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Modern satellites of Global Navigation Satellite Systems (GNSS) are equipped with laser retroreflector arrays for Satellite Laser Ranging (SLR). Laser range observations to GNSS satellites allow for the co‐location of two space geodetic techniques onboard navigation satellites. We search for the best network constraining strategy for the SLR and GNSS stations to realize the geodetic datum using combined microwave‐GNSS and SLR‐to‐GNSS measurements. We find that consistent imposing of no‐net‐translation and no‐net‐rotation for the unified GNSS and SLR network provides the best quality of station coordinates and the best common realization of the terrestrial reference frame (TRF). We employ the space ties using solely space geodetic techniques for the SLR and GNSS station coordinates and confront them with the ground‐based measurements, that is, local ties, conducted at the SLR‐GNSS co‐located sites. The common processing of the GNSS and SLR observations allows for the realization of the TRF using space ties that are independent of the a priori coordinates and independent of the errors in local tie measurements. The agreement of space ties with ground measurements is at the level of 1 mm in terms of long‐term mean values for the co‐located station in Zimmerwald, Switzerland. We also revise the approach for handling the SLR range biases which now considers the impact of the SLR observations to GNSS and LAGEOS satellites. The updated SLR range biases improve the agreement between space ties and local ties from 4.4 to 2.4 mm for the co‐located station in Wettzell, Germany. Plain Language Summary: Every natural phenomenon observed in the Earth system demands a stable and accurate terrestrial reference frame (TRF). Currently, TRF is resolved by a combination of observations provided solely by space techniques, that is, Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), Very Long Baseline Interferometry (VLBI), and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS). All the techniques are treated separately in the current realization of the International Terrestrial Reference Frame (ITRF2014), and a linkage between the observing stations of each technique is resolved by ground measurements as the so‐called "local ties" which cannot be obtained operationally. However, newly developed satellites of GNSS systems are equipped with laser retroreflectors for the SLR technique. As a result, the GNSS satellites comprise a platform for the integration of two techniques onboard navigation spacecraft in space. This study provides the first‐ever results of co‐location onboard navigation satellites of the Galileo and GLONASS systems. The new linkage between the GNSS and SLR techniques called "space tie" is consistent with local ties at the level of 1 mm and can be provided whenever GNSS and SLR data are available enabling, therefore, the realization of TRF in space on the operational basis. Key Points: Co‐location of Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS) space techniques onboard navigation satellites enables the realization of a terrestrial reference frame in spaceSpace ties computed using GNSS and SLR observations indicate a 1‐mm consistency with local ties for co‐located SLR and GNSS stationsDifferent methods of the handling of SLR range biases lead to different realizations of the terrestrial reference frame origin and scale [ABSTRACT FROM AUTHOR]

Abstract: All satellites of new Global Navigation Satellite Systems (GNSS) are equipped with laser retroreflectors dedicated to Satellite Laser Ranging (SLR). This paper demonstrates the contribution of SLR tracking of multi‐GNSS constellations to the improved SLR‐derived reference frame and scientific products. We show a solution strategy with estimating satellite orbits, SLR station coordinates, geocenter coordinates, and Earth rotation parameters using SLR observations to 2 Laser Geodynamics Satellites (LAGEOS) and 55 GNSS satellites: 1 GPS, 31 Globalnaya Navigatsionnaya Sputnikovaya Sistema, 18 Galileo, 3 BeiDou Inclined Geosynchronous Orbit, 1 BeiDou Medium Earth Orbit, and 1 Quasi‐Zenith Satellite System satellite for the period 2014.0–2017.4. Due to a substantial number of GNSS observations, the number of weekly solutions for some SLR stations, for example, Arkhyz, Komsomolsk, Altay, and Brasilia, is larger up to 41% in the combined LAGEOS + GNSS solution when compared to the LAGEOS‐only solution. The SLR observations to GNSS can transfer the orientation of the reference frame from GNSS to SLR solutions. As a result, the SLR‐derived pole coordinates and length‐of‐day estimates become more consistent with GNSS microwave‐based results. The root‐mean‐square errors of length‐of‐day are reduced from 122.5 μs/d to 43.0 μs/d, whereas mean offsets are reduced from −81.6 μs/d to 0.5 μs/d in LAGEOS only and in the combined LAGEOS + GNSS solutions, respectively. [ABSTRACT FROM AUTHOR]