VAHCOLI

Lidar array

VAHCOLI (Vertical And Horizontal COverage by LIdar) is one of IAP’s new concepts for investigating the middle atmosphere in four dimensions. In the future, a network of distributed compact lidars with multiple fields of view will be set up to investigate small- to large-scale atmospheric processes. Several systems are currently being built to better understand the atmosphere, especially its dynamic and thermal structures, as well as the layer coupling. The concept, its importance for various geophysical questions, and newly developed components are publically available (See references to publications below).

Versatile lidar platform

The Institute developed a 1 m³ versatile transportable Doppler lidar platform (250 kg; 500 W) for VAHCOLI. The first prototype of a compact lidar unit was sucessfully build and tested and includes components for automatic operation. The housing and optical system (patent pending) were 3D printed in large part.

The system is capable of studying Mie scattering (aerosols), Rayleigh scattering (air molecules), and resonance fluorescence on free potassium atoms in the middle atmosphere. Unique spectral methods allow precise wind, temperature, and aerosol measurements. This study uses laser spectroscopy to study the Doppler shift and broadening of scattered signals. The optical system's small spectral width leads to high quality measurements even during daytime. For the versatile lidar units, IAP developed, implemented, and tested novel components: (1) a diode pumped tunable alexandrite laser (in cooperation with ILT), (2) Doppler-free spectroscopy on potassium as a wavelength reference, and (3) high speed frequency stabilisation techniques. The spectra of various optical components of the lidar platform, and the atmospheric Doppler spectra are aquired about ten times per second. These extensive spectral informations are used permanently for laser and filter frequency stabilisation as well as for atmospheric measurements.

The IAP is currently assembling several upgraded lidar units to implement VAHCOLI. The alexandrite laser's extensive range of accessible wavelengths (about 700 nm to 800 nm) allows the lidar platform to be applied for other atmospheric research applications in the future. Diverse projects involve industry in technology transfer to promote, apply and spread the developments at IAP. The project ALISE has shown that components of the versatile lidar platform are suitable for future space missions. VAHCOLI will enable distributed lidar measurements of large and small-scale phenomena in the middle atmosphere with high spatial and temporal resolution at altitudes not covered by any other technique.

• J. Froh, J. Höffner, A. Mauer, T. H. Mense, R. Eixmann, F.-J. Lübken, A. Munk, M. Strotkamp und B. Jungbluth, Aerosol measurements in the tropo- and stratosphere by spectral splitting of Rayleigh and Mie signals within a compact lidar of 1m³, SPIE, 12265, doi:10.1117/12.2636289, 2022.
• F.-J. Lübken und J. Höffner, VAHCOLI, a new concept for lidars: Technical setup, science applications, and first measurements, Atmos. Meas. Tech., 14(5), 3815-3836, doi:10.5194/amt-14-3815-2021, 2021.
• J. Froh, Dissertation, Entwicklung spektraler Messmethoden für Doppler-Lidar, Universität Rostock, doi:10.18453/rosdok_id00003422, 2021
• J. Höffner, J. Froh, T. Mense, A. Mauer, M. Strotkamp, A. Munk, B. Jungbluth and H.-D. Hoffmann, Ground-based general-purpose Doppler lidar: A technology for Doppler aerosol measurements and beyond, International Conference on Space Optics, 11852, doi:10.1117/12.2599364, 2021.
• A. Munk, M. Strotkamp, B. Jungbluth, J. Froh, T. Mense, A. Mauer and J. Höffner, Rugged diode-pumped Alexandrite laser as an emitter in a compact mobile lidar system for atmospheric measurements, Appl. Optics, 60(16), 4668-4679, OSA, doi:10.1364/AO.422634, 2021.