The impact of SATCON recommendations on the safety and sustainability of large constellations

The collision risk posed to satellites is a key factor when assessing the long-term sustainability of activities in space. Additionally, advocates for the preservation of dark and quiet skies have raised concerns about the impacts of large satellite constellations in Low Earth Orbit (LEO) on astronomical observations due to satellite streaks and an increase in diffuse night sky brightness from the space debris population. In response, multiple astronomy-driven working groups have been established to develop recommendations designed to reduce interference with astronomy-related uses of space. For example, the Satellite Constellations (SATCON) workshops produced recommendations which are incorporated into guidelines published by the International Astronomical Union’s Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS). The DAMAGE computational model was used to study the effects of reducing large constellation altitudes to below 600 km on satellite conjunctions as has been recommended to reduce the impact on optical astronomy. The impact of this altitude reduction on both satellite collision risk and optical astronomy was evaluated. This study found that whilst operating satellites at lower altitudes reduces the contamination of astronomical images, the impact on collision risk for constellation satellites increases due to the reduced orbital volume within which the constellation operates. When formulating space sustainability guidelines, it will be important to consider this and other trade-offs arising from the perspectives of different users of the space environment.