Environmental Engineering Reference
In-Depth Information
good overview of these. One quite obvious improvement is to incorporate a
compact spectrometer into the camera providing spectral information in one part
of the image. The spectrometer can be used as a calibration point for the image
data. At a recent workshop (June, 2013) seven different SO
2
camera systems were
tested and inter-compared, showing a strong convergence towards a system with
two cameras (on- and off-band
filters), an integrated spectrometer and the use
of large (
c
. 50 mm) SO
2
cells for calibration.
Measurements from
field tests using the SO
2
camera are
published in the open literature and there is a growing body of data now available
to volcanologists. An illustration of the retrieval technique and analysis method-
ology can be found in the work of Mori and Burton (
2006
).
in the IR region. The system uses
field campaigns and
filters to isolate radiation in the 8.6
μ
m band and
extra
filters for monitoring plume temperateure and to correct for background
effects. Measurements from the IR camera and an SO
2
compact DOAS instrument
have been compared by Lopez
et al
.(
2013
) at Karymsky volcano.
7.5 Future prospects
At the present time (2014) there is a suite of satellite-borne instruments
capable of determining important properties of volcanic ash and SO
2
gas. These
instruments span the UV to the IR and even into microwave regions. None of the
instruments was specifically designed to measure volcanic emissions and so it is
serendipitous that they can. There are no plans to develop satellite remote-sensing
instruments for volcanic applications but we have learned to use existing measure-
ments; since many future instruments will inherit the speci
cations of their prede-
cessors there is every reason to believe that new instruments will be exploited well
for volcanic research. While the situation at the moment is remarkably good, it
seems there will be periods in the future where satellite coverage for volcanic
applications will be worse than now. There is a need for both geostationary (with
very high time resolution) coverage and polar orbiters (two to four would be good)
that provide adequate temporal resolution in the polar regions not sampled by the
geosensors. Europe
'
s Sentinel-5 geostationary platform carrying a high spectral
resolution imager will satisfy many of the needs for the region it images (about a
70
circle centred at 0
latitude and longitude).
In summary, the future looks bright for satellite remote sensing, at least in the
passive domain. The great success of the CALIOP lidar on board the polar orbiting
CALIPSO platform has shown that active sensing from space in the visible region
is of great value to volcanic research. Active microwave instruments (radars) have
