Rabaul volcano, New Guinea


This is a radar image of the Rabaul volcano on the island of New Britain, Papua
New Guinea taken almost a month after its September 19, 1994, eruption that
killed five people and covered the town of Rabaul and nearby villages with up
to 75 centimeters (30 inches) of ash. More than 53,000 people have been
displaced by the eruption. The image was acquired by the Spaceborne Imaging
Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the space shuttle
Endeavour on its 173rd orbit on October 11, 1994. This image is centered at 4.2
degrees south latitude and 152.2 degrees east longitude in the southwest
Pacific Ocean. The area shown is approximately 21 kilometers by 25 kilometers
(13 miles by 15.5 miles). North is toward the upper right. The colors in this
image were obtained using the following radar channels: red represents the
L-band (horizontally transmitted and received); green represents the L-band
(horizontally transmitted and vertically received); blue represents the C- band
(horizontally transmitted and vertically received). Most of the Rabaul volcano
is underwater and the caldera (crater) creates Blanche Bay, the semi-circular
body of water that occupies most of the center of the image. Volcanic vents
within the caldera are visible in the image and include Vulcan, on a peninsula
on the west side of the bay, and Rabalanakaia and Tavurvur (the circular purple
feature near the mouth of the bay) on the east side. Both Vulcan and Tavurvur
were active during the 1994 eruption. Ash deposits appear red-orange on the
image, and are most prominent on the south flanks of Vulcan and north and
northwest of Tavurvur. A faint blue patch in the water in the center of the
image is a large raft of floating pumice fragments that were ejected from
Vulcan during the eruption and clog the inner bay. Visible on the east side of
the bay are the grid-like patterns of the streets of Rabaul and an airstrip,
which appears as a dark northwest-trending band at the right-center of the
image. Ashfall and subsequent rains caused the collapse of most buildings in
the town of Rabaul. Mudflows and flooding continue to pose serious threats to
the town and surrounding villages. Volcanologists and local authorities expect
to use data such as this radar image to assist them in identifying the
mechanisms of the eruption and future hazardous conditions that may be
associated with the vigorously active volcano.

Spaceborne Imaging Radar-C and X-Band Synthetic Aperture Radar
(SIR-C/X-SAR) is part of NASA's Mission to Planet Earth. The radars illuminate
Earth with microwaves allowing detailed observations at any time, regardless of
weather or sunlight conditions. SIR-C/X-SAR uses three microwave wavelengths:
L-band (24 cm), C-band (6 cm) and X-band (3 cm). The multi-frequency data will
be used by the international scientific community to better understand the
global environment and how it is changing. The SIR-C/X-SAR data, complemented
by aircraft and ground studies, will give scientists clearer insights into
those environmental changes which are caused by nature and those changes which
are induced by human activity. SIR-C was developed by NASA's Jet Propulsion
Laboratory. X-SAR was developed by the Dornier and Alenia Spazio companies for
the German space agency, Deutsche Agentur fuer Raumfahrtangelegenheiten (DARA),
and the Italian space agency, Agenzia Spaziale Italiana (ASI), with the
Deutsche Forschungsanstalt fuer Luft und Raumfahrt e.v.(DLR), the major partner
in science, operations, and data processing of X-SAR.