that of the remaining 14 stations used to support MERCURY, the GEMINI program could be supported with 6 as originally equipped with the other 8 requiring augmentation. The APOLLO program will use the same manned space flight network modified further to meet requirements peculiar to the APOLLO program.

The APOLLO program will require stations at three geographical areas (Antigua, Northwest Pacific, and Ascension) not previously instrumented for manned space flight support. In addition, three large antenna stations (Goldstone, Spain, and Canberra) are being colocated with the deep space network stations to provide lunar and cislunar coverage. Six of the sites initially instrumented for MERCURY plus one station augmented for support of GEMINI are in locations not required for APOLLO lunar support. Upon completion of the GEMINI and orbital APOLLO programs the further need for these stations will be evaluated and phased out if not required for other programs.

Critical phases of the lunar APOLLO mission require stations at six geographical areas which are not in sight of land. Five ships will be used to cover these areas. One will be located down range from the launch site to cover insertion into orbit; two ships will be stationed to cover the postinjection phase one off the coast of southeast Africa and one in the west-central Pacific; two will be stationed in other areas of the Pacific to cover reentry- -one near Hawaii and one near Samoa. The west-central Pacific ship used to cover postinjection trajectory will also be utilized for coverage of the reentry trajectory. Instrumented aircraft will be required to provide astronaut voice and spacecraft telemetry coverage of the final critical S-IV-B injection burn phase. Since the geographic location of this phase of the flight varies widely throughout the lunar month, aircraft provide the only reasonable means of assuring coverage of this critical trajectory event.

A particularly significant change in support requirements from MERCURY and GEMINI to APOLLO was the development of a single frequency system to serve functions of tracking, telemetry, and command with a single antenna. Figure 233 indicates the three separate facilities required to support these functions for GEMINI, whereas these same functions are being performed by a single antenna on a single frequency in support of APOLLO. Furthermore, the unified S-band has the advantage of greater distance and much greater data handling capability which is required for the APOLLO lunar mission. A more detailed look at some of the station augmentation is shown in figure 234. This figure shows a typical 30-foot antenna station for support of APOLLO. A GEMINI station has been modified by the addition of the 30-foot antenna and components peculiar to the APOLLO unified S-band system, that is, the S-band transmitter, encoder, diplexer, preamplifier, and dual receivers. The GEMINI data processing equipment and display equipment have been augmented with additional equipment required for support of APOLLO.

In addition to the network support required for APOLLO, there is a requirement for a checkout station near the APOLLO launch facilities (fig. 235). The purpose of this checkout station is to conduct. the necessary prelaunch checkout, prior to the launch, of the service module, command module, and lunar excursion module. Following

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launch, and after orbit is established, the station will be used as an in-flight monitoring station during the early orbits about the Earth. Figure 236 illustrates the near-Earth portion of the APOLLO trajectory during which tracking will be accomplished by the 30-foot antenna stations. Upon completion of the in-orbit checkout, the near-Earth orbit phase will have been completed and the S-IV-B will be ignited to boost the spacecraft into a translunar trajectory. The S-IV-B injection burn period will mark the last period of thrust for final injection into translunar trajecto y. The position of this phase with respect to the Earth will vary as a function of launch time and position of the Moon relative to the Earth. The many possible positions in which this critical phase must be monitored demand high-speed, mobile instrumentation stations such as instrumented aircraft. These aircraft will be deployed for a given launch condition and then redeployed as conditions change. The aircraft will provide continuous voice contact with the astronauts as well as telemetry coverage during the critical injection burn phase.

The ground and ship stations are so located that the APOLLO spacecraft can be acquired not more than 7 minutes after injection into the lunar trajectory and tracking data can be sent to the Integrated Mission Control Center at the Manned Spacecraft Center.

As the spacecraft gets further from the Earth, it will be supported with the 85-foot antenna stations as shown in figure 237. As indicated previously, these stations are approximately 120° apart around the world. The space coverage is indicated in the figure. By use of existing 85-foot antenna facilities presently installed as part of the deep

space network, it is planned to obtain a backup capability for these critical facilities.

They will continue to provide support throughout the flight to the Moon, the lunar excursions and much of the period during the return flight from the Moon.

The next phase for ground support for APOLLO will be during its reentry. During this phase, the APOLLO command module will enter the Earth's atmosphere, bounce back out of the Earth's atmosphere and then assume a ballistic trajectory for the second and final reentry. A communications blackout is expected to exist, as shown on figure 238, during the first dip into the atmosphere and a second blackout will occur shortly after the final reentry into the Earth's atmosphere. Tracking and data acquisition requirements are imposed for that portion of the reentry trajectory immediately after the first communications blackout. In order to adequately cover the locus of the possible reentry areas, three ships will be required in the Western Pacific. Figure 239 indicates the areas that will require tracking coverage during the reentry phase. One ship will be stationed west of the Hawaiian Islands, another ship will be stationed west of the Samoan Islands, and a third ship will be stationed between these two. One of the ships will be redeployed from the station previously covered for postinjection tracking near the Gilbert/Ellice Islands.