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23 | 09 | 2019

 

Organisation of the Joint Research Project (JRP)


JRP Number:              ENV03

JRP Title:                     Traceability for surface spectral solar ultraviolet radiation (Solar UV)

JRP Timing:                 Start:   01/08/2011

                                       End:    31/07/2014


JRP Participants:

 

 

Short name

Organisation full name

Country

1

JRP-Coordinator

SFI Davos

Schweizerisches Forschungsinstitut für Hochgebirgsklima und Medizin in Davos (PMOD/WRC)

Switzerland

2

Funded JRP-Partner

Aalto

Aalto-korkeakoulusäätiö

Finland

3

Funded JRP-Partner

CMI

Cesky Metrologicky Institut Brno

Czech Republic

4

Funded JRP-Partner

EJPD

Eidgenoessisches Justiz- und Polizeidepartement (METAS)

Switzerland

5

Funded JRP-Partner

INRIM

Istituto Nazionale di Ricerca Metrologica

Italy

6

Funded JRP-Partner

LNE

Laboratoire national de métrologie et d'essais

France

7

Funded JRP-Partner

PTB

Physikalisch-Technische Bundesanstalt

Germany

8

Funded JRP-Partner

VSL

VSL B.V.

Netherlands

9

Unfunded JRP-Partner

CMS

CMS Ing. Dr. Schreder GmbH

Austria

10

Unfunded JRP-Partner

Kipp

Kipp & Zonen BV

Netherlands

11

REG-Partner I

IMU

Medizinische Universität Innbruck

Austria

12

REG-Partner II&III

UoM

University of Manchester

UK

13

REG-Partner IV

PHE

Public Health England

UK


Participants in Work Packages (WP)

WP

Work Package Name

Active JRP-Participants (WP leader in bold)

WP1

Spectral Irradiance Traceability

PTB, EJPD, SFI Davos, VSL, Kipp

WP2

Array Spectroradiometer characterisations

EJPD, Aalto, LNE, PTB, SFI Davos, VSL, REG(IMU)

WP3

Improvement of Reference Spectroradiometers

CMI, INRIM, PTB, SFI Davos

WP4

New Technologies

Aalto, CMI, EJPD, INRIM, LNE, PTB, SFI Davos, CMS, Kipp, REG(IMU)

WP5

Creating Impact

SFI Davos, All

WP6

JRP Management and Coordination

SFI Davos, All



 



Introduction to the JRP

The Joint Research Project "Traceability for surface spectral solar ultraviolet radiation" will significantly enhance the reliability of spectral solar UV radiation in the wavelength range 300 nm to 400 nm measured at the earth surface by developing new methods of observation (techniques and devices) to provide traceable solar UV irradiance measurements with an uncertainty of less than 2 %. This activity is essential to unambiguously quantify decadal changes in solar UV radiation due to the expected changes in the global climate system.

The project will shorten the traceability chain of the solar UV measurements to the SI unit and to reduce the associated transfer uncertainties. The goal is to approach uncertainties in the field comparable to those currently achieved only for primary spectral irradiance scale realisations at NMI level, i.e., at the level of 1 %. To provide traceable solar UV irradiance measurements with an uncertainty of less than 2 %, the portable reference spectroradiometer known as ‘QASUME’ will be fitted with an improved global entrance optic and newly developed solid-state detectors. A Fourier transform spectroradiometer will be adapted for spectral reference spectroradiometer.

To support the use of cost-effective array spectroradiometers in UV monitoring networks (as replacements for current UV filter Radiometers), significant progress needs to be achieved in the characterisation of these devices. New characterisation techniques and post-correction methods will be developed to determine and correct the stray light, linearity, and wavelength scale of array spectroradiometers. This will be supported by the design and construction of novel array spectroradiometers with improved stray light characteristics based on band pass filters and micro-electro-mechanical systems (MEMS) such as digital micro mirror devices.

The dissemination of the improved irradiance traceability and the developed tools and methods for using array spectroradiometers in the solar UV range will occur by a large field intercomparison of spectroradiometers organised at the end of the JRP at the World Radiation Centre, in Davos, Switzerland. Participants from the end-user community involved in solar UV measurements will be invited to the field intercomparison. Participating spectroradiometers from the end-users will be characterised and calibrated by the facilities developed in this JRP to provide traceability of spectral solar UV irradiance at this new level of uncertainty to the wider European UV monitoring community.

 

Motivation of the JRP

The quantification of UV radiation at the earth surface requires accurate measurements of global solar spectral UV irradiance in order to understand long-term trends in this parameter.

Long-term trends in surface solar radiation due to atmospheric induced changes (termed global dimming and global brightening), have demonstrated decadal changes of the order of 2 % per decade over Europe. These changes are currently explained by changes in the transparency of the atmosphere (aerosols) and possibly long-term changes in clouds (cloud fraction and cloud opacity). The effects on UV radiation have not yet been quantified due to the difficulty of observing these small changes over such long time scales. Future changes in UV radiation due to atmospheric changes are expected to be of the same order of magnitude and require measurements with significantly lower uncertainties of around 1 % to 2 % to detect such decadal changes.

The current knowledge on spectral solar UV radiation is limited to very few places worldwide where spectral solar UV monitoring instruments are located. Large-scale deployment of such instruments is limited by the required manpower and infrastructure to guarantee an adequate level of uncertainty. UV monitoring at additional locations is required to better understand the relationship between UV radiation and its influencing factors and to validate radiative transfer models and satellite-derived UV estimates.

Scanning spectroradiometers measure the solar irradiance spectrum sequentially, which requires several minutes of scanning time. The interpretation is thus rendered difficult in the case of fast varying atmospheric conditions. Also, the slow scanning speed does not allow fast sampling rates, limiting the number of measurements available per day.

Currently available array spectroradiometers are not suitable for solar UV measurements without complex correction methodologies due to the large dynamic range of the solar UV radiation between 300 and 400 nm and the significant stray light contamination of these instruments.

Due to the large decrease in UV radiation below 330 nm over many orders of magnitude due to the absorption of atmospheric ozone, wavelength accuracies of better than 0.05 nm are required to reach nominal uncertainties of 1% to 2% in the wavelength range 300 nm to 400 nm. Furthermore, a high dynamic range over at least five orders of magnitude is necessary to cover the wavelength range between 300 nm and 400 nm.

The rapid temporal variation of UV radiation due to atmospheric conditions (e.g. clouds) requires fast-scanning spectroradiometers with stray light rejection of at least 10-6 to reliably sample the whole solar UV spectrum between 300 nm and 400 nm.

Fourier Transform Spectroradiometers (FTS) hold the promise of recording solar UV spectra within a very short time span (typically less than 1 minute) and with a wavelength uncertainty below 0.02 nm due to the very nature of their measurement process.

The first major task of the JRP will considerably improve the uncertainties associated with current state of the art scanning spectroradiometers to reach uncertainties of ± 1 % to ± 2 % for spectral solar UV irradiance measurements over the wavelength range 300 nm to 400 nm.

The second major activity of the JRP will optimise array spectroradiometers and develop characterisation methods for CCD and diode-array spectroradiometers and similar fast-scanning spectroradiometers. In future these devices will be used as cost effective network instruments for solar UV radiation measurements, replacing current filter radiometers (narrow and broadband). Investigations will include: Stray light rejection which is particularly problematic at very short wavelengths below 320 nm, improved wavelength characterisation particularly in the UV range, and linearity of the devices including the electronics. Finally a methodology for uncertainty analysis of solar UV measurements using array spectroradiometers will be developed to account for the properties of the instruments, including the correlations among the spectral values. The objective is to achieve uncertainties under network conditions of ± 5 % with these fast-scanning spectroradiometers.



WP 1: Spectral Irradiance Traceability

The aim of this workpackage is to shorten the traceability chain of solar UV measurements in the wavelength range 300 nm to 400 nm to the SI unit and to reduce the associated transfer uncertainties. The goal is to develop uncertainties in the field comparable to those currently achieved only for primary spectral irradiance scale realisations at NMI level, i.e., at the level of ± 1 % to ± 2 % at k=2.

This workpackage will:

  • Develop a detector based spectral irradiance traceability chain at PTB. The improved European Reference spectroradiometer QASUME will be calibrated directly against a reference detector traceable to an absolute radiation standard using a tuneable laser facility. No intermediate source-based transfer standards will be required in this traceability chain (Task 1.1)

  • Develop two UV LED-based transfer standards: These are compact, stable and portable monitoring devices based on UV-LEDs, with two entrance optics geometries that will be used to maintain the spectral calibration of spectroradiometers while deployed at the UV monitoring sites (Task 1.2)

  • Develop a high output metrology (laser) light source for field calibrations with a spectral power distribution free of impurity features and spectrally flat to a level of a few percent over the solar UV range. This laser-based device has high radiation output and can be used in the far-field region (in contrast to the UV-LED devices) and thus calibrate spectroradiometers with diverse input optics (Task 1.3)

 

 

Description of Task 1.1

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

Start: August 2011, End: January 2014

The aim of this task is to develop tools and methods for entirely detector-based calibration of spectroradiometers (e.g. QASUME) in the solar UV spectral range.

Description of work: PTB will develop instrumentation to calibrate the spectral irradiance responsivity of the portable reference spectroradiometer QASUME. A modified tuneable laser suite (quasi-CW tuneable laser) and a reference detector traceable to the primary standard of radiant power will be used. The target uncertainties of the method of calibration is less than 0.5 % across the wavelength range 280 nm to 400 nm.

 

Description of Task 1.2

Development of a highly stable portable transfer standard, powered by LEDs (PTB, EJPD, SFI Davos, Kipp)

Start: August 2011, End: October 2013

Background: Currently the stability of UV spectroradiometer’s responsivity is monitored using compact low-power tungsten-halogen lamps. These are fragility and their stability is affected by aging and transportation. To overcome these limitations, more robust monitoring technique will be developed. This will be based on UV LEDs, which can form the basis of a new generation of transfer standards.

The aim of this task is to develop techniques for monitoring the responsivity of UV spectroradiometers (e.g. QASUME) over extended periods of time and also under field conditions. The monitoring techniques will cover the solar UV spectral range 280 nm to 400 nm and ensure stability and reproducibility of the spectroradiometer of ± 0.3 % for a lamp-burn time of 7 hours (i.e. representing about one year of calibrations).

Description of work: Two compact, portable UV LED-based transfer standards will be designed for use with the two global entrance optics (diffusers) designed by Aalto in D4.2.2 (due July 12). Since the geometry will be "near-field", they will be used to monitor the responsivity of the spectroradiometer, while the absolute calibration will be done with far-field sources in the laboratory.

 

Description of Task 1.3

Compact laser-induced high-flux UV source as metrology light source for field applications (VSL, Kipp)

Start: August 2011, End: March 2014

The aim of this task is to evaluate the suitability of a new commercially available high-flux laser-induced UV light source for use as a metrology light source in field applications. The Laser Driven Light Source (LDLS) technology may be implemented at NMI level and has high potential to be used as a new-generation compact transfer standard for field applications in the far-field region (therefore independent of detector’s entrance optic geometry.

Background: Compared to conventional light sources, such as the deuterium or electrode-based arc discharge lamps, the lifetime and available output in the solar UV wavelength range in both radiance and irradiance mode will be inherently better. Since a LDLS operates without electrodes, long lifetime and respectively good short and long-term stability of better than ± 0.5 % per 20 hours burn time is expected. Moreover, the power spectral distribution is free of impurity features and spectrally flat to a level of a few percent over the solar UV range, whereas conventional sources show a significant change of a few orders of magnitude in that same spectral range. The expected high output and good stability at moderate costs make this source also an ideal metrology light source for field usage

Description of work: Based on an instrument selection from a range of commercially available models of award winning LDLS technology (see www.energetiq.com), VSL will implement and characterise an LDLS system that can be operated in two different configurations at NMI level, i.e., flux mode and irradiance mode. Modifications will be made to enable transportability such that the LDLS system can be used for absolute spectral irradiance calibrations under field conditions.



WP 2: Array Spectroradiometer Characterisation

The aim of this workpackage is to develop new characterisation techniques for UV array spectroradiometers addressing the most relevant sources of errors.

Background: Measuring the UV part of the solar spectrum requires a high dynamic range due to the sharp cut off of the solar spectrum in the UVB-range by ozone absorption. Usually the resolution of array spectrometers is 12-14 bit, which is not sufficient for solar UV measurements. Additionally array spectroradiometers are designed for operation in a laboratory, and not in a continuous mode. Therefore the current limitations of array spectroradiometers make them unsuitable for solar UV measurement.

The main effects to consider when characterising UV array spectroradiometers are spectral stray light, bandwidth, wavelength accuracy and linearity. Quantifying these effects is not only fundamental for calculating the measurement uncertainty but it also allows correcting for the instrument imperfections and thus decreases the overall uncertainty of measurements

The workpackage will:

  • Identify requirements of array spectroradiometers for solar UV measurements in the range 300 nm to 400 nm, and the best measurement procedures. This will be encapsulated in “A guide to measuring solar UV spectra using array spectroradiometers” (Task 2.1)

  • Development of a complete model for uncertainty calculation of array spectroradiometers. It will include all relevant parameters including effects of correlations among spectral values (Task 2.2)

  • Characterise and correct UV array spectroradiometers for in-range and out-of-range stray light effects (Task 2.3)

  • Develop an algorithm to transform measured solar spectra onto a uniformly spaced wavelength grid with a nominal spectral resolution. It will allow correcting band pass effect of even low-resolution instruments by using a high-resolution solar reference spectrum (Task 2.4)

  • Develop two wavelength characterisation devices for array spectroradiometers.

  1. A Fabry-Perot multilayer structure working in the UV range. It will enable the characterisation of the wavelength scale at the ± 0.01 nm uncertainty level (Task 2.5)

  2. A polarisation gradient filter concept usable for field applications.

  • Compare three linearity characterisation methods based on complementary techniques (Task 2.6)

 

 

Description of Task 2.1

Requirements of array spectroradiometers for solar UV measurements (REG(IMU), PTB, SFI Davos)

Start: August 2011, End: December 2011

Background: Array spectroradiometers have generally been designed for operation in a laboratory, and not in a continuous mode. To enable array spectroradiometers to be used for solar UV measurements, improvements and adaptations are required particularly in the 300 nm to 400 nm range.

The aim of this task is to specify and report on the requirements of an array spectroradiometer, suitable for outdoor solar UV measurements.

 

Description of Task 2.2

Uncertainty estimation of array spectroradiometers (LNE, All)

Start: January 12, End: December 2012

The aim of this task is to develop guidelines for estimation of uncertainties in array spectroradiometer measurements of solar UV irradiance including effects of correlations among spectral values.

Background: Uncertainty of solar UV irradiance measurement data using array spectroradiometers depends on a number of device characteristics, such as linearity, stray light suppression, wavelength calibration, angular response, instrument stability, as well as calibration and measurement conditions.

A complete treatment of measurement uncertainties requires identification and inclusion of correlations among measured spectral values. Correlations are introduced via calibration of the spectroradiometer as well as instrument characteristics manifested in e.g. LSF characterisation results. Nevertheless, uncertainty propagation in solar UV irradiance measurements using array spectroradiometers so far tends to be accomplished without taking into account correlation effects.

 

Description of Task 2.3

Stray light characterisation and correction methodologies (PTB, EJPD, SFI Davos, REG(IMU))

Start: March 2012, End: July 2013

The aim of this task is to develop a stray light characterisation methodology for array spectroradiometers and eventually correction algorithms for stray light.

Background: Stray light can originate from inside the spectral range of the solar UV spectroradiometers, or outside of the working spectral range of the instrument (but still within the sensitivity range of the sensor, typically up to 1100 nm for a silicon CCD detector). Spectral stray light effects caused by the light within the spectral range of an instrument are usually corrected based on line spread function (LSF) characterisation results and a simple matrix method. For the solar UV measurements, however, such a correction is not enough due to a significant contribution to the stray light by the radiation at longer wavelengths than the working range of the instrument but still within the sensitive range of the silicon CCD sensor.

 

Description of Task 2.4

Bandwidth and wavelength correction methodologies applied to solar spectra (SFI Davos, REG(IMU))

Start: November 2011, End: October 2013

Background: Measured solar spectra are used by end-users to calculate biological weighted quantities such as the erythemal weighted irradiance, as well as quantifications of irradiance changes at specific wavelengths. Therefore nominal wavelengths grids and a constant nominal bandwidth over the whole measured spectrum are often required.

The aim of this task is to create an algorithm, which converts measured solar spectra onto a uniformly spaced wavelength grid with a nominal spectral resolution. The key feature of this algorithm will be its ability to cope with arbitrary spaced wavelength grids and spectrally varying slit functions which are both specific to array spectroradiometers. The application of such an algorithm to solar spectra requires the use of a high-resolution solar reference spectrum due to the Fraunhofer structure and the low resolution of the array spectroradiometers.


Description of Task 2.5

Development of two wavelength scale characterisation devices (EJPD, SFI Davos, VSL, REG(IMU))

Start: August 2011, End: January 2013

Background: High spectroradiometer wavelength calibration accuracies are key parameter for solar spectral measurements. Typically, spectroradiometers are calibrated with spectral discharge lamps, providing distinct and well-defined spectral emission lines. However, for small spectral ranges, where only one or two lines are present, the calibration becomes inaccurate. Furthermore, the accuracy of the calibration may locally vary according to the number of nearby calibration lines and their different intensity and the nonlinearity relationship between wavelength and recording pixel, or grating drive. This task will investigate the concept of broadband source filtering, direct laser source referencing and traceability.

The aim of this task is to develop improved wavelength characterisation devices for diode array spectroradiometers, and scanning spectroradiometers. The target expanded uncertainty in wavelength is ± 0.01 nm at k=2 over the wavelength interval 280 nm to 400 nm. Two methods are to be developed and compared.


Description of Task 2.6

Linearity of array spectroradiometers (PTB, Aalto, EJPD, VSL)

Start: January 2013, End: May 2014

Background: Solar UV irradiance measurements are carried out over a large dynamic range (up to 5 orders of magnitude between 300 nm and 400 nm). At a manufacturer’s site, linearity of the CCD instruments is typically characterised by varying the integration time of the array spectroradiometers. This is a simple but by far not complete characterisation method since it accounts mostly for the linearity of the signal processing electronics. In principle, varying the spectral irradiance level should test the linearity of such devices. Residual deviations from the linear regime will yield errors both in absolute values as well as in relative spectral distribution of the measured solar UV irradiance.

The aim of this task is to develop procedures for linearity characterisation of array spectroradiometers used for solar UV irradiance measurements. The objective is to determine the linearity of the array spectroradiometers over 5 orders of magnitude representative for local noon solar UV irradiances (between 10 µWm-2nm-1 and 1 Wm-2nm-1). Three alternative methods will be developed and evaluated.



WP 3: Improvement of Reference Spectroradiometers

Background: Currently even the best UV solar reference spectroradiometers do not provide sufficient accuracy for long-term analysis of atmospheric changes. Total uncertainty of these systems for in field measurement of solar spectral irradiance in UV reaches the level of 5 %. For monochromator-based scanning spectroradiometers a significant part of this uncertainty is due to the photomultiplier tubes (PMT). Although they offer high sensitivity and large dynamic range, they have some key issues such as non-linearity, memory effect and poor long-term quantum efficiency stability, which can range from 1 % to several percent diurnal variations during one day. In extreme cases, a continuous degradation of more than 10 % has been observed with particular PMT modules. The entrance optics for global UV measurements also need to be improved to reduce diurnal variations arising from the changing solar elevation and the ratio between diffuse and direct solar irradiance; the latter task will be accomplished in WP4.


 

Description of Task 3.1

Development of new detection systems for reference scanning spectroradiometers (CMI, INRIM, SFI Davos)

Start August 2011, End January 2013

The aim of this task is to study the viability and realisation of optimised, high sensitivity, large dynamic range, low noise solid-state detection system (SSDS) that may replace/outperform the photo multiplier tube (PMT) in scanning UV spectroradiometers.

The design objective for the SSDS is:

  • Linearity better than 0.1% over 5 orders of magnitude,

  • Memory effect smaller than 0.1 %,

  • Noise as low as 10 fW/Hz½ ,

  • Stable spectral responsivity at the level of 0.01 % over the period of one month,

  • Integration time for one measurement sample should be a maximum of 1 second for spectral solar UV irradiance below 0.1 mW/m2/nm and 0.1 seconds or less at irradiances above 1 mW/m2/nm,

  • Operational from 280 nm to 400 nm (minimum).


Description of Task 3.2

Validation of optimised transportable QASUME reference spectroradiometer (SFI Davos, CMI, INRIM, PTB)

Start January 2013, End: February 2014

The aim of this task is to optimise and validate the portable reference scanning spectroradiometer QASUME. The improved QASUME will be used for disseminating the improved UV irradiance scale to stakeholder instruments through the intercomparison in Davos (WP5).


Description of Task 3.3

Adaptation of a Fourier transform spectroradiometer as reference instrument for solar UV irradiance measurements (PTB, SFI Davos)

Start August 2011, End: March 2014

The aim of this task is to evaluate the suitability of this Fourier Transform Spectroradiometer (FTS) as a reference instrument for solar UV irradiance measurements. A commercially available FTS will be fitted with the global entrance optics, an absolute calibration of the instrument will be performed, and the instrument will be fully characterised.



WP 4: New Technologies

 The aim of this workpackage is to develop new techniques, technologies and equipment that can be used to improve the uncertainties of solar UV measurements.

State-of-the-art: Currently the commercially available cost-effective spectroradiometers have a number of limitations. They do not achieve the required sensitivities; deviations of at least 20 % in solar UV irradiance measurements at 310 nm are currently observed and this is thought to be due to:

  • Global entrance optics currently have angular responses which deviate significantly from the nominal cosine response, producing systematic deviations of up to 10 % between instruments measuring global solar UV irradiance.

  • Inadequate stray light rejection in the UV wavelength range and particularly in the UV-B range

This WP aims to resolve these issues by:

  • Developing a hyperspectral sensor for the determination of spectral UV sky radiance. This will be used as ancillary instruments to correct spectral measurements from current spectroradiometers with traditional (non-optimised) global entrance optics and by spatial integration to provide also the diffuse spectral irradiance as a traditional imaging spectroradiometer.

  • Developing new global entrance optics (diffusers) with improved angular responses.

  • Developing array spectroradiometers with optimised stray light rejection of 106 (for measuring solar UV irradiance). Two different approaches to stray light rejection will be investigated; Task 4.3 investigates the use of adaptive optics, whilst task 4.4 investigates filtering, both will be thoroughly characterised by the tools developed in WP1 and WP2.

 

 

Description of Task 4.1

Realisation of a UV hyperspectral camera (INRIM, EJPD, REG(IMU))

Start August 11, End October 2013

Background: At present only few hyperspectral imaging devices in the UV have been realised as research prototypes or commercial products (e.g. Headwall Photonics). All are based on the use of dispersive gratings or tuneable acousto-optic band pass filters. Both approaches have the disadvantage of being slow and expensive. INRIM have successfully developed two hyperspectral imaging devices for use in the visible and short wave infrared regions, but not yet in the UV. This JRP will develop a hyperspectral camera based on UV sensitive sensors, a UV compatible Fabry-Perot cavity and UV fisheye optics (that require development from scratch). The planned system would be a breakthrough in hyperspectral imaging; allows faster imaging and lower cost realisation.

The aim of this task is to develop a novel type of hyperspectral imaging device (or imaging spectroradiometer) for the measurements of diffuse sky UV radiance. The instrument allows measurement of the UV spectrum of each pixel of an image (about 300 kpixels) in a single shot, where each pixel is associated to a portion of the sky. The device will utilise fish-eye UV collection optics to get an image of a wide portion of the sky. This high-resolution image will be used to improve cosine correction methods of existing solar UV spectroradiometers with conventional entrance optics, as the picture gives exact knowledge on the spectral sky radiance distribution.


Description of Task 4.2

Realisation of improved entrance optics for global solar UV spectroradiometers (Aalto, CMS, Kipp)

Start August 11, End: July 2013

Background: One problem in manufacturing diffusers with a lambertian angular response is the translucency of diffusing materials. In addition to the desired diffuse transmittance, there is a specular component in the transmitted beam. The spatial transmittance profile can be accounted for in the design, but diffuser materials vary from material to material, although the trade name could be the same.

The aim of this task is to develop two improved global entrance optics (diffusers) for solar UV spectroradiometers, to better measure spectral global solar irradiance. One general-purpose diffuser connected to an optical fiber will be manufactured by CMS Schreder, while the second diffuser will be made specifically for the Brewer spectrophotometer by Kipp.


Description of Task 4.3

Array spectroradiometer with improved stray light rejection using adaptive optics (CMI, PTB, SFI Davos)

Start August 11, End June 2014

The aim of this task is to design and develop a pre-dispersing optical device used in conjunction with a standard array spectroradiometer. The design objective is to reach a stray-light rejection ratio of 106 or better in the combined system. The specifications of a solar UV array spectroradiometers will be set in Task 2.1, which leads to the deliverable 5.1.6 (Guideline document). Two alternative methods will be investigated and the most promising will be selected.

 

Description of Task 4.4

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

Start August 11, End June 2014

The aim of this task is to develop spectrograph specifically tailored for solar UV measurements. The device will be based on a commercially available diode array spectroradiometer (a Jobin Yvon VS140). This will be modified by the incorporation of a tailored band pass filter to reduce stray light error. The target value for the stray light rejection is 106.



WP 5: Creating Impact

The aim of this workpackage is to support the dialog between the JRP-Consortium and interested parties including; collaborators, stakeholders, the end-user community, academia, commercial companies, standards organisations and legislative bodies. The project results will be disseminated to the various interest groups via a number of mechanisms described below.

 

Description of Task 5.1

Knowledge Transfer/Dissemination (SFI Davos, Aalto, CMI, EJPD, INRIM, LNE, PTB, VSL, CMS, Kipp, REG(IMU))

Start August 2011, End: July 2014

The scientific results of this project will be disseminated through the following activities:

  • International Conferences attended by JRP-Partners

  • Peer-Reviewed Publications

  • Standards & Committees

  • Website

  • Newsletter “UVNews”

  • Guideline documents


Description of Task 5.2

Training (SFI Davos, Aalto, CMI, EJPD, INRIM, LNE, PTB, VSL, CMS, Kipp, REG(IMU))

Start August 2012, End: June 2014

Background: It can be difficult for end-users to gain access to the solar UV research facilities operated by NMIs

The aim of this task is to give end users access to the NMI facilities to characterise their instruments during the final year of the JRP. At this stage in the JRP, the methods and facilities will have been validated by the JRP-Consortium. In this JRP, the main facilities of interest to the end-user community are expected to be:

  • The characterisation of bandwidth and stray light of array spectroradiometers by means of tuneable laser sources (usually only available at NMIs);

  • Wavelength characterisation methods using newly developed methods and spectral irradiance traceability to primary irradiance standards using portable source standards or detector based standards.

The following activities will be undertaken:

  • Solar UV Intercomparison (at SFI Davos)

  • Stray light and linearity characterisation for stakeholders and colaborators (at PTB)

  • Linearity, wavelength and absolute spectral irradiance characterisation for Stakeholders and collaborators (at Davos Intercomparison)

  • Three stakeholder and collaborator workshops


Description of Task 5.3

Exploitation (SFI Davos, Aalto, CMI, EJPD, INRIM, LNE, PTB, VSL, CMS, Kipp, REG(IMU))

Start August 2011, End: July 2014

The aim of this task is to ensure the best exploitation of knowledge developed in the JRP.

The following new products are attempted to be achieved:

Devices:

    • UV LED-based transfer standards

    • Laser Driven Light Source

    • New solid state detectors

    • Modified Fourier Transform Spectrometer

    • UV hyperspectral imaging camera

    • Global input optics (new diffuser design)

    • Two UV array spectroradiometer systems (Pre-dispersing device, Prototype band pass spectrograph)

Software

    • Software to determine the uncertainty budget for array spectroradiometers

    • Software for bandwidth, and wavelength homogenisation, and stray light correction