Abstract
The Luojia 1-01 Satellite (LJ1-01) is the first professional night-light remote-sensing satellite in China, and thus, it is of pioneering significance for the development of night-light remote sensing satellites in China and the application of remote sensing in the social and economic fields. To ensure the application of night-light remote-sensing data, several studies concerning on-orbit geometric calibration and accuracy verification have been carried out for the complementary metal oxide semiconductor (CMOS) rolling shutter camera of LJ1-01 since the launch of the satellite. Owing to the lack of high-precision nightlight geometric reference at home and abroad, it is difficult to directly calibrate the nighttime light image of LJ1-01. Based on the principle of rolling shutter dynamic imaging, a rigorous geometric imaging model of the time-sharing exposure of the rolling shutter of LJ1-01 is established, and a geometric calibration method for daytime imaging calibration and compensated nighttime light data is proposed. The global public Landsat digital orthophoto image (DOM) with a 15-m resolution and 90-m Shuttle Radar Topography Mission digital elevation model (SRTM-DEM) are used as control data. The images obtained in England, Venezuela, Caracas, Damascus, and Torreon (Mexico) were selected as experimental data. The on-orbit calibration and accuracy verification of LJ1-01 were carried out. Experiments show that after on-orbit geometric calibration, the daytime calibration parameters can effectively compensate for the systematic errors of night-light images. After compensation, the positioning accuracy of night-light images without geometric control points (GCPs) is improved from nearly 20 km to less than 0.65 km. The internal accuracy of the calibrated night-light images is better than 0.3 pixels, which satisfies the requirement of subsequent applications.
Highlights
Launched on 2 June 2018, Luojia 1-01 is the first scientific experimental satellite launched by Wuhan University
It is used for remote-sensing applications in social and economic fields [4] and low Earth orbiter (LEO)-based navigation augmentation experiments
Luojia 1-01 Satellite (LJ1-01) is located in a 645-km solar synchronous orbit, and it is equipped with a high-sensitivity planar array complementary metal oxide semiconductor (CMOS) [5] night-light camera and a navigation enhancement test payload [3]
Summary
Launched on 2 June 2018, Luojia 1-01 (referred to as LJ1-01) is the first scientific experimental satellite launched by Wuhan University. To carry out on-orbit geometric calibration of the LJ1-01, the satellite is designed to support both daylight and night imaging. To ensure optimal imaging in different imaging modes, daytime and nighttime imaging use different combinations of imaging parameters. The sensor uses a combination of low-level gain and short exposure time. The sensor uses a combination of low-level gain and long exposure time, and both high and low gain data are effective in nighttime imaging scenarios. Irrespective of whether daytime or night imaging is being performed, the nighttime sensor of LJ1-01 uses an electronic rolling shutter exposure mode [6,7,8]. On-orbit geometric calibration is the key link to ensure the quality of night-light remote sensing dataOofnt-horebLitJ1g-e0o1msaettreilclictea.liIbnrathtiiosnstius dthye, fikresyt,licnoknstoideenrisnugreththeeeqxupaolsiutyreocf hnaigrahctt-elirgihstticrsemofottheeseronlsliinngg dshatuattoefrtohfeLLJJ11--0011, asartieglolirtoe.uIsngtehoismsetutrdicym, foirdste,lcoofnLsiJd1-e0r1inwg aths eesetxapbolissuhreedc. Fbientatellryt,htahne 0p.o6s5itkiomn,inangdacthcuerianctyeronfanl iagchctu-rliagchietsimofatghees cwaliitbhroautet dgenoimghett-rliicghcot nimtraogl epsowinetsre(GbeCtPtesr) twhaans n0o.3tepdixteolsb.e better than 0.65 km, and the internal accuracies of the calibrated night-light images were better than 0.3 pixels
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