Desktop Instrument for Measuring Boresight Error as a Function of Incident Angle

TECHNICAL POINT OF CONTACT (TPOC)
Christopher Kuhs
Henry Everitt
PROJECTED CMMC LEVEL REQUIREMENT
Level 1
TECHNOLOGY AREAS
Air Platform
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Materials
MODERNIZATION PRIORITIES
Hypersonics
KEYWORDS
Optics; Boresight Error; Supersonic; Hypersonic; Infrared; Optical Aberrations; Instrumentation
OBJECTIVE
A benchtop instrument that measures boresight error and boresight error slope as a function of window temperature, temperature gradient, and angle of incidence
DESCRIPTION
The infrared (IR) tracking system of an interceptor vehicle works by determining the position of an object via the line of sight (LOS) between the vehicle and the object of interest and then feeding that information into the guidance system. In all cases there is a protective window or dome in front of the IR tracking system. If a temperature gradient is formed between the front side and the back side of this protective window, such as might occur in supersonic and hypersonic flight, the measured LOS between the vehicle and the object of interest will be different than the actual LOS, resulting in a missed interception. The degree of this difference is referred to as the boresight error, or BSE. To complicate matters further, as the vehicle's angle changes, the BSE also changes, by an amount characterized by a quantity referred to as boresight error slope or BSES.1 Negative BSES tends to prevent the guidance system from accurately compensating for the BSE. To overcome this challenge, the DOW is exploring solutions in a variety of disciplines, including novel ceramic materials to replace the protective window and thereby minimize the BSE and BSES. Current testing facilities to assess the BSE and BSES of such IR window materials include wind tunnel and flight tests. These are effective but very costly and have limited time availability. Therefore, to reduce risk when such high-speed air flow tests are performed there is a need for measurements without high-speed air flow in a benchtop laboratory environment. This solicitation seeks to develop and deliver a desktop testing apparatus that would allow for iterative testing of the BSE and BSES of unmounted and mounted window materials as a function of temperature, incidence angle, and temperature gradient without high-speed air flow for DOW applications in supersonic and hypersonic environments.
PHASE I
Design an instrument that accurately measures BSE and BSES of unmounted or mounted IR window materials (25-100 mm wide) as a function of angle of incidence (0 -75 ) and temperature (room temperature - 1200 C) at three wavelengths (633 nm, 4 m, 10 m). The design must include a computer and a user-friendly graphical user interface for operating the instrument and presenting the results, as well as appropriate lasers and detectors for each wavelength. The instrument must evenly heat each side of the sample to a set temperature, and a highly responsive proposal will design a means to create and measure a controlled temperature gradient between top and bottom surfaces of the IR window. Simulations will demonstrate proof of concept operation, and designs and mockups for the data collection and analysis software will be provided as the final deliverable.
PHASE II
Construct, characterize, and deliver a working instrument to measure BSE and BSES following the specifications provided and designs developed in Phase I. Performance will be demonstrated by accurately measuring BSE and BSES for unmounted and mounted IR materials as a function of angle, temperature, and temperature gradient. The instrument will be delivered to the Army Research Laboratory at the end of Phase II, along with documentation on safe instrument operation and standard operating procedures, ideally with troubleshooting guides and training manuals as well. Following delivery, a representative from the performer will travel to the Army laboratory to install the instrument and train users on its operation.
PHASE III DUAL USE APPLICATIONS
Benchmarking and validating the temperature-dependent performance of IR optics has wide use in commercial space flight and military applications. This can include space reentry vehicles or hypersonic vehicles. Therefore, a tool that allows for rapid testing of IR materials would have interest in aerospace companies as well as military entities such as the tri-services and the Missile Defense Agency. Consequently, a tool such as the one described in this solicitation would find widespread use in government and contractor laboratories. A successful Phase III would spell out a clear transition plan of a prototype instrument described and built in Phase I and Phase II to a market ready instrument.
REFERENCES
Kelso, J. Boresight error slope predictions versus flight test results in a hypersonic flow field. In Annual Interceptor Technology Conference, 1993 (https://arc.aiaa.org/doi/abs/10.2514/6.1993-2688).
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