The Loyal Engineers Steering NASA’s Voyager Probes Across the Universe

Lovely profile of the engineering team still working to control Voyager I and II:

Fortunately, the malfunctioning backup receiver was still drawing current. They guessed that its oscillator, which allows it to accept a wide range of frequencies, had quit, essentially shrinking the target for transmissions from Earth. Assuming a much narrower bandwidth, and manually subtracting the Doppler effect, they recalibrated their signal. It worked — but to this day, the same calculation must precede every command. The original receiver remains useless: one engineer’s simple oversight nearly doomed humankind’s lone visit to Uranus and Neptune. ‘‘You like to think you have checks and balances,’’ Chris Jones, JPL’s chief engineer, who designed Voyager’s fault protection, told me. ‘‘In reality, we all worry about being that person.’’

Today the Voyagers are 10 billion and 13 billion miles away, the farthest man-made objects from Earth. The 40th anniversary of their launch will be celebrated next month.

I wasn’t aware of just how narrow the window of opportunity was that made it possible for these probes to visit all four of the outer planets:

One of the greatest obstacles to planetary science has always been the human life span: Typically, for instance, a direct flight to Neptune would take about 30 years. But in the spring of 1965, Gary Flandro, a doctoral student at Caltech, noticed that all four outer planets — Jupiter, Saturn, Uranus and Neptune — would align on the same side of the sun in the 1980s. If a spacecraft were launched in the mid- to late 1970s, it could use the gravity of the first body to slingshot to the second, and so on. Such a trajectory would add enough speed to shorten the total journey by almost two-thirds. What’s more, this orbital configuration would not appear again for 175 years.

★ Friday, 4 August 2017