Voyager 1 makes it to interstellar space
36 years, and still going strong. Potentially has another 20 years of life at best (but 2025 seems to be the accepted limit) before the nuclear power pack cools and dies. This supplies about 400 W for heaters and instruments. There’s also the small problem of running out of hydrazine, used to power thruster, and there’s no way to replace it as it’s used to manoeuvre the craft.
Researchers confirmed last Thursday (September 12, 2013) that Voyager 1 is officially in interstellar space. The spacecraft, which launched in 1977, then became the first ever human-made object to leave our cosmic neighbourhood and enter the space between stars. It probably did so on or around August 25, 2012, [Voyager 1 in Interstellar Space: Complete Coverage], but various circumstances led to this being debated for some time, before it was ultimately confirmed. There still a fight raging over whether or not it has left the Solar System though, so keep watching for that one to be resolved, or not: Voyager 1 Hasn’t Really Left The Solar System, But That’s OK – IEEE Spectrum
I spotted a note about the use of language in the context of ‘leaving’:
Whether or not Voyager 1 has technically left the Solar System depends on where you set the boundary. It now seems certain that Voyager 1 has left the heliosphere, but there’s the question of whether it has left the sphere inside which the Sun’s gravity takes precedence over the galactic tide. As the BBC’s Jonathan Amos points out, NASA’s Ed Stone “has always been very careful not to use the phrase ‘leave the Solar System’, mindful that his spacecraft still has to pass through the Oort cloud where there are comets gravitationally bound to the Sun.” This despite the fact that Voyager 1’s current distance from the Sun puts it beyond most estimates of the outer edge of the Oort cloud. Nevertheless, the BBC and many others seem happy to report that Voyager 1 has indeed left the Solar System, though it’s worth noting that this specific wording is not present in NASA’s statement.
Back in 1990, Voyager 1 was told to stop taking and transmitting images, partly to save energy but mostly because there was nothing left to photograph. The spacecraft continues to send back data, but it now takes 17 hours and 22 minutes for the signals to reach NASA’s lab in Pasadena.
Possibly the most impressive aspect of this is that we are still in contact with the spacecraft, now close to 12 billion miles from the Earth, it only has a 22 W transmitter, and some clever antenna to maintain that connection.
The sensitivity of the deep-space tracking antennas located around the world is impressive. They have to capture Voyager information from a signal so weak that the power striking the antenna is only 10e-16 W (1 part in 10 quadrillion). A modern-day electronic digital watch is said to operate at a power level 20 billion times greater than this minute level.
As tiny as that is, it still stands out as a bright spot in a dark sky when the most sensitive radio telescope is pointed that way:
The image, which looks slightly oblong because of the array’s configuration, is about 0.5 arcseconds on a side, according to NASA. One arcsecond — a unit of size for objects in the night sky — would describe the size of a penny as seen from 2.5 miles (4 kilometres) away. For comparison, the full moon is about 1,800 arcseconds across.
Voyager 2 is only about three years behind it in hitting interstellar space.
Don’t forget Pioneer 10 and Pioneer 11
Two other spacecraft – NASA’s Pioneer 10 and 11, launched in 1972 and 1973 respectively – also are departing the solar system. But Pioneer 11 went off the air in 1995, then Pioneer 10 fell silent in 2003 when their nuclear generators could no longer provide enough power.
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