The advantages of determining asteroid reflectance spectra (ARS) by removing atmospheric effects from their observed spectra using telluric standards (primarily spectra of sufficiently common A0V-class stars) and subsequently using the averaged extraterrestrial solar spectrum (Coddington et al., 2023) to derive the ARS are discussed. We compared this method with the traditional approach of calculating ARS using G-class star spectra as “substitutes” for the Sun. For this purpose, observations of four near-Earth asteroids (887, 4954, 103067, and 265196), which made close approaches to the Earth in February 2025, were carried out by us using the 2.5-m telescope of the Caucasian Mountain Observatory of the Sternberg Astronomical Institute, MSU, equipped with the two-channel TDS spectrometer. Processing of these observational data and calculation of ARS using the extraterrestrial solar spectrum show that a higher signal-to-noise ratio (SNR) is achieved compared to the case of using solar analog spectra. It is important to note that the A0V-class stellar spectral standards we used have been verified against the best spectrophotometric standards and agree with them within random errors (~3%). Furthermore, the removal of interstellar absorption from the spectral characteristics of the telluric standards instills confidence in the absence of systematic errors in the ARS obtained by the new method. An additional result of the work is the detection of material inhomogeneity on the S-type asteroid 4954 Eric. On one of its two consecutive reflectance spectra, obtained with a time interval of ~10 min, a spectral reddening and weak absorption bands at 0.415, 0.515, and 0.624 µm were recorded, likely related to the exposure of material with a younger exposure age due to the asteroid’s rotation.
Busarev et al. (Sun,) studied this question.