SI-traceable Laboratory inter-comparison experiment – LCE-1

NPL extends a global open invitation for LCE-1 to attract as many participants as possible who provide radiometric calibration for the OC community. This will potentially include key instrument manufacturers of ocean colour radiometers commonly in use as well as any other interested parties that have in-house radiometric laboratory facilities.

Having confirmed a list of participants, a review of their radiometric standards will be performed starting with their irradiance sources and power supplies. For example, there are different types of mounts for 1000 W FEL lamps and these have different alignment procedures. It is also important to determine which types and which alignment procedures participant’s use. The stability and accuracy of each individual participant’s power supply will also be important following the LCE-1 intercomparisons when a verified irradiance source will go back to their home lab and be used as a working standard there. In addition the review will allow the preparation of the laboratory at NPL sufficiently in advance of LCE-1 to accommodate all identified lamps during the intercomparison exercise and provide the level of detail required to prepare a full implementation plan for LCE-1. Training in absolute radiometric calibration and uncertainty evaluation will be given by NPL and any remaining differences between participant’s standards will be accounted for in the uncertainty budget evaluations of WP303.

Following the irradiance and power supply review, similar information on the partners’ radiance source set ups (e.g. shield position and laboratory stray light estimation) will be detailed as an input to the implementation plan for this part of the intercomparison. Further detailed practical considerations will also be included in the implementation plan. For example, for source stability through the duration of the experiments, NPL will recommend hand carrying lamps to and from LCE-1 where participants are able to attend in person. This does not preclude remote participation, although it is possible that a lamp can change during transportation and therefore, if possible, 3 lamps from each participant should be transported with an appropriate means to and from the comparison.

For the irradiance source inter-comparisons all FEL lamps submitted to the LCE-1 exercise will be measured at NPL against NPL primary standards. A training session on absolute radiometric calibration will be held at NPL at the beginning of LCE-1 for all participants and this will include detail on how to conduct uncertainty evaluation. Following this the participants will be shown the NPL Spectral Radiance and Irradiance Primary Scales (SRIPS) facility (please see below) and this will include training on the alignment process. The actual measurements of each of the participant’s irradiance sources will then be run on SRIPS.

As a result of this comparison, irradiance values will be obtained from each lamp as measured under the carefully controlled conditions of SRIPS at NPL and these will be compared with their certificate values and with each other.

The second phase of LCE-1 concerns the inter-comparison of radiance sources for OCRs. As a radiance source is formed by combining an FEL lamp and a diffuser panel, comparing several reflectance panels using one lamp provides only a partial solution for the comparisons. The most appropriate method for carrying out a complete radiance source comparison between labs, and one that follows the suggestions of the ITT is using an NPL fully characterised transfer radiometer. This will involve an NPL calibrated transfer radiometer sent back and forth in turn to each participant to perform radiance measurements. The transfer radiometer in this configuration will be used to compare the participant’s in-house radiance sources with the NPL derived radiance scale. As NPL do not own an OCR, and to purchase a set of transfer radiometers dedicated solely to the LCE-1 is out of the scope of the FRM4SOC budget, we have arranged with an external collaborator JRC to use one or more of their stable OC filter radiometers as the transfer radiometer(s) for the radiance source comparisons.

The FRM4SOC LCE-1 will take place on April 3-7, 2017 in London, United Kingdom – at the state of the art optics calibration facilities of the National Physical Laboratory (NPL) – and between April and December 2017 using an NPL transfer radiometer round-robin.

Registration form

National Physical Laboratory (NPL)
Hampton Rd, Teddington (London)
Middlesex, UK. TW11 0LW

(and/or participants laboratories)

It is the responsibility of all participants to ensure that any instrumentation required by them is shipped with sufficient time to clear any customs requirements of the host country, in this case the UK. This includes transportation from any port of entry to the site of the comparison and any delay could result in them being excluded from the comparison. For this part of the comparison, participants should send their equipment to: Dr. Andrew Clive Banks, Room F4-A10, National Physical Laboratory (NPL), Hampton Road, Teddington (London), Middlesex, UK. TW11 0LW. Any queries can be directed to Andrew on andrew.banks@npl.co.uk or by phone on +44 (0)20 8943 6081. As is stipulated on the application / expression of interest form for LCE-1, it is not obligatory for participants to be present at the comparisons and any form of irradiance source that is used for OCR calibration is acceptable.

However, IT IS HIGHLY RECOMMENDED THAT, WHERE POSSIBLE, IRRADIANCE SOURCES ARE HAND CARRIED to and from the comparisons to avoid the risk of damage. Please note that the coordinator and host laboratory have no insurance for any loss or damage of the equipment during transportation or whilst in use during the comparison, however all reasonable efforts will be made to aid participants in any security. Equipment that is sent to NPL will be stored until Monday 03 April 2017, when their owners can unpack them and assemble them for the lab comparisons.

Irradiance source power supplies are not needed as SRIPS/RefSpec has a carefully controlled and monitored power supply for the measurements. Nevertheless, electrical power (220 V AC) will be available to all participants, with a local UK plug fitting for the duration of the comparisons at NPL. Participants whose equipment require 110 V AC supplies should provide their own transformers. The area of NPL where participants will be located for the comparisons and training offers Wi-Fi reception.

Participants can stay in a number of hotels located around NPL during the duration of this Workshop. A list of local hotels is provided below.

HOTELS AROUND NPL

All subsistence and hotel costs will be at the expense of the participants. Participants can have lunch at the NPL main restaurant during the week of LCE-1. A selection of hot dishes, as well as salads and sandwiches are available throughout the day. Free tea and coffee will be available to all participants throughout the day. A wide choice of food and restaurants can also be found in Teddington town centre, a short walk from NPL.

Please note that visitors to the UK from some countries require entry visas. Please check and if you are coming from such a country, you should apply for the visa well ahead of the start of LCE-1. You may require supporting documents for your visa application. Please contact the UK Embassy/Visa facilitation centre in your country to find out what you require for your visa application. Alternatively you can find more information and potentially apply for a UK visa on https://www.gov.uk/apply-uk-visa. If you require supporting documents or invitation to LCE-1, please contact Andrew Banks at NPL (see details above) stating what documents you require. Please note that the Visa processing time may vary depending on your country of application, so please allow sufficed time for the application to be processed.

Heathrow airport is the nearest airport to NPL, being about 10 miles away. There is good public transport linking Heathrow airport and NPL. For example, No 285 bus starts from Heathrow Central Bus Station and passes outside the NPL main reception. The X26 bus provides a faster service from Heathrow airport but stops in Broad Street in Teddington, a five minute walk from NPL. Taxis can be used but they are expensive (about £50). It is cheaper to book a minicab to collect you from Heathrow and bring you to NPL or to your chosen hotel. The cost of a minicab to take you from Heathrow airport to Teddington would be around £25.

Flights are also available to other UK airports but the only other airport which could be considered is Gatwick airport, being some 35 miles away from NPL. However, public transport from Gatwick airport is not as good as from Heathrow. Visitors have to travel from Gatwick airport to Teddington by train, via Clapham Junction. This takes longer, it is more complicated and it is more expensive. A minicab can be booked to bring you to Teddington but the costs is likely to be just over £50.

You can find directions to NPL for different modes of transport (car, train etc.) on the NPL website: http://www.npl.co.uk/location . A map of the area around NPL can be found on http://www.npl.co.uk/upload/pdf/npl-map-col.pdf .

Three months prior to the start of the comparison, participants will be required to supply to the pilot a description of the instrumentation that they will bring to the comparison. This will include any specific operational characteristics where heights/mountings may be critical as well as a full description of its characterisation, traceability and associated uncertainties. These uncertainties will be reviewed by NPL for consistency and circulated to all participants for comment and peer review. Submitted uncertainty budgets can be revised as part of this review process but only in the direction to increase the estimate in light of any comments.

BIPM, IEC, IFCC, ISO, IUPAC, IUPAP and OIML, 1995. Guide to the Expression of Uncertainty in Measurement (Geneva, Switzerland: International Organisation for Standardisation).

Goodman, T., Servantes, W., Woolliams, E., Sperfield, P., Simionescu, M., Blattner, P., Källberg, S., Khlevnoy, B., Dekker, P., 2015. Final Report on the EURAMET.PR-K1.a-2009 Comparison of Spectral Irradiance 250 nm – 2500 nm (NPL Report OP12, NPL, Teddington, UK).

JCGM, 2008a. Evaluation of measurement data – Guide to the expression of uncertainty in measurement – GUM 1995 with minor corrections (Joint Committee for Guides in Metrology (JCGM), http://www.bipm.org/utils/common/documents/jcgm/JCGM_100_2008_E.pdf ).

JCGM, 2008b. Evaluation of measurement data – Supplement 1 to the “Guide to the expression of uncertainty in measurement” – Propagation of distributions using a Monte Carlo method (JCGM, http://www.bipm.org/utils/common/documents/jcgm/JCGM_101_2008_E.pdf )

Woolliams, E.R., Fox, N.P., Cox, M.G., Harris, P.M. and Harrison, N.J., 2006. Final report on CCPR K1-a: Spectral Irradiance from 250 nm to 2500 nm, Metrologia 43 (1A Tech. Suppl.), (2006) S98-S104

Event organizer and contact person on site

Andrew Banks, NPL, UK.
andrew.banks@npl.co.uk

Shipping Info

Dr. Andrew Clive Banks, Room F4-A10, National Physical Laboratory (NPL)
Hampton Road, Teddington (London), Middlesex, UK. TW11 0LW
Phone: +44 (0)20 8943 6081.