Precision laser tracker capable of tracking a low acceleration target to an accuracy of about 20 microradians rms is being constructed and tested. This laser tracking has the advantage of discriminating against other optical sources and the capability of simultaneously measuring range

Lang, K. T.

Lucy, R. F.

Mc~gann, E. J.

Peters, C. J.

English

NASA Technical Reports Server

December 1966	 Brief 66-10629 
NASA . TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Precision CW Laser Automatic Tracking System Investigated 
Retroreflector 
On Target I 
Beam Collimation
Atmospheric 
Path 
Electro-OpticOptics 
HeNe Gas Laser Modulator 
Range 
Photomultiplie;r 
Filter
Tracking 
Mirror 
And 
Mount 
Parabolic	 Filter 
Collector
Tmage
Spotting 
Mirror	 Periscop
I	
O I Dissector	 perators 
	
Photomul-j	 Eye	 -
Manual 
Acquisition 
Control
Servo 
Control 
System 
	
A precision laser tracker has been constructed 	 of this system is approximately 3 x 10_b watts/ 
	
and tested which is capable of tracking a low accelera- 	 meter2 ; the ultimate nighttime sensitivity is approxi-
	
tion target to an accuracy of about 20 microradians 	 mately 3 x 10-14
 watts/meter2. 
	
rms. In tracking high acceleration targets the error 	 Experimental tests were performed to evaluate both 
	
is directly proportional to the angular acceleration.	 dynamic characteristics of 'this system and the system 
	
For an angular acceleration of 0.6 radian/second2 	 sensitivity. Dynamic performance of the system was 
	
the measured tracking error was about 0.1 milliradian. 	 obtained using a small rocket covered with retrore-
	
The basic components in this tracker, similar in 	 flective material launched at an acceleration of about 
	
configuration to a heliostat, are a laser and an image 	 13 g at a point 670 feet from the tracker. The day-
	
dissector, mounted on a stationary frame, and a servo 	 time sensitivity of the system was checked using an 
	
controlled tracking mirror. The daytime sensitivity	 efficient retroreflector mounted on a light aircraft. 
(continued overleaf) 
WE
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Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
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This aircraft was tracked out to a maximum range 
of 15 km which checked the daytime sensitivity of 
the system measured by other means. The system has 
also been used to passively track stars and the Echo 
I satellite. The system also passively tracked a +7.5 
magnitude star, and the signal-to-noise ratio in this 
experiment indicates that it should be possible to 
track a + 12.5 magnitude star. 
The tracking accuracy against low acceleration tar-
gets is comparable to the accuracy of a star tracker. 
However, the laser tracker has the added capability 
of measuring range to the target. The accuracy ex-
ceeds that which can be provided by a high perform-
ance radar. 
Interest in high precision tracking results from the 
instrumentation tracking requirements that arise at 
the missile ranges and other test stations. The advan-
tage of optical tracking over radar tracking is that it 
is not affected by undesired reflections from surround-
ing objects, and the accuracy is somewhat less affected 
by variations in the index of refraction of the atmos-
phere. Laser tracking, as contrasted to passive optical 
tracking, has the advantage of discriminating against
other optical sources and also has the capability of 
simultaneously measuring range. High precision track-
ing is also a necessary part of long-range optical com-
munications which can be efficiently accomplished 
only by using very narrow beams. 
Note: 
Additional details are contained in the report: 
"Precision CW Laser Automatic Tracking System," 
by R. F. Lucy et al, Sylvania Electronic Systems, 18 
November 1965, which is available from: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10629 
Patent status: 
No patent action is contemplated by NASA. 
Source: R. F. Lucy, C. J. Peters, 
E. J. McGann, and K. T. Lang 
of Sylvania Electronic Systems 
under contract to 
Marshall Space Flight Center 
(M-FS-1606) 
Brief 66-10629	 Category 01


Precision CW laser automatic tracking system investigated

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