

Answer 5

There is a problem with radio waves travelling long distances.

The radiated power is disipated as it leaves the antenna, but with a dish antennea, pointed towards earth, the beam-width is focused toward the direction of Earth, but even then, the beam is disipated to a lesser degree, and the expotential signal strength falls off the further away from the source. Within one 100 meters from the transmitting antenna, a 10 watt signal will be something in the range of a milliwatt. At 7 billion miles, the signal will be in the order of a trillionth of a picowatt.

Now, with all the background radion, this signal can be lost in the interstella noise, with all the other, much stronger noise masking the wanted signal.

How do we overcome this problem? Well, we have nature on our side. We have a portion of the radio spectrum we call the Hydrogen Band. There is little noise in this portion of the radio spectrum, so we place our transmitter to transmit here, in the frequency band that is relitively quiet.

On Earth, on the otherhand, is a lot of radio noise, and the rafdio spectrum is deliberately kept free from any commercial usage. The signals received are so infintesimally weak, that the receivers on earth need gient dish antennas to colllect as much as the wanted signal as possible. Even so, the thermal and transient noise in the receives needs to be cut down to a reasonable level.

Incidentally, Voyager was the first deep space spacecraft to use X-band (7 to 12.5 GHz) as the primary telemetry link frequency. This higher frequency was needed so Voyager could send pictures from great distances.

Another major challenge is getting signals across millions — let alone billions — of miles without consuming great amounts of power. The radio assembly receiver can pick up a signal from Earth that’s infinitesimal — just .0000000000000000001 of a watt — that’s 10 to the minus 18th power, or a decimal point with 18 zeros after it. So you make the receiver very sensitive and the ground transmitter very powerful

Even the movement of random electrons will mask the signal; so the receivers are supper cooled with liquid helium. The signal is monitered for the low data rate (To store all the information that these instruments gather while the space craft cannot transmit to earth the Voyager has a 61 MB tape that can record at two speeds of 115.2 Kbps and 7.2 Kbps. Playback can be achieved at two speeds of 21.6 Kbps and 7.2 Kbps. Too fast a data rate will be lost amongst the noise from the Sun).

Modern computers can eek out data from random noise, and then disect that data and viola, there you have it....A nice looking picture of Mars or Jupiter; all pulled from the noise of the background radiation, too.

Kind regards

Dr Antony

Answer 6

Dr Antony explained it better than me.

In addition, the data is sent and recived with a method of noise rejection - Hamming Codes. More information is sent for one bit than just one bit. You can detect signals which are lower than the noise level using these methods.

Answer 7

You're forgetting that the 7.8 billion miles are EMPTY. No air. Nothing to block the signal. It just takes time for the signal to reach us since it can only travel the speed of light.

I can go faster on a bike...