Tag Archives: ASIRAS

NASA IceBridge flies Greenland EGIG line for CryoSat

From Michael (NASA), Greenland, 26 April

Today was our last opportunity to fly a science mission from Kangerlussuaq and the weather was favourable for Geikie 01, our last remaining high priority mission plan.

Geikie Plateau (credits: M. Studinger)

We expected some clouds over the interior of the ice sheet and down in the fjords and had to abort our flight up Nansen Fjord and Christian Gletscher because of a 3000 ft clouds base and 13 000 ft terrain.

Other than that, it was a perfect day. As the photo above shows, the razor sharp flood basalts of the Geikie Plateau are spectacular.

After we had finished the glacier runs around the Geikie Plateau, we went up Daugaard Jensen Glacier and continued on to the interior of the ice sheet back to Kangerlussuaq.

Daugaard Jensen Glacier calving front (credits: M. Studinger)

We flew along the EGIG (l’Expedition Glaciologique Internationale au Groenland) traverse route in support of ESA’s CryoSat campaign.

NASA IceBridge flight plan for 26 April (credits: M. Studinger)

The CryoSat-Validation and Calibration Experiment along the EGIG route is designed to provide ground truth data over the ice sheet for the airborne ASIRAS radar and CryoSat's SIRAL radar.

Geikie Plateau (credits: M. Studinger)

We will use IceBridge radar and laser altimeter measurements to link ground and satellite measurements to better quantify radar penetration issues over the various zones from the edge to the interior of the Greenland Ice Sheet.

Post adapted from Michael Studinger's NASA IceBridge flight report (F27/26 April)

Mapping sea ice up close with ASIRAS

From Malcolm (ESA), Alert, 16 April

Henriette on the Twin Otter monitoring the sensing instruments (credits: M. Davidson)

As an ESA campaign coordinator, I sometimes fly along with airborne scientists and observe how data are collected and how the different instruments on the plane are run. This part of my work has always been fascinating and of great value in understanding how to run campaigns together with participants.

Today, I was a guest on the Norlandair Twin Otter at Alert, Canada, carrying the CryoSat airborne simulator ASIRAS. Its cramped interior is packed with instruments and, thankfully, the odd seat for the scientists operating the instruments.

In the past few days, the ASIRAS team members – guided by their friendly and experienced scientist Henriette Skourup from Danish Technical University – have been showing off what the instrument can bring to validation for CryoSat.

Sea ice close to northern shore of Ellesmere Island (credits: M. Davidson)

With the help of good weather, ASIRAS has already flown an impressive 2300 km in three days. All three of the ground test sites have already been 'imaged' by ASIRAS. This is good news to the ground team who have been painstakingly measuring snow and ice properties and can now look forward to ASIRAS data over their site to make comparisons.

I’m particularly impressed with the precision with which the flights over the test sites where made. High-precision flights over the ground sites are difficult to execute, but crucial to the success of the campaign.

ASIRAS radar signature from corner reflector below (credits: M. Davidson)

ASIRAS needs to pass within 5 m of the corner reflectors that were earlier carefully erected by the ground teams to ensure that airborne and ground data can be properly compared later on. During the campaign, the pilots and scientists running ASIRAS on-board the Twin Otter have come through with flying colours, 'nailing' several passes over each site to within a few meters – no mean feat!

The clear ASIRAS signatures of the corner reflectors studied quickly after each flight show how incredibly good the data is.

Indridi keeping a check on ASIRAS (credits: M. Davidson)

The image on the left is for the techies out there - it shows the spectacular ASIRAS radar signature from a corner reflector below. The well-formed hyperbola in the middle highlights both teh quality of the measurement and the proximity of the plane to the position of the reflector.

Another spectacular 'first' that comes to my mind, has been the tandem underflight of a CryoSat track of ASIRAS on the Norlandair Twin Otter and the EM-Bird on board the Basler aircraft all the way up to 86° North, only 4° from the North Pole.

 Together – separated by only a minute or two – the two aircraft and their precious scientific crew carefully flew directly underneath the track of the CryoSat satellite orbiting at 7km/s overhead. To accomplish this feat, the pilots of both planes needed to keep in constant visual contact, as well as carefully follow the track laid down by CryoSat.

ASIRAS passes as seen by GPS (credits: M. Davidson)

The result of their efforts is a unique opportunity to bring together the ice-thickness measurements by EM-Bird and the high- and low-resolution radar altimetry of ASIRAS and CryoSat, respectively. This has resulted in a terrific chance to cross-compare all three measurements.

All in all, ASIRAS – the workhorse of CryoSat validation – guided by experts, Henriette and Indridi from DTU, has been showing its mettle and taken this campaign huge leap forward.

ASIRAS arrives in Alert

From Malcolm (ESA), in Alert, 13 April

The whole team was more than pleased – relieved and happy might be the right description – to see Henriette and her team from the Danish Technical University arrive from Greenland today.

Planes arrive in Alert - the plane on the left is the AWI Polar-5, the plane in the middle is the Twin Otter carrying ASIRAS and the plane on the right is used to ferry the team about (credits: M. Davidson)

Today's arrival of the Nordlandair Twin Otter plane in Alert marks a new and crucial phase of the CryoSat campaign. The plane carries precious cargo: the ASIRAS radar instrument which – much as the CryoSat satellite does much higher up in its orbit about Earth – emits a series of radar pulses as the plane travels over the ice and snow  surfaces and very carefully records the faint return echo from the surface. 

While ASIRAS has many similarities with the SIRAL instrument aboard CryoSat, it makes measurements with much higher resolution than the satellite. It is, thus, an essential tool for understanding the interaction between the CryoSat radar echoes and ice and snow.

GPS base station several kms from the Alert base (credits: M. Davidson)

The arrival also means that the full suite of 'ESA' planes, three in total, are all in place and raring to go. The photo shows the planes: the orange, white and blue plane on the left is the AWI Polar-5, the red plane with white dots in the middle is the Twin Otter carrying ASIRAS and the right-most plane is the Ken Borek Twin Otter, which is used to ferry the ground team on and off the sea ice.

The next days will be crucial as the planes are deployed across the frozen vastness of the Arctic Ocean.  The first flights early tomorrow will be to identify and mark ground sites where the Canadian and British ground teams will carry out detailed studies of snow and ice properties.

They will soon be followed by an armada of planes bristling with sensing instruments including ASIRAS, airborne laser scanners, visible and infrared cameras, electromagnetic ice-thickness sensors, snow radars of different guises and the list goes on.

A highlight on 15 April will be the joint flights with the NASA P-3, which will join the rest of the airborne fleet by travelling all the way up from Kangerlussuaq, 1500 km south of Alert in Greenland. At the same time, CryoSat will also be 'visiting', travelling at 7 km per second and crossing over near Alert.

Katharine & Rosie making corner reflector frames (credits: M. Davidson)

The team is of course hoping that the weather will play along. Luckily the signs are that tomorrow, 14 April, and the following day it will be sunny with the clear skies. This is that are essential – both to collect data, and even more importantly for the safety of all participants.

Meanwhile, preparations continue. The photo on the right shows Katharine and Rosie putting together wooden support frame that will be used in the coming days to hold up the corner reflector to be positioned on ice floes in the Arctic Ocean.

Chain saw lessons (credits: M. Davidson)

The photo on the left shows Christian Haas from the University of Alberta getting first-hand instructions on how to use the chain saw that will be used in the coming days to cut up blocks of snow off-shore on the wind-swept sea ice.

Given the daunting tasks ahead, the tension is rising but everyone is looking forward to these intense days ahead and the unique opportunity to bring the CryoSat mission a big step forward.