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NASA lost contact with its Mars helicopter
(www.theverge.com)
This is a most excellent place for technology news and articles.
This isn’t the first time they lost contact so it may not be a huge issue in the end.
It's almost definitely because it doesn't have Line Of Sight to establish the connection.
Sort of like how cheap fpv drones will lose video when you fly into another room because the thin drywall blocks the signal enough and the signal can't bounce off other objects in the right way.
So I'm going with "once the rover catches up like last time it'll be fine"