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Development of a Mirror Pointing Mechanism for an Atmospheric Gas Measurement InstrumentDevelopment of the Open Path Tunable Infrared Monitor of the Atmosphere (OPTIMA) instrument involved designing a pair of motion systems that could maintain a precise alignment and spatial distance between two mirrors installed on the NASA DC-8 research laboratory aircraft. This is the first airborne optical instrument that allows direct measurement of the gases in the freestream airflow on the exterior of the aircraft. One mirror is mounted within a specially constructed open port cavity in the cabin of the aircraft and the second is mounted 6 meters away on top of the inboard port side (number 2) engine pylon. Three co-aligned laser beams are reflected between the two mirrors 64 times in a Herriott pattern. The resulting sample path length of 384 meters is used to perform a spectral absorption analysis of the airflow between the mirrors. To compensate for normal wing movement and engine oscillations both mirrors were designed as continuously driven mechanisms to maintain alignment within allowable limits. The motion systems of the two mirror assemblies provide five degrees of freedom and are designed to maintain a pointing accuracy within seven arc-sec with a response frequency in 6xcess of 10 Hz. The pylon motion system incorporates controlled pitch and yaw movement. The fuselage motion system compensates for pitch variation as well as linear translation for focal length and vertical aiming of the laser beam via a controlled beam guidance mechanism.
Document ID
20000021230
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Graham, Michael (Sverdrup Technology, Inc. Moffett Field, CA United States)
Belous, Adel (Sverdrup Technology, Inc. Moffett Field, CA United States)
Brown, Jeffrey (NASA Ames Research Center Moffett Field, CA United States)
Podolske, James (NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
September 7, 2013
Publication Date
February 20, 1998
Subject Category
Instrumentation And Photography
Meeting Information
Meeting: 32nd Aerospace Mechanisms Symposium
Location: Cocoa Beach, FL
Country: United States
Start Date: May 13, 1998
End Date: May 15, 1998
Funding Number(s)
PROJECT: RTOP 538-08-12-31
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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