"All or Nothing!" that is what my Dean called it; "Just like the shootout at the OK corral, how exciting," were her final words to me after I described what I would be doing this January in Alaska. I am the Principle Investigator for the NASA Auroral Spatial Structures Probe (ASSP), a 70-foot, four-stage unmanned rocket loaded with scientific instruments sitting on the launch pad now in Alaska. After four years of planning, building and testing at NASA Wallops Flight Facility and at the Utah State University Space Dynamics Laboratory, it is all coming down to a call, my call, as to when to launch.
The aurora borealis is beautiful, awe-inspiring, and far more dynamic and crisp than pictures seem to capture. Those who see it for the very first time often comment on how much it moves in the sky and how detailed the structure of the curtains are and how quickly it can evolve into whole new patterns. They say it is more than they expected.
Yet the aurora is not just the pretty lights of what we call "the visible aurora." There is an unseen structure of voltages and flowing currents in which the visible aurora is embedded and which are not as well understood. The existence of these currents has been detected since antiquity through the slight tremor of magnetic compass needles when the aurora was active. Now we use sub-orbital rockets or satellites flying in or above the aurora to study these invisible voltages and currents. This current NASA mission is a whole new approach to making these types of measurements and has great promise in advancing our understanding of the invisible aurora and its relation to those ethereal curtains of light.
The basic idea behind this flight was to launch a rocket into an active aurora and then deploy multiple sensors in mid-flight to do something that's never been done before. Shortly after the fourth stage burned out, six sub-payloads, each about the size of a loaf of bread, were ejected away from the main rocket at high velocity using compressed air canons. This expanding formation of sensors arced high over the aurora, measuring voltages and currents.
The whole mission only lasted about 14 minutes with about eight of those minutes dedicated to science collection. After reaching an altitude of 600 km -- about half as high as the International Space Station -- the sensors and spent rocket boosters splashed down in the Arctic Ocean north of Alaska. The goal was to fly over the aurora somewhere near the north coast.
ASSP was the most complex sounding rocket mission NASA has ever done. It was like flying seven sounding rockets at once over the aurora. NASA even had to bring in additional telemetry dishes and equipment to the Poker Flat Research Range to augment the existing capability.
Prior to the launch, weather conditions around Fairbanks were poor with a winter storm blocking the views from our ground-based cameras. Once the skies cleared, we were able to make a prediction of what the aurora was likely to do over a 15-minute period.
We only had one shot, and even after using all of our best information and prediction methods, there were always elements of chance. The aurora can completely change, brighten, move, or disappear in just a few minutes. In a way, this was like a shootout, but a shootout with only one bullet.
With the rocket perched skyward on its rail, bundled up from the cold inside a warm foam box, we waited for just the right opportunity to launch. We held the launch count at T-3 minutes for some time waiting for the right conditions. Once it became clear that this was the right auroral event to launch into, I said to the team 'It is time to spend this rocket.' There were several strong arcs over the north coast of Alaska. It was spectacular to get the arcs we wanted.
At T-1 minute I gave the authorization to go for launch and ran outside to see it go up with my own eyes. At exactly 1:41 a.m. Alaska Time on Wednesday, January 28, we counted down to T-minus zero and launched into the aurora.
It was stunning. The sound was a body-penetrating roar, significantly delayed because I was a mile away looking down at the launch pad. All four stages went beautifully. It was such a relief to have the rocket away. I then ran back inside to watch the all-sky cameras to see if we were going to be successful flying our formation of seven sensors over the arcs.
The aurora we launched into did not read the textbooks and did not develop at the rate we expected. It seemed to be a slow motion development with the arcs breaking up over Poker Flat and then reforming further north over and over until they were at the north coast of Alaska. We launched just as they arrived and they remained constant for the 10 minutes it took the rocket to reach them.
I thought it would be a terrifying wait, but I was quite calm. The event contented to develop strongly and it was clear that we were going to get our science. It is a great privilege to have been part of this very special mission that so many had worked on for so long.
The telemetry data shows that we successfully ejected all of the payloads and created the constellation of sensors that we needed. We flew over the aurora as planned, and it was a stunning success for such a complicated mission.
The ejection of the sub-payloads by the compressed air-spring cannons is so violent that they had to be done in pairs in opposite directions so as not to send the main payload spinning out of control with the kick back. This was new technology devolved just for this mission by NASA.
I have had many congratulations from my colleagues around the country who are asking for quick-look plots of the data.
This has been a six-year effort and to see it all come down to 14 minutes was almost too much to bear. But it was a successful 14 minutes, and it is now a very satisfying feeling. To be part of a raging success by a team composed of so many organizations is humbling. We did it!