April 8, 2004 ASIRAS, a New ESA Airborne Instrument Sees Ice for the First TimeMaking sure that the measurements made by satellites are as accurate as possible has always been a difficult business and this will be especially true for ESA�s ice mission CryoSat. However, last week a new instrument, which is set to be the workhorse for validating CryoSat data, was successfully tested from an aircraft over the snow and ice not far from the North Pole. CryoSat, due for launch at the end of this year, will be the first satellite to be launched as part of ESA�s Living Planet Programme. From an altitude of 720 kilometers (447.4 miles) it will measure small changes, of no more than a few centimeters or so, in the thickness of polar ice sheets and floating sea ice. The main aim of this mission is to determine whether or not the Earth�s ice masses are actually thinning due to global warming. CryoSat will carry a SAR/Interferometric Radar Altimeter (SIRAL) to perform these precise measurements. However, there are a number of reasons why the data could possibly be flawed. For example, the different seasons cause the properties of snow and ice to change and this can mask or influence the signal reflected back to the SIRAL instrument. These, and other sources of error, have to be thoroughly investigated over the next three years through dedicated, independent ground-based and airborne measurement campaigns. A series of planned campaigns will allow scientists participating in the experiment to understand and characterise the uncertainties in CryoSat measurements and ultimately correct for them so that the final data is as accurate and meaningful as possible. During the last two weeks of March an
important step forward was made in the
preparations for the CryoSat validation
campaigns. For the first time, the ESA Airborne
Synthetic Aperture and Interferometric Radar
Altimeter System (ASIRAS) was flown and tested
over the snow and ice expanses of Svalbard, an
archipelago of islands lying in the extreme north
of Europe just 12 degrees from the North Pole.
The ASIRAS radar altimeter simulates CryoSat
measurements from an aircraft. The specific aim
of this campaign was to acquire the first data
sets of the instrument over snow and ice and to
make sure that the instrument could be operated
under the icy temperatures and high winds
prevalent in this part of the world. Constantin Mavrocordatos, the Payload Manager for CryoSat and responsible for the development of ASIRAS added, �This development is a good example of a successful research activity. The instrument was orginally developed for research purposes and now it is set to be an excellent operational tool for CryoSat validation experiments.� ASIRAS was built by Radar Systemtechnik (RST) of Switzerland with the support of the Alfred Wegner Institute (AWI) and Optimare for the implementation and operation on an aircraft. ### Frédéric Le Gall This text derived from http://www.esa.int/esaSA/SEMLR167ESD_earth_0.html Recommend this Article to a Friend Back to: News |
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