On January 15, 2022, Dr. Yu Hongjuan, under the guidance of the team teacher, successfully passed the opening defense of the dissertation and was unanimously praised.

During the doctoral defense, I had the honor to invite an expert in this field, researcher Wu Bin of Shanghai Observatory of Chinese Academy of Sciences, who highly affirmed Dr. Hong Juan's preliminary work and achievements, and put forward valuable suggestions for follow-up research ideas. Due to the lack of research in this field in the world, researcher Wu Bin emphasized the importance of the research on solving low-order earth gravity field based on SLR, and is expected to make relevant achievements with higher recognition in the world. In addition to Professor Shen Yunzhong, the team leader, the teachers who participated in the opening defense also included Professor Chen qiujie, Professor Xu Tianhe, Professor Li Bofeng, Professor Zhang Xingfu and Assistant Professor Ge Haibo. All the teachers put forward their own suggestions for Dr. Yu Hongjuan's graduation defense and future research work.