# Research into Image Point Positioning Compensation of a High-Orbit Thermal Infrared Staring Camera
## 4 Conclusions  
According to the periodicity of the temperature of the high-orbit thermal infrared staring camera, a two-dimensional internal and external positioning compensation model based on temperature change is proposed in this paper. In this paper, four kinds of experimental schemes of image point positioning compensation were designed: only internal parameter error compensation, only external parameter error compensation, first inside and outside, and first outside and inside. The internal and external parameters calculated by the four schemes were used to calculate the pointing angle of the compensated grid points in the body coordinate, and the pointing angle calculated by the real internal and external parameters was different (Figures 7-10), and the internal and external compensation parameters were calculated, respectively. The compensation calculation of the target trajectory image point positioning was carried out. The positioning error after compensation was obtained, and it was compared with the positioning result before error correction and the ideal value (as shown in Table 3). The experiment proves that the parameter error compensation scheme is the optimal solution. The experimental results show that the compensation accuracy was the highest when internal compensation was performed first, followed by external compensation. The phase angle of the external parameter compensation under different temperature conditions was consistent with the added installation error. In this paper, two schemes were used to compensate the image point positioning under different temperature conditions, namely, only external parameter compensation and internal and external compensation (as shown in Figure 11). The compensation results were compared with the installation angle of the original simulation. The two schemes could better recover the change rule of the relative installation angle and time, and the compensation scheme of internal and external compensation was better than that of external parameter compensation only. Even when the relative installation angle error was large, the two schemes could better calculate the real relative installation angle. Figure 11: The relationship between the relative installation angle and time change of the two schemes. (**a**) Compensation result of relative installation angle \(\alpha\); (**b**) compensation result of relative installation angle \(\beta\); (**c**) compensation result of relative installation angle \(\theta\). Despite the success of our approach, we acknowledge that there are still some limitations and challenges that need to be addressed in future research. For instance, in the process of solving the internal and external compensation parameters, due to the redundant observation virtual control points, the least squares evaluation method was adopted to solve the compensation parameters, but the method needs to give the initial value of the estimated parameters in the process, and in the process of establishing the error equation, it needs to be Taylor-expanded and linearized, and there is a certain error in the theory. Therefore, in follow-up research work, it is necessary to establish a compensation parameter solution method that does not require a linearization process in order to improve the accuracy and practicability of parameter compensation. In the experimental process of internal and external calibration compensation, although this paper proposes a two-dimensional pointing angle model to replace the internal distortion model of the early warning area array camera, it fails to fully solve the correlation between internal and external parameters, resulting in unsatisfactory solution results. Therefore, in the process of on-orbit application, a more preferred parameter compensation model than the two-dimensional pointing angle model should be found to minimize the influence of strong correlation between internal and external parameters.