Moondark for August: Roadtrip to the Edge of the Solar System

The 40th anniversary of the first lunar landing has come and gone at a time when NASA is once again struggling to determine where manned spaceflight is headed, how much it will cost, and when worthwhile goals can be accomplished. But it’s not fair to say that space exploration has only been spinning its wheels in Earth orbit for the last 30 years. Far from it: many countries have become space-faring nations, and we are seeing development of space for both commercial enterprise and consumers. Beyond Earth orbit, space science highlights include multiple visits to all the inner planets, asteroid and comet rendezvous, solar monitoring, and return missions to the biggest gas giants, Jupiter and Saturn and their many moons. A very significant milestone in space exploration was reached 20 years ago this August when Voyager 2 flew past the outermost planet, Neptune and its moon Triton (imaged at right, taken 3 days later). Launched on August 20th, 1977, Voyager 2 took advantage of the once every two-centuries planetary alignment allowing such a grand tour of the solar system. Departing Earth before Voyager 1, it flew by Jupiter and Saturn several months after Voyager 1 in 1979 and 1981, respectively. Voyager 2 kept going on an extended mission, encountering Uranus in 1986. Then on August 25th 1989, Voyager swooped over Neptune’s north pole and flew by Triton five hours later. This was the last planetary encounter for any of the four Pioneers and Voyagers. Of course you can learn much more of its discoveries – multiple rings confirmed, 6 new moons, Triton’s “cantaloupe” terrain – at official JPL or Wikipedia web sites, but I’ve found a much better way to relive the Neptune flyby. The Voyager Neptune Travel Guide was published as a bound book but is available online as a pdf file. Its 308 pages have been scanned, and the whole document has that fax-machine, high contrast appearance with assorted handwritten notations and rubber stamps. For all its retro look and feel, it’s a great read. Written before the Neptune encounter, the Travel Guide recounts the mission up to that point, and describes the planned Neptune-Triton campaign. You’ll read about constructing and launching such a huge, complex spacecraft and sending it far beyond any previous missions and everything about slingshot transfer orbits. And, of course, there’s much on the Golden Record as well. Despite its technical detail, the Travel Guide reads very much as a human story. Rocket scientists’ brainpower had to figure out how to shoehorn code into precious memory, ensure communications with the Deep Space Network, troubleshoot a glitchy camera platform and overcome antenna bandwidth limits using revolutionary image compression. While web sites have beautiful images and slick animations, I’ve seen nothing to compare with the flipbook included in the Travel Guide. In the bottom left corner of most even numbered pages, simple diagrams show the full Neptune and Triton flyby from Voyager’s point of view. Thumbing through the pages animates the full flyby, and that effect can be simulated with the downloadable pdf file by setting your viewer to zoom and single-page view settings. Enjoy this cropped version (14 MB pdf) I made: download it, set your view options and use the page up/down or arrow keys. My recollection is that the Neptune flyby occurred in the middle of the night, but I set the alarm anyway for “live” radio coverage (images would only come down later), interspersed with commentator’s reminders that it had all happened four hours before. While the solar system seemed awfully big at that moment, Voyager 2 had brought its far reaches just a little bit closer on that day. At present, twenty years later, Voyager 2 is nearly 90 AU from Earth in the southern sky constellation of Telescopium and has completed well over 11,000 days of operation. Its new mission is interstellar science, and even with limited power, it continues to function and return useful results. Voyager data recently determined that the solar system is squashed! I’m an unabashed fan of robotic exploration, but humans are integral to the mission even when they never leave the surface. Engineering and science are social, human endeavors. With engineering insight and constant tender loving care from inhabitants of Earth, the Pioneers and Voyagers have been for more than thirty years now on quite a trip through, and now beyond, the solar system. So, what did you do on your summer vacation? Moondark is written by Douglas C. Miller, published at the Moondark web site, and printed in the Delmarva Star Gazers' Star Gazer News. This document was last revised on 26 July 2009. Text on this web page are free for non-commercial use with attribution under a Creative Commons Attribution-Non-commercial 3.0 License. Ask Doug about other uses.