# Development of the Romanian Radar Sensor for Space Surveillance and Tracking Activities +
## 6 Initial Tests and Results  
The initial tests of the new Cheia SST Radar were carried out during the month of December 2021. The radar subsystems assigned to the tracking function of the antennas were not yet functional. The antennas were oriented in azimuth and elevation by the antenna positioning units according to the projected calculated trajectories of the targeted spatial objects. The hardware configuration used by the radar sensor was as follows:  
* The RF generator was implemented using an SMA-100B Rhode-Schwarz low-noise Microwave Generator, f = 5830-5850 MHz with a phase noise of \(-125\) dBc/Hz and triangular linear frequency modulation that was externally synchronized by a customized GNSS-Controlled Master Oscillator manufactured by Quartzlock (United Kingdom) with an Allen frequency deviation of 5\(\cdot 10^{-12}\) (at 10 s) and a phase noise of \(-170\) dBc/Hz at 10 KHz offset. * The power amplifier had a saturation power of 5 kW. It was a custom-made low-noise SSPA manufactured by TTI Norte (Spain) [25]. This high-power SSPA was not used during the initial tests, as it was not available at that time, so the original 150 W power amplifier of the transmitting antenna was used. * The receiver was a custom-made receiver produced by Ad-Hoc Telecom Solutions (Romania), while the signal processor was a computer featuring four high-performance16 bit ADCs and a Tesla V100 Graphic Processing Unit (GPU); both the hardware and software were customized by Silicon Acuity (Romania) [26]. * The antenna positioning system was designed and manufactured by Antech Space (Italy) [27]. The parameters of the initial radar tests were:
* Output power: 51 dBm (125 W). It would be increased to 67 dBm (5 kW) after installing the new SSPA;
* Frequency band: 5830-5850 MHz;
* Operating mode: CW (continuous wave);
* Modulation: triangular LFM (triangular linear frequency modulation);
* Antenna gain: 63 dB;
* Antenna count: two (one for \(Tx\) and one for \(Rx\));
* Receiver noise factor (F\({}_{Rx}\)): 1.1 dB;
* Processing loss (L\({}_{Rx}\)): 40 dB. This high value was due to the high level of the phase noise of the PA. This increased the noise threshold of the receiver through antenna coupling;
* Antenna noise temperature (T\({}_{\text{ant}}\)): 56 K;
* Detection signal-to-noise ratio (\(SNR\)): 6 dB (min). A number of five dead spatial objects were targeted, pending the operator's approval, to emit 5.85 GHz probing signals towards other active objects:
* COSMOS 2392 obsolete satellite (NORAD id 2740, International Designator 02037A) [28]. * ENVISAT obsolete satellite (NORAD id 27386, International Designator 02009A) [29]. * RADARSAT payload (NORAD id 23710, International Designator 95059A) [30]. * SS-18 R/B rocket body (NORAD id 25695, International Designator 99021C) [31]. * DELTA 1 R/B rocket body (NORAD id 13778, International Designator 83004B) [32]. The two-line elements (TLE) input data were generated by the management and control software within the MPU system by using international space objects catalogues. In Table 2 are presented the measured ranges and radial speeds derived from the received Doppler frequencies for the five objects in LEO targeted during the initial tests of the Cheia radar. The values resulting from the measurements and after applying an alpha-beta filtering process for range and Doppler speed were in good accordance with the estimated ones (calculated from the two-line elements data) [33]. In Figure 8a,b the two sets of values for range and Doppler speed are plotted for spatial object COSMOS2932. On the x-axis, the time unit is the trigger timing of the analog-to-digital converter, with the full scale of 151 triggers corresponding to approximately 237 s of measurement time.