NASA is today celebrating one of its most successful space programs ever: Voyager. Voyager 2 launched on Aug. 20, 1977, and Voyager 1 launched on Sept. 5, 1977 and between them, they have explored all the planets of the outer solar system, Jupiter, Saturn, Uranus and Neptune; 48 of their moons; and the unique system of rings and magnetic fields those planets possess. And the craft continue to run smoothly and send back information from distances more than three times farther away than Pluto. NASA notes that even though most of the launch vehicle's 700 ton weight is due to rocket fuel, Voyager 2's travel distance of 4.4 billion miles from launch to Neptune results in a fuel economy of about 30,000 MPG. As Voyager 2 zips out of the solar system, this economy will get better.
Some interesting facts about the Voyagers from NASA:
· Voyager 1 is the farthest away human-made object, at a distance from the sun of about 9.7 billion miles. Voyager 2 is about 7.8 billion miles from the sun.
· Each spacecraft carries five fully functioning science instruments that study the solar wind, energetic particles, magnetic fields and radio waves as they cruise through this unexplored region of deep space. The spacecraft are too far from the sun to use solar power. They run on less than 300 watts, the amount of power needed to light up a bright light bulb. Their long-lived radioisotope thermoelectric generators provide the power.
· The Voyagers call home via NASA's Deep Space Network, a system of antennas around the world. The spacecraft are so distant that commands from Earth, traveling at light speed, take 14 hours one-way to reach Voyager 1 and 12 hours to reach Voyager 2. Each Voyager logs approximately 1 million miles per day. The antennas must capture Voyager information from a signal so weak that the power striking the antenna is only 1 part in 10 quadrillion. A modern-day electronic digital watch operates at a power level 20 billion times greater than this feeble level.
· Both Voyagers carry a greeting to any form of life, should that be encountered. The message is carried by a phonograph record - -a 12-inch gold-plated copper disk containing sounds and images selected to portray the diversity of life and culture on Earth. The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University. Dr. Sagan and his associates assembled 115 images and a variety of natural sounds. To this they added musical selections from different cultures and eras, and spoken greetings from Earth-people in fifty-five languages.
· The total cost of the Voyager mission from May 1972 through arriving at Neptune is $ 865 million. At first, this may sound very expensive, but the fantastic returns are a bargain when we place the costs in the proper perspective. It is important to realize that: on a per-capita basis, this is only 20 cents per U.S. resident per year, or roughly half the cost of one candy bar each year since project inception. The entire cost of Voyager is a fraction of the daily interest on the U.S. national debt.
· A total of 11,000 workyears will have been devoted to the Voyager project through the Neptune encounter. This is equivalent to one-third the amount of effort estimated to complete the great pyramid at Giza to King Cheops.
· Each Voyager spacecraft comprises 65,000 individual parts. Many of these parts have a large number of "equivalent" smaller parts such as transistors. One computer memory alone contains over one million equivalent electronic parts, with each spacecraft containing some five million equivalent parts. Since a color TV set contains about 2500 equivalent parts, each Voyager has the equivalent electronic circuit complexity of some 2000 color TV sets.
· Like the HAL computer aboard the ship Discovery from the famous science fiction story 2001: A Space Odyssey, each Voyager is equipped with computer programming for autonomous fault protection. The Voyager system is one of the most sophisticated ever designed for a deep-space probe. There are seven top-level fault protection routines, each capable of covering a multitude of possible failures. The spacecraft can place itself in a safe state in a matter of only seconds or minutes, an ability that is critical for its survival when round-trip communication times for Earth stretch to several hours as the spacecraft journeys to the remote outer solar system.
· In December 2004, Voyager 1 began crossing the solar system's final frontier. Called the heliosheath, this turbulent area, approximately 8.7 billion miles from the sun, is where the solar wind slows as it crashes into the thin gas that fills the space between stars. Voyager 2 could reach this boundary later this year.
· Barring any serious spacecraft subsystem failures, the Voyagers may survive until the early twenty-first century (about 2020), when diminishing power and hydrazine levels will prevent further operation.