International Astronautical Congress

Current scientific findings on the effect of re-entry on stratospheric ozone range from negligible to severely adverse. Policy makers cannot draw conclusions on whether to restrict or allow continued large constellation expansion; hence, the current stance of deferral-until-certainty. The global impact of re-entry on the stratosphere has never risen above natural variation, so no empirical ozone-loss data are available to validate current prospective models, causing large uncertainties. This research shows: waiting for detectable ozone loss to prompt re-entry restriction can leave CFClevel ozone depletion due to satellites already in orbit. Despite the uncertainty, preventative policy is needed before it is too late. Extrapolation of ozone loss and radiative forcing anomaly due to yearly re-entering mass from previous climate model simulations shows that the planned large constellations, completing in 2042, emit alumina (Al2O3) and nitrogen oxides (NOx) that could reach −7.7% Total Ozone Column (TOC) loss after completion, larger than the CFC peak in 2000; alongside, radiative forcing could reach the same order of magnitude as the aviation industry. Trenddetection analysis further demonstrates that 8.9 years of record from 2030 are required to distinguish this ozone change from natural variability. Implementing a complete launch stop three years post-detection will commit 79%–100% of the cumulative ozone loss above the chosen limit of 0.5%–5.2% TOC deficit. Integrating over 20 years around the peak TOC loss, re-entry reaches 95% of the CFC impact. TOC loss due to large constellations reaches 0.5%–3.1% in a four-year span: 2035 to 2039. Findings indicate that mitigation efforts must be in place by 2035 to be effective. After this time, irreversible impact on the stratosphere could occur.

How accurate do SSA products need to be for flight safety? Is there “too much accuracy,” that is, is the added cost of further improving SSA accuracy warranted? In this paper, we explore these questions in several ways: (1) we review the encounter rate squared relationship for miss distance screening; (2) we examine the reduction of collision probability-based encounter rates stemming from positional accuracy improvements; and (3) we examine the applicability and effectiveness (in terms of Type I and Type II error statistics) of both miss distance and probability-based trending as a viable tool for collision avoidance maneuver go/no-go decision making.