and the study is summarized, with suggestions for future
research, in the final Section.
Materials and Methods
ZY3-02 Satellite
The
ZY3-02
satellite is the second in China’s ZY3 series of
satellites, and the orbital parameters are basically the same
as the first in the series. Apart from the stereo cameras and
multispectral camera as loaded on ZY3-01, an experimental
laser altimeter has been added to the
ZY3-02
platform. The
ZY3-
02
satellite’s parameters are listed in Table 1.
The relationship between the stereo cameras and laser al-
timeter of the
ZY3-02
satellite is illustrated in Figure 1, and the
pointing of the laser altimeter is almost parallel to the bore
sight of the panchromatic nadir camera.
Basic parameters of the
ZY3-02
satellite laser altimeter
(
SLA
) are listed in Table 2. The repetition rate of the laser is
only 2 Hz, and the distance of the neighboring laser points
is approximately 3.5 km on the ground. Moreover, the laser
footprint size of
ZY3-02
is designed to be approximately 75 m,
but 100 m according to the actual field calibration and valida-
tion. Another important parameter of the
ZY3-02
SLA
is that its
elevation accuracy is approximately 1.0 m or better in some
regions, which has been validated by field experiments (Tang
et al
., 2017; Li and Tang, 2017). Although the accuracy of the
ZY3-02
SLA
is worse than that of the
GLAS
with 0.15 m on flat
terrain (Duong
et al
., 2009), it is enough and still valuable for
1:50 000 stereo image mapping as an elevation control. The
ZY3-02
can obtain the stereo images and laser altimetry data
synchronously from the same satellite, which is the first such
capability in the world for Earth observation.
Experimental Data
Figure 2. Distribution of the four experimental regions.
Figure 1.
ZY3-02
satellite loaded with three-line array stereo
cameras and laser altimeter.
Table 1. Parameters of
ZY3-02
satellite and stereo cameras.
Parameter
Value
Orbit altitude
~505 km
Inclination
97.421°
Orbit type
Sun-synchronous circle orbit
Repeat period
59 days
Descending
10:30 AM
Image
resolution
Panchromatic nadir: 2.1 m
Forward and backward: 2.5 m
Multispectral: 5.8 m
Spectrum
range
Panchromatic 450–800nm
Multispectral
Blue: 450–520nm
Green: 520–590nm
Red: 630–690nm
Infrared: 770–890nm
Swath width
Panchromatic: 50×50 km
2
Multispectral: 52×52km
2
Table 2. Basic parameters of the
ZY3-02 SLA
.
Parameter
Value
Parameter
Value
Laser pulse width 6.5 ns Laser footprint size
>75 m
Pulse rate
2 Hz
Wavelength
1064 nm
Power dissipation 45 W IFOV, emitting
0.15 mrad
Weight
40 kg
IFOV, receiving
0.5 mrad
Single-pulse energy 175 mJ Laser channel number
1
Effective aperture 210 mm Accuracy of ranging
1 m
(3
σ
, slope <2°)
570
September 2018
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING
