Since 1958, the National Aeronautics and Space Administration (NASA) has been in service to all humankind envisioning, developing, implementing, and supporting hundreds of individual launches and missions expanding humanity’s presence in, and knowledge of, the Universe. Of the 113 probe missions NASA has undertaken, several loom extremely large in the human psyche. Of these the Pioneer and Voyager probes – now “going where no craft have gone before” – are high on the list of “vaunted-achievers”.
Pioneer 10 & 11 are now mute, the last Pioneer 10 signal was received April 27, 2002. A final attempt to receive telemetry from the debilitated craft – its nuclear power source degraded – occured on February 7, 2003. But four years earlier (on February 17, 1998) Voyager 1 surpassed Pioneer 10 as the most distant craft from the Sun in space. Today, both Voyager probes sport several fully functioning science packages (cosmic ray, plasma wave, and low-energy charged particle detectors, plus a magnetometer), healthy nuclear power sources, and operational 23 watt transmitters sending back a constant stream of data collected on conditions seen in the outermost reaches of the solar system. Despite this, NASA may be forced to say “farewell” to the Dynamic Voyager Duo – leaving their voices unheard in the night of interstellar space.
Voyager 1 took to the stars from Cape Canaveral on September 5th, 1977. Some two weeks earlier (August, 20th), Voyager 2 rode its own tail of flame skyward. Flight times and dates were scheduled to leverage a unique four-planet alignment not to recur until 2153. Voyager 1 took a short-trajectory path to make a pass at Jupiter 18 months later (March 5, 1979). Voyager 2 – on a longer route – flew by on the 8th of July. Using a wide range of instruments sensing across the lower and middle em spectrum (radio to ultraviolet), scientists and technicians at the California Institute of Technology’s Jet Propulsion Institute (JPL) soon published startling details of Sol’s largest planetary system. Unsurpassed image quality gave billion’s of human eyes extraordinary views only vaguely hinted at using earth-bound telescopes. Jupiter was found to possess a faint ring, volcanoes were seen to erupt from Io – inmost of the four galiliean satellites. Data related to Jupiter’s thermal characteristics and massive magnetic field was collected.
Even as data from Voyager 1 was being fully digested, mission specialists used emerging information to “fine-tune” Voyager 2’s upcoming view of Jupiter, its retinue of newly discovered satellites, fields, and rings. New information concerning this most dynamic of gas giants followed.
And so it went. Jupiter’s spinning globe propelled both probes further into space. Mission controllers watched as the probes scanned Saturn, then Uranus, and finally Neptune using on-board instrumentation. They resolved stunning details of Saturn’s exquisite ring system, and helped understand the role of “shepherd moons” in holding that ring together. They revealed unresolved features on the Ringed Wonder’s globe, and found surprisingly active storm systems. A ring system was discovered on Uranus too, and a large, powerful storm on distant Neptune was complete surprise. They even turned up a total of 22 new satellites. All of this at a cost of $865 million to US taxpayers.
The 1990’s saw Voyager 1 and 2 embark on a new quest – to explore the solar system’s Kuiper belt and beyond. Today with Voyager 1 traveling at the rate of 3.6 AU’s (Earth-Sun distances) per year, and located 95 AU’s from the Sun, it is poised to enter the interstellar medium. Despite 12 hour transmission delay times, these twin marvels of human imagination and creative technological genius still continue to “phone home” – garnering a wealth of data about the outermost reaches of the solar system at an annual cost of about $4 million a year.
This ongoing mission has been fruitful. Powerful solar storms caused a series of Coronal Mass Ejections (CMEs) during October 2003. By mid-April 2004, Voyager 2 had detected the resulting shock waves as they slowed to combine with matter in the Merged Interaction Regions outside the orbit of Pluto. Voyager 2 measured shock speed, composition, temperature, and magnetic flux. When included with data from spacecraft located nearer to the Sun (SOHO, Mars Odyssey, Ulysses, Cassini etc.), Voyager helped show how CMEs move through the Solar System.
From NASA’s own Voyager webpage:
“For the past two years or so, Voyager 1 has detected phenomena unlike any encountered before in all its years of exploration. These observations and what they may infer about the approach to the termination shock have been the subject of on-going scientific debates. While some of the scientist believed that the passage past the termination shock had already begun, some of the phenomena observed were not what would have been expected. So the debate continues while even more data are being returned and analyzed. However, it is certain that the spacecraft are in a new regime of space. The observed plasma wave oscillations and increased energetic particle activity may only be the long-awaited precursor to the termination shock. If we have indeed encountered the termination shock, Voyager 1 would be the first spacecraft to enter the solar system’s final frontier, a vast expanse where wind from the Sun blows hot against thin gas between the stars: interstellar space.”
NASA plans to make a final decision on continued JPL mission support for these two sturdy spacecraft by April 15.
Written by Jeff Barbour
Note from Jeff: If you are an American citizen, please call, write, email, or hand-deliver a message to your congressional representatives. Tell them that the last word sent by Voyager I and Voyager II shall not go unheard. Tell them that humanity must not orphan its children – be they human, or technological. Tell them that long-after some boondoggle project funded by taxpayer dollars in support of parochial interests has fallen by the way-side, Voyager I and II will continue to be our emissaries to the Universe.
And if you are a World citizen please petition your local government to speak plainly to the leadership of the United States telling them that all the world has entrusted its hearts and minds to the continued expansion of humankind’s presence in the Cosmos.
Voyager 1, Voyager 2 – on a mission for us all.