The insufficiency of the power system to supply the necessary electricity to drive the other systems added a second negative aspect to the Hughes proposal. The SEB found that the design did not provide enough solar  cells to produce the required electrical energy and that if more were added Hughes would be forced to change the configuration of its spacecraft. In addition the proposal had given an incomplete description of the communications system, leaving out items which NASA had specified in the Request for Proposal document.
Finally, the Source Evaluation Board concluded that the solid-fuel retro-rocket for deboosting the spacecraft into lunar orbit was inadequate to alter the orbital parameters around the Moon. All of these factors, taken together, constituted too great an element of unreliability, and this plus the development problems outweighed the strong points of the spin-stabilization concept.
The only other proposal for a spin-stabilized lunar orbiter came from Thompson Ramo, Wooldridge/Space Technology .Laboratories of Redondo Beach, California. The TRW/STL orbiter concept used spin-stabilization to control the spacecraft's attitude during the mission. This meant that it had to make the other major systems compatible with spin-stabilization. While the attitude control problem was easily solved, it put severe restraints on the photographic system. It would have to employ fast shutter speeds and a high-speed film which would be very susceptible to solar radiation fogging.
The use of a liquid developer in the film processing  system also presented greater risks than would accompany other existing photographic systems. Moreover, due to the absolute necessity to maintain constant image-motion compensation, the quality of resolution of a single exposure might vary considerably from one side of the film to the other. The proposed format of a single photographic frame was too narrow, requiring the camera to make a large number of frames of any given area on the lunar surface.12
If the TRW/STL photo-system was judged impracticably elaborate, the proposed communications system simply failed to meet the requirements of the NASA RFP. Neither the communications nor the power systems were capable of performing their functions for the minimum thirty-day spacecraft life span. Because of spinning, the solar panels of the orbiter could not produce adequate quantities of power at any given time to recharge the spacecraft's battery. Moreover, the capacity of the battery was such that it could not have accepted a greater recharging rate than it already had, even if the energy producing area of the panel s were enlarged. This amounted in the final analysis to a proposal with too many areas open to critical development  problems.
Ironically NASA had based its earlier decision to have a lightweight lunar orbiter on the STL systems research. STL had proven the feasibility of an Agena-class orbiter, but its concept of an orbiter proved to be less practicable than that of another bidder.
While Hughes and TRW/STL could claim experience in the increasingly complex realm of designing, building, and flying automated space probes, the Martin Company, which offered a third approach, had no such advantage in this respect. However, it presented a very satisfactory proposal from the standpoint of technical feasibility. Unlike the first two firms, Martin designed its orbiter to employ three-axis stabilization to serve as the attitude control system for a platform from which a very well-designed photographic system could take pictures of the Moon without having to compensate for rate of spin.
Although it had a limited capability to perform high-quality convergent stereo photography, its film processing, readout, and communications systems appeared to be highly capable of transmitting data to Earth in a very short time. This aspect of the Martin proposal greatly pleased the SEB evaluators at Langley. On the other hand the Martin orbiter lacked redundant systems which would ensure greater reliability in spacecraft performance, and the  proposed solar panels seemed to the Source Evaluation Board somewhat fragile for the task of supplying energy to the spacecraft.13
Martin's proposal showed its most serious weaknesses in the areas of launch and flight operations and in the use of the tracking and data-acquisition facilities. The proposal stressed launch operation procedures over flight operations, and the description of both was ambiguous. Moreover, Martin had failed to include an integrated plan of the functions and responsibilities of NASA, Martin, the Deep Space Instrumentation Facility, and the Space Flight Operations Facility and their personnel. Finally, because of limited experience in spacecraft design and fabrication, Martin would necessarily have to rely upon subcontractors, and this could present NASA with major difficulties in the event that relations between Martin and its subcontractors became disturbed. This, according to the SEB, made the Martin proposal the least practicable from the standpoint of program management.14
The two remaining bidders-the Lockheed Missiles and Space Company and the Boeing Company-presented the  Source Evaluation Board with an interesting challenge. The former had long years of experience in designing and building the Agena system for the U.S. Air Force. Indeed, its Agena had served as a photographic platform in Earth orbit. The rocket and the photographic systems were well mated, making a very efficient spacecraft for work in orbit around the Earth. Lockheed proposed to convert this to an orbiter for lunar photography. It would consist of the Agena with integrated photographic, power, Communications, and attitude control systems. Lockheed stressed that the Agena had been proved in space and would require only minor modifications, thus making It unnecessary for NASA to buy a new, expensive, and untested spacecraft.15
The Boeing Company, on the other hand, could not make such an offer, since it had never managed a major NASA space flight program. Aircraft manufacture was Boeing's big business, but competition in the aerospace industry motivated the Seattle-based firm to turn toward space projects and to invest in new capital equipment in order to meet and excel in the increasingly competitive world of rocket research and space exploration. Indeed as part  of the USAF Project Dynasoar, Boeing had constructed its new Kent Facility for testing spacecraft components under simulated space environmental conditions. This capability would enable Boeing to conduct its own testing without costly delays caused by the necessity to send equipment elsewhere to be tested. (Project Dynasoar was canceled about the time NASA became seriously involved in a new lightweight lunar orbiter.)
The Source Evaluation Board saw the facility with which Lockheed's proposal might be implemented and realized that Boeing did not have as much experience in spacecraft design and fabrication. But the Lockheed proposal had some serious flaws which outweighed the attractive possibility that NASA might obtain a ready-made orbiter.
First, the existing Agena system was designed for Earth orbit, and it had proved its ability to perform there very well. But sending a spacecraft some 385 kilometers into space and putting it into orbit around the Moon was an entirely different undertaking, and the configuration of the Lockheed orbiter presented special problems related to this. Any lunar orbiter would be useless if it could not orbit the Moon as NASA scientists and engineers desired it to do. Moreover, any orbiter would be a waste of money if it could not perform the desired photography in the most efficient, reliable way possible with existing technology. The SEB believed that the use of  any incompatible hardware for such critical work would impinge upon mission assurance.
This being the case, the Source Evaluation Board found the concept of sending a modified Agena. rocket to do lunar orbital photography too impracticable, because the Lockheed orbiter presented the extreme difficulty of deboosting the heavy deadweight Agena into a lunar orbit. Once deboosting was accomplished, the spacecraft's orbit would create severe restraints on photography. NASA would have to go to unnecessary trouble to obtain vital photographic data of the lunar surface, and this fact made the Lockheed 16 proposal much less attractive.16
Yet the SEB found the Lockheed photo system to be almost ideally suited to its task. It was a space-proven package with the capability of performing high-quality stereographic photography. However, the proposed processing and readout systems would require more development before Lockheed could use them in an orbiter, and this meant extra time and funds to accomplish basic development work. Even if this were surmountable, the necessity to carry the heavy deadweight of the burned-out Agena to the Moon still remained the major negative factor of the Lockheed Orbiter. It would require extra fuel to control the useless  bulk in lunar orbit. Hardly any of the Agena's weight would be directly involved in vital mission activity, and yet its presence would definitely affect orbital parameters and spacecraft velocity to the extent of reducing the versatility of the orbiter as a photographic platform. These features made the Lockheed approach less acceptable than that of the final bidder.