The revised NAA recommendation for a personal communications system consisted of a duplex capability with a simplex backup. Simultaneous transmission of voice and biomedical data with a break-in capability would be possible. Two changes in spacecraft VHF equipment would be needed: a dual-channel in place of a single-channel receiver, and a diplexer for use during duplex operation.
Collins Radio Company selected Motorola, Inc., Military Electronics Division, to develop and produce the spacecraft S-band transponder. The transponder would aid in tracking the spacecraft in deep space; also, it would be used to transmit and receive telemetry signals and to communicate between ground stations and the spacecraft by FM voice and television links. The formal contract with Motorola was awarded in mid-February 1963.
Also, Collins awarded a contract to the Leach Corporation for the development of command and service module (CSM) data storage equipment. The tape recorders must have a five-hour capacity for collection and storage of data, draw less than 20 watts of power, and be designed for in-flight reel changes.
North American selected Radiation, Inc., to develop the CM pulse code modulation (PCM) telemetry system. The PCM telemetry would encode spacecraft data into digital signals for transmission to ground stations. The $4.3 million contract was officially announced on February 15, 1963.
The contract for the development and production of the CSM C-band transponder was awarded to American Car and Foundry Industries, Inc., by Collins Radio Company. The C-band transponder was used for tracking the spacecraft. Operating in conjunction with conventional, earth-based, radar equipment, it transmitted response pulses to the Manned Space Flight Network,
After studying the present radar coverage provided by ground stations for representative Apollo trajectories, North American recommended that existing C-band radars be modified to increase ranging limits. The current capability for tracking to 920 kilometers (500 nautical miles), while satisfactory for near-earth trajectories, was wholly inadequate for later Apollo missions. Tracking capability should be extended to 59,000 kilometers (32,000 nautical miles), North American said; and to improve tracking accuracy, transmitter power and receiver sensitivity should be increased.
Christopher C. Kraft, Jr., of MSC's Flight Operations Division (FOD), advised ASPO that the digital up-data link being developed for the Gemini program appeared acceptable for Apollo as well. In late October 1962, representatives of FOD and ASPO had agreed that an independent up-data link a means by which the ground could feed current information to the spacecraft's computer during a mission was essential for manned Apollo flights. Kraft proposed that the Gemini-type link be used for Apollo as well, and on June 13 MSC ordered North American to include the device in the CM.
Grumman representatives met with the ASPO Electrical Systems Panel (ESP). From ESP, the contractor learned that the communications link would handle voice only. Transmission of physiological and space suit data from the LEM to the CM was no longer required. VHF reception of this data and S-band transmission to ground stations was still necessary. In addition, Grumman was asked to study the feasibility of a backup voice transmitter for communications with crewmen on the lunar surface should the main VHF transmitter fail.
Christopher C. Kraft, Jr., of the MSC Flight Operations Division, urged that an up-data link (UDL) be included on the LEM. In general, the UDL would function when a great deal of data had to be transmitted during a time-critical phase. It would also permit utilization of the ground operational support system as a relay station for the transmission of data between the CM and LEM. In case of power failure aboard the LEM, the UDL could start the computer faster and more reliably than a manual voice link, and it could be used to resume synchronization in the computer timing system.
MSC Flight Operations Division outlined the advantages inherent in the CSM's capability to use the HF transceiver during earth orbit. The HF transceiver would allow the CSM to communicate with any one tracking station at any time during earth orbit, even when the spacecraft had line-of-sight (LOS) contact with only one or two ground stations in some orbits. It would give the astronauts an additional communications circuit. Most important, this HF capability could alert the network about any trouble in the spacecraft and give the Flight Director more time to make a decision while the spacecraft was out of LOS communication with the ground stations.
At an MSC-North American meeting, spacecraft communications problems were reviewed. Testing had indicated that considerable redesign was essential to ensure equipment operation in a high-humidity environment. Also antenna designs had created several problem areas, such as the scimitar antenna's causing the CM to roll during reentry. The amount of propellant consumed in counteracting this roll exceeded reentry allowances. Further, because the CM could float upside down, the recovery antenna might be pointed at the ocean floor. In fact, many at this meeting doubted whether the overall communications concept was satisfactory "without having detailed ground receiver characteristics." The situation derived from "one of the primary problems in the area of communications system design . . . the lack of functional requirements specifications."
Grumman was studying problems of transmitting data if the LEM missed rendezvous with the CSM after lunar launch. This meant that the LEM had to orbit the moon and a data transmission blackout would occur while the LEM was on the far side of the moon. There were two possible solutions, an onboard data recorder or dual transmission to the CSM and the earth. This redundancy had not previously been planned upon, however.
Motorola, Inc., submitted a proposal to NASA for the Apollo Unified S-band Test Program, a series of tests on the unified S-band transponder and premodulation processor. Motorola had already begun test plans, analytical studies, and fabrication of special test equipment.
Representatives of MSC's Information and Electronic Systems Division, Flight Operations Division, Flight Crew Operations Division, Guidance and Control Division, Astronaut Office, and ASPO, Goddard Space Flight Center, and Bellcomm, Inc., met to discuss communications during LEM and CSM rendezvous.
Capability of the Manned Space Flight Network (MSFN) to provide data for rendezvous was studied. Aaron Cohen of ASPO stated sufficient data could be collected, processed, and transmitted via MSFN to the LEM to achieve rendezvous. Dr. F. O. Vonbun of Goddard showed that MSFN data did little to improve data already available in the LEM before launch. Although five tracking stations would communicate with the LEM during ascent and the first 10 minutes of orbit, there would be only a slight improvement in spacecraft position and motion data over the data already contained in the LEM computer. No decision was made concerning the MSFN's capability.
Alternate rendezvous methods were discussed.
North American selected Dalmo-Victor to supply S-band high-gain antennas for Apollo CSM's. (The deployable antenna would be used beyond 14,816 km [8,000 nm] from the earth.) Dalmo-Victor would complete the antenna design and carry out the development work, and North American would procure production units under a supplemental contract.
NASA awarded a $2,740,000 fixed-price contract to the Collins Radio Company for S-band telemetry equipment. Collins would install the equipment at three antenna facilities that supported Apollo lunar missions (at Goldstone, Calif.; Canberra, Australia; and Madrid, Spain).
MSC eliminated the requirement for relaying, via the LEM/CSM VHF link, transmissions from a moon-exploring astronaut to the earth. This change allowed the 279.0 megacycle (Mc) transmitters in both vehicles to be eliminated; cleared the way for a common VHF configuration; and permitted duplex voice communications between astronaut and spacecraft. For communicating with the LEM, MSC directed North American to provide a 259.7 Mc transmitter in the CSM.
North American, Hamilton Standard, Grumman, David Clark, and MSC representatives, meeting in Downey, California, resolved all interfaces between the space suit and the two blocks of spacecraft. As a result of these agreements, MSC directed North American and Grumman to make some minor changes (suggested by the Crew Systems Division) in the communications cables; to remove the portable life support systems from the CM; and to add a thermal-meteoroid garment - rather than one providing merely thermal protection - to the CM.
A Senior Flammability Review Board meeting at MSC reached a number of decisions on the CSM. Attending were Robert R. Gilruth, chairman; George M. Low, Kenneth S. Kleinknecht, Aleck C. Bond, Maxime A. Faget, Donald K. Slayton, Charles A. Berry, and Rodney G. Rose, all of MSC; Samuel C. Phillips, NASA Hq.; William B. Bergen and Dale D. Myers, North American Rockwell; and George Stoner, Boeing (nonvoting observer).
Several previous action assignments were reviewed:
The Board concluded that the material changes made in the CM had resulted in a safe configuration in both the tested atmospheres. The Board agreed "that there will always be a degree of risk associated with manned space flight," but the risk of fire "was now substantially less than the basic risks inherent in manned space flight."
Among decisions reached were:
Apollo Special Task Team Director Eberhard F. M. Rees wrote Dale D. Myers, Apollo CSM Program Manager at North American Rockwell, to convey the concern of ASPO Manager George M. Low and others over the status of the S-band high-gain-antenna system. (Of all the subsystems in the spacecraft, that antenna seemed to face perhaps the toughest technical and schedule problems.) On December 14, 1967, Rees had visited the subcontractor's plant (Dalmo Victor) at Belmont, Calif., and had heard optimistic status reports on the entire system, including quality control and delivery schedules. Shortly thereafter, when Dalmo Victor began quality testing, the company encountered serious technical difficulties and the delivery schedule, as Rees put it, "collapsed completely." He then recounted several efforts by analytical teams to pinpoint the technical problems and to put the program back into shape (including reviews in mid-February and again on March 1, when very little progress could be seen). This record of inability to remedy technical problems, said Rees, indicated a serious weakness among Apollo contractors regarding visibility of their programs as well as their analytical engineering capability.
In an effort to resolve the continuing technical and schedule problems with the high-gain antenna system at Dalmo Victor, Apollo CSM Program Manager Dale D. Myers named a Resident Subsystem Project Manager at the vendor's plant. This change provided a single management interface with Dalmo Victor. The representative had been given authority to call on whatever North American Rockwell resources he might need to accomplish program objectives.
S. C. Phillips, NASA Hq., suggested that for communications on the lunar surface a long, deployable antenna might work. He suggested that an antenna about 30 meters long could be used. The antenna would be rolled up like a tape measure and would curl into a cylinder when deployed, somewhat like an antenna that had been used on the CSM.