QA4EO-ATLAS:
A pulsed Tuneable LAser system for the characterisation of Spectrometers

   
Minimize Objectives

The project aims at improving the accuracy of array spectroradiometers that are widely used for satellite validation of various atmospheric products. More specific, to measure the stray light and linearity of spectroradiometers and to develop algorithms and post correction functions in order to deal with major instrumentation uncertainties such as stray light and linearity. The methodology will be applied initially to two systems belonging to two different surface networks of atmospheric trace gas measurements.

O1: Establish a laboratory for the radiometric characterisation of spectroradiometers using tuneable laser sources, focussing on the straylight and linearity properties.

Tuneable laser systems have become the tool of choice for measuring the response of a radiometer to radiation at a given wavelength. While for a long time these systems have been only operated by very few national metrology institutes (NIST, PTB, NPL) due to their complexity and cost, current systems have become more robust and affordable. Now, with the availability of cost-effective solutions, tuneable laser systems can now be operated by specialised laboratories such as PMOD/WRC and applied to tasks outside of the limited scope of metrology laboratories. Specifically, it is proposed to develop the required infrastructure in view of applying it to remote-sensing instruments used in surface-based networks to measure solar radiation and atmospheric composition.

 

 

Tunable laser in operation

 

O2: Determine the nonlinearity and in- and out-range straylight of two array spectroradiometers used in the Pandonia and the Phaeton networks and develop corresponding correction methodologies.

The objective will be accomplished within two complementary work packages. The aim of WP2  is to provide radiometric characterisations of two remote-sensing systems operating within reference networks for the validation of Earth observing satellites. WP3 will develop methodologies to improve the current retrieval algorithms by taking into account the results of WP2 and to produce a comprehensive uncertainty budget for the radiometric component of the measurement process. This activity will be performed in close collaboration with the operators of the Pandora and Phaeton networks.
 

 
Tunable laser in operation
 
Minimize Overview

Surface-based optical radiation measurements are a key requirement for the validation of remote-sensing products from satellites. State-of-the-art systems consist of array spectroradiometers measuring solar radiation in the UV-VIS-NIR range in order to determine a large range of parameters, from surface radiation to atmospheric composition products such as total concentrations of trace gases as well as their profiles. In order to fulfil their role as reference systems for the validation of satellite products, traceable surface-based measurements to the international system of units are required, including a comprehensive uncertainty budget based on an extensive characterisation of the measuring system. One key aspect in this chain is the radiometric characterisation of the optical system, including its stray-light characteristics and nonlinearities in order to produce correction functions for these parameters.

 

The project consists of three Work Packages:

WP1: Commissioning of tuneable laser system.

WP2: Radiometric characterisation of array spectroradiometers using tuneable laser sources

WP3: Development of correction methodologies for stray light and linearity

 

The Phase 2 of the project (01/07/2016-31/12/2017) foresees the following three Work Packages:

WP4: Upgraded ATLAS Tunable laser facility

WP5: Radiometric characterisation of Pandora #120

WP6: Validation of total column ozone and AOD from one Pandora system

 

The Phase 3 of the project (01/01/2018-30/06/2019) is subdivided in two Work Packages:

WP6: Validation of total column ozone and AOD from one Pandora system

WP7: Characterisation and operation of three precision solar spectroradiometers (PSR) at PMOD/WRC for the retrieval of absolute spectral solar irradiance and spectral AOD

Minimize Schedule
Phase 1  
Due Date
(KO+#month)

Deliverable Description

 

Work
Packages

KO+3

Commissioning of the Laser system

WP1

KO+6

Tuneable laser system operational

WP1

KO+8

SOP for LSF and Oor stray light

WP1

KO+9

SOP nonlinearity

WP1

KO+12

LSF, Oor stray light and linearity determined for System 1.

WP2

KO+15

LSF, Oor stray light and linearity determined for System 2.

WP2

KO+12

Report on nonlinearity correction method

WP3

KO+16

Report on In-range and out-of-range stray light method

WP3

KO+16

Final report, Presentation

all

*SOP: Standard operation procedures, LSF: line spread function, Oor: Out of range 

 

 

Phase 2
Due Date

(KO+#month)

Deliverable Description

Work

Packages

KO+3

Report on the Wavelength calibration of ATLAS

WP4

KO+6

Report on the field homogeneity of the beam conditioning unit

WP4

KO+9

Certificate for Linearity correction function

WP5

KO+10

Report on Bandpass and Line-Spread function and determination of stray-light matrix

WP5

KO+10

Report on wavelength dispersion function

WP5

KO+11

Calibration certificate for spectral irradiance

WP5

KO+15

Dataset from one Pandora system deployed at PMOD/WRC

WP6

KO+18

Report on the comparison of the TCO with Dobson and Brewer

WP6

KO+18

Report on the comparison of AOD to the WORCC reference Triad

WP6

*TCO: Total Column Ozone, AOD: Aerosol Optical Depth, WORCC: World Optical Depth Research and Calibration Center

 

Phase 3

Due Date
(KO+#month)

Deliverable Description

Work
Packages

 

Report on initial spectral responsivity calibration of Pandora #120

WP6

 

Report on final spectral responsivity calibration of Pandora #120

WP6

 

Report on the comparison of the TCO with Dobson and Brewer

WP6

 

Report on the comparison of AOD to the WORCC reference Triad and PSRs

WP6

 

Report on first spectral responsivity calibration of PSRs (dataset)

WP7

 

Report on the uncertainty budget for spectral irradiance measurements with PSR

WP7

 

Report on uncertainty budget for spectral AOD retrieved from PSR

WP7

 

Report on second spectral responsivity calibration of PSRs (dataset)

WP7

*TCO: Total Column Ozone, AOD: Aerosol Optical Depth, WORCC: World Optical Depth Research and Calibration Center, PSR: Precision Solar spectroRadiometer

 

Minimize News

New ESKPLA Laser

26 August 2015

The ESKPLA Laser has been installed and is working. A presentation of the system features has been performed from EKSPLA representatives in August 26th. The presentation included: a description of all individual parts of the system, presentation pf the software used for PC based system operation, basic system operation and maintenance features. 

Kick of meeting of QA4EO-ATLAS

22 June 2015

The kick of meeting of QA4EO-ATLAS project was held at PMODWRC, Davos, Switzerland on June 22, 2015 with the participation of B. Bojkov (ESA), J. Groebner, S. Kazadzis and N. Kouremeti (PMODWRC).

ESA-ATMOS 2015 conference

08 June 2015

The Project overview and objectives have been presented in Advance in Atmospheric Sciences and applications ESA-ATMOS 2015 conference, Heraklion, Greece, 8-12, June, 2015