Satellite data provide an important source of information for characterizing and monitoring land-cover and land-use change. In some regions it is the only feasible way to provide timely and reliable land-cover assessments and identify areas of rapid change. Recent land-cover history also provides a point of departure for modeling land-cover change.
NASA Current Missions for LCLUC Research
NASA currently has sensing systems at high, medium and low resolution, which meet the LCLUC program observation needs. NASA satellite systems supplement operational satellites providing systematic measurements to study long-term trends. For example, the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the EOS Terra (AM) and Aqua (PM) platforms have significantly improved on the capabilities of the operational NOAA Advanced Very High Resolution Radiometer (AVHRR). These moderate resolution data are used to classify and characterize land-cover at the global scale and to detect land-cover change at the regional scale. They also provide daily monitoring of fire activity which is often an indicator of land-cover change. The operational Defense Meteorological Satellite Program provides a capability to map the extent of night time lights and has been used by LCLUC scientists to document the extent and growth of urban areas.
Landsat 7 has provided the systematic high resolution observations necessary to map and quantify land-cover changes at the local to regional scale. The Landsat class observations are a critical underpinning for LCLUC research. The Landsat 7 global acquisition strategy providing multiple cloud-free scenes each year, has facilitated land-cover studies around the world. The LCLUC program has been pioneering methods for regional analysis of Landsat class observations setting the stage for periodic continental and global assessments of land-cover change. In this regard, the combination of systematic moderate and high resolution satellite remote sensing provides the opportunity for global scale studies and forms the basis for a global land observing system. Similarly, the NASA science programs are moving from Missions to Measurements with the aim of utilizing data from different instruments to address science questions.
Experimental measurements of limited duration are needed to better understand processes and to test new sensor technologies. For example, the Earth Observer 1 (EO1) system has provided a test-bed for new sensor technology and spaceborne hyper-spectral remote sensing. Similarly the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor has provided new high resolution thermal data collocated with MODIS data for improved surface characterization and validation of coarser MODIS thermal products. In the past experimental microwave satellite sensors operated by Europe and Japan have been used for mapping the extent of wetland areas. NASA LCLUC research in this part of the spectrum has been limited by the absence of a current US microwave sensing system.
NASA has also been exploring partnerships with industry for the commercial provision of data to meet the needs of its science community. In particular, hyperspatial data with 1-3m resolution from sensors such as IKONOS and Quickbird have been used to provide detailed validation of high resolution products.
NASA Future Missions for LCLUC Research
NASA as part of the Integrated Program Office is contributing to the NPOESS Preparatory Project (NPP). The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument is planned to transition MODIS class observations into the operational domain. The VIIRS instrument for launch in 2009 will continue the long term data records of vegetation indices, land-cover and fire. The NASA NPP Science Team is contributing to and evaluating the operational algorithms which will provide VIIRS Environmental Data Records (EDR's). The science team is determining whether these operational products will meet the needs of the science community and which additional or enhanced products will be needed.
NASA has been charged with providing a continuity mission for the Landsat class of observations. As the major science driver for this mission, the LCLUC program is concerned that the mission be launched as soon as possible to minimize the Landsat 7 data gap. There are a number of possible solutions to securing rapid high resolution data continuity including a micro satellite imaging constellation. Clearly, as part of this mission, it will be important to establish the pathway for operational provision of Landsat class observations. Additional mission requirements for LCLUC research are being developed through a NRC Decadal Survey for NASA.