NASA’s Voyager 1 approaches the edge of our solar system


Photo courtesy NASA.

“Space: the final frontier…to boldly go where no man has gone before.”–Star Trek Original series opening.

Last week, a meteor exploded over Russia. And while we often forget about “the final frontier” in our day to day lives, it served as a startling reminder that there is more out there to be discovered. But who will do that discovering? With the end of NASA’s shuttle program and a shift to the private sector, many wonder if America has given up on the exploration of space. Don’t worry, America is not done with space exploration. The Voyager space program, begun in 1972, is still active and sending data back to earth from places no man-made thing has ever gone.

In 1972, Edward Stone took the helm of the newly-conceived Voyager program that would push humanity’s exploration into space further than ever before. The Voyager program designed and built two spacecraft, Voyager 1 and Voyager 2, that have been sending data back to earth since they were launched in 1977.

For 12 years, the Voyager crafts sent data back to Earth, completing their primary mission with data on Neptune in 1989. With the primary objective completed, the crafts were tasked with the Voyager Interstellar Mission: “to extend the NASA exploration of the solar system beyond the neighborhood of the outer planets to the outer limits of the Sun’s sphere of influence, and possibly beyond.”

Today scientists are excited as they wait for data from the Voyager 1 to tell them it has reached the “heliopause.” The heliopause is the boundary of the solar system, where the sun’s “solar wind” is no longer stronger than that of other stars. Voyager 1 is expected to pass the boundary sometime between now and 2015. While some people argue that this isn’t really the boundary of the solar system, since to escape the influence of the sun’s gravity the Voyagers would have to travel 50,000 times further, it is still a great accomplishment for humankind.

Some say that Voyager 1 may have already crossed the heliopause “line,” but scientists just didn’t recognize it. “[Crossing] will not be an instantaneous thing,” said Stone. “[Voyager] won’t suddenly be outside.” He believes that for a time there will be a “a mix of inside and outside” that scientists will monitor carefully.

Scientists have done a lot of monitoring of the Voyager crafts. Through the completion of its Neptune run, NASA logged over 11,000 work-years on the Voyager project. Beyond construction of the Voyager crafts and data analysis, scientists worked hard in the early stages of the program to update and maintain the Voyagers’ systems. One major update made to the Voyager crafts’ computer programs was the Reed-Solomon encoder. The Reed-Solomon encoder reduced the bits needed for error correction. The original launch system required half of its transmissions to work on error reduction; today it takes only 1/5.

This is a big deal since as Voyager 1 and Voyager 2 continue to travel further away, their data streams will reduce. Currently Voyager 1 is about 121 astronomical units (AU) or 16 hours of radio transmission away. Originally close enough to send upwards of 115,0000 bps (bits per second), Voyager 1 is now constrained to 160 bps with a 1400 bps burst every six months. Without Reed-Solomon, scientists back on Earth would receive almost no data at all.

To really understand the extent of the Voyager accomplishment, it is important to understand that technology has come a long way since 1977. The original Voyager craft had only 68 kilobytes of memory. (Modern smartphones have over 2 gigabytes.)

Despite the low level of technology, Stone says that “both vehicles have far exceeded expectations.” Current estimates say that the energy on the Voyager crafts provided by plutonium-238 fuel should last until at least 2021. The program is planned to end, with the shutting down of the ship’s sensors, sometime in 2025. The Voyager crafts, the first man-made objects to leave the solar system, will be cut free to travel unaided before us into the further unknown.

For now all we can do is watch with expectation. As Stone says, we should enjoy it from a scientific point of view, because “you’re seeing something that nobody’s seen before.”