this post was submitted on 06 Mar 2025
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Im not sure then why mars was mentioned in the article. Is the power really limiting though assuming solar panels just for lunar transmission (earth retransmissions) and maybe more not only so that some are active at any point (seems almost better than battery but maybe battery would be better) but also using directed antenna to get info to the points we want to get the information to (so like ones that send info to the lagrange point and others that are more for lunar surface gps). I hope im getting what im thinking across clear enough.
Mars was mentioned because it was written by a journalist, not a scientist. If you read all the quotes from NASA and the Italian agency, they only mention the Moon. Mars is too far away for any use of Earth/Moon/Lagrange based PNT satellites.
For lunar applications, power isn't really the limiting factor. It is the one factor we weren't sure about before this mission, so we figured that out. Another factor is geometry, with the long distances to the moon but small distances between satellites. A final factor is antenna directions and gain patterns. GPS antennas are facing the Earth and directional to the Earth (though there is a VERY tiny omnidirectional on the rear). The main antennas shove most of their power to the Earth's surface and have a small amount that leaks to the sides away from Earth. This mission used those side lobes, but because of the distances involved you don't see very many side lobes out at the moon. Even at GEO, space based receivers are only seeing a small number of satellites at a time because the Earth blocks most of the signal.
If NASA wanted a real PNT solution on the moon, they would need to have dedicated satellites with moon facing antennas. Even better would be moon surface repeaters with large antennas.