In-orbit optical performance assessment of Geostationary Ocean Color Imager
After Geostationary Ocean Color Imager (GOCI) was launched at June 27th, 2010, it is operated to observe the Korean peninsula on the geostationary orbit as one of the three main payloads in COMS satellite. Generally, the performance indicators are Ground Sample Distance (GSD), Modulation Transfer Function (MTF), and Signal to Noise Ratio (SNR) that verify the optical performance of payload. Most of all, the MTF performance is widely used since it is closely related to reliability and accuracy of observational target information in aspects of satellite image application. Especially, in case of ocean color sensor, for confirming the ability of GOCI to separate the slight difference of ocean color information, on-orbit MTF performance test and SNR assessment should be performed.
A Dynamic Observation Capability Index for Quantitatively Pre-Evaluating Diverse Optical Imaging Satellite Sensors
Choosing a capable satellite sensor from a mass of homogeneous sensors to meet the requirements of observation tasks in various application scenarios is one of the basic challenges faced by the collaborative observation in an Earth Observation Sensor Web environment. This paper analyzed five main factors affecting the observation capability of optical imaging satellite sensors. This study proposed the concept of dynamic observation capability index (DOCI), which denotes the continuously changing observation performance of diverse sensors in various applications. A higher DOCI demonstrates stronger observation capability. The DOCI model consists of five subcapabilities: spatial-temporal covering capabilities (Coverage), thematic observation capability (Theme), environmental capability (Radiation), attribute capability (SpaceTime), and quality capability (Accuracy). We discussed the assessment methods on the basis of the DOCI model. To verify the proposed DOCI method, seven sensors (AVHRR/3, BGIS-2000, Hyperion, MERSI-1, MODIS, OLI, and SeaWiFS) were used in four different observation task scenarios: normalized difference vegetation index measurement, snow cover monitoring, oil spill detection, and vegetation-type mapping. The results showed that the changes in the observation capability of different sensors in different scenarios can be effectively assessed and modeled using the DOCI index, thus aiding in the scientific pre-evaluation of homogeneous optical sensors. DOCI can also be used as a quantitative, comprehensive, and all-purpose prior assessment method in web-based sensor planning.
Obtaining the Mtf of a Ccd Imaging System Using an Array of Point Sources : Evaluation of Performances
The in flight measurement of the MTF of a CCD imaging space sensor is of great interest to improve the technical knowledge of the system and to define a deconvolution model. We use the method developped by R.A. Schowengerdt (University of Arizona), whose principle is to measure the bidimensional PSF of the instrument by imaging a ground target constituted by a grid of point sources. With intent to employ this method for high resolution instrument, we have studied it, in order to define, for a given instrument, the optimal target and the associated method performance.