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EMRP ENV03 “Traceability for surface spectral
solar ultraviolet radiation”
The European Metrology Research Programme (EMRP) is jointly
funded by the EMRP participating countries within EURAMET and
the European Union.
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Project Objectives • Enhance the reliability of spectral solar UV radiation measured at the Earth
surface
• Improved 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
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• 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
• 5 Collaborators, open-call
Project Overview
http://projects.pmodwrc.ch/env03/
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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
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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
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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
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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 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)
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Cryogenic radiometer
(Aim of the project)
Spectral irradiance standard
cw-Laser Sources
Si-trap detector + aperture
Filter Radiometer
Blackbody + aperture
Tunable Lasers
Detector
Source
Spectroradiometer
Spectrally tunable source
QASUME QASUME
Stability controlled by relative measurements using UV-LED Sources
Traceability chain for the QASUME Spectroradiometer
(QASUME was calibrated directly against the blackbody in 2004)
Talk by P. Sperfeld 9:45
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0 20 40 60 80 100 120Burning time / h
0,94
0,96
0,98
1,00
Norm
alize
d sig
nal
2,00⋅10-2
2,01⋅10-2
2,02⋅10-2
2,03⋅10-2
2,04⋅10-2
2,05⋅10-2
I / A
6,6
6,8
7,0
7,2U
/ V
: E: I: U
250 300 350 400 450Wavelength / nm
0,0
0,2
0,4
0,6
0,8
1,0
Spec
tral
Irra
dian
ce /
a.u.
Stability investigation of UV-LEDs
2⋅10-4 h-1
AlGaN
Design goal: ageing rate of 0.05 %h-1
Irradiance using 4 LEDs
Talk by S. Nowy 12:30
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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
Poster by O El.Gawhary P105
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Talk by M. Blumthaler 10:00
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)
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Percentage of stray light in array spectroradiometer signal when measuring quartz-halogen lamp (calculated using the determined correction matrix)
Effect of stray light on irradiance measurements
200 400 600 800Wavelength / nm
1
510
50100
Frac
tion
of st
ray
light
/ %
0,00
0,05
0,10
0,15
0,20
Spec
tral
irra
dian
ce /
a.u
.: Stray light: E200 300 400 500 600 700 800
Wavelength / nm10-710-610-510-410-30.010.1
1
LSF
/ a.u
.
Slit Functions obtained from tunable laser setup (PLACOS)
1
Determination of Stray-Light contribution from Slit function measurements 2
Talk by F. Shindo 10:15
Talk by S. Nevas 11:30
Talk by A. Kreuter 11:45
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4 Bandwidth and wavelength correction methodologies applied to solar spectra (PMOD/WRC)
• Algorithm, which converts measured solar spectra onto a uniformly spaced wavelength grid with a nominal spectral resolution.
5 Development of two wavelength scale characterisation devices (METAS)
• For scanning and array spectroradiometers
• U = 0.01 nm, wavelength 280 nm - 400 nm.
• 1. Fabry-Perot etalon (METAS)
•2. Polarisation gradient filter (VSL)
6 Linearity of array spectroradiometers (PTB)
• Three different procedures and measurement setups for linearity characterisation of array spectroradiometers (broad-band source, monochromator-based and tunable laser source)
WP 2: Array Spectroradiometers …
Mica based Fabry Perrot
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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 at longer wavelengths
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)
Talk by M. Smid 12:45
Talk by P. Meindl 12:15
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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)
Talk by P. Kärhä 10:30
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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 …
Talk by L. Egli 12:00
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Knowledge Transfer • National and international conferences (IRS 2012, DACA13, NEWRAD12)
• Publications in peer-reviewed publications
• UV-Net mailing list and "UVNews" newsletters http://metrology.tkk.fi/uvnet/ • Guideline Documents
Training • Workshops (UV-NET 2013 , Davos 2014) • Stray light and linearity characterisation of array spectroradiometers using tunable laser
systems at PTB (open to collaborators)
• Spectral solar UV Intercomparison at Davos, June/July 2014 • Instrumental characterisations during the intercomparison
Exploitation
• Exploit the knowledge and Intellectual Property developed during the project
WP 5: Creating Impact (PMOD/WRC)