The Pluto Perspective

An Unforgettable Flyby

My Pluto Flyby day began with a final pre-encounter health check and image download at 9 p.m. EDT on July 13, 2015, and would end – after 22 hours of radio silence – with a 15-minute spacecraft status check (that we called "phone home") starting at 8:53 p.m. on July 14. (The communications "break" was because New Horizons, with no moving parts, could not point its antenna at Earth while it collected data on the Pluto system.)

I had been essentially living in my office and the New Horizons Mission Operations Center at the Johns Hopkins Applied Physics Laboratory since July 4, with short trips home for showers and a meal with my husband. No such break on Flyby Day: the operations team arrived at APL on the afternoon of July 13 and worked through the night, mostly to help configure NASA's Deep Space Network (DSN) antennas to transmit signals for the New Horizons' radio science experiment, called REX.

With New Horizons more than 3 billion miles from home, it took approximately four hours and 25 minutes for a signal from Earth to reach the spacecraft. The last transmissions to REX ended at 6:40 a.m. July 14.

A Celebration and a Reveal

I had to be at APL's Kossiakoff Center at 7 a.m. for a run-through of the NASA TV programs celebrating Pluto close approach and unveiling the "Pluto Revealed" image. At 6 a.m., the science and operations teams were to get a sneak peek at that image; unfortunately, the reveal was delayed and I missed it. Later that morning, live on NASA TV, Principal Investigator Alan Stern, NASA Associate Administrator John Grunsfeld and I revealed that closest-ever image of Pluto and since I had not been present for the preview, it was my first look – and I was stunned. It was amazing and so much different that I had ever imagined.

I went back to my office to check over the flyby commands that were now executing onboard New Horizons, and get in a little nap on the air mattress before the day's meetings and interviews. Our team had worked since 2008 – more than six years! – to perfect the nine-day Pluto encounter command sequence. In 2012, following the surprise discoveries of the small moons Styx and Kerberos, we even built another nine-day sequence that incorporated a protection maneuver, just in case we detected some unexpected moons or debris in the last few weeks of approach. (Fortunately, we didn't need it.)

Mission Systems Engineer Chris Hersman had identified 249 potential abnormal conditions that could crop up on the spacecraft or ground systems during those nine days, and with the spacecraft engineers and mission operations team had systematically prepared a response for each situation. Before July 4, we all felt very confident that flyby success was all but assured. Then the July 4 anomaly occurred; the condition that led to it was not on Chris' list, but the resulting action the spacecraft took, was. The response outlined was not the direction the team decided to follow. Nonetheless, over the next three days, we successfully recovered the spacecraft – and were reminded that space exploration is not easy nor for the faint of heart.

Phoning Home

For the July 14 "phone home" status check, there would be a live feed from the Mission Operations Center broadcast on NASA TV and the web. NASA, New Horizons and APL management would be in the small conference room adjacent to the MOC; we agreed that they would not enter the MOC until we had completed the check and I reported the status to Alan, our "PI," over the intercom. We did not want anything distracting us from acquiring the spacecraft signal, evaluating the telemetry, and troubleshooting any abnormal condition. A live feed from the MOC would mean, for better or worse, whatever happened would play out for the world to see.

Fifteen minutes is not a lot of time, and if the ground systems or even spacecraft experienced any abnormal conditions, we might not even be able to acquire a signal. APL Public Affairs Officer Mike Buckley, who was hosting the live broadcast in the Kossiakoff Center auditorium, and I had special key phrases that would allow him to know if everything was OK, or if we were having an issue.

In the MOC, I wear a headset and monitor two channels on the intercom, or voice loop. One channel is for voice traffic between our flight controllers and the DSN operators, and the other is internal for traffic between subsystem and mission operations staff. Additionally, it was important that I could hear and respond to any questions from Mike on the Kossiakoff set, so I had an earbud for that. None of these audio connections were wireless so I was pretty much tethered to my workstation and relied upon my brain to distinguish between the three audio connections. Additionally, there were GoPro cameras and microphones from various documentary crews set up at my workstation.
About 30 minutes before signal acquisition (about 8:15 p.m. EDT), I completed my voice check with the engineers and operations staff in the MOC as well as the PI in the situation room.
The team was in place; the cameras were on.

Sometime between 8:15 and 8:30 p.m., Mike asked me to bring all the subsystem and operations engineers down to the Kossiakoff Center for the post-flyby press conference. About 8:30 p.m., I gave a final synopsis of the timeline and asked the team to report subsystem status when they had sufficient telemetry. I closed with a huge thank you for the many years of dedication, the honor of being part of this team, and a personal reflection that this event was bigger than all of us, and we were about to make history.

At 8:52:44, the 70-meter antenna at the Madrid DSN station locked to the New Horizons carrier signal, This was the first clear indication to us that New Horizons had avoided any potential mission-ending space particles and survived the flyby. About a minute later, we saw the first telemetry, arriving just shy of 1,500 bits per second. Telemetry for each subsystem comes in sequentially, so this helps explain the sporadic reporting in the video from that night. The first subsystem to report was Michael Vincent from RF (telecommunications), with a nominal (normal) status. Next, Brian Bauer reported for the autonomy subsystem. It was a huge moment when he reported that no fault rules had fired, meaning that all was well on New Horizons. Quickly following was the command and data handling subsystem (main spacecraft computer) report from Steve Williams, who confirmed that the onboard data recorders were full.

As each successive subsystem reported nominal (normal) status, it started to become clear that this team had just accomplished something in the making since Clyde Tombaugh discovered Pluto in 1930. After all subsystems had checked in, it was time to report the final status to Alan. "PI, this is MOM on Pluto1. We have a healthy spacecraft. We have recorded data of the Pluto system and are outbound from Pluto."

Simple words, but very hard for me to say. After uttering the first sentence, the magnitude of the moment hit me: the many years of planning the first-ever Pluto flyby, the successful recovery from the July 4 anomaly, and a childhood dream of exploring space. I managed to hold it together, but if you look closely you will notice that I hesitate and lick my lips in an effort to push the emotion down and get those final, victorious words out of my mouth. At that point, Alan burst through the door with hands raised in victory, gave me a big hug, waved the American flag, and shook hands with Chris.

We shared a celebratory toast, then walked to the Kossiakoff Center, sharing our various stories and impressions of the night along the way. They were our team's last private moments before reaching the crowds at the auditorium – who treated us like rock stars, cheering the team for what we had just accomplished.

Even though it has been five years, I choke up every time I think about what we accomplished in spite of the challenges; when I look at that MOC video; or when I think about the reception we received at the auditorium. It was a day I will never forget.