Wide-Field Telescope Alignment Using the Model-Based Method Combined with the Stochastic Parallel Gradient Descent Algorithm

To acquire images with higher accuracy of wide-field telescopes, deformable mirrors with more than 100 actuators are used, making the telescope alignment more complex and time-consuming. Furthermore, the position of the obscuration caused by the secondary mirror in the experiment system is changed with the difference of fields of view, making the response matrix of the deformable mirror different in various fields of view. To solve this problem, transfer functions corresponding to different fields of view are calculated according to the wavefront edge check and boundary conditions. In this paper, a model-based method combined with the stochastic parallel gradient descent (SPGD) algorithm is used. The experiment results show that our method can correct the aberrations with a high accuracy in both on-axis and off-axis fields, indicating that the effective actuators are well chosen corresponding to different fields of view.

Application of the Correction Algorithm Based on the ME-LM Method for Improvement of Peak Identification in the Instrumental Spectrum of the Scintillation Gamma-Radiometer

The paper considers an algorithm for correcting the instrumental spectrum of the gamma-radiometer with a NaI(Tl) detector. The algorithm is based on the ME-LM method (Maximum Likelihood Estimation using Expectation Maximization), which uses a detector response matrix obtained by Monte Carlo simulation. The main advantage of the algorithm is the rescaling procedure, which significantly reduces the spectrum processing time.