Having obtained the evidence they needed, Chen Mo had the drone return to Earth through the Spatial Channel to let Dr. Selvig and the others know they were safe, so they would not continue worrying.
Watching the drone sink back into the ground from the spot where it had emerged earlier, Chen Mo and the other two immediately returned through the passage to the dungeon. Under the complicated gazes of the stone gate guards and Loki, they headed straight out to find Odin.
However, after the three of them left, many more identical drones flew out one after another from where the first drone had disappeared. They spread out along the route Chen Mo and the others had taken, forming a signal relay chain that transmitted signals from the underground space and from Earth on the other side of the wormhole through the subterranean barriers to the dungeon above.
However, because of the Golden Palace's special materials, the signals were still blocked and could not reach the upper levels.
Therefore, after walking out through the stone gate, Chen Mo began quietly releasing many even smaller micro-drones from his storage space, each no bigger than a fingernail. As he continued onward, he released them one by one and concealed them throughout the Golden Palace. Besides relaying signals, they could also help Chen Mo keep track of the dungeon and every part of the Golden Palace at all times!
This way, although Chen Mo was in Asgard, he could still remain in contact with Earth and monitor the dungeon and the Golden Palace whenever he wished.
Although Asgard's technology was also advanced, it was clearly not of the same kind as Earth's, and development in many areas was extremely uneven. At least in terms of communication and surveillance, there was practically nothing.