Close Encounters of the Solar Kind


Close Encounters of the Solar Kind

In order to really understand something, sometimes you have to get up close. That’s the idea at the heart of space exploration. And for this encounter, we won’t find any aliens, but we do expect to solve some of the biggest mysteries in the solar system. Before this week, no man-made object had visited the Sun. NASA’s Parker Solar Probe, launched in August, is making history, breaking records for closest approach to the Sun and spacecraft speed. Our team has helped provide assurance for critical mission capabilities that software on the spacecraft enable.

For something we’ve known of longer than any other celestial object, and which dominates our every day, the Sun holds surprisingly tightly to its mysteries. Its corona, the envelope of scorching plasma that forms the Sun’s tenuous atmosphere, is several times hotter than it should be. In fact, it’s 300 times hotter than the Sun’s surface. How could this be? Parker Solar Probe is going to solve this and other mysteries as it flies into the corona, armed with experiments to measure magnetic fields, solar particle counts, and other solar phenomena. In order to get close enough to count, PSP is equal parts tough and smart.

Nathan Tehrani, Engility IV&V Engineer Nathan Tehrani, Engility IV&V engineer, visited the Parker Solar Probe during tests at Goddard Space Center before it was transported to Cape Canaveral for launch.

Fire and Ice

As an Independent Verification and Validation engineer at Engility, I specialized in checking guidance and control software that ensures the spacecraft takes the right path and faces the right way.

The spacecraft carries a solar shield to keep it cool, a critical feature as it enters Encounter Mode near the Sun. The shield makes PSP tough against the Sun’s blazing heat. The two major guidance and control items during this phase are maintaining the right attitude—pointing directly at the Sun—and controlling the solar panels. PSP cleverly balances power and thermal needs, extending its panels to generate enough power to run the spacecraft, but not extend too far and get too hot. If the panels tuck in too far, ice could form in the radiators. The spacecraft must keep the solar shield oriented at the Sun every time it swings in close. If it rotates more than just a few degrees from the right attitude, parts of the spacecraft can be damaged by the intense light and resulting heat. A beautifully woven web of guidance and control algorithms, complemented by a set of autonomous decision-making abilities, will help to steer the probe correctly with absolute reliability.

The smarts on this spacecraft make for a complicated set of systems, and where there is a lot of complexity, there is a lot to be tested. On the IV&V team, we have approached mission assurance and safety with a scientific, evidence-based mindset. As the spacecraft moved from the concept phase to the requirements, design, code, and test phases, we independently checked that behavior that the spacecraft’s software governs matched the rigorous expectations. In doing this, we were able to provide assurance that the system covered the big-picture capabilities. By simulating the spacecraft dynamics on our own, we put the software through the paces, seeing firsthand how the spacecraft would react to more than 100 scenarios.

NASA Parker Solar Probe Launch The Parker Solar Probe, NASA’s historic mission to “touch the sun,” launched from Cape Canaveral in August 2018.

The Launch

After all this preparation, I was fortunate to travel to Cape Canaveral for the launch. It was surreal! Just a few miles away, across the water, stood the tall orange rocket. It looked regal, proudly lit with spotlights all around, with the spacecraft we’d come to know so well safely encapsulated on top.

Even at three in the morning, the crowd was vast and energized — probably with equal parts anticipation and caffeine. It was so cool to see everyone there watching this launch that my team had a part in. The launch itself began with a quiet flash as the three boosters ignited, and then a billowing flame as the rocket began to rise — slowly at first, then faster. As the rocket disappeared into a cloud, the sound hit. What a terrific roar! It all made for a fantastic show.

A little while afterwards, we heard everything was going well—the solar arrays had deployed, marking the end of the spacecraft’s post-separation to-do list. Soon enough, the Sun rose. Somewhere in between it and us, Parker Solar Probe was healthy and on its way.

What's Happening Now

As the spacecraft now begins its first close solar encounter, almost all spacecraft tasks are automatic because the communication delay from Earth is too long. With each lap around the Sun, PSP will get closer and gather more data over the next six years. Our IV&V team worked hard to get PSP this far, making sure that it would keep itself safe in the solar environment. Now is the first chance to see it happen for real, and everyone can watch without worry as PSP blazes its trail, breaks records, and makes important scientific discoveries.

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Posted by Nathan Tehrani

I am a Guidance, Navigation, and Control engineer at Engility with a background in physics, radio astronomy, and navigation engineering. I have supported the Parker Solar Probe project for NASA’s Independent Verification and Validation program and am now supporting the WFIRST space telescope.