Friday

The new megaconstellations of low earth orbiting satellites such as Starlink and OneWeb present astronomy with a serious problem. The satellites reflect sunlight, and so appear as bright optical and near-IR sources that can contaminate and in some cases saturate observations at these wavelengths (Hainaut & Williams 2020; McDowell 2020; Seitzer 2020). These satellites also pose a potential problem for instruments on satellites in low Earth orbit - 5% of HST images in the optical, for example, are already trailed by satellites or debris (McCaughrean 2020). The satellites also transmit in the radio, and these transmissions will impact frequencies used by radio astronomers, either directly or through leakage into astronomical bands (Clery, 2020; Braun et al., 2019). Studies are under way to measure the impact of the SpaceX Starlink satellites currently on orbit (eg. Horiuchi et al., 2020).
We here report observations of OneWeb satellites in the optical in several different bands, to determine the wavelength dependence of their brightness (measures taken by Starlink, for example to reduce the brightness of their satellites are found to be less effective in redder bands), and to determine how their brightness varies with elevation and time of night. Using simultaneous observations in Sloan griz filters with Muscat2 at Telecopio Carlos Sanchez (Teide Observatory), we found that Oneweb satellites are brighter in redder bands: g= 8.73 pm 0.04, r = 7.78 pm 0.03, i =7.20 pm 0.03, z =6.97 pm pm 0.02 (elevation ~ 27º). This is also confirmed at higher elevation (using the IAC80 telescope) where we found in average: g=9.70 pm 0.07 and r=7.73 pm 0.02 (elevation ~40º). We will continue monitoring the brightness of Oneweb satellites at different positions in its orbit to study how the brightness changes over the course of an orbit and time.