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 19. There are several accumulators in the mission flight plan. These are places where the spacecraft could essentially mark time to get ahead or behind mission planning in the event of any unforeseen problems. These accumulators are as follows:

1. Number of earth orbits.

2. Number of lunar orbits before landing.

3. Surface stay time.

4. Number of orbits before rendezvous.

5. Number of orbits after rendezvous

The nominal and backup modes and redundancy provided for systems operation are significant, but will not be covered for all systems, such as environmental control and electrical power.

21. There is essentially a continuous communication capability except while behind the moon and occasionally during coast when the space­ craft is in a thermal roll condition. These intermittent losses of spacecraft to ground communications are not considered to be seri­ous.

22. There are a reasonable set of precautions against contamination of both the lunar surface and the earth. It is recognized that as long as men are involved, there are biological products generated and there is a lower level of contamination at the moon which is essentially unavoidable.

23. There are some concerns of' which the major ones are listed: 1. Environmental effects can cause unexpected problems but these are not considered to be large.

2. The calibration of the Guidance and Navigation system is a more significant point. Experience has shown that when a system is operated for the first time it can cause problems. The concern is that the first lunar mission is the first time that the G&N system will be used at lunar distances.

3. The lunar landing is naturally of some concern. It has been simulated on earth, but lunar conditions cannot be completely duplicated.

4. Crew tasks must be carefully watched to keep from overloading the astronauts.