Observatoire Haute Provence (France)
This page describes the instruments present at Observatory de Haute-Provence (OHP).
Rayleigh-Mie-Raman LidarOzone DIAL lidar for the stratosphere
The first measurements of routine temperature were obtained in 1979 with a preliminary instrument also used for ozone measurements. Several improvements have been made since this date: a second channel for Rayleigh scattering , Raman channels for Nitrogen (1999), and water vapour. The pulse source is a Continuum Neodyme:YAG laser using a harmonic generator for providing the second harmonic at 532 nm. It provides 350 nm at 50 Hz. One receiver is composed by a mosaic of 4 parabolic mirrors of 500 mm diameter dedicated for Rayleigh scattering from high altitude, and a telescope of 800 mm diameter for the Raman signals and 2 telescopes of 200 mm diameter respectively for aerosols and the lower sensitivity Rayleigh channel used for the lower range. The photons were collected, using optical fibers. Photon counting were insured using photomultipliers (PM) of Hamamatsu R1477S.
This system allows measuring the ozone profile in the stratosphere (10-50 km) using the DIAL technique. Both wavelengths used have been generated with two different lasers. The third harmonic of a Nd/Yag (Neodyme-Yag) at 355 nm (50 Hz, 60 mJ par pulse) have been used for the non-absorbed wavelength. An excimer laser at 308 nm (100 Hz et 200 mJ par pulse) is used for the absorb wavelength. The receiver is composed of a mosaic of 4 telescopes of 500 mm diameter. Optical fibers at each telescope's focal point collect the backscatter light up to the (Jobin Yvon) spectrometer used to separate the different wavelengths including the Raman shifted lines that are used for the lower range where aerosols are present. Glass beam splitters (8% - 92%) are used to provide low sensitive channels for covering the whole dynamic of the signals. Photon counting is insured with a LICEL system. A mechanical chopper made with a rotating disc (24000 rps) is used to prevent the saturation of the photomultiplier by the large initial burst.
The tropospheric ozone DIAL lidar
This system is dedicated to the tropospheric ozone (3-12 km) and has been installed since 1988 and provides routine operation since 1990. As the stratospheric system it is using the DIAL technique. Different wavelengths have been used to provide a higher sensitivity in a region where ozone density is small. The both wavelengths (289 and 316 nm) are performed using the fourth harmonic of a Nd/Yag laser (0,8 W at 266 nm, 20Hz). Both wavelengths have been generated by the Raman shifting technique in a cell containing 30 bar of a gas including Helium (289 nm) and Deuterium (316 nm). The receiving telescope has a diameter of 800 mm and the wavelength separation is done using a spectrometer similar to the one used for the stratosphere. Analog channels are also used for the lower altitude channels.
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