This update aims to improve a lot of systems, features and bug fixes across all the modules (Mercury, Gemini and Apollo). It touches many of the core features of the game, and fundamental code. This can lead to issues not yet detected during testing. Please let me know if you stumble on anything new.

Note: If you are experiencing issues with this build you can roll back to the previous using the Steam Betas Tab accessible from the Steam client (games properties).

Apollo
Multiple systems has been updated and improved in the Apollo CSM, and various checklists and procedures has been updated.
The main procedures you will need to learn again is the:
- Lunar Module pressurization: New checklist added to the CM T&D section: CM/LM PRESSURE EQ.
- Docking Probe (use gas to retract (Prim or Sec) the probe after extending it), existing checklist updated.

Docking Probe
The general procedure is to extend the docking probe while leaving the RETRACT PRIM/SEC in their middle/OFF position. When the docking probe is extended, set it to RETRACT. When docked, set the RETRACT PRIM/SEC (one of them) to 1 or 2 to start retracting the probe. The probe can retract 4 times, 2x in PRIM and 2x in SEC (for redundancy).

LM Pressurization
The LM is pressurized after docking during T&D, quite early in the mission. I have updated the Lunar Module Academy lesson 1 to cover the procedure.
I have also corrected an issue with the attitude hold during lunar ascent. However, you will need to key V77E (if this is the requested mode) if ATT HOLD input does not generate a rate acceleration, even if the panels are correctly configured (the LGC will need to know, and some programs can override the setting).

I have also made an overhaul of the CSM SM/CM RCS system and its monitoring on MDC-2.
Mercury gyros
I have updated the logic around the Mercury gyros and the alignment of them. Please note that if you go back to the normal gyro panel setting, the gyros will be slaved to the Horizon Scanners.
Dynamic Skybox during landing
I have improved the landing areas to account for the correct time as you land. This will make it possible to land during the day, or during the night. The time of day at the landing location controls the lighting conditions. It will be quite dark when you land during night, so I will try to add some landing aid/lights if they existed. When you plan a retrograde burn for atmospheric entry, try to plan an entry that lands during the day.
Mercury horizon scanners
I have improved the Mercury horizon scanner logic to better detect the "temperature differences" between Earth and Space. An issue originating back to the TSS (True Scale System) updates has made them have a slight offset depending on various conditions. This has now been fixed.
Removed the Waterworld
The infamous "Waterworld" bug/feature has been removed. The reason for this was the way fog is rendered during landing.

Landing area
I have started the process of differentiating between water and land after entry. If you land in the ocean, you will see the normal ocean landing area as you are used, except for different lighting conditions based on time at the landing area. If you land on land, a temporary and very simple (currently) land model will be rendered instead. I will improve the land area, and maybe look into something more procedural generated landscape in future patches.

When you plan a reentry, always try to land in the ocean.

Please note that you will not complete the mission if you land on land (please let me know if you want this to change - I will also consider it based on feedback and reports I get).
Mercury lessons
I have updated the Mercury lessons to better teach you what the nominal values for the various gauges and instruments are.
The map tab in the Mercury Mission Pad has also received orbit info, as Gemini and Apollo has.
Apollo missions
I have updates all Apollo missions and states with sun positioning logic corrections. I have also improved multiple lessons, and specifically improved the Earth Entry lessons. The "Apollo 8" (Campaign 3) and "Apollo 11" (Campaign 4) fictional missions has received many updates and sequence fixes based on new features and procedure changes over the years.
Apollo Sun Positioning issue fixed
Finally tracked down a very old issue where the sun orientation data saved into Apollo (Apollo only) Save States are wrong. This has been corrected but it might require you to use the sp console command to correct the sun position in previous save states. However, the save states should have stored the position correctly, but incorrectly load it.

I have also fixed the issue where the sun gets a slight offset (~0 - 10 degrees) as you enter the Lunar Sphere of Influence.
0.99.19 release notes

• Updated the later Mercury lessons to cover what instruments and gauges should show.
  
• Mercury Gyro logic fixes
  
• Horizon scanner updates to better detect the Earth horizon
  
• Mercury capsule model slight rotation offset (8 - 10 degrees) removed
  
• Mercury Reflection Probe panel brightness fix
  
• Apollo Earth Entry Academy lesson updates
  
• Dynamic Skybox during landing
  
• Landing system updates
  
• Reentry plasma effect updates
  
• Apollo Sun Positioning issue fixed
  
• Added orbit info into the Mercury Mission Pad (as Gemini and Apollo has)
  
• Fixed the missing atmosphere in the Gemini Orbit View
  
• Updates to the CSM SM/CM RCS systems, and monitoring
  
• Apollo CSM cabin repress and ECS updates
  
• Apollo CSM LM pressurize updates
  
• Updates to the CSM docking probe logic
  
• Apollo Campaign 3 mission updates and fixes
  
• Apollo Campaign 4 mission updates and fixes
  
• LM Att Hold after Lunar Ascent (Key V77 if it does not work)
  
• Fixed the "Offscreen Switch Indicator" setting (the graphics that will lead you towards a highlighted switch). You can now disable the Offscreen Switch Indicator again, if you desired to do so.