# On the Integration of VLBI Observations to GENESIS into Global VGOS Operations
## 1 Introduction
The satellite will be equipped with a Global Navigation Satellite Systems (GNSS) receiver, Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) receiver, Satellite Laser Ranging (SLR) reflector, and Very Long Baseline Interferometry (VLBI) transmitter. eters following the proposed GRASP mission as well as LAGEOS-1. [PERSON] et al. [15] simulated and assessed the frame tie performance with a GENESIS-like satellite. [PERSON] and [PERSON] [16] presented a simulation study on the optimal distribution of VLBI transmitters on the Galileo space segment for frame ties. The most recent numerical simulations for a GENESIS-like co-location satellite were presented by [PERSON] et al. [17]. The authors followed a more extensive approach, simulating observations for all four space geodetic techniques and combining them at the observation level. [PERSON] et al. [18] evaluated the potential of VLBI observations of Earth-orbiting satellites for precise orbit determination. Based on combined schedules with both geodetic radio sources and either LAGEOS-1/-2 or a set of Galileo satellites, the authors derive orbit solutions as well as geodetic parameters, i.e., VLBI stations positions, Earth rotation parameters, and geocenter offsets. Despite previous efforts in this area, further investigations and simulations are required with regard to the integration of GENESIS into VLBI operations [19]. In addition to deficiencies in the employed antenna networks and the error modeling of observations, existing studies that consider a co-location satellite do not undertake a dedicated scheduling of experiments. Instead, scans of geodetic sources are replaced at regular intervals using standard VLBI schedules, or scans are simply assumed to be performed at regular intervals. This results in abstruse numbers of scans and observations, which are challenging to interpret and do not reflect realistic numbers in schedules with a co-location satellite. In VLBI experiments, the participating stations are coordinated to observe a list of geodetic sources in an optimized sequence. In this manuscript, the term \"geodetic sources\" is used to refer to compact extragalactic radio sources observed in VLBI experiments. When integrating GENESIS as an additional source, two principal consideration must be taken into account. On the one hand, a certain number of scans of GENESIS should be scheduled to link the VLBI frame to the GENESIS frame with high accuracy. However, on the other hand, a substantial number of scans of geodetic sources are required to estimate geodetic parameters, including station positions, Earth Orientation Parameters (EOPs), and geodetic source positions, with consistent accuracy. Given that the geodetic sources and GENESIS compete for the observing time of the participating stations, it is essential to conduct a thorough analysis to determine the amount of allocated observing time for GENESIS. This work addresses the uncertainties of the integration of GENESIS into global VGOS operations. VLBI experiments with the modern VGOS antennas are currently not running continuously as envisaged in [PERSON] et al. [20], but only two to four times per month. At present, data storage, data transfer, and correlation time are the bottlenecks of VGOS operations [21]. Therefore, we assess the feasibility of integrating observations of GENESIS within the 24 h experiments of the regular VGOS operations, rather than conducting additional dedicated experiments that would further strain the limited resources. Building upon previous simulation studies [13; 14; 15; 16], we present a dedicated simulation study from a VLBI perspective. We show a comprehensive analysis on the integration of GENESIS into VGOS experiments. The scheduling is conducted with the well-established scheduling software VieSched++ v1.34 [22], taking into account actual antenna characteristics. Based on realistic schedules with current and projected VGOS antenna networks, we perform extensive Monte Carlo simulations of VLBI observations of GENESIS and geodetic sources.