We all woke up at 5:15 to prepare our ground control station and make sure everything was ready for a 6:15 test countdown. Nervousness, excitement and anticipation were in the air as we checked over all of our computers and ground control software. This was it.
At 6:00 the experiment team leaders joined Eurolaunch for a pre-test countdown meeting. A brief procedure review took place along with all parties giving a go ahead for countdown. The group was asked if they had any objections and there were none. We were go for test countdown. The countdown timer was set at t-02:15:00 and it started to tick over at 6:15 exactly.
As I sat next to Axel at the RAIN localisation station we both turned to each other and suddenly realised that there really was not much for us to do at this point in time. Our job was to track the FFUs after they had deployed their parachutes. With all the nervous energy in the air though we couldn’t just sit still, we had to do something. So, we went a bit crazy on the blog and facebook and made sure RAIN followers around the world knew what stage of the test countdown we were at.
The test countdown passed by smoothly. Patrick and Tobias were at the main RAIN ground control station and they were in charge of checking the health of the experiment when it was activated, activating all flight routines and interfacing with the science centre manager. At t-00:10:00 Tobias and Patrick started their most pressing procedures. They started by verifying that the experiment had been activated. They then read through all of the sensor data from both of the FFUs, checking that all values were nominal. At t-00:05:00 they put the FFUs in mission mode. Mission mode is the routine that runs on the FFUs during flight. It is an automatic control routine that runs off a pre-defined schedule, making sure that the FFUs execute specific functions at different times during the flight. As soon as they had activated mission mode that was it. The RAIN team had no more control over the experiment. We had to trust that the software that we had written for the FFUs would guide them through their flight to a safe return to Earth.
As the countdown ticked over to t-00:01:00 the atmosphere in the room was tense. Everyone was watching their computer monitors and listening to countdown updates over the loudspeaker. As t-00:00:00 arrived I found myself craning my neck to look out at the launcher just to make sure that no one had pressed the ignition button by accident. There was no launch. Countdown soon stopped at t+00:05:00 and the entire room gave a sigh of relief. If this was just the test countdown, what was the hot countdown going to be like?
We didn’t have much time to contemplate given that no more than fifteen minutes later it had been decided to go ahead with a hot countdown. The hot countdown would commence at 09:45 and last for two hours. Over the course of this project I have developed an expectation that things will not go as planned. In the back of my mind I had been expecting that hot countdown would not go ahead. My instinct had told me that a technical problem would crop up with the payload or the weather would take a turn for the worse. But the rocket was functioning perfectly, it was a clear day outside… we were go for hot countdown!
Once again we all took our places. We began to repeat the processes that we had just performed, but this time there was a new feeling. The safety net had been removed; this was no longer a rehearsal. This was it. The seconds ticked by and Axel and I reviewed our localisation procedure partly to be one hundred percent certain that we were ready and partly to distract ourselves from the nervous wait.
At t-01:00:00 we were told that we should go and get some lunch because we would miss it otherwise. What? Eat lunch now? Most of the team went down to the cafeteria to get a quick bite. It was definitely the fastest meal I have ever eaten.
At t-00:20:00 the doors to the science centre were locked. Those who were present for launch would not be allowed to exit until after the countdown had been completed. Everyone stayed at their stations. The room went quiet as the final minutes approached. Tobias and Patrick checked RAIN as it was turned on at t-00:10:00. All nominal. Mission mode was activated at t-00:05:00. All nominal. We sat back knowing that that there was nothing more we could do to control the experiment at t-00:03:00. All still nominal.
At t-00:02:00 all experiment ground controllers gave a final “go” for launch.
t-00:00:10 a calm set over me. There was nothing to do but watch REXUS-11. t-5, 4, 3, 2, 1… REXUS-11 jolted to life with a flash and leapt off the launch pad. Within two seconds it had departed from view.
My attention turned to Tobias’ computer screen. I was looking for red lights on his screen. Red lights meant that the FFUs had left the rocket. I didn’t want to see red lights until t+00:01:07. The flight clock slowly crept up… green lights. The ejection system was holding our FFUs in the rocket. It was resisting the violent vibration and immense acceleration. Still green lights.
At t+00:01:00 the fear of the ejection system releasing the FFUs too early transformed into fear that it would not actually eject anything. Seven seconds passed and two red lights started flashing on Tobias’ computer screen. The FFUs were free. As they were relinquished from their rocket enclosure their automatic control timeline was triggered. As they each continued to rise along the same path as the rocket payload they activated their GPS experiments and started to collect raw GPS data.
At this point I turned to look at the large monitor in the science centre. The surface of what looked like a blue marble was wobbling around. I had to do a double take before I realised that I was watching a live feed from the Telescobe experiment directly above RAIN. The curvature of the planet was quite pronounced. In any normal circumstance I would have stayed to watch, however it would soon be time to monitor our FFUs.
The FFUs reached an apogee or highest point of 78.5 km. The FFUs lost their fight with gravity and began to accelerate towards Earth. At apogee they each activated their aerosol collection experiments. A gear in the base of each FFU began to rotate aerosol collection samples passed an exposure window in the FFUs’ base plates. As the FFUs fell it is hoped that any aerosol particles that collided with the FFU stuck to the collection samples.
By the time they reached 30 km the density of the atmosphere had dramatically increased and the FFUs were experiencing peak atmospheric breaking. Soon after the aerosol collection experiment stopped and the FFUs continued along their ballistic path with their aerosol collection samples now sealed.
It was t+00:06:00. Axel, Erik and I were at the localisation stations with our eyes glued to our computer screens. The FFUs would soon deploy their parachutes and begin transmitting their positions. We had to receive signals from the FFUs if we wanted to find them again. Time ticked by and we did not receive anything. By t+00:08:00 I started to get nervous. Were the FFUs going to stay silent?
t+00:09:00. Axel speaks. “Both FFUs transmitting.” I looked over Axel’s shoulder and sure enough radio beacon messages were streaming down his terminal window. About 20 seconds later Axel reports, “position fix for C,” and five seconds after that “position fix for E.” Both FFUs were transmitting their GPS positions. Erik then spoke. “I’ve got both FFUs drifting to the East.” Erik was displaying the FFU’s GPS positions on Google Earth. There they were, our experiments gliding across the Lapland skies.
10 minutes later the FFUs were still falling and we got STX2 fix. Each FFU is equipped with a satellite modem that sent its GPS positions to the Globalstar satellite network. These messages were relayed back to us over the internet. We now had two position locks on each FFU.
t+00:27:55. Both FFUs had landed. The GPS positions were not changing anymore so we knew that both of them had touched down. I wrote down the coordinates for each unit as Axel read them off. I repeated them three times before I was satisfied that those were the same positions that were displayed on the computer screen. I went next door and delivered the coordinates to the recovery crew.
As the recovery crew departed from Esrange the RAIN team grouped together and quietly smiled at one another. It looked like the experiment had worked. All of the experiment teams went around the room and congratulated one another. The rocket launch had been a success. The rocket payload deployed its own parachute and landed well before the FFUs at t+00:12:20. Another helicopter recovery crew had also recently left to pick up the payload.
Residual anxiety made me pace around the science centre. How long would it take the helicopter to find the two units? Would they be able to find them at all? After 20 minutes of this I went to find someone who was in contact with the helicopter for a status update. I searched the building but couldn’t find anyone who knew. Arriving back in the science centre I read the mission status screen and the message “Freeflyers located 13:23LT” was displayed. In my haste to find an update I had missed a representative from Eurolaunch come in to the science centre and tell the rest of the team that both FFUs had been found. Erik laughed as it slowly dawned on me that everything was okay. The experiments were coming back. Axel and I quickly went to the localisation computers and watched for new localisation messages. The FFUs were still transmitting so we were able to track the helicopter on its way back to Esrange.
We met the recovery crew in the lobby of the main building. They handed over the precious payload in a big black waterproof bag. The recovery crew told us that the pickup operation had been very straight forward. The high visibility orange parachute material had made the FFUs very easy to spot. It was also fortunate that the FFUs landed in open spaces with room for the helicopter to land. The flight and recovery was complete. Our experiment left Esrange and returned in little over an hour.
We quickly documented the state of each FFU and plugged each of them into a computer to read out all of the recorded sensor data from the flight. I’ll reserve our result summaries for another post. We then made sure that both units were sealed and packed away ready for delivery to Stockholm University where they will have their aerosol collection experiments analysed.
I’ll leave you with a photo of the RAIN team on launch day after the return of the payload. Don’t worry, the two FFUs in the photo are test ones.