BoraBora

Bora Bora, French Polynesia

P-48746 August 28, 1997

This radar image shows three of the Society Islands located 220
kilometers (136 miles) northwest of Tahiti in French Polynesia in the
south Pacific ocean. The twin islands in the center of the image,
Raiatea (south, lower island) and Tahaa (north, the upper island)
share a common lagoon fringed by a coral reef, which appears as the
thin bright line surrounding both islands. Bora Bora, the island to
the northwest (top of image) is also fringed by a coral reef. The deep
bay on the eastern side of Raiatea (right side of image) is fed by the
Faaroa River, the only navigable river in French Polynesia. The
volcanoes which created these islands were active 3 to 4 million years
ago. The two "motus" (islands) southwest of Bora Bora, within the
fringing coral reef, are remnants of the volcanic caldera rim that
remain above sea level. Ocean swell caused by trade winds are seen as
the small ripples on the ocean surface around all of the islands. The
local winds were blowing from east to west (right to left) when these
data were collected; large dark areas are areas of low wind while the
dark narrow bands just inside much of the reef likely indicate very
shallow reef zones. In addition to geological studies, scientists can
use such images to study the extent and condition of coral reefs. The
area shown is 39 by 67 kilometers (24 by 41 miles); north is towards
the upper right. Colors are assigned to the different radar
frequencies and polarizations as follows: red is L-band vertically
transmitted, vertically received; green is C-band vertically
transmitted, vertically received; and blue is the difference between
red and green. The image was acquired by the Spaceborne Imaging Radar-
C/X-band Synthetic Aperture (SIR-C/X-SAR) imaging radar when it flew
aboard the space shuttle Endeavour on October 4, 1994. SIR- C/X-SAR, a
joint mission of the German, Italian, and United States space
agencies, is part of NASA's Mission to Planet Earth.