Is MSFN ranging mandatory for C’?

See list attachedNovember 20, 196868-PA-T-255APA/Chief, Apollo Data Priority CoordinationIs MSFN ranging mandatory for C’?

During our C' Data Select Mission Techniques meeting a question came up which must be understood and answered prior to the flight. It involves the requirement for being able to obtain MSFN range informa- tion during the cis-lunar phase of the mission. It has been said unofficially that ranging is essential to do a decent job of orbit determination, although, I'm sure something can be done in its absence. The question is what confidence have we of being able to hit the entry corridor if ranging is not available. I have asked the Math Physics Branch to determine entry corridor targeting accuracy without ranging. If this turns out to be unacceptable, then a mission rule may be needed establishing that certain pieces of spacecraft equipment must be working prior to committing to TLI in support of this requirement. Further complicating the situation is our uncertainty as to just what the space- craft equipment is – specifically, how redundant and how reliable.