The present paper describes the cross calibration of the Remote Sensing Instrument (RSI) onboard Formosat-2 using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) onboard Terra as a reference, which has been continuously calibrated by means of the onboard and vicarious calibration methods. The data integration system for multi-satellite sensor databases on the Global Earth Observation Grid (GEO Grid) is used in order to find pairs of images acquired by both satellite optical sensors over the radiometric calibration sites on the same days. Radiative transfer simulations that consider different imaging conditions using the Second Simulation of a Satellite Signal in the Solar Spectrum (6S) code are performed based on the Moderate-resolution Imaging Spectroradiometer (MODIS) atmosphere and land products, and the optimum methodology for this cross calibration is discussed under the assumption of no ground-based measurements. The derived calibration coefficients are normalized by the values of preflight calibration and are compared with the results of in-flight cross calibration by the Centre National d'Études Spatiales (CNES) and vicarious calibration described in our previous paper. The average degradations of sensor sensitivity since preflight calibration until 2009 are estimated to be 10% (Band2), 11% (Band3), and 8% (Band4). The derived long-term degradation trends are almost consistent with the results of our vicarious calibration within the precision. The cross-calibration methodology used in the present paper facilitates the in-flight radiometric calibration of satellite optical sensors.

This paper presents an overview of the current status and data applications of FORMOSAT-2, Taiwanese's first earth observation satellite mission. Highlights of its contributions to monitoring of global natural disasters and earth environmental changes will be illustrated. The FORMOSAT-2 satellite successfully complements existing high spatial resolution imaging satellites such as SPOT-5, IKONOS, and QuickBird, among others, with its unique capability of daily revisits worldwide. The FORMOSAT-2 follow-up program to ensure data continuity to the user community is briefly introduced.

We describe the results of the in-orbit radiometric calibration of the remote sensing instrument (RSI) onboard Formosat-2, based on the ground data collected by the advanced spaceborne thermal emission and reflection radiometer (ASTER) calibration team at Ivanpah Playa and Railroad Valley during the regular field campaigns in 2006 and 2008. These results are normalized by the preflight values provided by Astrium, France, and are compared with the results of in-flight calibrations made by Centre National d'Etudes Spatiales, France. The radiometric calibration coefficients and the long-term degrading trend of RSI are derived from the results of vicarious calibration, which estimate that the degradations of sensor sensitivity until 2008 are 2.2% (B4), 8.0% (B3), 9.6% (PAN), 10.3% (B2), and 12.0% (B1). Considering the fact that the ASTER calibration team is able to achieve an accuracy of vicarious calibration better than 5%, we estimate a 7.3% to 13.4% overestimate would be incurred by using the existing in-flight cross calibration coefficients to calculate the spectral radiances. This paper supports the use of vicarious calibration as a reliable approach for the in-orbit radiometric calibration of RSI onboard Formosat-2 on a regular basis.

The sea ice in polar region has been shrunk and thinned considerably with the rampant global temperature during the last few decades. It has already shown dramatic effects on regional water balance, ocean circulation and global climate. Nowadays, an extensive investigation and understanding of the environmental change in polar region becomes a crucial task. However, difficulties resulting from transportation, extreme weather, and seasonal cycle, as well as the lack of satellite coverage make the polar research extremely challenging. Successful launch of FORMOSAT-2 satellite by National Space Organization, Taiwan (NSPO) in 2006 is supposed to resolve the limitation of polar observation by providing daily high resolution images (8 m MS and 2 m Panchromatic) near two poles. This paper presents preliminary findings from time-series FORMOSAT-2 images over the Arctic sea and Amundsen-Scott South Pole Station. Results indicate that wind erosion and ocean circulation shear force may take part in shaping the Arctic ice. In addition, the wind field over the Antarctic may be estimated.