# A New Online Service for the Validation of Multi-GNSS Orbits Using SLR
## 4 Conclusions  
The fully operational on-line service called GOVUS has been delivered to allow for analyzing and visualizing results of SLR validation of microwave-based multi-GNSS orbits. The GOVUS system not only fulfills a function of a web tool, but also acts as the advanced computational center, which generates unique operational products, delivered every day to the end-user. GOVUS provides information on multi-GNSS orbit quality, changes of parameters in the GNSS constellations, characteristics of SLR ground segment, as well as on quality and quantity of SLR observations to multi-GNSS constellations. The service contributes to the development of multi-GNSS in the frame of the IGS MGEX project. This paper describes and demonstrates examples of the analyses that can be generated using the service. The comparison with the latest literature [32] has confirmed the reliability of the results. The results for the particular types of satellites in the period January 2016-August 2017 equal: \(-13\pm 21\), \(-18\pm 26\) and \(14\pm 24\) mm, for GLONASS K1, M and M+, respectively; \(-43\pm 36\)  
Figure 8: SLR residuals as a function of time for Galileo satellites in period 1 June 2017–31 August 2017. \(-\)37 \(\pm\) 37, \(-\)29 \(\pm\) 29 mm, for Galileo IOV, FOC and FOC*, respectively; \(-\)8 \(\pm\) 72 and \(-\)8 \(\pm\) 61 mm, for BeiDou IGSO and MEO, respectively; and \(-\)107 \(\pm\) 110 mm for QZS-1. The offset for all Galileo satellites decreased after the implementation of antenna thrust and albedo models to \(-\)8 \(\pm\) 21, 0 \(\pm\) 20, and \(-\)1 \(\pm\) 23 mm, for Galileo IOV, FOC and FOC*, respectively. All of the examples presented in this paper are easily reproducible by any user. It highlights the usefulness of the service and the potential given to the scientific progress in the development and improvement of the multi-GNSS products and applications. As of today, the MGEX products do not contain information about the quality of the orbit products; therefore, GOVUS aims at filling this gap. As presented in Section 3, there are differences in orbit quality between each system of the multi-GNSS constellation, or even the particular types of the satellite are significant, hence the access to near real-time results of SLR validation of these products is beneficial for the multi-GNSS community. It may be very useful for all multi-GNSS users to employ this easily accessible database, which includes information about the multi-GNSS satellite parameters, such as the orbital plane, antenna and laser retroreflector offsets, slot in the orbital plane, type and generation, as well as historical changes of the assignation of satellite to PRN numbers and channels for different GNSS spacecraft (see Table 10). On the other hand, the GOVUS system serves as the quality control system for the laser stations and the ILRS authorities, which are informed about the derogation from the expected efficiency and accuracy of the measurements. The final product is operating in a fully operational stage, all over the world, without any restrictions for desktop and mobile users. The link to GOVUS service is available at [62; 63]. A complete list of the libraries and the terms of its licenses are attached in \"About\" subpage of the GOVUS web-application [63]. The ILRS and IGS are acknowledged for providing SLR and GNSS data. The SLR and GNSS stations are acknowledged for a continuous tracking of the geodetic satellites as well as for providing high-quality SLR and GNSS observations. [PERSON] and [PERSON] are supported by the Polish National Science Centre (NCN), grant No. UMO-2015/17/B/ST10/03108. [PERSON] and [PERSON] are funded by \"EPOS--European Plate Observing System\" co-financed by the European Union from the funds of the European Regional Development Fund (erdf), grant No. POIR.04.02.00-14-A003/16-00.