“traceability for surface spectral solar ultraviolet ... · pdf file“traceability...

EMRP ENV03

“Traceability for surface spectral solar

ultraviolet radiation”

Julian Gröbner

Physikalisch-Meteorologisches Observatorium Davos, World Radiation Center,

Davos Switzerland

The European Metrology Research Programme (EMRP) is jointly funded by the EMRP

participating countries within EURAMET and the European Union.

Duration: August 2011 to July 2014

Total Budget: 3.9 M€

Project coordinator : Julian Gröbner Davos, Switzerland

8 Partners from European Metrology Institutes and 2 from Industry

4 Researcher Excellence Grants (REG) from Universities & Health Institute

6 Collaborators

Project Overview

http://projects.pmodwrc.ch/env03/

Motivation

Challenges

Large natural variability

Dynamic range >105

Radiation levels as low as µW m-2nm-1

Wavelength uncertainty <0.02% (0.05 nm)

500

10

Project Objectives

• Enhance the reliability of spectral solar UV radiation measured at the Earth

surface

• Improved SI traceability, improved methodologies, improved devices

• Uncertainties better than 2% in the wavelength region 300 nm – 400 nm

(current state of the art is 5%)

• Develop techniques and devices for using cost-effective array-

spectroradiometers for solar UV measurements

Primary Irradiance

Standard

Transfer Standard Reference

Spectroradiometer

End-User Devices Calibrated UV Network

WP WP Name WP Leader Active JRP Partners

WP1 Spectral Irradiance Traceability

Saulius Nevas PTB, METAS, SFI Davos, VSL, Kipp

WP2 Array Spectroradiometer Characterisation

Peter Blattner METAS, Aalto, LNE, PTB, PMOD/WRC, VSL, REG(IMU)

WP3 Improvement of Reference Spectroradiometers

Marek Šmíd CMI, INRIM, PTB, PMOD/WRC

WP4 New Technologies Petri Kärhä Aalto, CMI, METAS, INRIM, LNE, PTB, PMOD/WRC, CMS, Kipp, REG(IMU)

WP5 Impact Julian Gröbner PMOD/WRC, All

WP6 Management Julian Gröbner PMOD/WRC, All

Project Structure

Devices:

• UV LED-based transfer standards (WP 1)

• Transfer standard based on Laser Driven Light Source LDLS (WP 1)

•Wavelength scale characterisation devices (WP2)

•Solid state detectors to replace PMTs (WP 3)

• Modified Fourier-Transform Spectrometer (WP 3)

• UV hyperspectral imaging camera (sky radiance) (WP 4)

• Global input optics (improved diffuser design) (WP 4)

• Two array spectroradiometers optimized for UV (WP 4)

Project Outputs

Software: Tool to determine the uncertainty budget for array spectroradiometers (WP 2)

Tool for bandwidth and wavelength homogenisation and stray light correction (WP 2)

Knowledge Transfer: Guidelines (WP 2)

Conference Presentations (WP 5)

Technical Workshops (WP 5)

Refereed publications (WP 5)

Intercomparison campaign at Davos

Project Outputs

Takes place now!!

Goal: Shorten the traceability chain of solar UV measurements to SI units and reduce transfer uncertainties (U = 1 - 2%)

1 Detector-based traceability chain using an absolute radiometer and tunable UV laser facility (PTB)

•Tuneable laser source 280 – 400 nm

• Traceability to the primary standard cryogenic radiometer via a trap detector

2 Development of stable, portable and robust reference sources based on UV-LEDs (PTB)

• For monitoring purposes, near-field conditions

• Replacement of halogen lamps susceptible to transportation and aging

3 Compact laser-induced UV source as transfer standard (VSL)

• Laser Driven Light Source (LDLS™) from Energetic

WP 1: Spectral Irradiance Traceability (PTB)

Cryogenic radiometer

Spectral irradiance

standard

cw-Laser Sources

Si-trap detector + aperture

Filter Radiometer

Blackbody + aperture

Detector

Source

Spectroradiometer

Spectrally tuneable source

QASUME

EMRP ENV03: Traceability chain for spectral irradiance

(QASUME was calibrated directly against the blackbody in 2004 and 2013)

Stability controlled by relative measurements using portable Sources

(Aim of the project)

Tunable Lasers

QASUME

Validated

in this

Project

Validation of the QASUME irradiance reference at PTB

Blackbody BB3200pg at PTB

Gröbner J., and P. Sperfeld, Direct

traceability of the portable QASUME

irradiance scale to the primary irradiance

standard of the PTB, Metrologia, 42, 134—

139, 2005.

Tuneable Laser facility TULIP

QASUME Validation at PTB in 2004 and 2013 and 2014

±1.2%

Portable sources using UV-LEDs

Compact LDLS source as transfer standard

Source stability < 0.2%

Spectral Irradiance output :

• comparable to 1000 W FEL Lamp

• Nearly Constant output over UV range

Preliminary results

Goal: New characterisation techniques for the most relevant uncertainty components – stray light, bandwidth, linearity, wavelength

1 “A guide to measuring solar UV spectra using array spectroradiometers” (IMU)

• Specification of array spectrometers to meet the requirements for solar UV measurements

• Recommended measurement sequences for typical measurement setup

• A standardized protocol for saving measurement data, and ancillary information

2 “Uncertainty estimation in array spectroradiometer measurements of Solar UV spectra” (LNE)

• Guideline, software and methodology

3 Stray light characterisation and correction methods (PTB)

WP 2: Array Spectroradiometer characterisation (METAS)

Stray-Light in Array Spectroradiometers

Main Problems:

Out-of-band stray-light

Spectrally variable slit function

Line Spread Function PSR_003

Array SRM have Si-detectors with Sensitivites

up to 1100 nm,

in contrast to solar-blind PMTs from scanning

SRMs

Goal: New characterisation techniques for the most relevant uncertainty components – stray light, bandwidth, linearity, wavelength

1 “A guide to measuring solar UV spectra using array spectroradiometers” (IMU)

• Specification of array spectrometers to meet the requirements for solar UV measurements

• Recommended measurement sequences for typical measurement setup

• A standardized protocol for saving measurement data, and ancillary information

2 “Uncertainty estimation in array spectroradiometer measurements of Solar UV spectra” (LNE)

• Guideline, software and methodology

3 Stray light characterisation and correction methods (PTB)

WP 2: Array Spectroradiometer characterisation (METAS)

Talks by

Saulius Nevas

JG and Natalia Kouremeti,

Jimmy Dubbard

Posters by

Antonio Serrano,

Betty Hooke

JA Bogeat,

Open-source Wavelength shift and bandwidth homogenisation software matSHIC

Same concept as shicRIVM,

PLUS: Adapt for array spectroradiometers:

Variable slit-width

extension to 1000 nm

matlab interface

open-source

Ask Luca.Egli@pmodwrc.ch or julian.groebner@pmodwrc.ch

Soon to be available via http://projects.pmodwrc.ch/env03/

WP 2: Development of two wavelength scale

characterisation devices (METAS, VSL)

For scanning and array spectroradiometers: U = 0.01 nm, wavelength 280 nm - 400 nm.

1. Fabry-Perot (FP) etalon (METAS) 2. Polarisation gradient Filter (VSL)

Goal: New detection systems and entrance optics for scanning spectroradiometers to achieve field measurement uncertainties of 2% for solar UV measurements

1 New detection system for reference scanning spectroradiometers (CMI)

• Solid state detectors (Si, SiC, ZnO) and switched integrator amplifier

• High sensitivity, high dynamic range, low noise

• Substitute to PMT

2 Validation of optimised transportable QASUME reference spectroradiometer (PMOD/WRC)

• New Detector-System

• New Entrance Optic with improved Cosine response

• Improved traceability to SI and stability check using UV LEDs

3 Adaptation of a Fourier-transform spectroradiometer as reference instrument for solar UV irradiance measurements (PTB)

• Evaluate suitability of Fourier -transform spectroradiometer as a reference instrument for solar UV irradiance measurements

WP 3: Improvement of Reference Spectroradiometers (CMI)

1 Realisation of a UV hyperspectral camera (INRIM)

• Imaging device for spectral UV sky radiance measurements

• Fish-eye UV collection optics

• Scanning Fabry-Perot device

• Improve cosine correction methods

2 Improved entrance optics for global solar UV spectroradiometers (Aalto)

• Cosine error less than ±1 % downto 80°

• Material studies and design software

• Study new fused silica-based diffuser materials

• Two designs for Brewer and fiber coupled optics

WP 4: New Technologies (Aalto)

Hyperspectral fisheye UV Camera Fabry-Perot Cavity Spectroradiometer

Catadioptric Design

Hyperspectral fisheye UV Camera

Catadioptric Design

390 370

350 330

310320

Task 4.2 New Diffuser design

1) Design software

2) Validation through prototype

measurements

3) Realisation and commercialisation

3 Array spectroradiometer with improved stray light rejection using adaptive optics (CMI)

• Studies and comparison of methods

• MEMS tuneable grating technology

• Digitally modulated micro mirror devices (DMD).

• Prototype of improved spectrograph

4 Array spectroradiometer with improved stray light rejection using band pass filters (LNE)

• Jobin-Yvon spectroradiometer optimized for solar UV measurements

• Target value for stray light rejection using a tailored band pass filter 106

WP 4: New Technologies …

• UVNET Mailing list at http://metrology.tkk.fi/uvnet/source/lists.html

Spectral solar UV Intercomparison at Davos & Final ENV03 Workshop, 7-16 July 2014

Knowledge Dissemination & Training

http://projects.pmodwrc.ch/env03/

Presentations, Guidelines, Publications can be found at the project web-site: