A Temporary Setback on the Approach to Pluto

The news came late yesterday (July 4) that the New Horizons spacecraft had temporarily lost communications with Earth, and then regained them after switching to the backup computer. The outage was only a few hours long (and you can read the announcement here)  Alan Stern commented on Facebook last night that the team was working through the problem. There’s also been an Anomaly Review Board convened to help solve the issues and take a fresh look at the data to figure out what might have caused the issue.

The spacecraft is on the same trajectory — nothing has physically happened to change that. It is still going to fly past Pluto on the 14th of July, and with whatever solution set the team works out, it should be back to taking science observations well before that time. The spacecraft is in good shape, its instruments work. However, right now (or, at least as of the time the announcement came out), the spacecraft is in safe mode, which means it isn’t taking any science observations until the team figures out what happened. So, no more images for a while, and no other observations from the spectrometers, the radio science instrument, the solar wind instrument, or the particles and dust sensors.

The timeline didn’t call for any images on July 4th, although some were to be taken today and tomorrow. Given the 9-hour round-trip travel time for signals to be sent to and from the spacecraft, diagnosing and adjusting whatever needs to be fixed is going to take some time. So, we may not have any images or other science for a few days, yet. When they’ve got it figured out, the team will resume full science ops and let the rest of us know about it.

Remembering Other Anomalies

When I first got the news last night, I was pretty dismayed. Not surprised, because space exploration has lots of gotchas. Anything from a random cosmic ray hit to debris hit (unlikely) could threaten the New Horizons spacecraft. Its internals are simple and well-designed, but as any spacecraft designer knows, things can fail. Stuff can happen that you have no control over. You just build the best craft you can, with the redundancy you can afford to send, and then send your baby on the way.

Reading the announcement, I was immediately reminded of the scan platform problem on Voyager 2, which jammed just before close approach to Saturn in 1981. The team members sussed out some possible ways to work around it (including doing some rotations of the entire spacecraft to let the cameras and photopolarimeter do their work), and eventually got the platform motor somewhat unjammed. I remember being incredibly impressed that they could analyse, diagnose, and try to fix the problem from billions of miles away. The spacecraft went on to explore Uranus and Neptune, and is now studying the outer solar system for us.

Or, think of the folks who built and used the Galileo spacecraft, when they found out the main antenna hadn’t unfolded completely, leaving them with less bandwidth to transfer their images and science data back. They figured out a way — yes, the transmission of data was threatened — but they managed to diagnose the problem and find work-arounds. They also had to contend with a finicky tape recorder, as well as a safe mode event right after a flyby of the moon Amalthea. In each case, the teams figured out the problems and worked around them when they could.

Hubble Space Telescope has often gone into safe mode, and the controllers always find a way to return it to mission performance (unless, as in the case with gyro failure, they have to change operating modes). Heck, I remember the day (I was on an instrument team for HST) that we got the news that the scope’ s mirror had spherical aberration. That was a couple of days before it was publicly announced. Even at that time, people were already putting their heads together to figure out a fix. Which they did.

The Kepler spacecraft, Spitzer Space Telescope, heck — even Apollo 13 — all fit into this panoply of space-exploration issues. Each time one had a problem, people figured out how to fix it or work around it. And, those are just NASA-led explorations.

Controllers with the Rosetta mission have had to continually monitor their spacecraft and take steps to protect it as it orbits the nucleus of Comet 67P/Churyumov-Gerasimenko.  They’re also working to bring the Philae lander back to a level of science mission operations, which is pretty incredible when you think about trying to communicate with a tiny spacecraft about the size of a card table, on the surface of a comet moving at 135,000 kilometers (84,000 miles) per hour. A comet that’s blowing dust and gases off to space, to boot!

Safe modes happen with spacecraft. They’re designed in for a purpose. New Horizons was designed to go into safe mode, do some diagnosis, and then put itself back to rights so it could communicate with its people. That’s what it did, and now the people are figuring out the solutions. Knowing Alan and the team, they more than likely had a procedure rehearsed for just such anomalies. I know they’ve trained and trained, practiced and practiced, drilled for every contingency they could think of — and then some.

The good news is, New Horizons DID phone home. I’m waiting anxiously for my friends on the mission to give us the thumb’s up that all is well again, and that science data-gathering has resumed!