Prototype for Multi-spectral Volume Scattering Meter (MVSM).
Reinart, Anu1; Reinart, Aivo1; Tõnnisson, Teofilus2; Kuuste, Henri1; Ligi, Martin1
1Tartu Observatory, ESTONIA; 2Interspectrum, ESTONIA

In the frames of ESA PECS for Estonia the project was funded "Services based on optical radiometery applications for aquatic environment- ORAQUA" for period 2011-2013.
The goal for the project is establishment of the Nordic reference testing center for optical parameters of aquatic environment relevant for remote sensing applications. Services include support to whole chain of ground measurements starting with instrument development, ensuring quality control and validation satellite products. Project will combine research competence of Tartu Observatory in remote sensing with expertise in photodetectors design as well as optical and FTIR spectroscopy instruments in Estonian companies. The international outcome will be reached through the ESA MERIS validation Team network.

The work is divided into three specific work packages (WP). WP1. Facilitating baseline optical laboratory for calibration and characterization spectroradiometers for validation satellite products.
WP2. Image analyses for validations and improving local algorithms
WP3. Development of unique equipment for multi-spectral volume scattering measurements (MVSM).

The MVSM instrument is intended to measure the volume scattering function of natural waters across a hemispheric angle range in up to twelve, narrow visible spectral bands down to 25m.
The tasks are: (1) Analyses of the availability of exciting experience, schemas and competences. Specify characteristics for design the instrument; (2) Development of optics, electronics and software for MVSM; (3) Producing one prototype of MVSM and user friendly sofware; (4) Comparison with modeling results, field tests and development.

First stage in a new multispectral volume scattering meter (MVSM) design was collecting user requirements and feasibility analysis of the requirements. Also analyses of optical and mechanical solutions of excisting multispectral volume scattering meters to measure the multispectral volume scattering function (MSVSF) has been carried out. As a result of analysis it was acknowledged that preference should be given to an optical scheme which uses a special periscope prism that allows the direct determination of the MSVSF over a wide range of angles (0.5° to 177.6°) with a high angular resolution (0.3°).
We present the first prototype of the instruments which has gone through laboratory test. Field tests in oceanographic towers and intercomparions will be made in this autumns.