## 2 Background and Previous Studies  
The Suomi NPP satellite was launched in October 2011, and the data became available a month later. However, the VIIRS DNB focal plane array was not cooled to its nominal operating temperature until January 20, 2012 when the cryo-radiator cooler door was opened. The VIIRS sensor data record (SDR) (also known as Level 1b calibrated and geolocated radiance data) has gone through extensive calibration/validation, and the data achieved beta maturity on 2 May 2012, provisional maturity on 13 March 2013, and validated maturity on 17 April 2014. There have been several changes in the VIIRS DNB SDR including the spectral response shift due to the rotating telescope Assembly (RTA) mirror degradation (Figure 1) [15; 16], geolocation improvements including terrain correction, and changes in methodology using onboard vs. dark ocean for calibration offset since 12 January 2017 [17]. Therefore, to avoid complications due to these changes, we focus on more recent data collected in 2018-2019. The VIIRS DNB is well known for its ability to detect low lights at night [18; 19; 20; 21]. It has three gain stages which allow for a wide measurement range spanning from \(1\times 10^{-11}\) to 0.02 W/(cm\({}^{2}\)-sr). The high gain stage can detect radiances typically ranging from \(1\times 10^{-11}\) to \(10^{-6}\) W/(cm\({}^{2}\)-sr) although the actual range depends on the scan angles from nadir. This is because 32 zones are used between nadir and end of scan (referred to as aggregation zones), and each zone uses different number of subpixels in the aggregation to derive one pixel to achieve constant spatial resolution across scan [22]. The DNB HGS noise is around \(2.5\times 10^{-11}\) W/(cm\({}^{2}\)-sr) (1\(\sigma\)) at aggregation zone 1 (as of 21 February 2012), and increased about 8% by the end of 2016. The noise is higher at high aggregation zones, and up to 10 times at the end of the scan than that at the nadir. By comparison, the lunar radiance reflected from the DCC has a nominal range of \(1\times 10^{-9}\) W/(cm\({}^{2}\)-sr) at half-moon to \(>50\times 10^{-9}\) W/(cm\({}^{2}\)-sr) near full moon. Therefore, the VIIRS DNB is able to measure reflected lunar radiances from the DCC with the high gain stage which is essential for this study. The illuminating capabilities of the VIIRS DNB for nighttime remote sensing are well demonstrated in [18; 19; 20]. A comprehensive review of the instrument characteristics and early on-orbit performance was fully covered in [19] which also included an early validation result using the vicarious site at the Railroad Valley. The result showed that the DNB measurements are in agreement with vicarious calibration on the order of 15%. This was followed by other ground based vicarious studies [21; 23; 24]. A major drawback of the ground based vicarious studies is that the validation relies on in situ measurements with atmospheric correction, and is limited to a short time period, or in some cases just a single event. Also, since the VIIRS DNB can detect very small signals (as small as lights from a 1 kW light bulb within a 1 km\({}^{2}\) area), the earth's atmosphere becomes a significant source of uncertainties for the ground based validation, as discussed in [19]. In this paper, the term uncertainty refers to a \"parameter associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand\" [25]. Uncertainty plays an important role in the International Systems of Units (SI) traceability, which is defined as \"property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty\" [26]. To reduce the uncertainties due to atmosphere, researchers explored alternative techniques such as the Dome C, DCC, and stars [23; 27; 28]. The stability of the DCC reflectivity in the visible spectrum and its use for calibration has been studied for many years by the science community.