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 From Chris Derksen (Environment Canada) 22 April 2013

Following completion of the SnowSAR flights and ground measurements near Inuvik, the entire operation transferred to Alaska.

This included a rather complicated effort to ship the SnowSAR and aircraft installation (modified aft baggage doors for the Cessna-208 Grand Caravan) fromInuvik,Northwest Territoriesacross the border toFairbanks, Alaska.

Although these two communities are only separated by about 500 km by air, they are not efficiently connected either by air or ground. TheAlaskaand Environment Canada field crews made the nearly 3000 km road trip, starting with a southbound drive on the infamous Dempster highway to DawsonCity.

The Dempster, with its rough gravel surface, is known for eating tires, and the Environment Canada truck did not emerge unscathed.

Nevertheless, three days after leaving Inuvik we crossed the Atigun Pass, through to the north slope ofAlaska, and arrived at theToolikLakefield station, operated by theUniversityofAlaska–Fairbanks.

Unfortunately, the shipping of the radar and aircraft doors toFairbanksdid not go smoothly. Owing to a series of missed steps beyond our control, the projected timeline for conducting the SnowSAR flights continued to slip.

Fortunately, our luck turned and thanks to some quick processing of our shipment by United States Customs. The SnowSAR instrumentation arrived safely inFairbanks, where the MetaSensing operator was waiting for the installation onboard a Cessna 208. The customised cargo doors for the SnowSAR antennas (X-band on the top window, and Ku-band on the bottom) can be readily interchanged among different C208 aircraft platforms, so we were ready for science flights on 18 and 19 April.

The acquisition site was 600 km north ofFairbanks, and was reached with a 1.5 hour ferry flight. Before beginning the radar acquisitions, a short stop and go was performed at a small landing strip (nearGalbraithLake, at the north end of theBrooks Range) for coordination with the ground team.

The SnowSAR acquisitions began overToolikLake, where 12 corner reflectors were placed for radiometric calibration.

The tracks left by the snowmobiles reveal the locations of the targets in three parallel lines, one for the co-pol corners, one for the cross-pol at X band, and one for the cross-pol at Ku-band. The field station facilities can be seen in the bottom right of the aerial image.

Our American colleagues had already started the snow measurements in the Imnaviat Creek watershed, which included an intensive 1 km by 1 km grid of snow survey lines.

One unique aspect of these ground measurements was a FMCW radar (designed, built, and operated by Dr. H-P Marshall,BoiseStateUniversity) operating in the same frequencies as the SnowSAR. This instrument was also deployed during SnowSAR flights inAustriain February. In the photos below, you can see 1 km snow survey lines (separated by 100 m) and ‘crop circle’ patterns where the FMCW acquired measurements in a spiral pattern.

The snow cover properties at Imnaviat Creek inAlaskawere markedly different from Trail Valley Creek nearInuvik. Meteorological conditions combined to create a depth hoar layer at Imnaviat that was remarkable. These large faceted grains are found at the bottom of the snowpack, and form as a result of temperature-induced vapor pressure gradients in snow. In over 30 years of snow surveys at Imnaviat, our colleague Matthew Sturm noted that he had never seen depth hoar crystals as large as what we measured this year. The grid spacing in the photo below is 2 mm, so this depth hoar crystal was approximately 14 x 12 mm in size. The impact of these large crystals on the airborne SnowSAR measurements will be important to determine.

Despite some stressful moments when our timeline was slipping, in the end we managed to acquire nearly coincident airborne SnowSAR and LiDAR measurements, with detailed ground-based surveys, in harsh Arctic environments, in two countries, separated by only 8 days. More than 15 hours of SnowSAR acquisition flights were achieved inAlaskaandCanadain the last two weeks, from which more than 250 SAR strip images will be obtained.

Over the coming months we will quality control all the ground measurements, and the final SnowSAR and LiDAR datasets will be processed. These various datasets will then be utilized to improve our knowledge of X- and Ku-band radar response to snow cover properties, and our ability to retrieve snow water equivalent (the amount of water stored in solid form by the snowpack) from these measurements.

Ultimately, we will combine our work with the analysis of SnowSAR data acquired inFinlandandAustria, to maintain the current momentum behind radar remote sensing of snow. Now that the melt season is imminent, the SnowSAR will take well deserved vacation…unti the next mission of course!

The success of this ambitious data acquisition plan (as well as the campaign periods in December and March) was due to the hard work of many people and organisations. A big thanks to:

• MetaSensing for the installation and operation of the SnowSAR, particularly Alex Coccia for his flexible travel schedule;
• Pilots and staff at North-Wright (Inuvik) and Wright’s Air Services (Fairbanks);
• Lake Central Aircraft Services for the development of a flexible aircraft installation for the SnowSAR;
• Staff at the Aurora Research Institute and Toolik Lake Field Station for their logistical support;
• The large group of participants who contributed to ground data collection, often under harsh Arctic conditions;
• EnvironmentCanada, the European Space Agency, and NASA Terrestrial Hydrology Program for financial and logistical support

  [caption id="attachment_1620" align="aligncenter" width="640"] View from plane (Environment Canada)[/caption]

From Chris Derksen (Environment Canada)12 April 2013

The final phase of the Canadian SnowSAR campaign is now complete, with successful flights conducted over the Trail Valley Creek study site on 8–9 April.

There was a major addition to the experiment – an airborne LiDAR system was also flown, onboard a turbo Otter aircraft on 6–7 April.

The same flight lines were covered by both the SnowSAR and the LiDAR. So, we will have 1 m resolution snow-depth estimates from the LiDAR to compare with the SnowSAR measurements and the blowing snow model simulations that will be conducted at Environment Canada.

The LiDAR flights, funded by NASA, were coordinated by collaborators at theUniversityof Alaska Fairbanks. Four scientists made the long drive fromFairbankstoInuvikto participate in the snow sampling during the campaign period.

Conditions were cold and windy during most of the ground sampling period. The focus was similar to the previous measurements made in December and March: long snow-depth transects along the flight lines, and snow stratigraphy measurements to understand the layered properties of the snowpack.

 Ground penetrating radar measurements were also performed. It was quite the achievement to keep all the cables untangled!

The Inuvik campaign is now complete and we are in the midst of transferring the SnowSAR toFairbanks,Alaska, after which flights will be conducted near theToolikLakeresearch station.

While the radar is on its way via air, the ground team is presently waiting out a blizzard in Inuvik before making the drive toAlaska. A final blog post will be provided fromAlaskain a few days.

The final photo for this post shows the tundra landscape of the western portion of the Trail Valley Creek watershed. TheMackenzie River, surrounded by forest, can be seen in the distance. If you look closely, you can see a wide path of trampled snow, left by a reindeer herd that recently moved through.

From Daniel Steinhage (AWI) and Steen Savstrup (DTU Space), Antarctica,  13 January

Since we arrived in Antarctica we’ve been able to install the two instruments on the aircraft and do a calibration flight in preparation for the campaign. This was all done at the NOVO station where we met the AWI plane before our planned flight to the Concordia station.

On 10 January we first removed various instruments from the plane that had been used for the previous geo-scientific mission. We kept the gravity meter, the basic data acquisition system and some auxiliary devices that were installed in the plane.

Immediately after lunch we started installing the EMIRAD-2 horn antennas and its rack, which will be used to validate the SMOS measurements.

We were lucky with the weather; it was nice and sunny with just a little wind so that we were able to spread out the transport boxes. This made packing the removed equipment and  the installation of the new stuff very easy.

We continued with this exercise the following day and managed to finish by the early evening. The alignment of the two horn antennas was measured and first tests were successfully carried out.

The ground test of EMIRAD in the morning of Saturday 12 January went well as did the short test and calibration flight which we finished in time for lunch. The calibration was carried out above the ocean just north of Novo runway.

In the afternoon we packed the POLAR 6 aircraft with our spare parts and all the remaining equipment into our container for storage. Also our own polar  gear had to be checked and reduced, since the weight on the transit flight is limited.

By then we were ready for the transit flight. Unfortunately the weather was overcast with light snow and drifting. This stopped us going on to the Kohnen German research station, which was to be our first stop on the way to the Concordia station.

The other stopover will be at Amundsen-Scott station, which is an US scientific station at the geographic South Pole and where we will refuel.