Researchers at NASA’s Armstrong Flight Research Center have identified and evaluated recently available miniature spectrometers that enable compact and robust pyrometry systems capable of measuring aircraft surface temperatures and emissivity during flight.

Radiometric temperature measurement system based on a digital light processing (DLP) spectrometer.

Pyrometers measure high temperatures by observing emitted radiation; however, aircraft vibrations can render unreliable pyrometer measurements made during flight. Armstrong researchers believe these miniature spectrometers will mitigate this problem by using digital light processor (DLP) technology to measure the intensity of multiple wavelengths in the near infrared (0.9-1.7 micron) range.

This work seeks to apply newly released, commercial components in a new way for which these systems were not originally designed. Developed for use in televisions, the DLP technology is used here within a robust scanning array that is nearly impervious to vibration and requires a single detector, as opposed to more complex, multi-element array detectors. The result is a mechanically stable device that is the first use of a spectrometer of this type for temperature measurements.

In addition, the DLP-based pyrometer allows for increased control over wavelength measurement in the near-infrared range via a digital interface. The measurement of multiple wavelength intensities combined with multi-spectral methods provides accurate calculations of an object’s emissivity and surface temperature.

The device is more compact than previous multi-wavelength pyrometers, and with its single detector rather than the array of detectors often present in conventional pyrometers, results in lower costs. The smaller size and robust nature of the new device allow it to be mounted onto various aircraft, providing engineers with an improved method for an in-flight temperature measurement system. Beyond its use in aviation, the DLP-based pyrometer has potential commercial applications for space exploration and in the glass, metal processing, and ceramics industries.

This work was done by Timothy Risch, Christopher Kostyk, and Jeffrey Beard of Armstrong Flight Research Center. For more information, contact the NASA Armstrong Technology Transfer Office at This email address is being protected from spambots. You need JavaScript enabled to view it.. DRC-017-009.