Research On Radiation Reference Drift Law Of COCTS

The impact of changes in the marine environment on the global marine ecological environment and marine basic productivity is crucial.As a big ocean country,China is duty-bound to develop ocean satellite remote sensing.So far,China has launched three ocean color satellites in solar synchronous orbit.HaiYang-1 A(HY-1A)and HaiYang-1 B(HY-1B)were launched into orbit in 2002 and 2007 respectively,and HaiYang-1 C(HY-1C)was successfully launched in September 2018.Among them,HY-1B didn't stop working until 2015,and its main load ocean color water temperature scanner(COCTS)has accumulated nearly nine years of ocean observation data.However,as the radiation datum of the water color water temperature scanner,the cold space signal is disturbed by unknown radiation sources,which results in the drift of the radiation datum corresponding to all detection channels.The target signal is much smaller than the expected value,and the near infrared channel even cuts off in the abysmal sea area.Although the remote sensing data of HY-1B water color water temperature scanner are polluted by cold air radiation,it can be seen from the image data that the water color water temperature scanner works stably and the image is clear.Therefore,according to the downloaded image data and cold air data,it is very meaningful and urgent to explore the main problems affecting the drift of radiation reference and their changing rules,and to establish a correct mathematical and physical model for the effective recovery of its data.This paper will focus on the following aspects of work to solve this problem:1.A large number of investigations have been carried out on similar problems existing in optical remote sensing instruments related to solar synchronous orbits at home and abroad.It is found that in-orbit radiation reference drift is a common phenomenon.After defining the rule of reference drift,good recovery is achieved.2.The structure of water color water temperature scanner and the working principle of clamping circuit are analyzed.After analyzing the change rule of cold air signal which is very close to clamping angle,it is found that the 10 cold air code values of 8 channels of visible light/near infrared light increase from the first to the tenth,and the 10 cold air code values of different scanning lines of the same track in each channel have excellent correlation.3.In this paper,the relationship between the flight orbit of water color thermometer,the reflection of earth target(season,solar altitude angle,etc.)and the size of cold air signal is analyzed in detail,and the possible external factors of reference drift are determined preliminarily.This paper deals with the historical data of HY-1B/COCTS,analyses the correlation between the solar altitude angle,season of the satellite's subsatellite point and the reflectance of the covered object and the change of the cold air signal,determines the drift rule and main influencing factors of the radiation datum of COCTS,and provides the research direction and the drift recovery of the radiation datum for the reuse of the historical data of HY-1B/COCTS.Complex model building technology foundation.