First space-borne high-spatial-resolution optical imagery of the Antarctic from Formosat-2

Abstract

Coordinating and collecting satellite data of changing polar environments is one of the prime activities of International Polar Year (IPY) 2007–08 (Rapley et al. 2004). Within this framework, the requirements to obtain spaceborne snapshots of the Polar Regions and key high latitude processes have been prepared by the international cryospheric community under the auspices of the approved IPY project titled the Global Inter-agency IPY Polar Snapshot Year (GIIPSY). Earlier efforts in manoeuvring Radarsat-1 in a special mode provided radar images with a spatial resolution of 30 m over the entirety of Antarctica during September–October 1997 (Jezek et al. 1998). Limited to their altitude (AL), swath (SW) and pointing capability (PC), however, the operation of optical satellites with high-spatial-resolution sensors is generally restricted to certain latitudes. For example, Landsat (AL:705 km/SW:185 km/PC:0°) mission has been able to provide high-spatial-resolution optical imagery only to ~81°N to ~81°S since the 1980s. The coverage is now extended to ~86° by ASTER (AL:705 km/SW:60 km/PC:24°) (Kargel et al. 2005), but there has been no availability of space-borne optical image of the polar regions with a resolution equivalent or higher than Landsat type sensors with latitudes higher than 86°, until the successful operation of Formosat-2 (AL:891 km/SW:24 km/PC: ± 45° across and along track). Equipped with two-axes high torque reaction wheels, Formosat-2 is able to point not only to ± 45° across track, but also to ± 45° along track (Liu et al. 2007). Figure 1 shows the accessible areas (longer lines: along track ± 0°, across track ± 45°; shorter lines: along track ± 0°, across track ± 30°) and the corresponding ground tracks (solid curves) of Formosat-2 in the Polar Regions. Note that the accessible areas would be even greater if the pointing direction is also set to ± 45° along track. The detailed comparison of Formosat-2 with other similar sensors, including the multi-spectral bands and imaging repeat period, can be found in table I in Liu et al. (2007). To support IPY 2007–08, the National Space Organization (NSPO) of Taiwan launched a Polar Imaging Campaign (PIC) in March 2006. Up to September 2007, a total of 1 131 624 km2 in the North Polar Region and a total of 57 408 km2 in the South Polar Region had been imaged by Formosat-2. All Formosat-2 images taken during the NSPO PIC are available from the authors.