If you liked the “astronaut(s) on a distant world do science and meet interesting aliens” aspect Robert L. Forward's Camelot 30K and his Dragon's Egg and Rocheworld series might have a similar vibe.

Maybe also Iain M. Banks' The Algebraist or The Player of Games, though they're much further from “hard” science fiction and focus on the characters rather than the science.

Also maybe Larry Niven's The Mote in God's Eye? Maybe somewhere between the previous ones when it comes to science I'd say.

Or possibly James P. Hogan's Giants aka Minerva series, starting with Inherit the Stars..? It ends up a bit space opera-y, but the first books are about astronauts solving a mystery on the Moon...

(And if you get into that you might also enjoy Frederik Pohl's Heechee saga, starting with Gateway...)