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IT 

To: R. Geiger Date: 31 December 1968 

Subject: Dorian Blockll Study From: A. J. Boardman 

On 1Z December 19-68 we listened to Jim Collinge brief us on the results 

of the ONF four-month Phase I study of the potential improvements to the 

Dorian payload that might be incorporated in the second block of vehicles. 

The emphasis was clearly on improved resolution. In summary. Collinge 

concludeci that "significant" improvements are possible within the configuration. Specifically: 

a. Theillbaseline resolatinet cm)11.‘t be improved to by increasing the COF from percent, by decreasing the 

obscuration attributed to the spider holding the Newtonian flat, 

by making the Newtonian flat elliptical and beveling its edges, 

by making the tracking mirror elliptical, by optimizing the 

lens prescription. and by improving the shutter efficiency. 

These changes would re irenew test glass, new corrector 

elements, new War.% designs. ir.oinets, a new barrel yoke and 

drive, and improvement of manufacturing and test techniques. 

b. The ground resolution can be improved to by the 

addition of a partial field relay system which magnifies (ZX) 

the center of the format. It is interesting to note that the 

implications on smear rate requirements for this scheme 

are such as to show a re,soiution advantane of SO 121 (color) 

over 3404 at smear rates above per second. 

The resolution cart be further improved to by reducing 

the altitude. As far as I can tell this ten or so nautical mile 

reduction in altitude need not be specifically geared to Block II 

changes. 

Although we have not participated in this study, I feel obligated to offer 

my candid comments to the briefing. ONY initiated this study sometime 

after our interest peaked in the shallow angle intersection of the Dorian 

MT F and AIM curves. They, as well as we, are quite aware of the 

deleterious effects on resolution, contrast, and information content of an 

eine:re.:e 

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MTF curve which falls so drastically in the midfrequencies. Conversely, 

it is clear to all the large improvement potential of boosting the MTF in 

this region. Collinge, several times in his briefing, made references to 

this phenomenon when he indicated the various ways considered for improving 

contrast by reducing obscuration. He went into some detail about the one 

or two percent MTF improvement that could be obtained by redesigning 

the Newtonian spider. He had details on the improvements made by "streamlining" the Newtonian flat. He talked about the fact that some of these 

relatively minor improvements would seem much more significant at 

contrasts lower than 2:1. But he offered no significant means of boosting 

the values of MTF in the region of the AIM intersection. 

Dr. Meinel. Dr. Baker. and our own people have discussed somewhat 

enthusiastically the possibility of a redesigned optical system which causes 

the image of the primary mirror to converge at the folding flat to be then 

relayed through corrector elements to the focal plane. Such a concept 

allows large improvements in MTF by the virtual elimination of the large 

obscuration. This concept was not altogether unthought of at ONF. Collinge 

did mention that a relay system was considered as a means of doubling 

focal length. (To digress. increasing focal length in a highly smear limited 

system seems to be a questionable thing to consider but in partial answer 

to that Collinge discussed the possibility of decreasing the Zo smear rate 

from per second to per second.) ONF's 

investigation of a relay system left them with no design solution. Collinge 

stated that they developed the scheme to the point that they had a design 

which was not diffraction limited and had eleven refractor elements. In my 

opinion a more detailed investiaation should be conducted of this relay 

concept (but maintaining the effective focal length) in search of a low 

obscuration diffraction limited design. 

The Phase I study did not deal with any aspect of achieving thellibaseline 

resolution--perhaps understandably. But treating theMas an accomplished fact 

can lead to some unjustified conclusions. Consider_ 1-1Y way of example, 

the matter of OQF. Programming the OQF from-percent might be 

meaningful if percent were a demonstrated achievement throughout the 

lives of a fair number of Dorian payloads, and if the increase were to 

occur over a reasonable time base. Of course, this is not the case. Most 

of the work required to reduce the ground resolution from (above) 

is in many respects tantamount to building a new optical system. There 

certainly will be a discontinuity in the learning curve which is incompatible 

with any positive change in OQF. Therefore, the statement that.can be 

bettered by raising OQF is toothless. To minimize the expenditure of effort 

leading to recommendations of questionable practicality, I propose that 

theilnumber be thrown open to scrutiny in future phases of this study. Some 

portion of the Collinge effort should be addressed to an objective and 

detached view of the program, a determination of the phenomena most likely 

to prevent the achievement (and maintenance) of the promisedilland the 

definition of the hardware improvements desirable to cover all bets. 
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CoHinge recommended that follow-on study effort be directed toward the 

suggested modifications to the lens design. a better look at the 2X center 

format magnification scheme and further sensor work. I urge that the 

contractor be directed during the next phase of the program to investigate 

in depth the potential of the low obscuratioa scheme and the question posed 

in the preceding paragraph relative to obtaining and maintaining the 

promised 

j.J1).-- 

A. S. Boardman 

cc: R. Stephenson