Database
[{"desc":"Sip Ave"},{"desc":"Vesey Pl &; River Terrace"},{"desc":"Murray St &; West St"},{"desc":"E 81 St &; York Ave"}]
Query
db.collection.aggregate([{$facet:{list_of_station_names:[]}},{$set:{list_of_station_names:{$map:{input:"$list_of_station_names",as:"n",in:"$$n.desc"}}}}])