# On the Integration of VLBI Observations to GENESIS into Global VGOS Operations
## 2 Concept  
The concept of this work comprising four main steps is visualized in Figure 2. In step 1, we perform a schedule optimization following the work by [PERSON] and [PERSON] [PERSON] and [PERSON] (2018). VLBI scheduling is a complex optimization problem in which scheduling weight factors play a crucial role. For example, they determine whether stations slew long distances between scans to benefit from evenly distributed sky coverage or keep the slew time between scans short to maximize the number of observations. Because scheduling weight factors decisively impact the results, they should be optimized for each VLBI experiment. The VGOS schedule optimization performed in step 1 uses schedules which only contain geodetic radio sources, further referred to as VGOS schedules. Based on sets of scheduling weight factors, schedules are created and simulations are performed to estimate station position, EOPs, and source positions. The result is a set of optimal scheduling weight factors that correspond to the best estimation precision. In the following steps 2, 3, and 4, these optimal scheduling weight factors are applied to the generation of schedules using both geodetic sources and GENESIS, further referred to as mixed schedules. We assume that the optimal scheduling weight factors for VGOS schedules are also optimal for the estimation of geodetic parameters for mixed schedules. In step 2, we analyze the VGOS performance in mixed schedules. Or, in other words, we investigate to what extent the integration of GENESIS into VGOS experiments impacts the estimation of geodetic parameters. Applying the optimal scheduling weight factors from step 1, we generate schedules containing both geodetic sources and GENESIS. Consequently, the number of scans and observations of geodetic sources is reduced in mixed schedules compared to VGOS schedules. From the mixed schedules, the geodetic parameters are estimated solely from the observations of geodetic sources. In this step, observations of GENESIS do not contribute to the analysis and are disregarded. The simulated results are compared to step 1 to derive the degradation of the parameter estimates. In step 3, the mixed schedules from step 2 are used to estimate the frame tie between the VLBI frame and the GENESIS frame from 24 h VLBI experiments. We assume that the GENESIS orbit is determined through observations of the satellite techniques (GNSS, SLR, and DORIS). As this orbit is assumed to be imperfect, we simulate orbital errors as further detailed in Section 3. In this study, the VLBI frame is then attached to the GENESIS frame through observations of the satellite. We define the frame tie as the VLBI station positions  
Figure 2: Concept of this work. Four main steps will be performed to investigate the impact of GENESIS on VLBI Global Observing System (VGOS) operations, the valid estimate of the number of scans and observations of GENESIS, as well as the achievable frame tie accuracy. derived only from VLBI observations of GENESIS. It is assumed that with a set of VLBI station positions given in the initial VLBI frame and a set of estimated VLBI station positions given in the GENESIS frame, a frame tie can be established to link the frames. The repeatability of the station position estimates is a measure for the expected frame tie accuracy. This analysis builds upon previous studies by [PERSON] et al. (2014), [PERSON] et al. (2015), [PERSON] and [PERSON] (2016), and [PERSON] et al. (2013). The optimal scan repetition rate with which GENESIS will be integrated into mixed schedules is derived from a compromise between the results from steps 2, the impact of GENESIS on VGOS, and 3, the estimated frame tie accuracy. On the one hand, GENESIS ideally does not degrade the estimation of geodetic parameters. A low repetition rate for GENESIS scans leads to larger numbers of observations of geodetic sources. On the other hand the GENESIS mission and its goals are supported by performing large numbers of VLBI observations of the satellite.