Abstract
Planet Labs currently operates a fleet of 21 high resolution Earth observation satellites known as SkySats. These sub-meter resolution satellites have high intra-day revisit rate capabilities, can image scenes in a range of viewing angles, create 3D scene composites and take videos even in regions traditionally difficult to observe due to low satellite capacity. The radiometric calibration of other satellite models within Planet’s fleet (Dove Classic, Dove R and SuperDove) is currently achieved using simultaneous crossovers with Sentinel-2. Radiometric calibration of SkySat imagery using Sentinel-2 poses unique challenges as it has relatively wide spectral bands and frequently takes images off-nadir. In order to achieve optimal radiometric calibration, SkySats are tasked to image Radiometric Calibration Network (RadCalNet) and Pseudo Invariant Calibration (PIC) sites daily to generate numerous near-simultaneous crossovers of these sites with Sentinel-2. Using a reference satellite to cross-calibrate is a common approach in radiometric calibration, however bidirectional reflectance distribution (BRDF) effects may affect accuracy especially if the viewing angles of the satellites are substantially different. Here we will discuss some of the current challenges and effects of applying this approach to SkySat imagery.
Radiometric Calibration of SkySats Using Near-Simultaneous Crossovers with Sentinel-2 over Calibration Sites
Planet Labs currently operates a fleet of 21 high resolution Earth observation satellites known as SkySats. These sub-meter resolution satellites have high intra-day revisit rate capabilities, can image scenes in a range of viewing angles, create 3D scene composites and take videos even in regions traditionally difficult to observe due to low satellite capacity. The radiometric calibration of other satellite models within Planet’s fleet (Dove Classic, Dove R and SuperDove) is currently achieved using simultaneous crossovers with Sentinel-2. Radiometric calibration of SkySat imagery using Sentinel-2 poses unique challenges as it has relatively wide spectral bands and frequently takes images off-nadir. In order to achieve optimal radiometric calibration, SkySats are tasked to image Radiometric Calibration Network (RadCalNet) and Pseudo Invariant Calibration (PIC) sites daily to generate numerous near-simultaneous crossovers of these sites with Sentinel-2. Using a reference satellite to cross-calibrate is a common approach in radiometric calibration, however bidirectional reflectance distribution (BRDF) effects may affect accuracy especially if the viewing angles of the satellites are substantially different. Here we will discuss some of the current challenges and effects of applying this approach to SkySat imagery.