What do the alphabetical Orokin Void mission types mean?

Question

I've recently started grinding for prime parts on Warframe with the help of the Warframe Wiki. However, when I view the desired warframe, weapon, etc. in the wiki for drop locations, it shows the mission type along with a letter from A-C (e.g. Tower III Exterminate C). I am unsure about what the letter value represents.

Are there several layouts of each mission type's map and if so, is the letter value indicative of that layout? If that's not the case then what does it represent?

Answer 1

The letters A-C basically represent different loot tables at periodic times when rewards are dispersed.

For Exterminate and Capture keys where the reward is distributed and revealed upon mission completion, the letter system doesn't apply. Sabotage is similar and has one prime drop for mission completion and one for finding all three caches (the first two caches act similar to A rotation drops).

However, for keys like Survival, the wave distribution is based on AABC. Meaning that at:

• 5:00 pick loot from Reward Table A
• 10:00 pick loot from Reward Table A
• 15:00 pick loot from Reward Table B
• 20:00 pick loot from Reward Table C
• repeat again for every 5 minute increment

This reward table varies differently with the four tiers of Void Missions, namely T1, T2, T3, T4.

In defense, it's the same concept.

• 5 waves, pick loot from Table A
• 10 waves, pick loot from Table A
• 15 waves, pick loot from Table B
• 20 waves, pick loot from Table C
• repeat again for every 5 wave increment

Interception, same deal:

• 1st round, pick loot from Table A
• 2nd round, pick loot from Table A
• 3rd round, pick loot from Table B
• 4th round, pick loot from Table C
• repeat every 1 round increment