# Development of the Romanian Radar Sensor for Space Surveillance and Tracking Activities +
## 7 Conclusions  
This article presented the CHEIA SST Radar, a new space tracking radar sensor developed and installed in Romania with the purpose of being included in the EU SST sensor network and of contributing to the joint database of space objects orbiting the Earth. The paper described the processes of design, simulation, and implementation of hardware and software building blocks that made up the radar system. It emphasized the particular case of using an already existing system of two large parabolic antennas that required an innovative design of retrofitting to function as the basis for a new quasi-monostatic radar using LFMCW probing signals. The preliminary design was validated by extensive simulations, and the initial operational testing carried out in December 2021 demonstrated the good performance of the radar in measuring the range and radial speed of LEO space objects. The radar tests proved the correct operation of the design even in highly detrimental conditions (low transmitted power and high phase noise). Because of this, the received data contained significant noise, but the final implementation of the radar will be able to precisely detect and track small targets according to the requirements of ROSA, the ESA, and the EU SST.  
The comparison between the measured and filtered and the estimated ranges obtained during the initial tests for the COSMOS2932 satellite showed that the obtained results were very close to the theoretical ones, with the error being approximately \(\pm\)0.6 km for range and \(\pm\)0.02 km/s for Doppler speed. By increasing the \(Tx\) power and decreasing the phase noise of the PA, better accuracy of the radar measurements is expected.  
The full configuration of the Cheia SST Radar will be completed during the beginning of 2022, with further works of installing a 5 kW SSPA, a tracking coupler block, and a monitoring system, as well as rack optimization. The commissioning of the system to initial operational status is ongoing and it is expected to be finalized in the first half of 2022. Several functional tests will be conducted in order to evaluate the full performance of the final configuration and to calibrate it according to EU SST procedures.  
Figure 10: Difference between the measured and the TLE-computed values for Doppler speed as a function of trigger number (time) for COSMOS2932.  
**Author Contributions:** Conceptualization, L.I. and R.S.; data curation, C.B. and I.T.; formal analysis, L.I., A.R.-C. and A.T.; funding acquisition, R.S. and D.I.; investigation, L.I., A.R.-C., C.B. and A.T.; methodology, L.I. and A.R.-C.; project administration, L.I. and D.I.; resources, R.S. and D.I.; software, C.B., I.T. and A.-E.P.; supervision, A.R.-C., R.S. and D.I.; validation, D.I.; visualization, L.I. and C.B.; writing--original draft, L.I. and A.R.-C.; writing--review and editing, C.B., I.T. and R.S. All authors have read and agreed to the published version of the manuscript.  
**Funding:** The research and development activities described in this paper were carried out within a series of three contracts financed by the European Space Agency (ESA) and awarded to a consortium led by RARTEL S.A., Bucharest, Romania: SSA for Romania, Contract No. 4000108671/13/D/MRP; SSA P3-SST-IV-CHEIA PHASE 1; SSA P3-SST-V-CHEIA PHASE 2.  
**Acknowledgments:** We would like to thank RARTEL's, Silicon Acuity SRL's, and AdHoc Telecom Solution's employees for their hard work in making this paper possible.  
**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the writing of the manuscript or in the decision to publish the results.