The IAP operates two similar potassium lidars for temperature, density and NLC profiling in the Mesopause region (about 80 – 105 km). The stationary lidar is located at the IAP (54°N, 12°E) whereas the mobile lidar is operated at remote locations.
The potassium lidar is designed to probe the terrestrial potassium atom layer using the K(D1) resonance wavelength. Over the distance of 80 - 110 km it performs a remote spectroscopy of the potassium layer. Thus, scanning the Doppler broadened hyperfine structure it measures a height resolved picture of the thermal movement of the atoms. From this picture the temperature profile can be calculated.
The heart of the transmitting unit as shown in the right column is a specially developed solid state alexandrite laser, emitting light pulses with the necessary properties. The wavelength is controlled by the seederlaser and measured for every single laser pulse with the spectrumanalyser. Since 2000 the receiving unit is equipped with a daylight filter which allows measurements under full daylight conditions.
|Laser active material||2 alexandrite crystals, Cr3+ :BeAl2O4|
|Geometry||ring resonator, unidirectional|
|Wavelength||770 nm, tunable|
|Bandwidth||<< 20MHZ (FWHM)|
|Repetition rate||35 pulses per second|
|Energy jitter||5% (1σ)|
|Pulse length||250 ns (FWHM)|
|Beam width||2.5 mm, behind AWT 6.7 mm|
|Beam divergence (full angle)||0.45 mrad, behind AWT 0.3 mrad|
|Telescope||d = 80 cm, f = 199.5 cm|
|Field of view||192 µrad|
|Broad band filter||IF filter (1nm, Τ=70%)|
|Narrow band filter||2 potassium FADOF (1800 G), 124° C, T = 75%|
|Band width (FWHM)||6.7 pm|
|Temperature shift||±0.5 K|
|Photon efficiency||68% @ 770 nm|
Dr. Josef Höffner
- Tel. +49 (0) 38293 68 130
- Fax +49 (0) 38293 68 50