WP7: AERONET-EUROPE Calibration Centre

WP7 Objectives
The main objective is to support, mostly in Europe, long-term aerosol observation and monitoring efforts from a ground-based automatic photometer network. This activity is a support from EU to the NASA AERONET program producing routinely, in real time and publically available, high quality aerosol column integrated properties such as AOD (Aerosol Optical Depth), optical and microphysical properties and many others derived-radiative properties quite relevant and widely used by academic and industrial actors involved in climate and air-quality fields. This activity is strongly contributing, at the European level, to several relevant integration/synergetic activities with LIDAR, in situ observation, satellite and modelling. This TNA is therefore clearly a continuation based on the success and strong demand we had, during ACTRIS, to provide a fast and efficient calibration and standard maintenance service for sun/sky/polar photometers as requested by the users. This is only possible in Europe thanks to the unique AERONET-EUROPE research infrastructure operated by France and Spain. In ACTRIS-2, we will offer the same service plus the monitoring of the instrument status (Quality Check) during operation in the field and Quality Assurance (QA) both increasing the observation period). Moreover, thanks to partnerships developed between academic research and industry within ACTRIS, a lunar photometer has been developed and will offer, for the first time, night-time observation capability. ACTRIS-2 will offer calibration and maintenance service to users operating this new instrument.  
Provision of access to the following infrastructure(s): 335 units of access or calibrations (165 for LOA, 100 for GOA and 70 for AEMET). During ACTRIS, 300 units of access were provided.

Description of the infrastructure

Name of the infrastructure: AERONET-EUROPE Calibration Centre (AERONET-EUROPE)

1- LOA
2- GOA
Location of the infrastructure: The infrastructure is composed of separate and complementary installations:
The leading and entrance installation is CNRS-LOA (Laboratoire d’Optique Atmosphérique), University of Lille 1, Villeneuve d’Ascq city (France). The other complementary installations are in Spain (AEMET-CIAI-IZANA) and GOA-UVA (Group of Atmospheric Optics, University of Valladolid UVA)

Web site address:

Annual operating costs (excl. investment costs) of the infrastructure (€): 995 521 € divided in  648 309 € (LOA) -149 556 € (GOA) - 197 656 € (AEMET)

Description of the infrastructure

As TNA, AERONET-EUROPE Calibration & Maintenance Centre offers a unique sun/sky/lunar photometer facility, complementing the NASA calibration centre in the USA, for calibration and basic maintenance in the frame of AERONET (AERosol RObotic Network). AERONET is a ground-based standardized automatic sun/sky-photometer network devoted to the characterization and monitoring of aerosol properties, water vapour content and, more recently, cloud optical deptAs TNA, AERONET-EUROPE Calibration & Maintenance Centre offers a unique sun/sky/lunar photometer facility, complementing the NASA calibration centre in the USA, for calibration and basic maintenance in the frame of AERONET (AERosol RObotic Network). AERONET is a ground-based standardized automatic sun/sky-photometer network devoted to the characterization and monitoring of aerosol properties, water vapour content and, more recently, cloud optical depth.
The AERONET-EUROPE Calibration Service is a unique European infrastructure enabling AERONET operation and potential network expansion, thanks to complementary Calibration Centres developed in Europe, under the leadership of (CNRS-LOA), in Lille (France), in Valladolid (Spain) at GOA (University of Valladolid) and at Izaña Observatory, Tenerife Island, Spain at AEMET-Izana). CNRS-LOA and GOA-UVA facilities are designed for maintenance and calibration transfer from reference instrument to field instrument. It must be outlined that both CNRS-LOA (more relevant for users from Northern Europe) and GOA (more relevant for users from Southern Europe) installations are necessary since none of them can, separately, provide enough access to the European users. AEMET-Izana installation is designed for calibrating reference instrument required by CNRS-LOA and GOA.

CNRS-LOA (Laboratoire d'Optique Atmosphérique) calibration/maintenance facilities are composed of indoor and outdoor platforms (60 m a.s.l). The indoor platforms include a dark room for calibration relying on NASA-NIST traceable integrating spheres, solar-simulator. This facility is the only one in the world operating a dedicated polarized light source for the calibration of the polarized version of CIMEL sun/skyphotometer.
A maintenance and repair room as well as a spectrometer for filters characterization and a thermal chamber for temperature response characterization are also available. A dedicated computer, linked to AERONET/NASA database, is operated for computing the calibration coefficients and data reprocessing. Outdoor platforms (about 100 m2 horizon) are used for transferring sun calibration from reference instrument to field instruments and for functional tests. Since 2010 CNRS-LOA has a permanent capability to calibrate simultaneously 8 field instruments thanks to 2 reference instruments.

GOA-UVA (Group of Atmospheric Optics of the University of Valladolid) installation is composed of one outdoor horizon-free platform located at Valladolid (705 m a.s.l.) designed for transferring calibration simultaneously to 6 field instruments thanks to 2 reference instruments. One indoor lab equipped with dark room with integrating sphere, thermal chamber, NIST-traceable calibration references, plus a maintenance and repair room. A computer is linked to AERONET/NASA centralized database for calibration coefficients computation and data reprocessing. GOA receives every 3 months a new set of 2 reference instruments calibrated at Izaña by CNRS-LOA.

AEMET-IZANA (Izaña Atmospheric Research Centre-CIAI) is a platform (2400 m a.s.l) hosting permanently a set of 6 reference instruments continuously in operation and available for the needs on the CNRS-LOA and GOA-UVA installations. These reference instruments are recalibrated every 3 months in order to preserve measurements accuracy in the network. The facility, also unique in Europe, is equivalent to the NASA site located in Hawaï on Mauna Loa island. This facility also maintains a reference lunar photometer for nocturnal calibrations

Services currently offered by the infrastructure

In the framework of ACTRIS, the infrastructure has been designed to provide annual calibration, maintenance, weekly checks (QC), quality assurance (QA), and production of Near Real Time Aerosol Optical Depth, downward sky total and polarized radiances and derived columnar aerosol optical and microphysical properties, Water Vapour (WV) and Cloud Optical Depth (COD).  In average, the infrastructure provides, each year, 80 access units to international users. ACTRIS demonstrated the wide interest of several communities for using AERONET EUROPE. The “LIDAR” community, for example EARLINET in Europe, is now widely using AERONET EUROPE since joint aerosol retrievals, as those developed in ACTRIS, require sun-photometer products. AERONET EUROPE also supported other sun-photometer networks, for example in China, through the regular calibration of reference instruments used by these networks. The satellite community is strongly relying on AERONET EUROPE for the main purpose of aerosols products validation (for example, CCI program from the European Space Agency). The “modelling” community makes also intensive use of the data provided by the instruments calibrated by AERONET-EUROPE with, as main examples, AEROCOM, MACC-II, GMES-COPERNICUS, SDS-WAS projects or programs. Finally, AERONET EUROPE provided support to several SMEs aiming at developing both advanced instruments (sun/sky/lunar photometer alone and combined with micro-LIDAR) and low-cost instruments for educational purposes.

All users operating either a standard or a polarized CIMEL sun/sky/lunar photometer located in Europe or in the world can request access by submitting a proposal to the Selection Panel, at any time. Accounting for recent introduction in the market of the advanced-CIMEL sun/sky/lunar photometer, any new instrument sold by CIMEL SME is now including both sun and lunar capability. AERONET-EUROPE will provide this additional calibration to the user. Calibration and maintenance are performed free of charge and proposals are granted on the basis of a TNA selection panel review process. Instrument shipments expenses from and to the user site are not included and must be covered by the user institution. This TNA strongly contributes to reduce calibration time, to increase observation time at user site, to reduce shipping time and custom’s issues and is offering a unique polarization calibration facility at CNRS-LOA;

The overall services provided yields:
- Improvement of measurement technology (advanced instrumentation, day and night)
- Improvement of calibration methodology (accuracy and speed)
- Improvement of data processing capacity (including synergies with in situ and profiling systems)
- Increasing of data quality, dissemination of good practices
- Acceleration of the calibration process (reducing data lack and lost)
- Increasing the number of relevant stations, networks contributing to an harmonized ground-based observation relevant for satellite remote sensing and modellers communities (large user communities).

Description of work

Modality of access under this proposal: Remote Access

AERONET-EUROPE is a remote access infrastructure providing access for calibration and maintenance. Access is offered for sun/sky/polar/lunar photometer belonging to two types of users: (1) owners/users of CE318 sun/lunar/sky-photometer (including AERONET users), (2) other types of instrument (mobile systems, other networks, prototypes, supports for innovation in link with SMEs). The instrument stays within the infrastructure for, on average, 1 month (excluding shipment time).

The access costs are declared on the basis of a unit cost. The unit of access is one calibration (i.e., instrument calibration and/or maintenance), the access provision per instrument will depend on user type 1 or 2 since dealing with other type of instrument requires more time to the staff. The general sequence defining one unit access is summarized in several actions: (1) reception of instrument sent by the user to CNRS-LOA or GOA-UVA; (2) post-field calibration; (3) maintenance; (4) pre-field calibration; (5) final functional test at CNRS-LOA or GOA-UVA; (6) inform user when his instrument is ready for the shipment back to the site; (7) calibration coefficients update in AERONET database; (8) deliver the Calibration Certificate to the user; (9) request for the Quality Assurance analysis to GSFC/NASA. There are two additional options yielding adjustment of the number of access units provided. For the most recent instrument including both solar and lunar capabilities, the infrastructure will count 2 access units. Additionally, if training at the infrastructure is requested by new users, an extra 0.5 unit access unit will be applied to each calibration. Finally, when the previous standard sequence (calibration) has to be repeated due to instrument failure then the access provided will be adjusted in accordingly.

The call for access to AERONET-EUROPE is continuously open (permanent call). Proposals are accepted at any time and from any eligible researcher in charge of a sun/sky/lunar photometer deployed for long-term measurements or specific field campaigns. The trans-national access to AERONET-EUROPE will be jointly coordinated by the project management team (PMT) and WP7 leader (CNRS-LOA). CNRS-LOA will manage and follow-up on the proposals onsite.

Support offered under this proposal

- Provide standard access/services for sun/sky/polarization calibration (daytime downward sky total and polarized radiances, AOD, Aerosols columnar properties, water vapour content, cloud optical depth).
- Monitoring of the instrument, warning, data quality assurance as added-value service.
- Provide lunar calibration and nighttime AOD and water vapour to cover expected new user needs (added-value from AERONET-EUROPE).
- User will be given access to calibration and standard cleaning/maintenance services. Standard maintenance includes filters, polarisers and internal batteries changes for head and control box parts as well as microswitch and belt for robot. Once the calibration is achieved, data reprocessing and Quality Assured data/products will be made available via AERONET (
- User benefitting from TNA adheres to the AERONET QA rules which includes the following local maintenance procedures:
    (i) weekly check and local maintenance of instrument following AERONET rules
    (ii)prompt reply to any alarm sent regarding instruments problems detected by LOA, GOA. In the framework of AERONET, all instruments in operation in the field are monitored in near real time. A system of error detection is in operation and, after analysis by operator of the infrastructure, alarms/recommendations are sent to the user for solving the technical problems.
    (iii) management of shipping issues to the infrastructure and back (ULISSE/CNRS service recommended).
- For QA reasons, in the AERONET network it is strongly recommended to re-calibrate any instrument every 12 months, on average. A new proposal must be submitted each year to the infrastructure.

Outreach to new users

Promotion of AERONET-EUROPE is made through AERONET, CNRS-LOA, GOA-UVA, AEMET-Izana and ACTRIS-2 websites and through meetings, conferences. Additionally, during ACTRIS, AERONET-EUROPE reached a high level of efficiency and has already high relevance status within Europe and beyond. Moreover, the new eligibility criteria will allow new users out of Europe and in yet poorly covered regions to apply for TNA.

Review procedure under this proposal

All users operating for their research activity a sun/sky/lunar/polar photometer must submit a proposal to the PMT at any time (template available on ACTRIS-2 website).  CNRS-LOA will coordinate the proposal review with the AERONET-EUROPE User Selection Panel. The User Selection Panel is composed of three AERONET representatives (AERONET-USA, AERONET-EUROPE and four independent scientists involved in the operation of other international sun-photometer and LIDAR networks (Canada, China, Germany, Switzerland; at least half of them will be independent from ACTRIS-2). The proposal evaluation and selection will be based on scientific merit, priority will be given to new users. It will apply the principles of transparency, fairness and impartiality, The main criteria for the selection are (i) relevance/originality of the scientific and/or technical project, (ii) interest to the scientific community, (iii) relevance of the geographical location and optimization of the geographical coverage of the network (support user in region poorly or not yet covered); (iv) supporting multi-instrumented atmospheric stations; (v) ability to follow the rules of the AERONET network (not applicable for new user), and (vi) possible impact on SME activity. Recurrent users are asked to send a new proposal (new publications, evolution of the project), each year to CNRS-LOA.
The calibrations of LOA/GOA reference instruments are performed at Izaña under supervision of LOA. For that purpose, LOA submits a unique proposal per year with the number of reference instruments/access needed for operating the network with corresponding tentative schedule.