Sodankylä Measurement Campaign, 18-26 June, 2015

From Thursday 18 June to Friday 26 June, 2015, we took part in a campaign at Sodankylä, Finland. The campaign was organised by Huilin Chen (University of Groningen, the Netherlands) and hosted by the Finnish Meteorological Institute (FMI), especially by Rigel Kivi. The goal of the campaign was focussed around AirCore measurements, with 3 groups launching AirCores, namely University of Groningen, the National Oceanic and Atmospheric Administration (NOAA) from the USA, and University of Bern, Switzerland. In addition, a Romanian group were involved to test a system for guided descents of AirCores, which would be very useful for island and coastal sites, or anywhere with difficult terrain. Sodankylä is a useful site for these type of activities, because it is fairly remote, meaning that flight restrictions are not too bad and AirCore retrieval is relatively straightforward. It is also a TCCON site, and has a bunch of other measurement equipment present. They regularly launch sondes (ozone and regular radiosondes), so have lots of experience with balloon launches as well. In addition, at this time of year it is light 24 hours a day!

Thursday 18 June, 2015

Today we successfully met Rigel and each other in Helsinki airport, and flew to Rovaniemi. The flight was relatively unexciting, but there were impressive views of large green swaths of land, and many wetlands as we were coming in to land. We collected the car, and looked at the Arctic Circle running through Rovaniemi airport.

Rigel was quite excited to take us to Santa Claus land just outside Rovaniemi. At 10.30pm it was still bright, and the shop was still open, so we stopped in and bought postcards and a couple of other things. Nothing else seemed to be open there, and there was no sign of St Nick himself - apparently he can still get to sleep relatively early despite the sunlight hours. He did leave some offensively annoying music playing to make sure that we didn't linger, though we did have time to visit the Arctic Circle again.

Santa's Lapland Village
One of the "attractions" at Santa's Village, just outside Rovaniemi, in Finnish Lapland. The Village lies on the Arctic Circle. This photo is from about 10.30pm

The rest of the trip to Sodankylä was relatively uneventful. There was not much traffic on the roads, and we got to Sodankylä about 11.45, still in time to stop at the kiosk for a Super Burger (the only item on the menu that we could understand and pronounce) in the midnight sun. Then we proceeded to the site, where we were introduced to our house, which we are sharing with Huilin Chen, campaign organiser. Eventually we hit the sack to get some sleep before the initial campaign meeting the following morning.

Friday 19 June, 2015

Woke up at 2.45, convinced it must have been after 5pm until I looked at my mobile phone. Despite wearing an eye mask, it was quite bright. Managed to get back to sleep, however, and it was a struggle to drag myself out of bed at 7.30.

The campaign meeting was held in the main building, after everyone had livened themselves up with coffee or tea. We did our introductions - there are several groups here, 3 of whom are testing AirCores, 1 testing gliders (with another to come later), and 1 with an EM27/SUN low-resolution solar FTIR, plus the locals. Each group seems to have 2 or 3 members present, at least for the start of the campaign. The Groningen and NOAA groups already have their AirCores here at Sodankylä, while the group from Bern are waiting for theirs to arrive on Monday. A Romanian group have 2 gliders to test for guided landings, with the goal of performing launches over the TCCON site at Le Reunion. This is particularly tricky, because Le Reunion is a relatively small island, and therefore a difficult target to hit with an AirCore without some sort of control on descent.

Map of Reunion Island with scale
A map showing Reunion Island, complete with a scale. Try hitting this with an AirCore! Especially when the middle is occupied by an active volcano.

The plan for the first day was the perform a few AirCore test launches as well as a test of the lighter of the 2 Romanian gliders. The AirCore launch plans were hampered by the fact that neither of the two Picarros, which are used to analyse the samples, was functioning. There was a lot of general running around trying to contact Picarro, with efforts made by the Groningen group, the Finns, and people remotely at NOAA.

Due to the fact that today was a public holiday, the shops closed early (at 2pm), so Rigel found somewhere that served lunch until late, and we headed out to the exquisite gas station, via the local supermarket. We stocked up on various stuff to cook in the house, and then went and chose from the vast array of options for lunch at the gas station (pork or chicken).

The weather was also not great, but eventually cleared, and we watched the group from BIRA (mostly Mahesh, with help from Mianqiang and Martine) set up the EM27/SUN. Mahesh kindly took it apart so we could see inside (don't tell Bruker), and it's quite neatly set up - compact, but not too crowded. Once it was fine, it was hoisted via an external cage lift onto the roof of the building. Mahesh set it up, first a relatively coarse N-S alignment, then sending the CamTracker to the calculated solar position (based on the local altitude, latitude, longitude). There was then still a relatively coarse (but finer) adjustment to bring the solar image into CamTracker's field of view. After this, there was a finer adjustment of the offsets to centre the solar image with CamTracker's expected ellipse location.

We left Joel in charge of the EM27/SUN, with instructions of how to rescue it if rain came, and went to watch the trial launch of the smaller Romanian glider.

The small Romanian glider
The small Romanian glider - basically a test bed for a large, heavier vehicle with almost identical characteristics, but space to carry an AirCore.

After a couple of false starts, we found a location with enough room for the launch. This happened to be near a small local farm, where the locals (including the sheep) showed great interest in what was happening, particularly the filling of a large balloon with helium (necessary for the launches remote from the site).

The locals - very interested in what was happening outside
The locals, who showed a lot of interest in what was going on outside, and who kept asking to be kept informed.

After the glider operators and the balloon fillers spent a good 10 minutes waiting for the others to do something, we eventually got underway. The glider was launched, and cut away the balloon at 700m. After this it was programmed to circle around its designated home position, while slowly (it has a 30:1 glide ratio) descending. Florin also had a remote control to be able to operate it. The flight proceeded successfully, and Florin took over control, with a not quite textbook landing, but no damage to the glider.

Romanian glider on its way up
The smaller version of Romanian glider being lifted by a helium filled balloon for its first test flight.

By the time we got back, the weather had remained good, and one of the Picarros was functioning again, so spirits were relatively good. We took a short run around the site, which is big, but not really big enough for extensive running, and certainly not as much as the 30 miles Jack had run at 3am when he woke up jetlagged. Joel cooked dinner, and we had a few beers (Karhu seems to be the local beer of choice - Karhu means bear in Finnish).

Saturday 20 June, 2015

The goal today was to launch 3 AirCores relatively early in the piece. These were one from Groningen, which was to be launched alone, and 2 from NOAA, which were bundled together in one package. We learnt a lot about the construction and analysis of the AirCores today. All these 3 AirCores were a combination of 1/4" and 1/8" tubing, about 50:50 in each case, but with different total lengths (and hence volumes). The consensus seems to be to go for longer tubing but all in 1/8", to minimize diffusion, so that is what we will probably do as well. They use stainless steel tubing, treated with SilcoNert 1000 coating to make it inert. There was talk even about going down to 0.005" wall thickness, instead of the current 0.01". The tubing and coating seem to be quite expensive, so we will have to carefully consider how much we actually want. Before launch, they flush the tubes with a fill gas, which has ~normal concentrations of CO2 and CH4, but enhanced CO. This is both to dry the tubes, and also to leave a marker in the small section of tube that is not evacuated. A small drier is used - it was interesting to watch Tim (NOAA) very carefully pick out the ideal pieces of magnesium perchlorate to put in the drier; the bigger the better, to avoid potential pressure drops across the drier.

Groningen AirCore #1
The Groningen AirCore #1, the first to launch during this campaign. It weighs about 3.6kg, and is a combination of 1/4" and 1/8" tubing, for a total volume of about 1L.

Each of the AirCores is contained within an insulating styrofoam container, roughly circular, and probably about 50cm diameter and 20cm high. The lid (a single matching diameter piece of styrofoam) is generally just taped on, and then they chose to wrap the whole package in glad wrap, leaving the inlet exposed of course! Each group had different valves, data loggers, and various sensors within the AirCore itself. Groningen have 5 temperature sensors, for example. All systems have many redundant tracking devices, generally 3. NOAA generally use a dog tracker, an Iridium communication device, and a GPS within the AirCore itself. The Iridium is boxed separately to prevent interference, and flies above the AirCore, attached by a separate string.

2 NOAA AirCores
2 NOAA AirCores, being packaged up for a comparison flight by Bert (left - Uni of Groningen) and Tim (right - NOAA)). These are lighter and shorter length than the Groningen version, as US regulations can allow them to fly without FAA approval if the package is below 6 pounds (about 2.7kg).

We eventually got launched - the Groningen AirCore flew first, about 30 minutes before the NOAA package was launched. Because the launches occurred at the site, the balloons (3000g each) were filled with hydrogen rather than helium - this is cheaper, but harder to deal with if transport is needed. The Groningen AirCore flew until the balloon burst, but NOAA cut their package from the balloon before then, at around 28,000 m.

Lift off
The Groningen AirCore, with the first AirCore liftoff of the campaign, escorted to the stratosphere by a hydrogen filled balloon

Jack and Marco went tracking the AirCores, and returned with all of them relatively easily. Neither of the NOAA AirCores had their valves automatically close, using either of their different valve systems.

Off to hunt AirCores
Want to go hunting AirCores in northern Finland? Pack your ATV!

The Groningen AirCore was analysed first. They sample from the "top" end of the AirCore first, pushing through with the fill gas (the spiked CO one) to have a marker for when the sample itself is finished. Before running the AirCore through the Picarro, they run several minutes of fill gas, then several minutes of calibration gas, letting each run until it is approximately stable for about 5 minutes, before switching to the next and then the AirCore itself. This is repeated afterwards. Several 3-way valves (manual) are necessary to avoid swapping fittings and so forth, and therefore to avoid wetting the lines. Wetting the Picarro itself is less of an issue, though it should be dried out to a reasonable level before analysing the AirCore.

Retrieved AirCores, off for analysis
The retrieved AirCores being shepherded off for analysis in the building containing the Picarros (bottom) as well the TCCON spectrometer (above - the solar tracker for the FTIR is located to the right of the dome as we are looking at it).

The 2 NOAA AirCores were analysed afterwards. This was relatively straightforward, but there were a few difficulties in changing over the various fittings. Groningen use quick connect Swagelok fittings, while NOAA use regular threaded nuts. Bert (Groningen) told us that the metal on metal binding of the quick connects (or any metal-metal connection, like from a valve) causes a small release of methane, something else to consider, and a reason that he was keeping everyone well away during the analysis. On one of the NOAA samples, they almost forgot to open the valve for the fill gas that would push the sample through- this was a mistake that apparently Colm Sweeney made last year, and invalidates the sample. Luckily we spotted that before it was critical.

NOAA AirCore up for analysis
One of the NOAA AirCores, as set up for analysis through the Picarro. Also connected to the Picarro and/or AirCore are a calibration gas (left, at back) and the fill gas (also left, directly in front of the calibration gas). The battery pack visible to the right of the AirCore is used to fire their valves open or closed via the connections to the front right of the AirCore package. The open and close connections are independent to avoid confusion about whether one is opening or closing the valve.

The samples generally looked good, with a few interesting features. The Groningen sample had a water peak, with a smaller trailing shoulder, come through before the end of the sample. CO2 showed a similarly shaped feature later on. The water still only reached maybe 250 ppm, but it was above the 50ppm that the rest of the sample seemed to sit around. The NOAA sample was drier in general, down around 10ppm or lower (hard to say with the Picarro's resolution).

Watching on with the analysis
Concerned/interested scientists watching on with the AirCores analyses: Huilin Chen (front right, Uni of Groningen) and Tim Newberger (behind, NOAA).

At the same time as the AirCore samples were being run, Joel and others went off to watch the next Romanian glider launch - same glider, but going to higher altitude. After a couple of hours one car load came back - the news was not good. Apparently they lost communication after only 350m. Mahesh got a photo that showed that the glider had successfully detached from the balloon, but it had not returned. So that was a bit of a let down, but in truth, no one was overly surprised. After a while longer, the others came back, and reported that the glider had in fact reappeared. Everything, except the communication, had functioned okay, and because of the long glide ratio and the clouds, it had taken a long time to return but was not able to be seen from the ground.

That meant that all in all, it was a pretty successful day. We also learnt from the Swiss group about a company from Germany called StratoFlights, who make and sell various things specifically designed for high altitude scientific flights. Especially of interest was a €199 datalogger board, complete with GPS, pressure, humidity and temperature sensors.

Sunday 21 June, 2015

We hoped to launch 2 AirCores (one NOAA, one Groningen for an intercomparison) earlier today, so that meant being out of bed a little earlier than the previous days. Things moved slowly though. Also, to complicate matters, the total payload of the launch was above 6kg, which is the magical Finnish cutoff, above which you have to fly a transponder. Unfortunately the transponder available weighs 2.3kg - we couldn't get hold of the 100g version! So there was a bit of coordination involved in that, and we ended up with many packages in serial attached to the balloon... parachute, Iridium, Camera and radiosonde, AirCores and the transponder... possibly also something else that I've forgotten. Eventually we looked to launch at around midday. After having many hands on deck, to support the various packages, the balloon broke away as we were preparing to launch, because the upper string broke. That upper string, provided by NOAA, was only rated to 50 pounds - a US requirement so that planes can easily break through it. That was somewhat fortunate, as Bert had forgotten to remove the inlet valve from the Groningen AirCore. The string was replaced with a thicker string, and about an hour later we successfully launched.

Comparison launch preps
Preparations for the comparison launch for the NOAA and Groningen AirCores.

Joel went off with Jack and Marco to chase AirCores, and most of the remainder of us went to lunch in two separate cars, Rigel leading in the first, and me following. We had agreed to go to a pizzeria, after the previous two lunches at the gas station (we had skipped the second one). When we turned up there, Rigel turned around and proceeded to say that they were going to the gas station again. Our car revolted and stayed at the pizzeria, ate massive pizzas, and then went to the supermarket to restock. We still got back about the same time as the gas station devotees.

Marco heads off to chase AirCore
Marco heads off on the ATV to hunt AirCores, a favourite Finnish pastime.

Not much was happening during the afternoon while the AirCore hunt was on, so I caught up on some washing, and then went for a run. As I was leaving on the run, the AirCore hunters returned. By the time I finished running, Joel then went to watch the AirCore analysis. Apparently the NOAA AirCore seemed to work well (and the valves closed today), but one of the push fittings on the Groningen AirCore hadn't connected properly, and it was still filled with fill gas.

The AirCores return
Spotted: A Finn in his natural habitat: on an ATV and returning with AirCores
The successfully retrieved AirCores
The successfully retrieved AirCores in the back of the ATV.

The remainder of the evening was relatively uneventful, but we did start to make notes and plans for the development of our own AirCore based on what we have learned so far. They are aiming for a 9am launch tomorrow, which means that they might be ready before midday :)

It could be worse
The site could be worse: this is the river that runs alongside the site, pictured in the depths of the evening.

Monday 22 June, 2015

Damn midnight sun. Didn't fall asleep until around 3am, after a walk a midnight to look at the river. Joel decided it was a good idea to go for a swim. That seemed refreshing. Anyway, the 9am launch did not eventuate, but they did manage to launch 2 balloons before midday. The first was a copy of yesterday, with one Groningen and one NOAA AirCore, and almost exactly the same versions of everything else, just missing a couple of dataloggers.

Preps for NOAA Groningen comparison
Preparations for the launch of another attempted NOAA/Groningen AirCore comparison, with Joel giving directions. Mahesh (front right) had responsibility for the transponder, and ensuring it did not clatter into the ground or collect the trees on the way up.

The second balloon was a new Groningen AirCore only, and therefore did not need the balloon to have so much lift and was not filled to the same degree. They still used a 3000g balloon, but Huilin says that they often use a 2000g balloon for that size, something of potential interest to us.

Launch 2 for the day
Launch of the new Groningen AirCore as observed from the top of one of the measurement towers on site.

As for most of the days to date, the EM27/SUN was set up by Mahesh and Mianqiang on the roof of the sounding building. This meant loading it into the external lift, along with its support box and laptop, and then hoisting it up without crashing into anything.

EM27/SUN on its way to the roof
Like most days, the EM27/SUN had to take the lift to the roof, where it was setup to track the sun and take measurements.

We took a bike ride into Sodankylä itself, and had some lunch there, before collecting some paraphernalia from the tourist information centre to try to plan some extra-curricular activities for the coming days. Huilin and Martine left in the afternoon.

Testing out the local bikes
Off on the local chariots to investigate the sites and tastes of Sodankylä.

After returning we walked over to the wetlands across the main road from the site, as recommended by Bert. I didn't realise until we got over there that this was also a bunch of stuff belonging to the site. There was a boardwalk running out, which gradually got thinner the further we got from the road. There were also a bunch of chambers and lids, some Licors for CO2 and H2O flux or eddy correlation measurements (hard to tell as they were reasonably well hidden), and a bunch of other stuff.

One of the many (open) chambers in the wetlands. There seemed to be pairs of chambers, only one of each looked like they were near to operation, in a variety of subtly different biomes of the wetland.

There was also this bad boy, which was being monitored by security cameras.

We discussed a little with Tim regarding the tubing. They are moving to 0.005" wall thickness (0.127 mm), which is thinner even than standard aluminium foil. This makes me a bit nervous, because it would be very fragile to handle. The current standard thickness is 0.010" (0.254 mm). For 1/8" outer diameter, this obviously reduces the sample volume and increases the weight, so this is something we have to carefully consider. He currently buys 1000' rolls, which he then gets coated, and subsequently uses to build the AirCores. We might consider getting a 1000' roll and building 2 500' (150m) AirCores from it. He also said that 4" diameter of the coiling is about the minimum, though we would probably want larger anyway, especially if we want to mount the datalogger and other stuff in the centre of the coil.

What the hell is in here?
What on earth is in this cupboard?

We also went on a quest to try to get a photo of the midnight sun. Unfortunately there was cloud around the horizon, meaning the sun wasn't out itself. We did have a midnight journey back up the tower.

Not the midnight sun
It's not the sun, but this photo was taken from the top of the tower at midnight.

Tuesday 23 June, 2015

Today we got our first experience chasing AirCores, at the same time as the Swiss group had their first ever AirCore launch. It was also an OCO-2 target day at Sodankylä, and Mahesh set up the EM27/SUN 15km north of the site, along with Mianqiang. We rescued Mahesh for lunch and checked out their location at the same time. It seemed okay, but not great, for satellite and ground-based data, but hopefully there will be something from the exercise. We also stopped and collected some food with the plan of BBQing in the evening.

The EM27/SUN set up remotely from the site. We've just come back from lunch, so Mahesh is checking on how the instrument has been running, and Mianqiang is gratefully tucking in to the pizza we brought to him.

After lunch we went and checked out the solar FTIR, which is housed in the same building as the Picarros that are used to analyse the AirCores. It's on the second floor. It's a fairly typical Bruker IFS125HR, without a sample compartment, and with all chambers except the detector compartment covered with perspex instead of the original covers, meaning that one can quite easily see what's going on. They use a Norhof like we have in Wollongong to deliver the liquid nitrogen to the InSb detector for MIR measurements.

Sodankyla Bruker IFS125HR
The Sodankylä Bruker IFS125HR, complete with perspex covers so that you can keep an eye on its internal movements.

They have a typical Bruker tracker, with flip-top cover, sitting on the roof. It's behind the giant dome when the sun is to the north, so unfortunately they cannot get measurements 24 hours a day, even during polar day.

Sodankyla solar tracker
The Sodankylä solar tracker in operating mode.

On the way through the building we stopped in to see what was happening with analysis downstairs. The Groningen folks had launched their two AirCores together in the morning on the same payload, and were into analysis. Upon launch, the transponder just managed to miss the trees on the way up. The transponder was necessary, because their AirCores are a bit more than 3kg each. Bert explained to us the virtues of not using a mass flow controller (apparently they still generate some noise in the flow rate), but rather a critical orifice, to control the flow. They have theirs made to deliver a flow of 39 mL/min.

Gas plumbing on the Picarro
The plumbing on the Picarro used for gas handling. This includes a critical orifice to control the flow, instead of a mass flow controller.

The Swiss performed their first AirCore launch, with the aim of sending it to 5km. They are largely interested in the troposphere, so are not aiming to go as high as for the NOAA and Groningen AirCores, which go well into the stratosphere (30km is regularly reached, which is around 10hPa).

First Bern AirCore launch
The Bern AirCore off on its first balloon powered vertical trip!

While we were waiting to see where the Bern AirCore got to, we went to have a look at another of the measurement towers, which seems to be largely set up to be part of the ICOS (Integrated Carbon Observation System) network - essentially a large EU infrastructure project. One of the Juhas was responsible for it. There are many inlets at various levels, and quite a lot of associated instrumentation, some of which is redundant. Juha seemed less than impressed with one of the instruments that has been regulated by ICOS, which was one reason that there was some redundancy - he wanted a better instrument for the task.

ICOS measurement tower
ICOS measurement tower, with inlets at 3 levels for sampling atmospheric constituents, and various other instrumentation. The tower is about 60m tall.

We set off in two cars to try to track down the Bern AirCore, chasing each other through the roads and dirt/gravel trails around Sodankylä. It hadn't travelled too far - about 25km I guess. Some of the NOAA and Groningen AirCores had gone about 3 times as far. Not only that, but it landed only about 100m from the road (well, trail). Rigel spotted it quite easily, and it appeared to have had quite a smooth landing as well. Marcel retrieved it, and took it back for analysis.

How many scientists does it take to retrieve an AirCore?
How many scientists does it take to retrieve an AirCore? Joel, Marcel, Rigel and Juha set off to retrieve the Bern AirCore after it's first landing.

10 points for the landing
The aftermath of the AirCore's landing. The AirCore is in the foreground, complete with Vaisala RS92 radiosonde. Further back along the line are the Iridium, and the parachute.
Success! Marcel celebrates the first, successful, launch, landing, and hunt of the Bern AirCore.

The Romanian glider also flew again today - still the small one, as there is no place to hold the large transponder on the larger glider - this time to 25km, from which it also returned successfully.

We gathered in the evening for a BBQ, and also some time in one of the 7 saunas on site. That was very warm, especially compared to the river, which we ran and jumped into straight from the sauna. We each lasted about 30 seconds in the river before getting out. Much beer was also consumed and we eventually left the BBQ room at about 1.30am. Of course it was still light!

Wednesday 24 June, 2015

We took today off "work", and went for a drive to the Pyhä-Luosto National Park, just south of Sodankylä. We set off to find some walking, and decided to start in the vicinity of the Amethyst mine - the only operating amethyst mine in Europe, and possibly the world. On the drive up to the carpark, we ran into these guys, leisurely strolling along the road.

The locals of Pyhä-Luosto National Park, enjoying a summer stroll.

We walked to the amethyst mine shop, checking out the quiz along the way (10 questions, no idea how many we got right), and got some lunch. We also took the opportunity to try to pick an appropriate walking route. We decided on one marked "difficult" that went from somewhere near the shop to the top of a hill. Unfortunately, we missed that path, and ended up on an easier one that skirted around the bottom of the hill. As an (unfair) exchange, we completely failed to miss the mosquitoes. Once we realised that we had taken the wrong path, we decided to make things a bit more challenging by scaling up the side of the hill, which was at a reasonable steep, but not extreme, angle. The mosquitoes scaled with us. The view from the top was quite nice.

View from the top of Ukko-Luosto (514m). Shortly before this we were in the valley below, and came up almost in a direct line in the direction of the photo.

Joel contemplates why the Finns put their world cup trophy on a radar dome on top of Ukko-Luosto.

We went back to the beaten track, and headed down the other side of Ukko-Luosto. It was much greener on that side of the hill, but there was still some snow remaining. Joel indulged his inner child.

A little winter sport.

The view from the other side of Ukko-Luosto.

From there we headed back to the carpark. We decided to head on towards Pyhä in search of some sustenance. We encountered some slow moving traffic on the way.

Traffic jam in Luosto.

After clearing the traffic, we made it to Pyhä. The recommended restaurant looked very deserted, so we went to the cafe next to the tourist information centre, and indulged in some traditional Finnish fare - burgers! From there we then walked to the Isokuru gorge. There were some waterways there, and the water was unbelievably clear. For some reason people had felt the need to throw coins into one particular pond. We weren't desperate enough to go swimming to get them out, either for our own profit or for charity.

One of the unbelievably clear ponds in the Isokuru gorge.

We didn't continue too far, as by now we'd done quite a bit of walking, and there was a threat of bad weather coming before too long. We continued just far enough to get a good look through the gorge, and headed back to the car.

The view along the Isokuru gorge.

After that, we made our way back to Sodankylä via the alternative route (basically along the other side of the river). We had a couple more "traffic jams" along the way - the reindeer didn't seem to be too fussed about getting out of the way for cars in a hurry.

Once we got back to the site, we checked in to see how everything had progressed for the day. The Swiss had launched their AirCore again, this time to about 7km. It travelled a little further than yesterday, but generally in the same direction. It was apparently a bit more difficult to retrieve (they needed us there!), but nothing like some of the others. Unfortunately, their sample analysis didn't go so well. Due to the weather (it was cloudy most of the day, and rained as well), there were also no EM27/SUN measurements - they had planned to make the instrument mobile, and drive to various sites to measure, but the lack of sun put paid to those plans.

Thursday 25 June, 2015

Leaving day! After a week here, today is time for us to leave. Before then, there is a debrief scheduled for 10am, meaning we can attend for a little while before heading off to Rovaniemi to catch the flight. In the debrief, there is a general overview from Huilin, and updates from each of the other groups. All in all, the campaign has been a success. There were high altitude AirCore flights on 4 days, corresponding to fine weather, which will enable comparisons with TCCON and EM27/SUN data. There were also shared launches on several occasions to be able to check between AirCores. The Swiss got there first AirCore launches as well, and are still planning for 1 or 2 more before they head home. The EM27/SUN collected data most days, as did the TCCON instrument as well. Even the Romanian glider seemed to work well. Florin told us that on the high altitude flight on Tuesday, in the initial descent period, the glider reached 300m/s!! That's damn quick. With an AirCore mounted, you wouldn't get much sample in that time, so it would ultimately need to be slowed down, if possible. Apparently the larger glider doesn't have quite such a good glide ratio (15-20:1 compared to 30:1), and should also fall slower in the initial phase.

Eventually, we made our escape, and hurtled down the road to Rovaniemi. There was a lot more traffic than at 11pm on the way to Sodankylä, and to make matters worse, it also rained for the second half of the trip. The driving, including from me, was interested. In the end, we made it to Rovaniemi airport about 20 minutes before take off. I got on the flight, but Joel had been placed on standby. In the end, he had to take a train to Helsinki, before heading back to Wollongong. I made it successfully to Bremen, as did my luggage, despite the threats of the woman on the check-in counter.

From our perspective, the campaign was also a great success. We learnt a lot about what to do, and especially about what not to do, when building an AirCore. In addition to that, we got to make contact with other groups making AirCore measurements, and they were all very supportive of us. Not only that, we got to visit Finland, experience the midnight sun, partake in the traditional Finnish experience of going between a hot sauna and cold water, and see reindeer in the wild.

Now, back to reality, and constructing our very own AirCore.

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© Nicholas Michael Deutscher, 2015