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(S) NATIONAL RECONNAISSANCE OFFICE

. (.1 WASHINGTON. D.C.

THE NRO STAFF 19 February 1974

MEMORANDUM FOR MR. SINGEL

SUBJECT: High Oblique Sensor Briefing

Bob:

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We have reviewed the briefing charts from

are applying contemporary white-world technolo to a generalized aircraft problem. A semiconductor array is used to

line-scan the scene and the output is stored on magnetic tape.

A photodiode array is used to transfer the image back to film

for analysis.

The primary customer for the pitch ought to be the Air

Force Avionics Lab. The NRO, the Avionics Lab, and OD6E are

all aware of the technology evident in this proposal.

For your convenience, the attached sheet summarizes the

performance claimed. Note that little technical detail was

given - not even the type of semiconductor array nor array

geometry.

Brigadier General, USAF

Director

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Attachments

Summary Sheet

Additional Considerations

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OBLIQUE SENSOR'

•Scanned array operating in visual region cutting off in blue.

Type of semiconductor and array geometry are unspecified.

Signal-to-noise quoted @ 600:1, but SNR not defined.

Aperture is 18 inch, 223 inch focal length, f/12.4.

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Resolution appears to b t.

Diode array used to transfer data back to film image.

Overall Evaluation:

The contractor has applied contemporary white technology of a generalized aircraft problem, and has taken

a sensible systems approach. While it is difficult and

probably not even productive to attempt to define the

detailed operating parameters of the proposed system,

the contractor could probably be quite clever, given a

specific operational problem.

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HIGH OBLI UE SENSOR

ADDITIONAL CONSIDERATIONS 

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While it is agreed that the fundamental technology noted could

be applied, there are some additional pragmatic considerations

to address:

1. a following table lists various parameters based on

the paper when applied to aircraft at various altitudes

and at 50 NM:

A/C ALTITUDE OBLIQUITY ANGLE AT A/C GRAZING ANGLE AT TARGE

5 NM (30K ft) B4.50 5.50

10 NM (60K ft) 78.50 11.5°

15 NM (90K ft) 73.5° 16.5°

As can be deduced from the table, the 5 NM altitude

provides a 5.5° grazing angle at the target. Such a low grazing

angle raises several questions as to the imaging effectiveness

considering target aspect and ground/object blockage. For

instance, at the 16.5° grazing angle, a 100 ft tall object would

block the view of an object 300 ft away; or a 10 ft object would

block the view 30 ft or less away. At lower grazing angles it

is worse.

With increasing altitude, the grazing angle becomes

Somewhat more tractable, although still of concern. However,

a new variable is added at the higher altitudes - clouds

and cloud heighths. Nominally, cloud tops peak at approximately

50,000 feet. Thus, the range of cloud layering can be portrayed

in the 3rd dimension as ranging from nominally 2,000 to 50,000

feet, with individual clouds having thicknesses of nominally

2,000 to 30,000 feet. Thus, the clouds as opposed to haze or

gazing angle may block some of the desired high o

0 is some evidence that the use of

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It should be noted that the

EDI sensor is a high resolution,

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June 1973. The LMSC

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On 1 etary &Lucas approved a memo which undertook

a fund* vestigation of reconfiguring the. SR-71/XF-12

for four . One mission was to "monitor a configuration

of Warsaw Pact forces vs NATO foces in Eastern Europe" in a

near-real-time context. Program D is the manager.,

Six more points are germane:

LMSC used a 1.8X conversion f en GSD and GRD.

If indeed the LMS r holds, the ffective GRD

would approximat It at 50 NH.

oach would not, evidently, be able to

image at 1 5 NM range. This would appear to be an

undue operational inflexibility. It leads to a b y data rate

(56 obits) which precludes "close in" coverage.

It should be recognised that "contrast stretch" enhancement

is not the province of ELI alone. A possibly parallel improvement

ised on film if it is but applied, Note that the

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is assumed at 600:1. This corresponds to 28 db power

"Everyday" film has 20-25 db. If Free Radical turns out

well, it might have a 40-50 db range and very low noise characteristics.

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4. NRT imaging can be of definite assistance to A/C reconnaissance.

Care must be taken, though, in assessing the presumed results and/

or effectiveness and the degree to which film is dismissed.

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