Geology Reference
In-Depth Information
Table 7.1
Space‐borne radar sensors (past and future) used for sea ice applications.
Satellite
Country/ Agency
Sensor
Band
Pol.
Life Span
Res. (m)
Swath (km)
Seasat
United States
SAR
L
HH
1978
25
100
Almaz‐1
Russia
SAR
S
HH
1991-1992
10-100
350
ERS‐1
ESA
SAR
C
VV
1991-1999
30
100
ERS‐2
ESA
SAR
C
VV
1995-2011
30
100
ERS‐1/2
ESA
Scattermeter
Ku
VV
1991-2011
25/50
500
JERS‐1
Japan
SAR
L
HH
1992-1998
18 × 24
75
Radarsat‐1
Canada
SAR
C
HH
1995-
10-100
50-500
QuikSCAT
United States
Scattermeter
Ku
HH, VV
1999-2009
4.5 km
resamp.
1400 (i), 1836 (o)
Envisat
Europe
SAR
C
Single,
dual
2002-2012
30-500
5-406
PALSAR‐ALOS-1
Japan
SAR
L
S, D, Q
2006-
7-100
20-350
Radarsat‐2
Canada
SAR
C
S, D, Q
2007-
3-100
10-500
TerraSAR‐X
Germany
SAR
X
S, D, Q
2007-
1-18
100 × 150
OSCAT
India
Scattermeter
Ku
HH, VV
2009
4.5 km
resamp
1400 (i), 1836 (o)
Cryosat‐2
ESA
Radar altimeter
Ku
‐
2010
250
Profile
Sentinel‐1
ESA
SAR
C
S, D
2014
5 × 20
80-400
PALSAR-ALOS-2
Japan
SAR
L
S, D, Q
2014
3-100
25-350
RCM
Canada
SAR
C
S, D, Q
2018
Variety
Variety
Note
: S, D, and Q refer to single, dual, and quad polarizations. The symbols (i) and (o) refer to the inner and outer beams of
the scatteromete according to Figure 7.10.
(light detection and ranging) instrument. From 2003 to
2009 the mission provided data on surface elevation of FY
and MY ice. The measurements were affected by optically
thick cloud cover and weather patterns in the polar regions.
Moreover, measurements were allowed only over periodic
intervals. Data were provided to users in patchy time series.
A summary of ICESat‐1 measurements of Arctic sea ice
thickness is presented in
Kwok et al
. [2004] and
Kwok and
Rothrock
[2009]. The second generation of the orbiting
laser altimeter ICESat‐2 is scheduled for launch in 2016.
Tonbeo et al.
[2009] used a scattering model to evaluate
the uncertainty of sea ice thickness retrieval from a radar
altimeter caused by snow cover contribution to ice floe
buoyancy as well as radar penetration in snow and ice.
One of their findings was that in areas where ridges repre-
sent a significant part of the ice volume, the simulated
altimeter thickness estimate is lower than the real average
thickness from the footprint. They presented a sound dis-
cussion about the sources of uncertainty. For the much
thicker ice shelves (compared to sea ice thickness)
Griggs
and Bamber
[2011] estimated the accuracy of the Antarctic
ice shelf thickness estimates from the radar altimeter
onboard ERS‐1 and the laser altimeter onboard ICESat‐1.
Based on comparison with airborne data, they found
biases ranging from −13.0 to 53.4 m. Ice shelf thickness
varies between a few hundred to 1000 m.
Among the space-borne SAR systems that are being
developed is the Canadian Radarsat Constellation Mission
(RCM), scheduled for launch in 2018. The RCM will
consist of three‐spacecraft fleet operating in constellation
approach. The system will ensure continuity of measure-
ments after Radarsat‐2. The system does not aim to repro-
duce Radarsat‐2 but rather to meet core demands at less
cost. It will provide fully polarimetric data as well as data
from circularly polarimteric polarization configuration.
This will be one of the highlights of the system because it
will make nearly polarimetric data available for the first
time from the ScanSAR mode, the most operationally
desired SAR mode.
An incomprehensive list of the satellite platforms that
carried (or will carry) radar sensors (SAR, scatterome-
ters, and radar altimeters) is presented in Table 7.1. The
letters (i) and (o) that accompany the scatterometer
swath denote the inner and outer beams, respectively (see
Figure 7.10).
7.3. electromaGnetic Wave Processes
and ProPerties
Information in this section highlights a few definitions
and processes of electromagnetic wave propagation rele-
vant to remote sensing observations. Since microwave
remote sensing is at the center of the sea ice applications,
the section starts with discussions on polarization of EM
waves, its definition, mathematical description, and mech-
anisms of depolarization in the case of radar data. This
furnishes a necessary background to proceed through dis-
cussions of radar polarimetric data in section 7.6.2.3 and
to understand the passive microwave observations. This
is followed by discussions of the five processes of EM
