# Laser Observations of GALILEO Satellites at the CBK PAN Astroegodynamic Observatory in Borowiec
## 5 Summary and Outlook  
The BORL station is conducting laser measurements on the GALILEO satellites. The list of objects being tracked will be expanded to include more satellites. Currently, the BORL laser sensor observes 83 cooperative objects from the ILRS list, which includes 28 LEOs and 55 MEOs. The BORL sensor has a range of 24,500 km and provides high-quality laser distance measurements to GALILEO satellites. On average, each pass yields 100 returns and 4 normal points, with an average RMS of 13.5 mm. However, a major challenge for the BORL station is to increase the number of successful measurements. This challenge is due to the technical limitations of the sensor, specifically tracking inaccuracy caused by the outdated 3-ton telescope assembly from the 1980s. Objects in MEOs face difficulty in being visually observed due to this issue. The worn-out [PERSON] auxiliary telescope with a 20 cm aperture and the Tayama CCD camera model TC-3102-08D are unable to capture images of the GNSS satellite on the observation monitor. As a result, the observer must search for the satellite's photon trace in the observation program. The BORL station is still using the HAMAMATSU H5023 photodetector, which currently has a low quantum efficiency of several percent. Efforts are underway to install a  
Figure 8: Pass of GALILEO-202 (E14) registered by the BORL sensor on 21 September 2023, 22:37 UTC, showing slant ranges (**a**) and fit residuals (**b**) with 310 valid returns. The min. and max. distances to the satellite were 19,701 km and 20,292 km, respectively. new auxiliary telescope and a digital camera to observe the sky during laser measurements in the coming months. The new high-resolution system will enable the observation of satellites from the GEO region. Attention should be focused on the issue of the low number of active laser stations operating within ILRS. The number of satellites equipped with reflectors that need laser measurements has been increasing rapidly in recent years. Only 7 new laser stations have been added in the past decade. However, several stations were shut down during the same period and some were marked as \"inactive\". There are 11 upcoming laser stations that are yet to be opened. This indicates that there are essentially no additional active laser stations, as there are currently 44 in operation. The number of satellites on the ILRS tracking list is increasing rapidly, with a current count of 122. This poses challenges in maintaining a sufficient number of measurements for each mission. Additionally, the distribution of laser stations is uneven, primarily concentrated in the northern hemisphere, particularly in Europe. Some stations do not track during the day, and weather conditions play a significant role in reducing the number of measurements. Other factors that contribute to fewer measurements include failures of the laser sensors and ongoing modernization and repair work at the stations. The BORL laser station is one of the stations that only observe at night. The fair-weather factor for the station's geographic location is approximately 40%. This means that the station has around 146 nights suitable for making laser measurements, which are referred to as good observation nights. All laser stations must participate in observing all satellites listed on the ILRS. The stations need to allocate the majority of their observation time to GNSS satellites, which currently number 96, making up 75% of all objects on the ILRS list. A potential solution could involve using a specialized compact laser sensor designed to measure GNSS satellites. For instance, the miniSLR laser sensor proposal by DLR and DIGOS is a notable example. This system is contained within an aluminum housing measuring 130 \(\times\) 180 cm [31]. Deploying a suitable number of these automated sensors globally would guarantee comprehensive coverage for the laser measurements of the GNSS satellites, thereby ensuring consistent data collection and precise orbit determination for GALILEO satellites. Conceptualization, P.L.