China has already considered enhancing its space situational awareness capabilities by placing a satellite in a retrograde orbit out at the geostationary belt (GEO). This satellite is used for monitoring activities and predicting warnings. 

According to the paper published by authors from the Xi’an Satellite Control Center, it indicated that the researchers found out a new way, which using swing of the moon to put a monitoring satellite in retrograde geostationary orbit. The altitude of the GEO matched the Earth’s rotational period, which means that it is thus useful for detecting some activities of telecommunication and weather. Then, a monitoring satellite out at GEO is usually placed about tens of kilometers above or below the belt and it could take a closer inspection to those satellites in the belts by moving in different directions at a relatively slow velocity. 

As we know, the satellites in GEO orbit are of great value to the government and businesses, and this is also the reason why China want to place a monitoring satellite out at GEO. 

However, putting the satellite into retro-GEO is really a big challenge because its trajectory is the opposite of other objects in GEO.The spacecraft launching to the west will be failed due to the high energy loss, and this’s why the author citing earlier Western papers on the topic, to consider a path to retro-GEO via the moon. launching to the east will solve this problem and the spacecraft could achieve the orbit through the rotation of Earth. However, the idea of putting satellites into specific orbits through the oscillation of the moon was mentioned early, and this new method can indeed greatly reduce fuel costs, but there are many unknown risks, so it has not yet been used, one is that the monitoring satellite will pass through the GEO at a higher relative speed than other objects, which increases the probability of collisions, and also higher speed of the satellite in retro-GEO are difficult to detect in detail. Due to these concerns, China has not used this new approach.

In my opinion, new ideas are beneficial for exploration and development, but the premise is that we need to ensure the feasibility of this approach, we need to conduct a rigorous evaluation, and if the current technology cannot be achieved, we should choose a relatively safe way to place a monitoring satellite in retro-GEO.