NASA/GSFC has a requirement for several models of the CIMEL CE318-T family of Sun-Sky-Lunar Spectral Photometers and necessary parts for the repair, maintenance, and upgrade of the photometers; tracking robots; and advanced control boxes. These photometers monitor aerosol optical properties and provide a uniform database for the long-term characterization of aerosol optical properties within NASA's global climate change and satellite validation programs. NASA/GSFC intends to issue a sole-source, Firm Fixed Price, Indefinite Delivery/Indefinite Quantity (IDIQ) contract to acquire the items from CIMEL ELECTRONIQUE in support of NASA's Aerosol Robotic Network (AERONET) program. The period of performance for this contract will be 5 (five) years. This requirement is being is pursuant to 10 U.S.C 3204(a)(1), Only One Responsible Source. The network has been in existence for over 30 years, and no other source is available within the market to provide instrumentation that meets the Government's needs, other than CIMEL. The AERONET Project has grown due to standardization across all aspects of the program. This includes data processing, data measurement protocols, calibration procedures, and scientific equipment. With respect to the latter, one fundamental photometer produced by CIMEL ELECTRONIQUE, the CE318-T, has been the only instrument used in and designed to the specific requirements of the AERONET program. Award to any other vendor would not meet the Government's instrumentation schedule requirements. The Government intends to acquire a commercial product or service using FAR Part 12. Interested organizations may submit their capabilities and qualifications to perform the effort electronically via email to Kermit Stanbach, Contracting Specialist, at Kermit.S.Stanbach@nasa.gov, not later than 4:00 PM EST on June 23, 2026. Such capabilities/qualifications will be evaluated solely for the purpose of determining whether to conduct this acquisition on a competitive basis. A determination by the Government not to compete this acquisition on a full and open competition basis, based upon responses to this notice, is solely within the discretion of the Government. NASA Clause 1852.215-84, Ombudsman, is applicable. The Center Ombudsman for this acquisition can be found at: https://www.hq.nasa.gov/office/procurement/regs/Procurement-Ombuds-Comp-Advocate-Listing.pdf.