Study on the improvement of instrument's image spatial resolution on the three-axis stabilized platform
Guo Qiang 1,2, Xu Jianmin 2
1 .Chinese Academy of Meteorological Science, Beijing, 100081
2 .National Satellite Meteorological Center, Beijing, 100081
No 46, Zhongguancun Nandajie, Haidian distric, Beijing, 100081, China
Tel: (86)-10-68406123 Fax: (86)-10-62176805
ABSTRACT: As for the space-to-earth observation, high spatial resolution is always what the
remote-sensing instrument’s designers and application users pursue. However, it is usually
limited by the instruments’ optical diffraction in theory. Fortunately, with the development of the
high accurate scanning control and positioning technologies, the sensor’s manufacture
techniques as well as the high speed processing on ground, it can be reality that the spatial
resolution of the images generated by the optical instruments with linear sensors on the
three-axis stabilized platform could be improved in a certain degree by changing the sensors’
relative positions, increasing over-sampling ratio with high enough accurate positioning controls
and some image-processing operations. The full physical and mathematic models and their
corresponding algorithm realizations, namely two main processing ways, one is the pure
mathematic method and the other is the mixed method based on the real physical process, are
discussed in this paper completely. At the same time, the spreading error induced by the
technology is quantitatively analyzed and the relationship between the image spatial resolution
and the image SNR based on the model, which is verified by the simulation samples, is also
presented. The feasibility of the method is proved by the patent technology of the SPOT-5 HRG.
Considering that doubling the spatial resolution is sacrifice of 10.2dB in image SNR, this
technology firstly can be applied in the polar orbit three-axis stabilized platform at current
technological conditions. And, with development of the sensor’s and the cooler’s performances
further, it can be also used in the geostationary orbit platform in the future. The researching
results may offer the new philosophy for the instruments’ designs and will promote the
observation performance of the total system.
1. Introduction
As for the space-to-earth observation, the higher spectral and spatial resolutions are always
pursued in development of remote sensing instruments. It is considered that the spatial
resolution of the instrument, under the condition of the proper signal to noise ratio, is
determined by the instruments’ instant field of view (IFOV) to a large extent. In other words, the
spatial resolution of instrument is determined by optical and physical character of instrument.
On the other hand, for the imaging instruments, attention is focused on the spatial resolution of
remote sensing images (below referred as images) processed on ground.
With the development of modern high accuracy servo control technology and the high speed
digital signal processing technology, the accuracy of the two-dimension scan servo control
system of the instruments on board of the geostationary satellites may reach five micro-radians
in orbit which equals to one-fifth to one-sixth VIS pixels as well as one micro-radian in lab.
Taking into consideration of the present technical conditions, it is proposed that changing the
sensors’ relative positions as well as increasing over-sampling ratio could improve the spatial
resolution of the images, which is generated by the optical instruments with linear sensors on the
three-axis stabilized platform, by a certain degree. At the same time, the digitalized process is
adopted to enhance the image spatial resolution. Based on the strict mathematic model, the
technical possibility of the method was analyzed by relative application examples and
simulation results.
