Citizen Sleeper

Follow the lengthy Lem/Mina/Sidreal/Castor mission chain.

1. Help Lem work by watching Mina
2. Complete preparations of the Sidreal
3. Attend the Drawing (appears this drive always fails)
4. Scout the Sidreal once moved to the hub.
5. Steal the Celis data in the shipyard
6. Speak with Lem and show him the ID's
7. Go with Lem and Mina on to the Sidreal on the departure day.

This is one the most beautiful endings. You can continue from start of the day afterwards to choose the LEFT BEHIND ending instead.

Short version: Build the Sidereal ship, babysit Mina, get Sidereal IDs for everyone, tell Lem you have IDs, and board the Sidereal when it departs.

Long version:

This is 1 of 4 endings/achievements (Solo Ticket, Left Behind, Long Journey, and Three Body) related to Lem & Mina and the Sidereal colony ship. You can't get all 4 endings/achievements in a single playthrough unless you mess with cloud saves/save files; I believe there are minimum 3 playthroughs required to get all 4 endings. Notes on this in the comments.

Go to the Shipyard and complete the Yard Hand wheel through either "Assist a Shipbuilder" or "Haul Materials". You'll then get a story bit where you're introduced to Lem & Mina. Choices here don't matter.

Go to Unit Assembly and complete the Junior Tech wheel by successfully completing "Systems Fitting" enough times, or complete the Welder's Mate wheel by successfully completing "Welder's Mate" enough times. (If you get a negative outcome 3 times, you'll fill the Quality control wheel and have to do the Shipyard portion again.) You'll get a story bit with Lem & Mina where you have to watch Mina while Lem works; again, dialogue choices don't matter. (This does not count towards "babysitting" Mina; babysitting is done specifically at their apartment.)

Lem & Mina's Unit will unlock in Lowend, with babysitting Mina being an option. Complete action "Babysit Mina" enough times to fill the "A Ticket Out" wheel. Go through another dialogue with Lem where choices don't matter. Make sure to complete all of Mina's babysitting before completing the "Sidereal Horizon" wheel, which is detailed next.

Go to Sidereal Bridge and complete Interface action "Sidereal Fit-Up" enough times to fill the "Sidereal Horizon" wheel (24 sections total; positive outcomes count for 2 sections). After this is done, go through another dialogue with Lem (choices don't matter). A 3-cycle countdown "Sidereal Draw" will start on Shipyard, and a 6-cycle countdown "Moving the Horizon" will start at Sidereal Horizon. Keep yourself alive and healthy until the 3-cycle countdown finishes.

Go to the Lem & Mina icon at the bottom of the Eye to go through a story bit where - surprise - you weren't even eligible to win the tickets. Afterwards, there will be a 3-cycle countdown timer on Lem & Mina's unit. Wait it out.

Talk to Lem at the apartment, choices don't matter. Then take the Ascender car up to the central hub, where there's a new icon for Sidereal Dock.

Warning: the next step will start an 8-cycle countdown timer; by the end of this timer, you will need to complete the section after that. Not hard, but just make sure you're not also chasing a bunch of other quests at the same time.

Repeat Intuit action "Scout the Dock" enough times to fill the 6-section "A Way On Board" wheel. After completing this step, you'll have a dialogue with Castor, who makes you an offer to get you onto the Sidereal. This starts an 8-cycle countdown; you will need to complete the section below before this timer runs out.

Go to Celis Ship at the bottom of the Eye. Repeat Engage action "Bluff Past Security" and/or Intuit action "Observe and Explore" enough times to fill the "Celis Infiltration“ wheel. Avoid negative outcomes as they will fill the negative "Celis Lockdown" wheel. After this is complete, go to Celis Servers and do critical action "Extract Celis Data". (A negative outcome still results in getting the data, but you'll lose 2 points of condition.)

Warning: dialogue choices DO MATTER in the next two dialogues with Lem detailed below.

Return to Castor, where you'll give him the data and he'll give you the IDs. This will follow immediately with a conversation with Lem. The first option between Sit and Stand doesn't matter; after that, choose these options when they appear:
"I have some news."
"I have Celis IDs for us."
The above choices lock in the ending. Choices in the remainder of this dialogue do not matter.

After this dialogue ends, keep yourself alive and healthy while the countdown timer runs out at the Sidereal Dock. After it does, go back up the Ascender Car to find Lem & Mina. During the final story bit, choose the following options:
• "Lem!" (between "Lem!" or Wait.)
• "Doesn't matter (between "You ready?" or "Hi Mina!")
• Board. (between Wait. or Board.)
The choices after this don't matter. After the story ends, the achievement should unlock.