With the increasing availability of colocated geodetic space techniques on ground and in space, particularly microwave and laser systems, combining these techniques is becoming more relevant. Future missions will extend this to colocation in time by connecting both techniques to the same reference clock. This applies particularly to applications like validating current GNSS, next-generation GNSS, and missions such as Genesis or “Atomic Clock Ensemble in Space”. A relatively new geodetic observation technique is the laser one-way observation technique. This technique is used, for example, in missions such as “Time Transfer by Laser Link” and “European Laser Timing”. The colocation of current and new techniques, and the combination of their observations, makes it possible to estimate parameters jointly. Least-squares parameter estimation is a suitable method for this combination, as it allows the relative weighting of observations from different techniques. Such a relative weighting can be performed, for example, based on the respective instrument noise, as is the case when combining GNSS code and phase observations. This study analyses the impact of additional laser one-way observations and of different relative weighting strategies. Therefore, we use a dataset created by a closed-loop simulation software. The dataset contains different combinations of one-way microwave, one-way laser, and two-way laser observations between the International Space Station and the geodetic fundamental station Wettzell. Two main results are obtained from our studies. Firstly, expansion of geodetic missions to include optical one-way observation techniques in addition to microwave one-way and optical two-way observation techniques enables relative microwave bias calibration and significantly improves the accuracy and precision of time transfer. The one-way laser observations determine the time parameters in addition to the geometry parameters determined by the two-way laser observations. Secondly, a high weighting of laser-based observations significantly improves accuracy and precision of estimated parameters. Although the tropospheric fluctuations in the microwave observations remain unmodelled in this study, the higher weight of the laser observations, dominated by white noise, acts as a geometric constraint that stabilizes the parameter estimation. White noise averages over time, so it does not introduce systematic effects into the solution. The results demonstrate the potential of additional laser-based one-way observations when combined with traditional geodetic space techniques and provide valuable insights for future missions.