Absolute Radiometric Calibration of TESS-W and SQM Night Sky Brightness Sensors

We develop a general optical model and describe the absolute radiometric calibration of the readings provided by two widely-used night sky brightness sensors based on irradiance-to-frequency conversion. The calibration involves the precise determination of the overall spectral sensitivity of the devices and also the constant G relating the output frequency of the light-to-frequency converter chip to the actual band-weighted and field-of-view averaged spectral radiance incident on the detector (brightness). From these parameters, we show how to define a rigorous astronomical absolute photometric system in which the sensor measurements can be reported in units of magnitudes per square arcsecond with precise physical meaning.

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A survey of night sky brightness at College, Alaska

Transactions American Geophysical Union ◽

10.1029/tr031i004p00541 ◽

1950 ◽

Vol 31 (4) ◽

pp. 541 ◽

Cited By ~ 1

Author(s):

John B. Wilcox

Keyword(s):

Sky Brightness ◽

Night Sky ◽

Night Sky Brightness

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Remote Sensing of Aerosols at Night with the CoSQM Sky Brightness Data

10.20944/preprints202108.0181.v1 ◽

2021 ◽

Author(s):

Charles Marseille ◽

Martin Aubé ◽

Africa Barreto Velasco ◽

Alexandre Simoneau

Keyword(s):

Remote Sensing ◽

Aerosol Optical Depth ◽

Optical Depth ◽

Low Cost ◽

Empirical Relationship ◽

Important Indicator ◽

Sky Brightness ◽

Night Sky ◽

Remote Sensing Techniques ◽

Night Sky Brightness

The aerosol optical depth is an important indicator of aerosol particle properties and associated radiative impacts. AOD determination is therefore very important to achieve relevant climate modeling. Most remote sensing techniques to retrieve aerosol optical depth are applicable to daytime given the high level of light available. The night represents half of the time but in such conditions only a few remote sensing techniques are available. Among these techniques, the most reliable are moon photometers and star photometers. In this paper, we attempt to fill gaps in the aerosol detection performed with the aforementioned techniques using night sky brightness measurements during moonless nights with the novel CoSQM: a portable, low cost and open-source multispectral photometer. In this paper, we present an innovative method for estimating the aerosol optical depth by using an empirical relationship between the zenith night sky brightness measured at night with the CoSQM and the aerosol optical depth retrieved at daytime from the AErosol Robotic NETwork. Such a method is especially suited to light-polluted regions with light pollution sources located within a few kilometers of the observation site. A coherent day-to-night aerosol optical depth and Ångström Exponent evolution in a set of 354 days and nights from August 2019 to February 2021 was verified at the location of Santa Cruz de Tenerife on the island of Tenerife, Spain. The preliminary uncertainty of this technique was evaluated using the variance under stable day-to-night conditions, set at 0.02 for aerosol optical depth and 0.75 for Ångström Exponent. These results indicate the set of CoSQM and the proposed methodology appear to be a promising tool to add new information on the aerosol optical properties at night, which could be of key importance to improve climate predictions.

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