Monday 12 Oct 2009

Worldview-2 is a significant advance in satellite imaging capability. It is capable of imaging with 460 mm resolution in its pan sensor, although the US government will only allow it to sell half metre imagery on a commercial basis.


Worldview-2 Launched

Monday 12 October 2009

The satellite also carries a multi-spectral sensor that will offer coastal, yellow, red-edge and a second near infrared band in addition to the traditional Landsat-type MSS bands. They are approximately the same as in Digitalglobe's earlier Worldview-1 satellite. All of these will have a spatial resolution of about 1.8 metres at nadir.

Thus it will be able to image at coastal (400-450 nanometres); blue (450-510); green (510-580); yellow (510-585); red (630-690); red edge (705-745); NIR1 (770-895) and NIR2 (860-1040).

The four additional bands are situated at strategic points. The blue band, centred around 425 nm is called the coastal band for its applications in water colour studies. The red edge band is centred at 725 nm where the high reflectivity portion of vegetation response begins. The longer wavelength near infrared band, centred at 950 nm is sensitive to atmospheric water vapour.

The satellite offers a 16.4 km swath, and is capable of rotating up to 20 degrees off nadir. This degrades the resolution somewhat, but it makes it possible to offer more frequent revisits. For instance, pan resolution degrades to 520 mm when the satellite is rotated 20 degrees of nadir, but then the revisit time is reduced to 3.7 days.

This rotation can be accomplished in 9 seconds. During this period, the satellite will have travelled 300 km along its track. Digitalglobe will be able to gather much more data with Worldview-2 that from any of its previous satellites. It is a 25 per cent improvement on Worldview-1, for instance. It has 2.19 Tbytes of on-board storage and an 800 Mbps X-band data downlink.

It will be able to collect up to 975,000 square kilometres per day (equivalent to the area of France and Germany combined)


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