## 4 Tests and Results
### \"Mid-Gap\" Scenario
The explanations of C, K, and R clocks are given in Figure 10.  
Figure 10: Sentinel-3B satellite clocks determined using the Kalman filter-based kinematic model with the CNES real-time products without latency (black line); using the BLS-based reduced-dynamic model with the CODE final products (red line); the connected near-real-time clocks estimated in a Kalman filter using the CNES real-time products without gaps (blue line). Figure 12: Near-real-time Sentinel-3B clocks based on a Kalman filter-based kinematic model, using CNES products with different “mid-gap” durations. (**Top**): Sentinel-3B clocks for the entire day; (**Bottom**): Sentinel-3B clocks from the first epoch affected to the last epoch affected. Figure 13: Near-real-time Sentinel-3B clock errors using the Kalman filter-based kinematic model with the CNES real-time products suffering from different “mid-gap” durations, compared with those using continuous CNES real-time products. (**Top**): Sentinel-3B clocks for the entire day; (**Bottom**): Sentinel-3B clocks from the first epoch affected to the last epoch affected. As inferred from Figure 3, to generate LEO satellite clocks for a full day of 86,400 s, the number of sessions that need to be initiated periodically is \(86,400/\Delta T\). If the arc length of the mid-gap period is \(M\), then the number of affected sessions is \(\left((AB)+M\right)/\Delta T\), where \((AB)\) is the length of the near-real-time processing arc. The first epoch of the LEO satellite clocks affected is the epoch when \"mid-gap\" begins, while the last epoch affected for the LEO satellite clock determination is the moment when \"mid-gap\" ends, extended by the length of near-real-time determination arc \((AB)\). For example, assuming that each processing arc is 4 h, \(\Delta T\) is set to 120 s, and the \"mid-gap\" starts from 4:00, as mentioned before; when the mid-gap duration is 60 min, the number of affected sessions is 150. The first affected epoch is 4:00, and the last affected epoch is 9:00. The top panel of Figure 12 displays the near-real-time Sentinel-3B clocks based on the kinematic model with Kalman filter, using CNES products with different \"mid-gap\" durations. The bottom panel shows the Sentinel-3B clocks from the first affected epoch to the last affected epoch (with a \"mid-gap\" duration of 5 min up to 60 min), with the clocks during the mid-gap period removed. It can be seen that as the \"mid-gap\" duration increases, the number of gross errors in the Sentinel-3B clocks increases, and the fluctuation range becomes larger. After the gap period, the LEO satellite clocks are no longer affected. Figure 13 illustrates the near-real-time Sentinel-3B satellite clocks determined based on the use of the Kalman filter-based kinematic model and using the CNES real-time products with different \"mid-gap\" durations compared with those determined using the CNES real-time products without gaps. Figure 14 illustrates its counterparts compared with the BLS clocks determined using the CODE final products. As shown in Figures 13 and 14, the clock errors become larger as the mid-gap duration increases. Based on the analysis presented in [16], with \(\Delta T\) set to 120 s and the near-real-time processing arc set to 4 h, the prediction arc (BD) needs to be set to at least 150 s to ensure supporting real-time applications. Table 7 illustrates the error budget of near-real-time clocks and the predicted clocks, compared to the Sentinel-3B clocks based on the Kalman filter-based kinematic model using the CNES real-time products without loss (denoted as \"K\") and the BLS Sentinel-3B clocks processed using the CODE final products (denoted as \"R\"). Figure 14: Near-real-time Sentinel-3B clock errors determined using the Kalman filter-based kinematic model with CNES products of different “mid-gap” durations, compared with the BLS clocks determined using the CODE final products. (**Top**): Sentinel-3B clocks for the entire day; (**Bottom**): Sentinel-3B clocks from the first epoch affected to the last epoch affected.