# Impact of Mega Constellations on Geospace Safety
## 4 Impact of Starlink on Control Avoidance Strategies for low-orbiting Satellites in Geospace  
### Impact on ACPL Values for LEO Space Target Satellites  
According to the flux, we can get the ACPL value of the target satellite with its corresponding average daily manipulation frequency, risk variation curve, etc. The manipulation frequency and risk (collision probability) corresponding to different ACPL values are shown in Figure 7. Risk Reduction is the risk that decreases with the number of manipulations, and Residual Risk is the risk that remains. In the following analysis, only the variation of risk of known objects is discussed. For ACPL, \(10^{-4}\) is a more acceptable value at present [15], attributed to its balance of safety as well as economy. ACPL-\(10^{-6}\) is added for comparison to reflect the nature of the value. In Figure 7a,b when Starlink is not considered, the ACPL value chosen for \(10^{-6}\) corresponds to a manipulation frequency of \(0.201\), \(10^{-4}\) to \(0.036\), and a risk of \(2.27\times 10^{-6}\). After adding Starlink, the manipulation frequency corresponding to ACPL-\(10^{-6}\) is \(1.24\), the manipulation frequency corresponding to ACPL-\(10^{-4}\) is \(0.0811\), and the risk is \(1.27\times 10^{-5}\), which reaches the yellow warning threshold. Before and after changes, the manipulation frequency of ACPL-\(10^{-4}\) becomes \(2.252\) times that of the previous one, and the risk of known objects becomes \(5.5947\) times that of the previous one. Considering Starlink before and after the change, ACPL-\(10^{-6}\) operates \(5.58\) and \(15.28\) times more frequently compared to ACPL-\(10^{-4}\), which reflects the more reasonable choice of ACPL-\(10^{-4}\) from the side. The addition of Starlink to Earth's low-orbit space has not reduced any risk, even though the frequency of operations has changed several times, indicating that the overall risk is greater than before, i.e., Starlink has introduced harsher changes to the Earth's space environment and it would be difficult to alter the current environmental conditions within the range of conventional changes. Figure 7c,d shows the ACPL value of CORVUS BC5 versus the manipulation frequency and risk, with the manipulation frequency of \(1.76\) for ACPL-\(10^{-6}\), \(0.0834\) for ACPL-\(10^{-4}\) and \(1.22\times 10^{-5}\) when Starlink is not added. After adding Starlink, the manipulation frequency of ACPL-\(10^{-6}\) becomes \(6.73\), the manipulation frequency corresponding to ACPL-\(10^{-4}\) is \(1.16\), and the risk is \(5.4\times 10^{-5}\). In comparison of the situations before and after change, the manipulation frequency corresponding to ACPL-\(10^{-6}\) changes to \(3.823\) times of the previous one; the risk of known objects does not change; the manipulation frequency of ACPL-\(10^{-4}\) becomes \(13.9\) times of the previous one, and the risk of known objects becomes \(4.5\) times of the previous one. While taking Starlink into consideration, the manipulation frequency of ACPL-\(10^{-6}\) compared to ACPL-\(10^{-4}\) is \(21.103\) and \(5.80\) times of the previous one, respectively. The overall change pattern of CORVUS BC5 is similar to GAFEN. Figure 7e,f shows the relationship between the ACPL value of YAOGAN-35C and the manipulation frequency and risk; without Starlink, the manipulation frequency of ACPL-\(10^{-6}\) is \(0.334\), the manipulation frequency corresponding to ACPL-\(10^{-4}\) is \(0.0809\), and the risk is \(2.63\times 10^{-6}\). After adding Starlink, the manipulation frequency of ACPL-\(10^{-6}\) becomes \(12.7\), the corresponding manipulation frequency of ACPL-\(10^{-4}\) is \(1.68\), and the risk is \(1.65\times 10^{-4}\), which has exceeded the yellow warning threshold.