Basic component of system is infrared spectrometer designed for manual target acquisition, pointing and tracking, and data-take initiation. System incorporates three main subsystems which include: (1) viewfinder telescope, (2) control panel and electronics assembly, and (3) IR-spectrometer case assembly

Casey, W. L.

English

NASA Technical Reports Server

April 1975	 B75-10040 
NASA TECH BRIEF 
Lyndon B. Johnson Space 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. 
Viewfinder/Tracking System for Skylab 
A viewfinder/tracking system (V/TS) was develop-
ed as a part of an Earth-resources experiment 
package (EREP) for the Skylab program. The basic 
component of the system is an infrared (IR) 
spectrometer designed for manual target acquisition, 
pointing and tracking, and data-take initiation. The 
spectrometer system is guided with a two-axis hand 
controller operating two servos. It is rate-aided in 
pitch to provide rapid uniform scanning, and it
contains sufficient magnification and resolution to 
acquire a 1-second spectral scan of 1 square nautical 
mile (3.6 km2), by pointing a 1-milliradian field of 
vision at the center of the target. 
The system incorporates three main subsystems 
which include: (1) a viewfinder telescope, (2) a control 
panel and electronics assembly, and (3) an IR-
spectrometer case assembly. 
Camera	 .- Head Rest 
Hand	 \ tiir 
Controller V/TS 
Electronics 
V/TS Control :.::.:.i:} :: .: Electrical 
Panel	
-.i-j J / Fee dthroughs IR Spectrometer 
Telescope Electronics 
MDA Window
MDA 
Skin 
Base 
Plate 
^4 Optical 
Gimbal Mounting 
Assembly L Bench 
Gimbal
j//f'
IR 
Allnenn ent . 
Prism Pickoff 's,cassegrain 
Mirror Optics 
Black	 Collimator 
Body 
IR Spectrometer Case Assembly 
iI Control Panel Electronics Assembly 
Telescope Assembly
Viewfinder/ Tracking System
(continued overleaf) 
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The viewfinder telescope is a variable power 
telescope with a reticle reference boresighted to the 
spectrometer line of sight. Magnification power is 
changed by a manually-controlled but electrically-
operated zoom lens (10 to 1 ratio). Low magnification 
provides wide latitude in target acquisition, and high 
magnification provides fine pointing and tracking. 
An integrally-mounted camera optics provides an 
optical image, taken from the telescope field of view, 
for photographing by a data-acquisition camera or for 
viewing by a color-television camera. Only one of the 
two cameras is mounted on the optics housing at one 
time. 
The viewfinder control and display panel houses a 
hand controller and other necessary controls and 
displays, to actuate and operate the V/TS, 
The control panel and electronics assembly contain 
tracking reference position loops, feedback networks, 
and servo-amplifiers that arc necessary to position the 
gimbaled mirror assembly. The electronics also 
provide image-motion compensation drive to the 
gimbaled mirror assembly in the along-track axis. 
The IRspectrometer assembly is externally mount-
ed to the multiple docking adapter (MDA), and it 
contains the gimbaled mirror assembly, a cassegrain 
optics system, a pickoff mirror, and a collimator. 
The gimbaled mirror is an elliptical plane mirror 
mounted in a two-axis gimbal configuration; the 
crosstrack gimbal rotates inside the along4rack 
gimbal. The viewfinder optic axis coincides with the 
spectrometer optic ads. The mirror is driven in both 
axes by servodrivers to permit acquisition and 
tracking of ground targets. It is controllable through a 
range necessary to permit the line of sight to be 
directed 10° aft, 45° forward along the ground track, 
and ±20° across the ground track. 
The cassegrain optics system consists of primary 
and secondary mirrors suspended on a framework, 
which serves to fix the relationship between the two 
mirrors. The framework also provides a means of
adjustment for the assembly, to permit focusing the 
total collected energy on the IR-spectrometer ob-
jective. A 45° pickoff mirror is mounted on the same 
framework as the cassegrain-system secondary 
mirror, to allow ground-scene viewing with the 
telescope and boresighting the viewfinder telescope to 
the spectrometer optical axis. 
The collimator, which consists of two lenses, a 
mask target, and a light source, supplies a two-degree 
(full-field diverging beam) image of the mask to a 
dual 450 prism located in the center of the blackbody 
reference source. 
Notes: 
1. The described system can be modified for aircraft 
to study atmospheric, oceanographic, pollutant, 
and geological targets. 
21 This system is described in the following reports: 
Reference: NASA CR-133967 (N73-73509) 
Ground Operating and Handling Procedure 
for Viewfinder/Tracking System 
Single document price $5.25 
(or microfiche $2.25) 
Reference: NASA TMX-69040 (N73-70355) 
Skylab Experiment Operations Handbook 
Single document price $3.2 
(or microfiche $2.25) 
These reports may be obtained from: 
National Technical Information Service 
Springfield, Virginia 22151 
Patent status: 
NASA has decided not to apply for a patent. 
Source: W. L. Casey et al. of
Martin Marietta Corp.
under contract to
Johnson Space Center 
(MSC-14407)
. 
. 
. 
B75-10040
	 Category 03 (Physical Sciences)


Viewfinder/tracking system for Skylab

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