Envisat was was launched on 01/03/2002, by ESA and operated until 08/04/2012. It provided suitable imagery for the austral winters (May - November) of 2007 to 2011. Envisat caried a C-band (5.33 GHz; wavelength ∼ 5.6 cm) Advanced Synthetic Aperture Radar [ASAR], capable to acquire data in multiple modes (image, alternating polarization, wave, ScanSAR (wide swath), and ScanSAR (global monitoring)) at various incidence angles and in several polarisations. Of ASAR's five distinct measurement modes, the following two modes may be used to derive sea-ice motion from overlapping images in our project: 1. ASAR Wide Swath Mode -- 400 km by 400 km wide swath image. Spatial resolution of approximately 150 m by 150 m for nominal product. VV or HH polarization. 2. ASAR Global Monitoring Mode -- Spatial resolution of approximately 1000 m in azimuth by 1000 m in range for nominal product. Up to a full orbit of coverage. HH or VV polarization. For further detail, see ESA's Copernicus web portal. Sea-ice motion is derived from suitable SAR image pairs with sufficient spatial overlap but relatively short time separation, i.e. ideally 6days or less. Image-crosscorrelation analysis is employed to identify displacement vectors within the image pair. The underlying processing and analysis is part of the (mostly) automated IMCORR [IMageCORRelation] Processing, Analysis and Display System [IPADS]. This study uses C-band (HH polarisation) ASAR scenes, with an image pixel size of 75 m across a 405 km swath. -- For further information see Giles et al., Semi-automated feature-tracking of East Antarctic sea ice from Envisat ASAR imagery, Remote Sensing of Environment, 115, 2267-2276, 2011. Acknowledgement: All Envisat ASAR data are courtesy of the European Space Agency, and were obtained under agreement with ESA. The International Space Science Institute (ISSI), Bern, Switzerland, is acknowledged for supporting this study via Projects 137 and 169.

This dataset comprises high spatial- and temporal-resolution maps of coastal landfast sea ice (fast ice) distribution in the vicinity of the Cape Darnley Polynya in East Antarctica, in the June-November (winter-spring) periods of 2008 and 2009. The maps were derived from cross-correlation of pairs of spatially-overlapping Envisat Advanced Synthetic Aperture Radar (ASAR) images, using a modified version of the IMCORR algorithm to determine vectors of sea-ice motion (as described in Giles et al., 2011). Fast ice is then distinguished from moving pack ice by the fact that it is stationary. The raw ASAR WSM data (swath width 500 km) were processed using ENVI image processing software to produce geo-referenced images with a 75m pixel size. Use of SAR data ensures coverage uninterrupted by cloud cover or polar darkness. Image pairs were chosen with a time separation between 2 and 21 days. IMCORR processing of the image pairs for mapping fast ice follows Giles et al (2011) – using a reference tile size of 32x32 pixels and a search tile size of 64 x 64 pixels. A land mask was applied to avoid contamination from matches on stationary features over the continental ice sheet. The grid spacing was set to 16 x 16 pixels, so the images were over-sampled by a factor of 2 to provide a more dense set of results. Stationary fast ice vectors were chosen from the IMCORR results using a combination of the cluster search technique and a variation of the z-axis threshold technique as detailed in Giles et al (2011). The cluster search technique was applied to the IMCORR results from each image pair to derive the initial set of valid vectors – this set could contain both stationary fast ice vectors and non-stationary pack ice vectors. Due to registration errors in the image pairs, the stationary vectors will not necessarily be centred around zero, so using a simple window around the zero offset mark to differentiate the fast ice vectors was not possible. To select the stationary vectors, a 2D histogram was constructed from the X-Y vector displacements, and a 2D Gaussian was fitted to this histogram. The fast ice vectors will dominate because of the large image pair time separation and small search tile size, so the Gaussian peak should correspond to the centre of the stationary fast ice vectors. All vectors that are within 5 standard deviations of the Gaussian peak are tagged as valid fast ice vectors. This is a minor modification to the method of Giles et al (2011), who used a simple threshold cut on the z-axis of the 2D histogram to define the fast ice vectors. Data format – one fully annotated (self-describing) netCDF file per image pair containing latitude/longitude coordinates of the stationary fast ice vectors. This technique and dataset complement a lower resolution but longer-term dataset (2000-2014) derived from satellite MODIS visible and thermal infrared data. (AAS_4116_Fraser_fastice_mawson_capedarnley).