The (TOPography EXperiment) TOPEX/Poseidon (T/P) altimetry mission operated for 13 years before the satellite was decommissioned in January 2006, becoming a large space debris object at an altitude of 1,340 km. Since the end of the mission, the interaction of T/P with the space environment has driven the satellite's spin dynamics. Satellite laser ranging (SLR) measurements collected from June 2014 to October 2016 allow for the satellite spin axis orientation to be determined with an accuracy of 1.7°. The spin axis coincides with the platform yaw axis (formerly pointing in the nadir direction) about which the body rotates in a counterclockwise direction. The combined photometric and SLR data collected over the 11 year time span indicates that T/P has continuously gained rotational energy at an average rate of 2.87 J/d and spins with a period of 10.73 s as of 19 October 2016. The satellite attitude model shows a variation of the cross‐sectional area in the Sun direction between 8.2 m2 and 34 m2. The direct solar radiation pressure is the main factor responsible for the spin‐up of the body, and the exerted photon force varies from 65 μN to 228 μN around the mean value of 138.6 μN. Including realistic surface force modeling in orbit propagation algorithms will improve the prediction accuracy, giving better conjunction warnings for scenarios like the recent close approach reported by the ILRS Space Debris Study Group—an approximate 400 m flyby between T/P and Jason‐2 on 20 June 2017.

The basic aim is to contribute to the world geodetic space in line with today’s scientific achievements. Riga geodynamic site is a thankful place for this, as it has long-term SLR observations and the longest GNSS records in Latvia. The goal is establishment of regional long-term geodetic monitoring station at LU Institute of Astronomy, Riga, Kandavas street 2, by joining at least two space geodetic technologies – the already installed laser-telescope LS-105 and GNSS − collocated, but not sufficiently linked. The capability of geodetic GNSS observations would uniquely complement Riga GNSS station and allow to determine more accurate coordinates of the LS-105 laser telescope and the long-term changes needed to accurately measure the positions of Earth satellites and other similar space objects. GNSS Observation Station will contribute to the development of positioning and position long-term change to accuracy of less than 1mm, one of the current global goals of GGOS. We plan to solve the problem with the exact position of the telescope LS-105 it will contribute to the development of scientific research and applied potential of the LU Satellite Laser Ranging station. From the national point of view geodetic station serves as an important point for Latvian National Geodetic Network, long term large infrastructure planning, engineering communications, cartography, etc. From a global perspective the station will be one of very few such stations in the region and the only one in the Baltics capable of valuable contribution to ITRF network. Preparatory work for the study has started by selecting and consolidating geodetic points for further measurements.

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Joint VLBI and SLR satellite tracking is a novel tracking approach to explore potential applications and to work out common procedures to coordinate observations between astronomical observatories in Latvia. Global Navigation Satellite System (GNSS) satellites equipped with laser retroreflectors have been chosen as test targets because they are accessible by both measuring techniques – satellite laser ranging (SLR) and Very Long Base Interferometry (VLBI).The first Joint SLR and VLBI observations of selected GNSS satellites using three of Latvian large-scale astronomical utilities – VIRAC radio telescopes RT32 and RT16 (Ventspils International Radio Astronomy Centre of Ventspils University of Applied Sciences) with L band receivers and SLR station Riga (Institute of Astronomy of University of Latvia) were obtained in 2016 (NKA16) and 2017 (NKA41 and NKA42).