Application of ERS-1/2 SAR and SIR-C/X-SAR Data in Geologic Studies at Bir
Safsaf, Egypt

G.G. Schaber, J.F. McCauley and C.S. Breed; U.S. Geological Survey
(Emertii) 2255 N. Gemini Drive Flagstaff, Arizona 86001
(gschaber@flagmail.wr.usgs.gov), and Northern Arizona University
(Flagstaff, Arizona USA)

Bir Safsaf, in southern Egypt (lat 22=B036'N, long 29=B030'E), is a small an=
d
inconspicuous oasis of grasses and a few palm tress that lies within the
hyperarid "core" of the eastern Sahara.  Bir Safsaf and vicinity has
earlier been shown from analyses of SAR images acquired during the Shuttle
Imaging Radar (SIR) missions A-C to possess optimal geologic conditions for
demonstrating the use of spaceborne SAR in sand penetration and mapping
features of geologic, economic, and paleoclimatic importance in the
northeastern Sahara.  Recently acquired SAR images of Bir Safsaf and
vicinity from ERS-1/2 have been mosaicked together and are being used as
C-band basemaps in the field.  They are being interpreted in conjunction
with the multifrequency (X-, C-, and L-band) and polarimetric SIR-C/X-SAR
images to document, for example, the roles of SAR wavelength, incidence
angle, and polarization in portraying geologic contacts and associated
fracture zones in weathered granite and migmatite crystalline rocks exposed
below a thin cover of blow sand at Bir Safsaf.  These contacts and fracture
zones are mostly obscured on conventional imagery such as Landsat TM.
Other examples of SAR frequency-dependent enhancement of geologic features
at Bir Safsaf and recently described by the authors included (1) a
north-trending bedrock lineament system of eolian origin discriminated
specifically at X-band, (2) portrayal of local late Quaternary channels on
images acquired at all three radar bands (X-, C-, and L), and (3) remote
detection of shallow (1-2 m deep) ground water at Bir Safsaf itself.
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NOTE: The above abstract must stand by itself and will not be immediately
followed by a formal paper for the symposium volume.  A formal paper
describing our interpretation of SIR-C/X-SAR images acquired for us (as
SIR-C/X-SAR Investigators) at Bir Safsaf is currently in press for the
Special SIR-C/X-SAR Issue of Remote Sensing of Environment (December,
1996).  The ERS-1/2 SAR data that covers Bir Safsaf (Egypt) (acquired
during the tandom operation using the portable receiving deployed in
Israel--late 1995 and 1996) was only brought to our attention and acquired
by the authors in recent months.  Prior to the tandom mission, ERS SAR data
covering latitudes as far south as Bir Safsaf (22 degrees N.) in Egypt were
notavailable from the Frascati receiving station.   We are planning however
to check out the new ERS SAR images of Bir Safsaf in the field (at Bir
Safsaf) during the two weeks just prior to the Florence meeting.
Therefore, G.G. Schaber hopes (pending availability of travel funds) to
present the results of these field studies (using both ERS-1/2 and
SIR-C/X-SAR) at the meeting.

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry