Dumont d'Urville (Antarctica)
The French Antarctic station Dumont d'Urville is located on Petrels island (66°40'S, 140°01'E), 5 km from the continent and is supplied by the polar ship Astrolabe only during summer campaigns (November to February).
Logistics and the implementation of scientific programs are managed by the French Polar Institute Paul-Emile Victor (IPEV). The station can accommodate up to 30 during the winter. Ice and strong katabatic winds often prevent landings, either by Zodiac or by helicopter. In summer, a maximum of about 100 persons can be accommodated.
The French stratospheric monitoring program: NDACC measurements
Since 1989, France leads a monitoring program investigating human influences on the Antarctic polar stratosphere. A set of instruments designed to measure ozone and parameters linked to its chemical equilibrium were implemented on the French Antarctic base, Dumont d?Urville. The IPEV provides recurrent funding and logistics. The program is a key element of the Network for Detection of Atmospheric Composition Change.
NDACC station instruments include:
- Aerosol-PSC lidar (since 1989)
- Temperature lidar (since 2006)
- Ozone lidar (1992-2000 and since 2008)
- SAOZ (UV-Visible spectrometer, since 1988)
- Balloon ozone sondes (since 1993)
- UV-B detector (since 1995)
NDACC Lidar implementation history
NDACC Lidar system description
In this frame, ground-based lidar aerosol and PSC observations were first conducted within POLE (Polar Ozone Experiment), a French-Italian collaboration between the Service d?Aéronomie-IPSL and the IROE-CNR. In 1989, a backscatter lidar to measure stratospheric particles was implemented. In 1991, this lidar became a multi-wavelength system allowing sequential observations of the vertical distribution of ozone and stratospheric particles. Failures of this out of date instrument forced to completely stop ozone measurement in 2000. Stratospheric particles observations continued, but were almost unexploitable.
A new instrument was then studied, since 2002, within a new French-Italian collaboration between Service d?Aéronomie-IPSL (LATMOS-IPSL since 2009) and ISAC-CNR. Named LOANA (Lidar Ozone and Aerosols of NDACC in Antarctica), this new lidar system in Dumont d?Urville includes the upgrade of the aerosol/PSC lidar, of the ozone lidar and addition of a temperature lidar. Field implementation started in 2005 for a one year test. Stratospheric particles and temperature measurement are operational since 2006. Ozone measurements only started in 2008, due to THG (Third Harmonic Generator) and PM (Photo-Multipliers) failures. Today, this lidar system is the most complete and is unique on the Antarctic continent. In particular, the ozone lidar in Dumont d?Urville was and is now again the sole instrument of that type running in an operational mode in Antarctica.
The LOANA system in Dumont d?Urville is able to measure sequentially aerosol/PSC/temperature on the one hand, and ozone on the other hand. Some parts of the instrument are common to both type of measurements and some are specific (see below).
The aerosol/PSC/temperature lidar is a backscatter Rayleigh-Mie lidar designed to observe particles in the lower stratosphere, roughly between 8 and 32 km and to measure upper stratospheric temperatures at altitudes higher the 30 km. It is very similar to the McMurdo instrument, as it was build within collaboration with the Italian group in charge of the McMurdo system.
LOANA emits at the wavelengths of 532 and 1064 nm using an Nd:YAG 10 Hz pulsed laser. The optical path is manually changed using a switch box for aerosol/PSC/T and O3. For the ozone retrieval, there is a third harmonic generator after the switch box.
The emission is biaxial (~ 60 cm out of alignment) and a beam expander is used to get 0.5 mrad beam divergence. The system has a 80 cm Newton telescope and a mechanical obturation (chopper) to eliminate the signal at 0-5 km.
First wavelength separation that takes place splits the return signal into UV wavelengths (for ozone) and wavelengths other than UV (for aerosol/PSC and temperature). Signal acquisition is in analog mode at 1064 nm (15 m vertical resolution, 2048 points) and is in photon-counting mode for all other wavelengths (60 m vertical resolution, 2048 points).
|Aerosol/PSC and temperature specific parts
||Ozone specific parts
- High 532 nm channel (for temperature)
- Low 532 nm channel, 10% of the high channel (for aerosol/PSC)
- 608 nm Raman channel
- 1064 nm Infrared channel
|Separation Box using a spectral grating:
- High 308 nm channel
- Low 308 nm channel
- High 355 nm channel
- Low 355 nm channel
- 331 nm Raman channel
- 387 nm Raman channel
|New Hamamatsu photomultipliers for 532 nm and 608 nm
||Old Hamamatsu photomultipliers