When I look in the drawer where my dad's drafting/navigational tools are, and think about the navigation of a spacecraft, I am very humbled
The twin spacecraft VOYAGER 1 and VOYAGER 2 were launched by NASA in conjunction with Jet Propulsion Labratory in the summer of 1977, 45 years ago, from Cape Canaveral. As originally designed, the VOYAGERS were to conduct closeup studies of Jupiter and Saturn, Saturn's rings, and larger moons of the two planets.
To accomplish their two-planet mission, the spacecraft were built to last five years. But as the mission progressed, and with the successful achievement of all its objectives, additional flybys of the two outermost giant planets, Uranus and Neptune, proved possible -- and irresistible to mission scientists and engineers at JPL in Pasadena.
As the spacecraft flew across the solar system, remote-control reprogramming by JPL astrophysicists, led by Alex Bratenahl, Milly's father, was used to endow the VOYAGERS with greater capabilities than they possessed when they left Earth. With over 10,000 possible trajectories studied, two were chosen and the two-planet mission became four. Their five-year lifetimes stretched to 12 and is now 45 years.
Bratenahl and his associates designed the VOYAGER mission to take advantage of a rare geometric alignment of the outer planets in the late 1970s -80s which allowed for a four-planet tour for a minimum of propellant and trip time. This layout of Jupiter, Saturn, Uranus and Neptune, which occurs about every 175 years, allows a spacecraft on a particular flight path to swing from one planet to the next without the need for large onboard propulsion systems. The flyby of each planet bends the spacecraft's flight path and increases its velocity enough to deliver it to the next destination. Using this "gravity assist" technique, pioneered by Bratenahl, it was first demonstrated with NASA's Mariner 10 Venus/Mercury mission in 1973-74, and VOYAGER'S flight time to Neptune was reduced from 30 years to 12.
Eventually, between them, VOYAGER 1 and 2 explored all the outer planets of our solar system, 48 of their moons including 21 new moons, and the unique systems of rings and magnetic fields those planets possess. Had the VOYAGER mission ended after the Jupiter and Saturn flybys alone, it still would have provided the material to rewrite astronomy textbooks. But having doubled their already ambitious itineraries, the VOYAGERS returned to Earth information over the years that has revolutionized the science of planetary astronomy, helping to resolve key questions while raising intriguing new ones about the origin and evolution of the planets in our solar system.
To this day, the VOYAGER continues to press onward into outer space while "calling home." Eventually, their instruments may be the first of any spacecraft to cross the heliopause -- the boundary between the end of the Sun's magnetic influence on our solar system and the beginning of interstellar space.
The photo clue of our "Blue Marble," above in post #5166, is an iconic photograph of Earth taken Feb. 14, 1990, by VOYAGER 1. VOYAGER 1 was speeding out of the solar system — beyond Neptune and about 3.7 billion miles from the Sun — when mission managers commanded it to look back toward home for a final time. And this is the photo returned to Earth of the Earth.
As well as a solar physicist, Alex Bratenahl was an avid sailor, musician, artist, and teacher. He loved conversing with young people and sailing with his family. Below is a photo of Alex sailing FUN on Tomales Bay. Milly, age 13, bought FUN from her father, who didn't realize the piece of paper he'd just signed was a Bill of Sale. No problem. To continue competing, Alex bought another 110, US 418 SOLAR FLARE. Both boats continuing sailing to this day.
So VOYAGER is the answer. And unless there is a collision or is retrieved, will continue on a voyage into Outer Space for All Time.
And here is Alex sailing FUN, #445 (later BIG PINK), with daughter Laura and son Carl. According to Milly, her father never wore a shirt when sailing. Thank you all for playing.