Fired Up

Technician load the 'golden record' Earth's official communication with extra-terrestrials, onto Voyager 1 - NASA photograph

THE VOYAGE CONTINUES: Some astounding and impressive news came across our desk here this morning (via social media, truth be told). 

We read news about the Voyager 1 and 2 any time an article comes up and are always impressed that these spacecraft keep sailing along after four decades, no to our solar system's fringes.

Today's news involved the fact that a set of thrusters aboard the Voyager 1 spacecraft were successfully fired up Wednesday, Nov. 29, after 37 years without use. Wow! Imagine trying to start your car here on Earth if it sat in your driveway for 37 years. Not likely that it would fire up. Now imagine your vehicle 11.7 billion miles down the road ... Remarkable!

The press release from NASA read, in part: 

Voyager 1, NASA's farthest and fastest spacecraft, is the only human-made object in interstellar space, the environment between the stars. The spacecraft, which has been flying for 40 years, relies on small devices called thrusters to orient itself so it can communicate with Earth. These thrusters fire in tiny pulses, or "puffs," lasting mere milliseconds, to subtly rotate the spacecraft so that its antenna points at our planet. Now, the Voyager team is able to use a set of four backup thrusters, dormant since 1980.

"With these thrusters that are still functional after 37 years without use, we will be able to extend the life of the Voyager 1 spacecraft by two to three years," said Suzanne Dodd, project manager for Voyager at NASA's Jet Propulsion Laboratory, Pasadena, California.

Since 2014, engineers have noticed that the thrusters Voyager 1 has been using to orient the spacecraft, called "attitude control thrusters," have been degrading. Over time, the thrusters require more puffs to give off the same amount of energy. At 13 billion miles from Earth, there's no mechanic shop nearby to get a tune-up.

The Voyager team assembled a group of propulsion experts at NASA's Jet Propulsion Laboratory, Pasadena, California, to study the problem. Chris Jones, Robert Shotwell, Carl Guernsey and Todd Barber analyzed options and predicted how the spacecraft would respond in different scenarios. They agreed on an unusual solution: Try giving the job of orientation to a set of thrusters that had been asleep for 37 years.

"The Voyager flight team dug up decades-old data and examined the software that was coded in an outdated assembler language, to make sure we could safely test the thrusters," said Jones, chief engineer at JPL.

In the early days of the mission, Voyager 1 flew by Jupiter, Saturn, and important moons of each. To accurately fly by and point the spacecraft's instruments at a smorgasbord of targets, engineers used "trajectory correction maneuver," or TCM, thrusters that are identical in size and functionality to the attitude control thrusters, and are located on the back side of the spacecraft. But because Voyager 1's last planetary encounter was Saturn, the Voyager team hadn't needed to use the TCM thrusters since November 8, 1980. Back then, the TCM thrusters were used in a more continuous firing mode; they had never been used in the brief bursts necessary to orient the spacecraft.

Hats off to Aerojet Rocketdyn, who developed all of Voyager's thrusters. On Wednesday, the aged thrusters were tested for their ability to orient the spacecraft via 10-millisecond pulses. 

Due to Voyager 1's distance from Earth, the team working on the project had to wait while test results traveled through space, taking 19 hours and 35 minutes to reach a NASA's Deep Space Network antenna in Goldstone, California.

Upon receiving the positive results, "The mood was one of relief, joy and incredulity after witnessing these well-rested thrusters pick up the baton as if no time had passed at all," said Todd Barber, a JPL propulsion engineer.

The plan going forward is to switch to the TCM thrusters in January. To make the change, Voyager has to turn on one heater per thruster, which requires power -- a limited resource for the aging mission. When there is no longer enough power to operate the heaters, the team will switch back to the attitude control thrusters.

Because the thruster test was so successful, the team is likely to do a similar test on the TCM thrusters for Voyager 2 in a few weeks.

Here's a cool lookback to the Voyagers' launches. https://youtu.be/C1UBg4TPqX4

IT TAKES A VILLAGE: For a few hours this week, the kids and I worked on a monthly bulletin board we decorate. Its purpose is to highlight kids' birthdays that month. The hardest part is coming up with a different theme each month. We bandied about several ideas for December (Nutcracker, penguins, snowmen, reindeer), but settled on a gingerbread village for whatever reason. (Actually, probably due to my love of gingerbread.)

We used colored foam sheets, cardboard, pufff paint, decoative tape, beads, buttons and more.

CJ helped cut out any a 'gumdrop' shingle.

 And here's how it came together. (I blurred the students' names and birthdates in the photo below.) It's about 5 by 4 feet.