NASA's Mission to Pluto and the Kuiper Belt
Posted on July 17, 2020
Gabe Rogers, an engineer at the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, was the New Horizons Guidance and Control subsystem lead during the mission's historic flyby of Pluto in July 2015. He currently serves as New Horizons' deputy mission system engineer.
Guidance and Control system lead Gabe Rogers awaits the outcome of a May 2015 trajectory correction maneuver in the New Horizons Mission Operations Center at the Johns Hopkins Applied Physics Laboratory. (Credit: NASA/Johns Hopkins APL/Southwest Research Institute)
By the Pluto flyby on July 14, 2015, most of the New Horizons engineering team was running on fumes. The spacecraft had been operating in 3-axis (observation) mode for most of the year, conducting optical navigation, long-distance science, and the occasional trajectory correction maneuver to stay on course. Given the cadence of communications with New Horizons through NASA's Deep Space Network, sometimes I would be on shift starting at 6 a.m., only to start another shift at 8 p.m. the same day.
At the same time, most of the Guidance and Control subsystem team was also supporting the final activities of the MESSENGER mission. Essentially, we didn't sleep for seven months.
Things really began to pick up when the hazard-search campaign started; this is when the team would review long-distance images of the Pluto system to look for new moons, debris or other potential hazards in New Horizons' path, and determine if we would have to divert the spacecraft to a backup trajectory. In between my shifts I would bug the scientists -- asking if they saw anything in the images -- so at this point I really wasn't even going home, let alone sleeping.
When nothing turned up in the hazard search, we committed to the prime Pluto encounter trajectory. On June 30, we completed our last trajectory correction maneuver before the flyby: a 23.5-second thruster firing that executed flawlessly. Perfectly on target and fully committed to the mission timeline, we started to load the sequence of commands for the Pluto flyby into New Horizons' onboard computer.
Then, on July 4, the spacecraft went into an unexpected "safe hold." Much has been said about that activity so I won't go into details here, but by July 7 we were back on track to execute the encounter sequence. After that, everything was just as we had practiced – except now, the whole world was watching.
In between uploads of critical ephemeris (Pluto position) data to the spacecraft, we'd run across campus to the Johns Hopkins Applied Physics Laboratory's Kossiakoff Center, where guests and media had started assembling for the flyby, to meet with a VIP or a documentary or news crew. Then we'd run to APL's Building 200, where the science team was stationed, to see the latest images before heading back to the Mission Operations Center. To make sure all was well on New Horizons we monitored activity onboard the spacecraft and checked the occasional image release. We knew the best images, which New Horizons would send home after the flyby, would be the hardest to get -- because if we messed up the geometry by even a small fraction of a degree, the spacecraft would point to the wrong place, and we would get black space in all the images taken around close approach. No pressure.
It was right about that time my mother called. It was 1½ days from closest approach and my 102-year-old grandmother was getting very sick. She had been sick for several months, but she was holding on for the flyby because we had been talking about it for years, and she was really excited for me. I still have a few voice mails of her asking questions about the flyby.
Unfortunately, she passed away on July 13. I had 30 minutes to share the news with my kids and talk to my mom, and then I had to head in for the final contact with New Horizons before closest approach. It was a short "everything is healthy, see you on the other side" contact; after that, 14 years of engineering investment in our spacecraft took over – along with hope that New Horizons wouldn't run into a tiny grain of mission-ending space ice on its way. I joked with my mom that grandma left a day early to clear our path.
During the 22 hours on July 13-14 that New Horizons was out of contact with Earth – more than 3 billion miles away, feverishly collecting data on the Pluto system -- we had a celebration in the Kossiakoff Center on July 14 to mark the close-approach moment at 7:50 a.m. The Navigation team and I actually counted down and celebrated in the back of the room before the rest of the crowd, because we knew we were arriving about 70 seconds early. A few of the visiting dignitaries looked at us strangely, but we laughed it off because we were way too tired to care.
That evening was the first contact with New Horizons after the flyby. Autonomy lead Brian Bauer and I monitored telemetry in the back of the room, while all cameras were focused on Mission Operations Manager Alice Bowman. I also had a screen with a backup window to the radio signal at the DSN station, and had a direct eye on the RF (telecommunications) team of Chris Deboy and Michael Vincent, who were going to give me the high sign as soon as we saw the first hints of a signal. What the cameras didn't catch was the signal come in about 10 seconds or so before anyone else started to see any indication on the screen, so Chris and Michael were already smiling.
The autonomy data came down right away, showing that the observation sequence had completed normally. Brian and I jumped out of our seats and hugged each other while everyone else was wondering if we smoking something. Then everyone started clapping in the front of the room, and Alice began polling the leads of each subsystem. The flyby was a success!
We had two more weeks of observations before we could set the spacecraft to spin mode and start to downlink the observations from closest approach, so we still didn't get to sleep. I had to miss my grandmother's funeral because of all the activity, but I like to think she forgave me, as we put on one heck of a show for her -- and that she got to see Pluto a day before anyone else.
What amazes me for both the Pluto flyby and the follow-on flyby of Kuiper Belt object Arrokoth (in January 2019) was how perfect all the images were, and how fortuitously all of them lined up. Remember, we didn't really know where Pluto was to the degree most flyby planners know their target, and quadruple that challenge for Arrokoth. Yet every image was about as perfectly oriented as we could have hoped. All of closest approach was "non-smeared," a testament to a bit of code written years before by the late Gene Heyler (another angel who got to see Pluto early, in March 2013). Everything had to line up to make the flybys work, and it did – twice.
So we got to celebrate. And I finally got a nap.