Changes in the Telemetry System

The success of the Saturn V flights depended in large part on the performance of the telemetry system. A characteristic of all spacecraft programs, telemetry transmitted prelaunch and flight performance data from the vehicle to ground stations. From the start of the planning for Apollo, NASA realized that many more varied and sophisticated demands would likely be placed on the system. The development of launch operations at KSC was, in part, conditioned by those demands [see chapter 16-5].

For prelaunch operations, the ability of the launch vehicle to check itself out was limited by requirements for ground support. A digital computer in the Saturn V instrument unit was primarily intended for guidance and navigation. It had triple redundancy throughout, except in memory and power sources, and its self-check capability was limited primarily to flight. Support for prelaunch operations came from the digital data acquisition system located in each stage. Tailored to the specific needs of its stage, this system transmitted data either through the data link or by means of pulse-code-modulated radio transmissions. The radio link could be used either on the ground or in flight.22

The Saturn V launch vehicle had 22 telemetry links carrying more than 3.500 instrumentation measurements during flight. In prelaunch checkout each link and instrumentation channel was tested to assure operation within specified tolerances. Since the vehicle instrumentation system was used to acquire data during tests on other vehicle systems (such as pneumatics and control), frequent prelaunch checks of the instrumentation were required.23

The S-IC contained six very-high-frequency links, including the single-sideband-frequency-modulated telemetry system, one of the Saturn V components that had evolved throughout the launch vehicle development program. Because data during staging might be concealed or lost due to the effects of the engine exhaust, a tape recorder was included in the stage to collect that information, which was subsequently recovered by playback over radio. Range-rate data for the tracking of the vehicle was provided by the offset doppler transponder in the stage. Two other telemetry links used ultra-high-frequency receivers for range safety purposes. If the safety officer on the Cape issued a destruct command to these receivers, they would trigger the explosive network.24

The second stage had systems similar to those on the S-IC, but had one less single-sideband link. The S-IVB (third stage) carried no tracking transponders; otherwise, its telemetry equipment was identical to that of the first stage. The instrument unit carried an offset doppler, an Azusa (or Mistram) transponder, two C-band beacons, and a command and communication system. It had no range safety receivers.25

Long before the first Saturn V flew, the configuration of the vehicle allowed the use of either the Mistram or Azusa tracking systems, but not both at once. To reduce the complexity of the system, Phillips in 1965 directed that Azusa be used on future Saturn flights. Real-time support at the Cape would be required at least through the AS-503 mission. Experience in tracking early Saturn vehicles indicated a need for only one beacon, and some viewed even that as possibly unnecessary. It was later confirmed that the Saturn V was large enough to reflect enough radar energy to be visible on ground indicators to the limits of safety responsibility. Though a beacon might not be required for tracking purposes, range safety personnel considered it desirable.26

To receive telemetry from its vehicles, NASA maintained three ground networks. One of these, the Manned Space Flight Network, was under the operational control of Goddard Space Flight Center, Greenbelt, Maryland, during Apollo missions. In order to operate effectively for the lunar landing program, the system had to be able to control the spacecraft (both the command and lunar modules) at lunar distances. While the equipment had been adequate for earth-orbit missions, the greater distances, as well as the complexity of Apollo, led to the introduction of the unified S-band system.27

The term S-band derived from the period of the Second World War when letters were used to designate bands of frequencies. The band selected for Apollo lay between 1,550 and 5,200 megahertz. For use with its unmanned space probes, the Jet Propulsion Laboratory (JPL) had developed equipment that operated on these frequencies. A useful feature of the JPL equipment was the combination of several radio functions into a single transmission from only one transmitter to a given receiver. For Apollo, these functions included tracking and ranging; command, voice and television communications; and measurement telemetry. The versatility of the system was inherent in its structure.28

For the lunar mission the unified S-band offered the twin advantages of simplicity and versatility. The line-of-sight signal lost little of its strength when it passed through the atmosphere, and transceiver and power supply equipment could be relatively small. In providing direct communications between the spacecraft and ground stations, the unified S-band worked equally well in near-earth operations or circling the moon.

Apollo's tracking system required close, continuous communication among the major centers and the Manned Space Flight Network. This was accomplished by means of digital data, teletype, and voice links which were the responsibility of the NASA communications system centered at Goddard. A combination of land lines, undersea cables, high frequency radio, and satellites linked more than 100 locations throughout the world. For Apollo, the system had to be augmented. Major switching centers ensured maximum sharing of circuits, while giving Houston priority for real-time data during Apollo missions.29

During Apollo operations, the three manned spaceflight centers were connected outside the Goddard system by two links - the launch information exchange facility and the Apollo launch data system. Operated by Marshall during launch operations, the former was primarily an information transfer link between Huntsville and KSC with connections to Houston. It carried real-time telemetered data, closed-circuit television, facsimile, classified typewriter, voice, and countdown information. The Apollo launch data system was the primary information link from KSC to Houston. It had four independent subsystems that handled telemetry, television, countdown and status data, and launch trajectory data during prelaunch and launch operations. By using the Apollo launch data system, personnel in Houston could conduct closed-loop tests of the spacecraft while it was at KSC. During powered flight, the system transmitted trajectory data from the impact predictor for the information of the flight director at Houston.30

The Apollo program significantly increased the tracking and data acquisition requirements for KSC and the Air Force Eastern Test Range. To ensure uniformity, the Office of Tracking and Data Acquisition, NASA Headquarters, was designated in August 1964 the "single point of contact" with the Department of Defense for such coordination. Although heavily involved in the development of the unified S-band system for Apollo operations, the Jet Propulsion Laboratory and Goddard were directed to support the planning and operations.31 The agreement that resulted between NASA and the Defense Department emphasized colocation of KSC and Air Force Range facilities whenever possible "to achieve a maximum of mutual assistance, to avoid unwarranted duplication, and to realize economies where practical and consistent with mission requirements. . . ."32 To support Apollo, range facilities needed considerable modernization. During 1965 about 85% of the existing Air Force tracking equipment was modified. Over three years, the cost exceeded $50,000,000, including the updating of telemetry stations downrange as well as at the Cape.33

The entire Apollo tracking and data acquisition network, including ships, planes, and unified S-band ground stations, was integrated with the Manned Space Flight Network between November 1966 and June 1968. The AS-202 mission in August 1966 provided the first test under actual operating conditions. By the launch of Apollo 9 the new system was operational at stations in Texas, Mexico, Ascension Island, the Canary Islands, Bermuda, Spain, Hawaii, Australia, Wales, and California.34

There was no major change in tracking and data acquisition comparable to the introduction of the mobile concept. The primary alteration in tracking was the increasing sophistication of the hardware.35 From early Saturn I missions through Apollo 9, development of hardware had tended to proceed steadily, dependent largely upon launch vehicle requirements. At the same time, less and less direct control over telemetry was allowed to KSC. In this respect, the attempt of NASA to spread the R&D among several centers had led to an unexpected constraint upon launch operations at LC-39. In the end, the Saturn V was measured and tracked by a telemetry system largely outside the control of KSC.

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At Long Last

Apollo officials in the launch control center during the countdown for Apollo 10. From left, standing: George M. Low, Apollo Spacecraft Program Manager; Lt Gen. Sam Phillips, Apollo Program Director; and Donald Slayton, Flight Crew Operations Director, MSC. Seated, John Williams, Spacecraft Operations Directior; Walter Kapryan, Launch Operations Deputy Director; and Kurt Debus, KSC Director.

The liftoff of Apollo 10 on 18 May 1969 would mark KSC's fourth manned Apollo launch in the short space of seven months. The mobile concept was proving its efficiency. Before Apollo 8 moved out of the vehicle assembly building on 9 October 1968, the crews had already stacked AS-504 for Apollo 9. Before Apollo 9 was subsequently moved out, crews had stacked AS-505 for the Apollo 10 flight. Apollo 10 rolled out on 11 March to pad B, the more distant of the two pads on LC-39. This would prove the only use of pad B for an Apollo mission and the only use of firing room 3.

On the flight of Apollo 9, McDivitt, Scott, and Schweickart had checked out the lunar module in flight and docking maneuvers with the command-service module. On Apollo 10, the crew of Thomas Stafford, John Young, and Eugene Cernan took the spacecraft to the vicinity of the moon where the lunar module closed to within 16 kilometers of the surface before redocking with the orbiting command module. At long last, KSC was set for the Apollo 11 mission that would put men - Neil Armstrong and Edwin Aldrin, Jr. - on the moon while Michael Collins waited for them in the command module.

Launch Escape System Apollo

Testing the Apollo 11 spacecraft in the operations and checkout building. (1) The command and service modules in an altitude chamber. Segments of a workstand, used to work near the top of the spacecraft, have been lifted and pulled back against the circular walls ofthe chamber.

(2) Testing the landing gear of the lunar module.

Lunar Operations Command

(3) Mating the command and service modules with the spacecraft-lunar module adapter.

Apollo 11 stages had been arriving at KSC since the beginning of the year, the second stage undergoing rigorous inspection on account of a stormy barge voyage from California via the Panama Canal. During March the prime and backup crews participated in the spacecraft tests, with mid-April bringing the docking tests in the altitude chambers. During a checkout of the lunar module descent stage, technicians discovered faulty actuators in the machinery that would push out the legs of the lunar module for the moon landing. The repair area was inaccessible to men of average build, and Grumman scoured its rosters for two qualified technicians who were "very slim." The two men - William Dispenette and Charles Tanner - squirmed into the narrow space and replaced the actuators.36

The lunar module on Apollo 11 differed in several respects from that on Apollo 10. A very-high-frequency antenna would facilitate communications with the astronauts during their extravehicular activity on the moon's surface. The lunar module would also have a lighter-weight ascent engine, increased thermal protection on the landing gear, and a packet of scientific experiments. The only change in the command-service module was the removal of a blanket of insulation from the forward hatch. On the launch vehicle, the first stage was stripped of its research and development instrumentation. Insulation was improved on the second stage, and slight changes were made in the connections between the third stage and the instrument unit.37

The crawler-transporter picked up the 5,443-metric-ton assembly and started for pad A at 12:30 p.m. on 20 May while Apollo 10 was still on its way to the moon. The countdown demonstration test got underway 27 June with vehicle and spacecraft fueled, powered up, and counted down for simulated launch on 2 July. On the following day, with the fuel tanks drained, Armstrong, Collins, and Aldrin participated in a dry test.38

Meanwhile, KSC was preparing for the hundreds of thousands of people who wanted to see the men off to the moon. Special guests, members of the press, and dependents of Apollo team members would number close to 20,000. Some 700,000 people were expected to watch the liftoff, possibly the largest crowd to witness a single event in the history of the world. The anticipated traffic jam prompted KSC to arrange for helicopters to fly in key personnel, should they be otherwise unable to reach their work. Guests included Vice President and Mrs. Spiro Agnew, former President and Mrs. Lyndon Johnson, Army Chief of Staff General William Westmoreland, four cabinet members, 33 senators, 200 congressmen, 14 governors, and 56 ambassadors. Close to 3,500 accredited members of the news media were occupying the press site. Over two-thirds were American; 55 other countries, including three Iron Curtain nations, sent representatives, with Japan's 118 leading the way. All western European countries except Portugal were represented, and all western hemisphere nations except Paraguay.39

Brilliant lights illuminated the launch area and Apollo 11 during the night of 15 July. The crawler-transporter carried the mobile service structure to its parking area a mile away. In the early hours of 16 July, the tanks of the second and third stages were filled with liquid hydrogen. More than 450 people occupied the 14 rows of display and control consoles in firing room 1. Sixty-eight NASA and contractor supervisors occupied four rows; seated at the top, nearest the sloping windows that looked out toward the launch pads, were the KSC chiefs, the Saturn V program manager for Marshall, and the Apollo program manager for the Manned Spacecraft Center. One hundred and forty Boeing engineers occupied consoles linked to the Saturn IC stage and mechanical ground support equipment. North American Rockwell had 60 engineers at consoles connected with the S-II stage, while 45 McDonnell-Douglas engineers monitored the S-IVB stage. Ninety IBM engineers manned three rows of consoles hooked up to the instrument unit, IBM stabilization and guidance systems, and flight control. About 8 kilometers to the south two automatic checkout stations in the operations and checkout building monitored the spacecraft.40

The fueling of the launch vehicle was completed more than three hours before liftoff. Then the closeout crew of six men under the direction of Gunter Wendt and Spacecraft Test Conductor Clarence Chauvin returned to the pad.41 They opened the hatch and made final cabin preparations. The backup command pilot, Fred Haise, Jr., entered the spacecraft at 3 hours and 10 minutes before liftoff. With the assistance of Haise and a suit technician, Neil Armstrong entered Apollo at 6:54 a.m. Michael Collins joined him five minutes later in the right couch, and Edwin Aldrin climbed into the center seat. The closeout crew shut the side hatch, pressurized the cabin to check for leaks, and purged it. At two hours before liftoff Houston participated in a final checkout of the spacecraft systems. At one hour before liftoff, the closeout crew left the pad. Almost a kilometer to the west, protected by a sand bunker, 14 rescue personnel stood watch. Equipped with armored personnel carriers and wearing flame protective gear, they could move to the pad quickly if the astronauts needed help.42

To make the occasion more memorable, the day was ushered in by a beautiful dawn. A few fleecy clouds scarcely cut the warm sun. The slight wind cheered the assemblage. As the moments ticked off, loud speakers reported that everything was moving according to schedule. The countdown became automatic at 3 minutes, 20 seconds, when the sequencer took over. Ignition commenced at 8.9 seconds with a wisp of white smoke indicating that the first engine would soon come to life. All five engines built up full thrust with an awesome roar. For a moment Apollo 11 seemed to stand still; then at 9:32 a. m. on 16 July 1969, the moon rocket rose slowly and majestically. A voice broke the tension: "The vehicle has cleared the pad." Apollo 11 had gone beyond KSC's control and the men in firing room 1 turned for a moment from their consoles to view the rocket rising over the Atlantic.

Apollo Launch Control

The departure of Apollo 11.

Many people moved away from the viewing sites as soon as the vehicle disappeared from view. Others stood silently, or chatted quietly, or sat on the grass if they were not among the privileged visitors in the stands. Exhaustion held some - others simply did not want to fight the traffic. A cameraman asked how the launch looked. He had not seen it, because he had been busy photographing the reactions of the


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