There are 30 collectible in Relicta. Each of them could be found at base areas, none of them found at puzzle areas. You can backtrack to get these collectibles until you stat the last puzzle area, which is the tropical jungle. Collectibles listed in chronological order in this guide, with some additional information.
1: First is a PDA and should be on the middle of your way as it is also the part of the tutorial, the game warns about it and it also mentions you need to push button I.
2: Inside your room after talking with your daughter and your boss via your computer. It is a picture on the desk.
3: PDA "Propaganda - Opporutnines out of this world". When leaving your room and living quarter area head to the other living quarter area, it is inside of a room and then inside of a cabinet.
4: PDA "News - A brief chronology of the Orbital Era". Inside the main area of the dome complex, on a desk.
5: PDA - Can be found while heading to the Shoemaker Taiga, after leaving the Maglev it is on a bench.
6: Artifact - Coffee Mug. Inside of a room while heading to Shoemaker Taiga.
7: Artifact - Patels Picture. Inside Assembly Room, after Taiga while heading to Shoemaker Caves Elevator.
8: PDA - "Diary Logs - Angie's Logbook". At Maglev station on a bench while heading tho Shoemaker Caves elevator.
9: PDA - "Emails - Ethical Concerns" On a bench after leaving Shoemaker Caves before the Maglev Station.
10: PDA - "Emails - The Thing in Ibn Bajk" while heading to the De Gauche crater Cliffs after Relicta Lockdown event. Need to take stairs down to laboratory.
11: Artifact - "Relicta Fragment", same room as 10th collectible (The Thing in Ibn Bajk).
12: Artifact - "Kwarizmis picture" after De Gerlache Cliffs, after leaving elevator go straight, down stairs to the laboratory.
13: PDA - After Kwazimis Picture head back and inside a glass corridor it is on a green box, slighlty missable because of the orange box covering it from the angle you coming.
14: PDA - "Documents - Chandra Expedition Hearing Transcript" Just once you arrived to Fauistini, not far from the maglev station.
15: Artifact " Sassanid Order 2nd cl." not much after previous collectible there will be a corridor and stairs to your left, go down to that laboratory, collectible is there.
16: PDA "News - Chandra Expedition to reopen moon base" At Faustini arid canyon maglev station, after the Faustini Arid Canyon Puzzles.
17: PDA "Diary Logs - Kwarizmi Private" While heading to tropical beach puzzles in Svendrup Crater dome, inside of laboratory room.
18: Artifact "Hardcover Book". Inside equipment room which is right next to the room with previous collectible.
19: PDA "Propaganda - Ragnar Nquyen's acceptance speech" Right after previous 2 collectible, in next room.
20: PDA "Let the red moon Rise!" Svedcrup crater dome, after Tropical Beach puzzles.
21: Artifact "Maglev" After previous collectible, downstairs, under the stairs.
22: PDA "Diary - Laia's Dirty Secret" While heading to Shoemaker Glacier puzzle area, inside "test Area" room.
23: Inside of a Laboratories room, while heading to Shoemaker Glacier puzzle area, right before the elevator.
26: Artifact "Music Poster" When heading to Fauistini the second time, to the desert area it is in like the second room after leaving the maglev room.
29: Once this collected you should get the Senior Researcher achievement.
30: Once this collected you should get the Master Collector achievement.