Agriculture Reference
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Table 7.1 Characteristics of passive microwave satellites
Horizontal
Equatorial
Frequency
resolution
crossing time
Polarization
a
Satellite
(GHz)
(km
×
km)
(local)
SSM/I
19.4
H and V
69
×
43
0543 h
22.2
V
60
×
40
0922 h
37.0
H and V
37
×
28
1000 h
×
85.5
H and V
15
13
×
TMI
10.7
V, H
59
36
19.4
V, H
31
×
18
21.3
H
27
×
17
Changes
37.0
V, H
16
×
10
85.5
V, H
7
×
4
AMSR (NASA)
6.9
H and V
75
×
43
[96],
10.7
H and V
48
×
27
18.7
H and V
27
×
16
23.8
H and V
31
×
18
1330 h
36.5
H and V
16
×
9
Line
——
0.1
——
Shor
PgEn
89.0
H and V
7
×
4
AMSR (Japan)
6.9
H and V
71
×
41
10.7
H and V
46
×
26
18.7
H and V
25
×
15
23.8
H and V
23
×
14
1030 h
36.5
H and V
14
×
8
89.0
H and V
6
×
4
a
H
= horizontal; V = vertical.
[96],
instrument operated on the Nimbus-7 satellite between 1978 and 1987.
It was a polar orbiting satellite and SMMR had a constant view angle of
50.3° and a swath of 780 km. Dual polarization
T
B
was measured at fre-
quencies of 6.6, 10.7, 18, 21, and 37 GHz. Spatial resolution for C band
was very coarse (
150 km), and peculiarities of operation resulted in a long
repeat cycle. SMMR data are also available
(http://nsidc.org/data/nsidc-
Recently several multifrequency passive microwave satellite systems
have been launched, and more systems are planned. These systems offer
lower frequency channel operating at C or L band, which should provide
a more robust soil moisture measurement, and better spatial resolution.
These satellites include, for example, the National Aeronautics and Space
Administration (NASA) Aqua, the Japanese Advanced Earth Observation
Satellite (ADEOS-II), the Naval Research Lab Windsat, the European Space
Agency Soil Moisture Ocean Salinity Mission (SMOS), and the NASA Hy-
drosphere States Mission (Hydros).
Aqua was launched in May 2002 (
http://aqua.nasa.gov/AMSRE3.html),
and ADEOS-II was launched in the same year. Each includes an instrument
called the advanced microwave scanning radiometer (AMSR). As shown in
∼
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