Tag Archives: radar

It’s a wrap – airborne measurements of ice complete

From Henriette (DTU-Space), Denmark, 12 May

We ended our DTU-Space part of the CryoVEx campaign on 9 May. The Norlandair Twin Otter has flown about 85 hours, covering about 20 000 km. This is about the same distance as half way around the world at the equator.  The map below shows our flight tracks.

Twin Otter carrying ASIRAS (credits: M. Davidson)

We have been able to underfly several CryoSat passes. A few of them were in formation flight with the AWI Polar-5.

We have visited five main validation sites, circled in red on the map: Devon ice cap, Austfonna ice cap, the EGIG line Greenland interior, as well as sea ice north of Alert and sea ice around Svalbard in the Fram strait with our colleagues down on the ice below.

Flight tracks from DTU Twin Otter carrying ASIRAS (credits: H. Skourup)

It has been a pleasure to working with all those involved and I want to thank everybody for the great collaboration and excellent timing.

As you may have already have noticed, the corner reflectors are giving very valuable information of the radar penetration depth.

The updated version of the ASIRAS radar has a realtime display so we can see whether we have hit the reflector as we fly over. This demands very precise navigation as the reflector has to be within 10 m of the aircraft track.

Thanks to our highly-skilled air crew we only missed 2 or 3 reflectors out of 45 passes.

For our part, the airborne campaign has been a success, and we have now a collection of unique measurements to work with.

Time to bid farewell to Alert

From Katharine (UCL), Alert, 19 April

Time to leave Alert now, but here's a quick update on the last couple of days here on the ice before we head off home.

The team before leaving for Resolute (credits: S. Laxon)

We were all very happy to have got the break in the weather we needed to land at our sites on the Arctic Ocean and we were even luckier that good weather continued to prevail at Alert. We were able to make it out onto the fast ice site on both the 17 and 18 April.

Beautiful day on the fast ice (credits: K. Giles)

The ice has lots of lump and bumps so some careful skidoo driving by Seymour made sure the radar got to the site in one piece, but from then on it didn’t go so well for the radar we use on the ground.

The radar operates at 21°C, so there is a heating system inside its container. Usually it heats up pretty quickly, but we made the mistake of leaving it outside for an hour while we had our first hot lunch in days before we headed to the site. So, it took much longer than usual to heat up.

We spent a bit of time scouting out good test site, but just as it was approaching operating temperature our generator broke. Justin and Malcolm came to the rescue and headed back to the base to find a new one, while Rosie, Seymour and I got on with one of the snow-depth surveys around a corner reflector.

We eventually got the radar back up to temperature, but after already being out for eight hours or so, it was becoming very hard to keep our concentration and we decided to call it a day after taking a few calibration shots – which is definitely better than nothing.

In a snow pit (credits: S. Laxon)

Monday 18 April went much better. Stephan, from the Polar-5 team joined Seymour, Rosie and I on the ice, the radar kept its temperature well, the generator worked and we got all the measurements we had hoped to take the day before – and made it back for dinner.

Lunch on the ice (credits: S. Laxon)

It was a really good day on the ice and a great way to end our experiment. We had lunch on the ice, but I’ve had enough of frozen sandwiches. We kept these ones warm in the radar box – but it only takes about 5 mins of them being exposed before they freeze solid.

There has been a pair of wolves roaming around the warehouse next to the airfield over the past couple of days. While we were waiting for permission to cross the airfield on our way to the fast ice site, one of them was basking in the sunshine next to us.

Arctic wolf at Alert base (credits: K. Giles)

Today, just as we were about to leave in the Twin Otter for Resolute one of the wolves was hanging around, posing for photos.

Justin left his rucksack on the ground, turned his back and the wolf nicked it! Luckily the wolf dropped it when Justin chased him.

Getting off the ground

From Katharine (UCL),  on the sea ice, 14 April
 
Today our pilots, Troy and Derek, gave us the all clear to fly and begin our experiment for real, setting out the corner reflectors and transect lines.

Landing on the sea ice (K. Giles)

So, after a last check on the weather, we loaded up the Twin Otter and were airborne by about 9.00. Due to the early start I managed to sleep all the way there and woke up when I felt the plane losing altitude. Troy and Derek were circling around the ice looking for a safe place to land, where the ice was thick enough to support our weight without us ending up in the ocean beneath.

After a few low passes, at about 15 m, to scout out a makes-shift runway, we landed pretty smoothly. After we had landed they taxied around for a bit to compress the snow and make a runway for us to take off from. This was my first 'unseen' (i.e. no one has ever been there before and one has to test how thick the ice is) landing on sea ice and it was pretty exciting.

Our first site was at 85.6° N 69.8° W, the furthest north I have ever been and will probably ever get to. The conditions were great around –25°C and not very windy. We set up the corner reflectors and marked their locations with large coloured sheets of material and bin bags full on snow, so Henriette and the other Twin Otter could see them from the air.

Set up (credits: K. Giles)

 The photo shows one end of our site marked by an orange sheet and bin bags. The corner reflector can just be seen behind the flag, which we use to line the site up.

Malcolm then used a satellite phone to call back to the base and tell the Henriette that they could leave to overfly our ground site, taking measurements with their airborne radar and laser. We also measured the ice we landed on. It was about 1.80 m thick – floating on the deep ocean waters.

We then headed south again to 83.3°N 62°W to set up our second site. It was colder and windier here, but the set up went well again. We saw that the snow cover at the two sites appeared to be different. This is important for our experiment as we want to see if the radar sees through the snow the same way when the snow has different properties.

Drilling to test ice thickness (credits: K. Giles)

We only needed about 30 m of runway to take off from the second site as we were lighter after leaving the corner reflectors on the ice and we made it back to Alert for dinner. Rosie, Seymour and I have spent the rest of the evening making sure that our ground radar is working. Malcolm has been using the data from the GPS buoys we put with the corner reflectors to track where they are moving as the ice moves.