Paris, 30 Jun 2004
Camping out, for anything up to two months, on vast ice sheets in the Arctic is just one of the challenges scientists faced performing the first of a series of six validation experiments in support of ESA's CryoSat mission.
CryoSat will be the first Earth Explorer to be launched as part of ESA's Living Planet Programme. Due for launch at the end of this year, it will measure changes in the elevation of ice sheets and sea ice with unprecedented accuracy in order to determine whether or not our planet's ice masses are thinning due to global warming.
This series of validation experiments are crucial to ensuring that the mission runs smoothly and that the aims of the mission are achieved. Carrying out experiments in the harsh conditions of the Arctic is always punishing, and this first validation campaign, which has just been completed, proved no exception as scientists had to overcome a number of unique challenges.
One of the challenges the scientists faced was the sheer scale of the experiment. It included research scientists from over five different countries and different institutes, all participating in a coordinated measurement program that was to be conducted on the ground as well as from aircraft.
The ground experiments were carried out in remote, and sometimes inhospitable, areas on some of the main ice sheets in the north of Canada, Greenland and Norway. In addition, an aircraft managed by the Alfred Wegner Institute (AWI) in Germany, carried out surveys over each of the in-situ sites using both the ESA radar-altimeter ASIRAS, to simulate CryoSat measurements, and a laser scanner to support the interpretation of the radar measurements. Additional laser measurements were also taken from an Air Greenland plane managed by KMS of Denmark. This plane, equipped with skis so that it was capable of landing on snow and ice, also supported the ground crews in Greenland.
"At this scale, with each of the field teams isolated on the ice, separated from each other by hundreds of kilometres , the key to a successful validation campaign lay in organisation and coordination", says Malcolm Davidson, ESA's Validation Manager for CryoSat. "Through a series of planning meetings, at ESA, with the participants, we were able to carefully define the experiments ahead of time and identify how to bring together the aircraft and ground measurements most effectively."
Taking the ground measurements posed a particular challenge. Scientists spent anything between two weeks and two months camped on the ice sheets collecting data, that will eventually allow ESA to better characterise the performance of the CryoSat mission and lead to better, more accurate measurements of the changes in ice thickness and mass balance. Ground activities included travelling by skidoo across the vast icy expanses with GPS instruments to measure surface topography, digging snow pits to assess the effects of layering below the surface on the CryoSat signal and so-called 'coffee can' measurements to determine ice density and depth.
An unexpected challenge during the campaign came when the usually reliable Dornier-228 aircraft, the workhorse for the airborne measurements, experienced technical difficulties with the on-board navigation system. Fortunately, these were solved by flying a technicican to Svalbard to service the aircraft, and developing the appropriate procedures to calibrate the precision navigation-system before each flight.
Uwe Nixdorf, the airborne coordinator from AWI, stated that, "The technical problems with the aircraft posed an additional and unforeseen challenge. However, I am very glad that in the end they were able to be resolved so that we could go on to collect key data at the different sites for the validation of the CryoSat mission. With so much effort that had been put into this campaign, in the air and on the ground, we did not want to fail."
Following the end of the first campaign, the scientists have only a few months to recover, review the data and draw some preliminary conclusions before heading back onto Canada and Greenland's inhospitable ice sheets for the second validation campaign planned for this autumn.