Highly folded 5 m Fourier transform spectrometer for spaceborne wind lidar

Area of Science:

• Spectroscopy
• Atmospheric science
• Optical engineering

Background:

• Wind lidar systems require precise atmospheric measurements.
• Fourier transform spectroscopy (FTS) offers high spectral resolution for wind speed determination.
• Existing FTS designs may face limitations in size, diffraction management, and sensitivity.

Purpose of the Study:

• To design and construct a prototype Fourier transform spectrometer (FTS) specifically for wind lidar applications.
• To address challenges related to instrument size, optical path management, and signal detection sensitivity.
• To enable more accurate and reliable wind speed measurements using lidar technology.

Main Methods:

• Developed a compact optical layout folding a 5.8 m maximum optical path difference into a 1.2 m cavity.
• Incorporated two confocal parabolas to counteract beam diffraction across the extended optical path.
• Utilized a photon-counting detector to achieve high measurement sensitivity.
• Employed a heterodyne technique to generate a reference beam collinear with the data beam for vibration compensation.

Main Results:

• Successfully designed and built a functional prototype FTS.
• The compact design integrates a long optical path within a reduced cavity size.
• Confocal parabolas effectively compensated for beam diffraction.
• The photon-counting detector demonstrated high sensitivity for signal acquisition.
• Heterodyne reference beam successfully mitigated mechanical vibrations.

Conclusions:

• The prototype Fourier transform spectrometer is suitable for wind lidar systems.
• The innovative optical design achieves compactness and manages diffraction effectively.
• High sensitivity and vibration compensation enhance measurement accuracy for wind profiling.