## 7 Access and Use of Polar Remote Sensing Data  
Both the public and the scientific community are interested in polar Earth observation, aesthetically, operationally and intellectually. Indeed, the success of efforts like NASA's Earth Observatory ([[http://earthobservatory.nasa.gov/](http://earthobservatory.nasa.gov/)]([http://earthobservatory.nasa.gov/](http://earthobservatory.nasa.gov/))) testifies to this curiosity and relevance, as well as the consistently expanding fields of cryospheric and polar science. We have presented information on many (but not an exhaustive list of) sources of open access polar Earth observation, past, present and future. Now, we keep in mind the current widespread attention on the poles, as well as the global importance of polar research, as we consider some of the important trends influencing polar Earth observation science and free, open data access. Within polar science, and Antarctic science in particular, data sharing has a long legal and traditional basis, with both success stories and ongoing challenges [170]. As mentioned in the sections above, there has been an increasing trend towards free and open data access for remote sensing data products. Data rescue projects, such as scanning and providing free access to over 330,000 aerial photographs by the USGS, is a strong case of Antarctic remote sensing data sharing. Indeed, there are many examples of polar research that could not have happened without free (to researchers) access to remote sensing data, a notable example being [PERSON] _et al._'s synoptic survey of the emperor penguin populations [171], due to the specialized nature of the work and the high commercial cost of the imagery involved. It is worth noting, however, that free access of this imagery is often available only for particular subsets; in the case of WorldView imagery, it is limited to U.S. federally-funded researchers. Landsat data, on the other hand, is available to all and was also crucial to the [PERSON] work [172], as well as other studies, for example global glacier mapping (which has benefitted from free ASTER access, as well) [154]. Still, particularly in commercial missions, although the (raw) data themselves are still very expensive, operational or research products (DEMs, for example) can be freely distributed, the decentralized nature of which raises its own issues, such as access to information about processing chains and associated uncertainties. Nevertheless, the trend in open access remote sensing data was a driving interest behind compiling this paper and indeed seeking to publish it in an open access journal. In many fields, the cost of Earth observation data is hampering scientific progress, for example in biodiversity and tropical forest assessments [173]; in these fields, calls for interagency and inter-platform combinations of imagery are at a roadblock without low-cost or free and open data. Therefore, it is imperative in polar and cryospheric sciences that the research community takes advantage of the open data that are available, proving the value of these data for gaining new knowledge about the poles and the changing cryosphere and how they influence the planet. It is only through showing in practice the true value of free and open remote sensing data and tools that the trend of further data opening will continue to expand. Particular success stories include the opening of the Landsat archive [2]. However, this success results from many factors, including wide areal coverage of data, the long time period in the Landsat archive, the significant resources dedicated to producing high quality and radiometrically consistent images, the quality of the metadata and the ease of data access. Some of these considerations are discussed below. Even perceived difficulty in data access is often enough to deter usage, especially when potential alternatives are available. A good case study in data access and use are the MODIS, VIIRS and MERISsensors. All are low resolution multispectral imagers, operated by NASA, NOAA and ESA, respectively.