SI-traceable Laboratory inter-comparison experiment – LCE-2

The core action of the FRM4SOC project is to ensure that ground-based measurements of ocean colour parameters are traceable to SI standards in support of ensuring high quality and accurate Sentinel-2 MSI and Sentinel-3 OLCI products. The FRM4SOC project contributes directly to the work of ESA and EUMETSAT to ensure Sentinel-3 OLCI and Sentinel-2 MSI instruments are validated in orbit.

Laboratory Calibration Exercise 2 (LCE-2) links the ocean colour (OC) field measurements to the SI-traceable calibration and verifies whether different instruments measuring the same object can provide consistent results within the uncertainty limits.

Involvement of all relevant expertise available in Europe and worldwide is in line with the objectives of the project and in the interest of the EO/ocean colour community. Therefore, it is anticipated that all interested parties in this wider community, but outside the Consortium, should be able to participate in the comparison exercise as external participants. TO will publish a global open invitation for LCE-2 to involve as many active users of Field Ocean Color Radiometers as possible. Information about participating instruments will be gathered and Tartu Observatory will work together with the participants in order to make sure that all the necessary hardware for mounting the instruments in the lab and during the outdoor intercomparison will be available for the time of LCE-2. The OC radiometers participating in the exercise will be gathered to TO prior LCE-2 for absolute calibration. Participants will join afterwards for comparison measurements. TO will help the participants with all aspects concerning travel, accommodation, customs, shipping of instruments, etc.

The LCE-2 will serve as a preparation stage for the AAOT-FICE field intercomparison exercise. The LCE-2 can be divided into three sub-tasks:

a) Provide SI-traceable radiometric calibration for participating radiometers;
b) Organize indoor intercomparison of radiometers in controlled environment;
c) Organize outdoor intercomparison of above-water radiometers over terrestrial water surface.

It is not feasible to calibrate all parameters (wavelength accuracy, straylight, field of view, temperature stability, linearity, angular response for irradiance sensors, etc.) of all the participating instruments during LCE-2. However, protocols and best practices for all these calibrations will be included in the TR-5 and all participants of LCE-2 are encouraged to have their instruments as well characterised as possible prior to LCE-2. Absolute radiometric calibration will be performed for all the participating radiometers just before the LCE-2.

SI-traceable Laboratory Comparison Experiment 2 (LCE-2) for verification of FRM OCR in Estonia

The LCE-2 will take place before AAOT-FICE in 8 – 13 May 2017 in Estonia  –  Tõravere and Lake Kääriku. It will serve as a training session for the participants of AAOT-FICE as well as provide SI-traceable radiometric calibration of participating radiometers. During indoor intercomparison all the participants will measure stabilized radiance and irradiance sources and compare the recorded radiance and irradiance values. The outdoor intercomparison will be carried out on a diving platform of a small lake.

The inter-compared data products will be downwelling irradiance E_d, sky radiance L_s, and total water surface radiance L_t. The view configuration will be 40° from the nadir and 135° from the Sun as suggested by Mobley (1999). Uncertainty budgets will be calculated for all the measurements.

Schedule

24 April 2017 – OC radiometers participating in the exercise have arrived to Tartu Observatory (Estonia) for absolute radiometric calibration
8 – 13 May 2017 – LCE-2 in Estonia – Tõravere and Kääriku

Sun, 7 May – Arrival to Tartu

Mon, 8 May – Training session

9:00 Transport from Tartu to Tõravere
9:30-18:00 Lectures and training sessions, lunch in Tõravere
18:00 Joint dinner in Tõravere, after dinner transport to Tartu

Tue, 9 May – Laboratory measurements

9:00 Transport from Tartu to Tõravere
9:30-17:00 Group A – irradiance measurements; Group B – radiance measurements
17:00 Transport to Tartu

Wed, 10 May – Laboratory measurements

9:00 Transport from Tartu to Tõravere
9:30-17:00 Group A – radiance measurements; Group B – irradiance measurements
17:00 Transport to Kääriku

Thu, 11 May – Field measurements in Kääriku

Fri, 12 May– Field measurements in Kääriku

In the evening social event

Sat, 13 May – Excursion in Setomaa (South-East of Estonia)

The tour will end in Tartu

Previous inter-comparison of ocean colour radiometers has shown that the consistency of results improved when all the instruments participating in the inter-calibration were radiometrically calibrated in the same laboratory. Tartu Observatory will serve as the main organizer for this comparison supported by the NPL. TO will be responsible for inviting participants and for the analysis of data, following appropriate processing by individual participants. TO will be the only organisation to have access and to view all data from all participants. This data will remain confidential to the participant and TO at all times, until the publication of the report showing results of the comparison to participants.

As the maximum number of participants to be handled is 15, the participants for LCE-2 will be selected by the following criteria in the following order:

1) Partnership in FRM4SOC
2) Participation in FICE
3) Participation in LCE-1
4) Fully characterised radiometers of the participant
5) For the rest, first come, first served By their declared intention to participate in this intercomparison, the participants accept the general instructions and the technical protocols written down in LCE-2 Implementation Plan and commit themselves to follow the procedures strictly.

Registration is opened from 01.11.2016 to 20.12.2016. As the site for field measurements is with limited size, only one set of radiometers is allowed per participating institute. The acceptance/rejection on the participation will be sent to all applicants in the beginning of January 2017.

A limited budget for travel grants is available for the participants who do not have other funding sources available. The application for funding support must be written in free form and sent to the event organizer. The grant can cover travel costs for one person. The applications for support will be forwarded to ESA for approval.

The radiometric calibration and indoor intercomparison will take place at Tartu Observatory, located in Tõravere, Estonia. The outdoor intercomparison will take place at Lake Kääriku, Estonia, 58° 0′ 5″ N, 26° 23′ 55″ E.

Location of the LCE-2 venues

Main building of Tartu Observatory

Tõravere is about 20 km from Tartu, the second largest city of Estonia. Tartu Observatory has modern, well equipped facilities for research work and an excellent visitor centre. In 2012, a new laboratory complex at the premises of Tartu Observatory has been established for development and testing of new technologies including stations for development, prototyping, and assembly of electronic circuits; facilities for climatic, thermal-vacuum, vibration, and electromagnetic compatibility (EMC) testing; workshops for mechanical construction and repair works of scientific instruments. The laboratories have independent and automatic control for temperature and humidity. Special conditions as electrostatic discharge protected environment (ESD), anechoic chamber, and cleanrooms (EN ISO 14644 Class 8) have been established. Three rooms in cleanroom environment with total area of 100 m2 are available for optical measurements. Optical laboratory includes passive damping setup tables, one of them on separately built foundation for vibration-free measurements.

Lake Kääriku

The outdoor intercomparison will take place at Lake Kääriku, Estonia, 58° 0′ 5″ N, 26° 23′ 55″ E. Kääriku is a small village located in southeastern Estonia, 30 km south of Tõravere (approximately 45 minutes drive by car). In 1959 a sporting centre was established in Kääriku which has been the main training centre for many Soviet and Estonian top level athletes.

Pier and diving platform of Lake Kääriku

Lake Kääriku has a 50 m long pier and a diving platform on the southern coast. The upper level of the platform is 5.7 m above water surface.

Depth of water around the diving platform is 2.6 m to 3.6 m. Closest trees are about 65 m south of the platform, the treetops are less than 20° above the horizon when viewed from the upper level of the platform.

General information about Estonia

Official name: Republic of Estonia
Area: 45 227 km2
Location: North East Europe
Population: 1.3 million
Capital city: Tallinn
Official language: Estonian
Local time during LCE-2: Eastern European Summer Time, GMT +3 hours.
Currency: Euro (EUR, or €).
Credit cards: Major credits cards are accepted at hotels, restaurants, shops and the leading banks.
Telephone: IDD system is available at all hotels. GSM and LTE networks provide nearly complete coverage of Estonia.
Electricity: 230 V AC, 50 Hz, European-style 2-prong plugs (Type F and C) are in use.
Taxi: All licensed taxis charge according to the meter.
Visa: Estonia belongs to EU and Schengen Visa area regulations apply. For further information regarding the visa requirements please visit the website of the Estonian Ministry of Foreign Affairs http://www.vm.ee/en/node/6978

For more information please visit http://www.visitestonia.com

All the instruments that will take part of the LCE-2 must be transported to the TO by 24th of April 2017. The package must include cables, user manuals (printed or electronic), calibration files (electronic) and if existing, also the mounting frames for fieldwork.

The address information for shipping is

Attention: Joel Kuusk
TARTU OBSERVATORY
Observatooriumi 1, Tõravere
Nõo parish, 61602 Tartu county
ESTONIA
Phone: +372 696 2510
Fax: +372 696 2555
E-mail: joel.kuusk@to.ee

If the participants are coming outside of the EU, they will receive additional information from TO prior to the shipment that includes paperwork information for customs.

Mobley, C.D., 1999. Estimation of the remote-sensing reflectance from above-surface measurements. Applied Optics, 38(36), pp.7442-7455.

Event organizer and contact person on site

Joel Kuusk (joel.kuusk@to.ee)

Shipping info

TARTU OBSERVATORY
Observatooriumi 1, Tõravere
Nõo parish, 61602 Tartu county
ESTONIA

Phone: +372 696 2510
E-mail: info@to.ee