Aerosol Robotic Network (AERONET) Project

1 AERONET Sun Photometer Procurement Contract Description of Sun Photometer and Components STATEMENT OF WORK March 23, 2026 TABLE OF CONTENTS SUMMARY 1. General Description 2. Instrument Specifications Capabilities 2A – Non Required specification items (These items are part of the specifications but will not be ordered) • 2-1 Sun and Sky Measurement Mode Selections • 2-2 Automatic Selection of Geometrical Conditions • 2-3 Optics • 2-4 Detectors • 2-5 Filters 2B – REQUIRED SPECIFIATION ITEMS • 2-1 Advanced Control Box • 2-2 Tracking Robot • 2-3 Microprocessor • 2-4 DCS Compatibility • 2-5 Instrument Sensitivity • 2-6 Power Requirements • 2-7 Environmental Requirements 3. Description of Daily Measurement Program • 3-1 Optical Thickness and Water • 3-2 Langley Plot 3-3 Sky Radiance Measurement -- 1 of 10 -- 2 • 3-3.1 Almucantar • 3-3.2 Principal Plane Measurement • 3-3.3 Hybrid Scan Measurement Summary NASA owns and or manages over 600 Cimel Sun-Sky-Lunar Scanning photometers as part of the EOS Aerosol Validation Program called AERONET. The program is part of a larger Federated Global Network of identical instruments designed to measure aerosol properties from land and ocean sites. In order to ensure compatibility within the network, any additional instruments must be identical in optical characteristics, measurement protocol, data acquisition and field hardness. The CE 318 T Sun photometer functions reliably in the harsh environmental conditions (humidity, rain, insects, dust and sea spray.) expected in our remote sites. The instrument is required to have multiple data communication options including the data collection system (DCS) of the international constellation of geostationary meteorological satellites, cellular and PC/internet. The measurement protocol requires direct solar and lunar plus diffuse sky measurements to be automatically taken according to reprogrammed solar zenith angles and scattering angles optimized for analysis of data to estimated aerosol properties. We are adding additional systems to the AERONET program. The additional systems being procured for the AERONET program must be identical in function and be electronically compatible with the existing instruments. Sun and sky-scanning spectral radiometers are used in the AERONET program to monitor aerosol optical properties and precipitable water in near real-time for the validation of satellite-derived retrievals of aerosol properties and provide a uniform database for long-term characterization of aerosol optical properties within NASA's Earth Science program. To develop such a database, AERONET has imposed a standardization in data measurement, data collection, data format, and data processing that is fundamental to the objectives and success of the program. Any deviation -- 2 of 10 -- 3 from these standards will erode the quality control necessary for network operations. The following instrument specifications are required to meet the requirements of the AERONET network measurement program. 1. GENERAL DESCRIPTION The radiometer system will measure both sun and lunar irradiances and sky radiances using a combination of spectral filters and a fully- autonomous azimuth/zenith viewing microprocessor-controlled robot. The daily data stream will be transmitted via the internationally-standardized Data Collection System (DCS) aboard the geostationary satellite system GOES, METEOSAT and HIMAWARI. The radiometer must be capable of unattended operation for up to eight weeks in any environmental conditions and be powered by rechargeable batteries and a five watt solar panel. Place of Performance Radiometers to be built at the Contractor facility and sent to NASA Goddard Space Flight Center. CIMEL Electronique,172 Rue de Charonne, 75011 Paris, FR Period of Performance Oct 1 2026 to Sept 30 2031 -- 3 of 10 -- 4 2. INSTRUMENT SPECIFICATIONS CAPABILITIES The Sun and Sky radiometers must have a broad spectral range from the UV to the short wave infrared. It shall incorporate the digital electronics in the sensor head, and its components are compatible with earlier models of the CE318 including the robots. The instrument shall incorporate polarization to the standard measurements. It will be an important instrument for new research activities and synergism with future satellite validation activities. It shall be fully compatible with existing system components and network standardization. The instrument shall be able to take the atmospheric and ocean radiances. It shall be fully compatible with the existing network components. The instrument shall be able to be used to extend measurement from daylight only to day and night time measurements with lunar observations in addition to solar observations and support validation of all Earth viewing satellite monitoring systems. It shall be compatible with the existing robot infrastructure. A. NON REQUIRED SPECIFICATION ITEMS 2.1 SUN AND SKY MEASUREMENT MODE SELECTION The radiometer must automatically change gains from the sky radiance measurement mode to the sun-measuring mode without saturating the signal response. It is fundamental that a two-detector two-collimator system be used in order to assess the quality of data from each detector system. 2.2 AUTOMATIC SELECTION OF GEOMETRICAL CONDITIONS The automatic instrument is set up on an axis which is able -- 4 of 10 -- 5 through step-by-step motors to move in two directions, in the zenith and in the azimuth planes. The step-by-step motors piloted by the microprocessor card are able to reach any geometrical conditions. Computations of the equation of Sun are performed by the microprocessor and combined with a four- quadrant detector system enables accuracy of sun position to ±0.05°. Therefore, the specification of accuracy in pointing to any direction is ±0.05, relative to the sun. 2.3 OPTICS Collimator Detector Sun, 1.2 degree FOV, no optics sky, collimator 1.2 degree FOV, lens required, …