What is an aerosol?
An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or anthropogenic.
See : https://en.wikipedia.org/wiki/Aerosol
What is a photometer? What does it measure?
A CIMEL CE318T photometer proposes three different types of measurement.
1. Direct Sun measurement to provide the spectral Aerosol Optical Depth (AOD)
2. SKY measurement (Principal Plane, Almucantar or hybrid): The instrument points in a set of specific direction to explore a range of scattering angle to help recovering the scattering phase function of the aerosol. At the end of the process, it help determining the Volume Size Distribution (VSD) of the aerosol.
3. Direct Moon Measurement: it is the same as the Sun direct measurement but pointing at the Moon. The main difficulty being that the Moon irradiance is varying depending on the time and position and is also very low compared to the sun irradiance.
Regarding the wireless data transmission through satellite, is it part of the system or this is provided with extra cost?
The instrument works with geostationary satellites MeteoSat, Goes, GMS .. The user has to ask to the satellite manager to obtain a channel. The transmissions period has to be 30 minutes on MeteoSat or 1 hour on Goes. In both cases the instrument has to transmit about 1200 characters / hour.
How can the data be retrieved (from the internet or do we need to install another receiving antenna) ?
On MeteoSat, data can be retrieved on Eumetsat web site. It should be the same for other satellites too.
Regarding the data transmission via RS232 cable, do you provide the cables according to the required length?
Yes, CIMEL provides the cable according to the required length with a maximum length of 100m
What is the Cimel CE318-T product power consumption ?
The power consumption is < 2W.
Is there a possibility to have data transmitted wirelessly via GSM modem?
The instrument can send data by GSM on a FTP site.
How is the data managed inside? How often do we need to download the data?
The instrument has a 8 Go SD card standard which can store years of data. There is no limitation of the storage capacity. When the instrument is connected to the PC by usb the SD card is viewed as a hard disk, mass storage.
What is the difference between the Factory calibration and the AERONET calibration ?
When the photometer is manufactured, a factory calibration is operated allowing it to be functional and to perform measurement campaigns on our IAAMS software. The AERONET calibration allows the photometer to be integrated into the NASA AERONET network, the worldwide federation of networks dedicated to the measurement of atmospheric aerosols and federated by the NASA. The major distinction is your decision whether or not to integrate your instrument into the AERONET network.
Technically CIMEL and AERONET calibration are almost similar. The only difference is that AERONET wants to handle the calibration themselves in order to accept an instrument in its network.
What is a LiDAR ? How does it work ?
A LiDAR is like a RaDAR working in the optical domain. It emits light pulses that are scattered by the particles in the atmosphere. A tiny amount is sent back to the instrument (backscattering) and measured. The time of the backscatter signal is linked to the distance, so the LiDAR provide a profile of the backsattered signal.
Why adding a low altitude extension module ?
This module provide particles concentration distribution at low altitude. If the Telescope can detect backscattering from 5km up to 20km, the low altitude extension module can detect backscattered signal from 50m to 6 km. This option is available for below Planetary Boundary Layer measurements.
What is the difference between an eye-safe and non eye-safe LiDAR ?
Eye-safe : It is a system which is eye-safe according to the EU standard for laser safety NF_EN_60825_1_A2. However, the more powerful the laser, the farthest the detection range.
What are the advantages of a depolarization channel ?
Depolarization provides a measure of how non-spherical particles are. This can enable distinction of spherical water droplets from volcanic ashes or aerosol particles.
Why a dual-wavelength LiDAR ?
Scattering is depending on the ratio of the size of the particle and the wavelength. Multiple wavelength detection therefore allows a measure of relative particle size distribution and of Angström coefficient.
Why combining the LiDAR and the photometer?
To retrieve the aerosol extinction profile with a single wavelength LiDAR, another set of information is needed such as the AOD. Combining the two instruments helps providing the VSD, the extinction profile, the backscattering profile, and if the density is known, the vertical distribution of the mass concentration. One derivative of the mass concentration is the PM2.5 and PM10 mass concentration.
What a radiometer is used for?
CE312 is a thermal radiometer. It measures the radiation between 8 and 15 µm (the thermal band). Once calibrated, the instrument provides the brightness temperature and the spectral radiance of the target (cloud, solid target, …).