Reticles designed with quartz bases are masked with desired pattern and then are coated with highly adherent layers of chromium, chromium silver alloy, silver, copper, and black chromium (mixture of chromium and chromium oxides). Black chromium final layer produces required nonreflective surface

Smith, W. O.

Toft, A. R.

English

NASA Technical Reports Server

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urn 
Copper
Alloy	 Base 
Figure 2. Reticle Segment Construction 
Figure 1. Finished Reticle Configuration
April 1974	 B73-10488 
•	 NASA TECH BRIEF 
Goddard Space Flight Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Process for the Production of Star-Tracking Reticles 
The problem: 
A star tracker was required as a component of the 
guidance system in an unmanned spacecraft. The design 
incorporated two counter-rotating reticles (Figure 1) 
that must operate at 2800 to 9000 rpm, without 
distortion, and withstand the effects of the spacecraft 
launch environment. Further requirements were that the 
reticles have a high level of transmission in the ultra-
violet and have nonreflective surfaces. 
The solution: 
. Reticles designed with quartz bases are masked with 
the desired pattern and then are coated with highly 
adherent layers (Figure 2) of chromium, a chromium 
silver alloy, silver, copper, and black chromium (a 
mixture of chromium and chromium oxides). The black 
chromium final layer (not shown in Figure 2) produces 
the required nonreflective surface.
How it's done: 
To form a reticle, a quartz blank is cut, ground, and 
ttern polished to obtain the optical properties required for the 
application. The reticle pattern is then produced in 
artwork form and is reduced to the size of the quartz 
blank. A beryllium-copper alloy substrate is fabricated, 
also to the dimensions of the quartz blank. Using the 
reticle pattern, a positive-working photoresist is applied 
to the beryllium-copper substrate, and the uncoated 
areas are then gold plated. The positive-working photo-
resist is removed and replaced with a negative-working 
photoresist, which is developed to expose the base 
metal of the pattern. The unplated side of the pattern 
is then chemically etched to produce the mask. 
The mask is then used in the vacuum deposition of 
the layers shown in Figure 2, plus a final layer of 
elect rodepo sited black chromium. The final product is 
as shown in Figure 1. Two of the reticles are used in a 
star tracker. They are superimposed and operate in 
counter rotation.
(continued overleaf) 
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	 Government assumes any liability resulting from the use of the Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19730000488 2020-03-17T07:34:43+00:00Z
Note: 
Requests for further information may be directed to 
Technology Utilization Officer 
Goddard Space Flight Center 
Code 207.1 
Greenbelt, Maryland 20771 
Reference: B73-10488
Patent status: 
This invention has been patented by NASA (U.S. 
Patent No. 3,702,808). Inquiries concerning nonexclusive 
or exclusive license for its commercial development 
should be addressed to: 
Patent Counsel 
Goddard Space Flight Center 
Code 204 
Greenbelt, Maryland 20771 
Source: Albert R. Toft and Wade 0. Smith 
Goddard Space Flight Center 
(GSC.1 1188) 
B73-10488
	 Category 03, 04, 08
	
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Process for the production of star-tracking reticles

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