PolarGAP - Validation of the European Space Agency GOCE and CryoSat satellites

Start date
1 October, 2015
End date
31 October, 2017

The polar regions have the capacity to amaze and astound, but despite the considerable progress of recent decades we still know far less about them than less remote parts of the world.

PolarGAP is an ambitious international mission to capture new and critical data about the Earth’s global gravity field.  Innovative radar systems and Lidar technologies will also be deployed from Twin Otter aircraft to fill the ‘data gap’ in measurements of surface elevation over the South Pole region south of 83.5°.

Two earth observing satellite missions (GOCE and CryoSat 2) mounted by the European Space Agency (ESA) revolutionised scientists’ ability to ‘map’ the Earth’s global gravity field and monitor how Earth’s ice fields are responding to global change.  However, because GOCE’s orbit did not cross the Poles there is a data gap at the South Pole.

The PolarGAP project will collect new gravity data and combine them with datasets from other Antarctic missions to build the first accurately constrained global gravity model. This is essential as global gravity data provide unique information on mass distribution and transport in the Earth System, linked to processes and changes in the Solid Earth, hydrology, cryosphere, oceans and atmosphere. Key applications of gravity data include geodetic studies (levelling and mapping), navigation (GPS/GLONASS) and satellite orbit planning.

This ESA video showing the GOCE geoid deviations in height (–100 m to +100 m) from an ideal geoid. The blue shades represent low values and the reds/yellows represent high values.

The aircraft mission and deep-field work are challenging.  Using experience and expertise in aerogeophysical data collection, together with extensive logistical capabilities, the British Antarctic Survey (BAS) teams, working in partnership with experts from the Technical University of Denmark (DTU), Norwegian Polar Institute (NPI), with logisitical support from the US National Science Foundation (NSF), will explore one of the key frontier regions in Antarctica – an area that has rarely been before been seen, let alone studied.

Gap in satellite gravity data coverage in Antarctica shown by an orange circle.
The orange circle show the area where there is a gap in satellite gravity data coverage in Antarctica.  New airborne survey data, combined with data from other international data gathering missions will fill the gap.

The field team will face harsh and challenging conditions working from two remote field camps high up on the East Antarctic Plateau. Additional flights will be carried out from South Pole Station to complete the survey.

BAS geophysical survey equipment Twin Otter, FP – VBL, with sun-dogs at Talos Dome East Antarctica

Find out more about ESA’s two earth observing satellite missions GOCE and CryoSat 2



The main focus of the PolarGAP project is to provide new high-resolution gravity data for global gravity and geoid models (the Geoid is a model of the Earth’s surface that represents the mean global sea level).

These global geodetic models have been revolutionised in terms of resolution and coverage by satellite gravity data. However, the satellite orbits do not track over the poles, leading to significant gaps and potential errors in the global models. Airborne gravity data provide the key bridging dataset completing these global models. Improved geodetic models are critical for a number of applications ranging from improved planning of satellite orbits, to better definition of surveying datum’s.

Primary aims

  • Fill the Antarctic polar gap in GOCE satellite gravity coverage through collection of new airborne gravity data and combination with data from existing surveys in the South Pole region.
  • Validation of differences in surface elevation observed by CryoSat-2 when traveling in opposite directions, by using airborne Lidar and the the innovative ASIRAS Radar System to measure the ice sheet surface and structure of the shallow snow pack.

Additional aims

  • Exploring the geological structure and evolution of East and West Antarctica in the South Pole region with new magnetic and gravity data
  • Investigating Antarctic ice sheet dynamics around South Pole using airborne radar to map the sub-ice mountains and valleys, distribution of subglacial water and internal ice sheet structures.

Science challenges

During the PolarGAP survey we will be exploring one of the key frontier regions in Antarctica using a range of geophysical techniques. East Antarctica is a geological composite, made up of a mosaic of tectonic fragments scarred by ancient sutures and cut by rifts.

This survey will allow linking between the sparse rock outcrops towards the coast and previous geophysical surveys in the continental interior. The data will provide unique new insights into sub-ice geology and the evolution of the crustal architecture of East Antarctica, laying the foundations for future research.

The study area we are targeting includes the catchments of several massive glaciers which link the vast East Antarctic Ice sheet to the potentially less stable West Antarctic ice sheet. Our new radar measurements of ice thickness, subglacial topography, basal water and ice sheet structure will better constrain both the processes operating beneath the ice sheet interior today, and the past and possible future evolution of the ice sheet. This is particularly critical close to the subglacial Recovery Lakes, which could be a store of water capable of lubricating down-stream ice flow.

Our final science target relates to the processes operating on the ice sheet surface. Satellite data shows an unusual pattern of cross-over errors in surface elevation depending on the direction the satellite is orbiting. This pattern is hypothesised to reflect unusual shallow snow fabric developed due to the consistent prevailing wind direction. By flying the ASIRAS radar, an analogue of the space-borne system, over these anomalies we will test this hypothesis. Additional data from a scanning LIDAR system will provide new information about the ice sheet surface, unattainable by satellite observations.


International partners include:



Rene Forsberg PI Technical University Denmark (DTU)


Arne Olesen Gravity specialist Technical University Denmark (DTU)


Norwegian Polar Institute

Peter Leopold DSC_7064 Kenny

Kenny Matsuoka PI Norwegian Polar Institute (NPI)


Jack Kohler Norwegian Polar Institute (NPI)

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