2.2 Specification
According to the above mission
requirements, we determined the technique
parameters of the C-HRIS prototype as
shown in Table 1. The satellite is a solar
synchronous polar orbit satellite. Its
altitude is 800 km and the inclination angle
is 99
°. The local time of crossing point is
10:30. The circle time is 101 minutes and
the ground velocity is 6.6Km/s. Every 16
days, the satellites will passe over the same
swath of ground.
Table 1. The main technique parameters of the
prototype
| Ground resolution |
40m |
| IFOV |
0.05mrad |
| Spectral range |
0.43~2.4um |
| Spectral resolution |
VNIR: 10nm (0.43~1.0 um)
SWIR: 20nm (1.0~2.4 um) |
| Spectral channel number |
128 (VNIR64, SWIR64) |
| Optical system |
f=600mm
FN=3 |
| Focal plane array ( prototype) |
VNIR: Si-CCD
256pixel*64spectrum
SWIR: InSb
256pixel*64spectrum |
| Pointing mirror crosstrack |
±30° |
3. Instrument description
C-HRIS uses two area array detectors
and operates in pushbroom mode. Two slits
are used at the focal plane of the telescope
to separate the spectral waveband into
VNIR and SWIR. 128 waveband imaging
spectral data ranging from 0.43
mm, which is obtained through two flat
field spectrometer and CCD and InSb area
array detectors. The principles and the
photo of the prototype are as shown in
Figure 1 and 2, respectively.
The experiments on the prototype
show that the imaging quality is good. Its
MTF reaches 0.6, the spectral transmittance
is very high over the whole spectral range,
and spectral resolution meets the design
requirement.
Fig.1 The schematic digrams of C-HRIS.
Fig.2 The photo of C-HRIS prototype.
A pointing mirror is arranged in front of
the telescope to provide ±30
° view
variation in the direction of crosstrack, so
any stripes on the ground in the width of
±230km perpendicular to the ground can
be observed.
3.1 Optics
The optics of the C-HRIS is special and
complicated, which is composed of one
telescope and two-flat-field spectrometer,
as shown in Fig.3.
Fig.3 The optics of C-HRIS.
The telescope is an all-spherical-surface
5-reflector Shafer system. The flat field
spectrometers VNIR and SWIR are prism
chromatic dispersed, off-axial spherical
surface spectral imaging system (OASIS).
3.2 Optomechanics
The optomechanical system adopts a
module structure, and is arranged in three
lays: the upper, the middle and the lower.
Module unit is composed of pointing
mirror, telescope objective, imaging system,
spectral band splitter, VNIR and SWIR
spectrometers, CCD detector, InSb detector,
and a main box.
Fig.4 CAD diagram of the optomechanic system of
C-HRIS.
