You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Apollo_program

Context:
In September 1967, Mueller approved a sequence of mission types which had to be successfully accomplished in order to achieve the manned lunar landing. Each step had to be successfully accomplished before the next ones could be performed, and it was unknown how many tries of each mission would be necessary; therefore letters were used instead of numbers. The A missions were unmanned Saturn V validation; B was unmanned LM validation using the Saturn IB; C was manned CSM Earth orbit validation using the Saturn IB; D was the first manned CSM/LM flight (this replaced AS-258, using a single Saturn V launch); E would be a higher Earth orbit CSM/LM flight; F would be the first lunar mission, testing the LM in lunar orbit but without landing (a "dress rehearsal"); and G would be the first manned landing. The list of types covered follow-on lunar exploration to include H lunar landings, I for lunar orbital survey missions, and J for extended-stay lunar landings.

Question:
What type of missions were approved by Mueller after the incident?

sequence