Update index.md

Author: fhyuancn

docs/index.md

@@ -42,7 +42,7 @@ This project presents a physics-based signal correction framework for removing
     [ESIIL staff edit in Markdown](https://github.com/CU-ESIIL/Summit_group_2026_14/edit/main/docs/index.md?plain=1#L28){ .md-button target="_blank" rel="noopener" }
 
 ![Team hero image](assets/Picture3.png)
-![Team hero image](assets/hero/hero1.png)
+![Team hero image](assets/hero/hero2.png)
 
 ![Team hero image](assets/Picture2.png)
 ![Team hero image](assets/fig2.png)