http://arxiv.org/abs/2003.07251
Measure the Sloan g’ magnitudes of the SpaceX STARLINK-1130 (Darksat) and 1113 LEO communication satellites and determine the effectiveness of the Darksat darkening treatment at 475.4\,nm. Two observations of the SpaceX STARLINK Darksat LEO communication satellite were conducted on 2020/02/08 and 2020/03/06 using a Sloan r’ and g’ respectively. While a second satellite, STARLINK-1113 was observed on 2020/03/06 using a Sloan g’ filter. The initial observation on 2020/02/08 was a test observation when Darksat was still manoeuvring to its nominal orbit and orientation. Based on the successful test observation, the first main observation was conducted on 2020/03/06 along with an observation of a second STARLINK satellite. The calibration, image processing and analysis of the Darksat Sloan g’ image gives an estimated Sloan g’ magnitude of $\mathbf{7.57\pm0.04}$ at a range of 976.50\,km. For STARLINK-1113 an estimated Sloan g’ magnitude of $\mathbf{6.69\pm0.05}$ at a range of 941.62\,km was found. When scaled to a range of 550\,km, a reduction of (55\,\%\,$\pm$\,4.8\,\%) is seen in the reflected solar flux between Darksat and STARLINK-1113. The data and results presented in this work, show that the special darkening “treatment” used by SpaceX for Darksat has reduced the Sloan g’ magnitude by $0.88\pm0.05$\,mag (55\,\%\,$\pm$\,4.8\,\%), when the range is equal to a nominal orbital height (550\,km). This result will serve members of the astronomical community modelling the satellite mega-constellations, to ascertain their true impact on both the amateur and professional astronomical communities. Concurrent and further observations are planned to cover the full optical and NIR spectrum, from an ensemble of instruments, telescopes and observatories.
J. Tregloan-Reed, A. Otarola, E. Ortiz, et. al.
Tue, 17 Mar 20
15/63
Comments: Letter submitted to A&A. 5 Pages, 3 figures and 4 tables