Abstract
Night-light remote sensing imaging technologies have increasingly attracted attention with the development and application of focal plane arrays. On-orbit signal-to-noise ratio (SNR) test is an important link to evaluate night-light camera’s radiometric performance and the premise for quantitative application of remote sensing imageries. Under night-light illumination conditions, the illuminance of ground objects is very low and varies dramatically, the spatial uniformity of each pixel’s output cannot be guaranteed, and thus the traditional on-orbit test methods represented by variance method are unsuitable for low-resolution night-light cameras. To solve this problem, we proposed an effective on-orbit SNR test method based on consecutive time-sequence images that including the same objects. We analyzed the radiative transfer process between night-light camera and objects, and established a theoretical SNR model based on analysis of the generation and main sources of signal electrons and noise electrons. Finally, we took Luojia 1-01 satellite, the world’s first professional night-light remote sensing satellite, as reference and calculated the theoretical SNR and actual on-orbit SNR using consecutive images captured by Luojia 1-01 satellite. The actual results show the similar characteristics as theoretical results, and are higher than the theoretical results within the reasonable error tolerance, which fully guarantee the detection ability of night-light camera and verify the validity of this time-sequence-based method.
Highlights
With the development of focal plane detectors and the needs of engineering applications, night-light remote sensing imaging technologies have increasingly attracted more attentions from remote sensing, economics and other research fields [1]
Taking the night-light camera carried by the Luojia 1-01 satellite as example [27], on the orbit with an altitude of 645 km, the spatial resolution is about 129 m, which means that a ground object with an area of 129 × 129 m2 is projected onto a single pixel with an area of 11 × 11 μm2
In this paper, considering the characteristics that the illuminance of ground objects is low and varies dramatically under night-light, we propose an on-orbit signal-to-noise ratio (SNR) test method based on time-sequence images for low-resolution night-light cameras
Summary
With the development of focal plane detectors and the needs of engineering applications, night-light remote sensing imaging technologies have increasingly attracted more attentions from remote sensing, economics and other research fields [1]. Theoretical analysis and on-orbit test of SNR is of vital importance to night-light cameras. It is urgent to find an effective on-orbit SNR test method for low-resolution night-light cameras. Luojia 1-01 satellite, developed by Chang Guang Satellite Technology Co., Ltd and Wuhan University, which have been successfully launched on 2 June 2018, could provide night-light remote sensing images with 129 m spatial resolution and 15 bits dynamic range. Aiming at the problems above, this paper proposed an on-orbit SNR test method for night-light cameras based on time-sequence images, which is quite different from the usual used methods based on spatial-sequence images represented by variance method. To verify the validity of this method, we took the night-light camera carried by the Luojia 1-01 satellite as example and calculated the theoretical SNR using its system parameters
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