# Role of Radio Telescopes in Space Debris Monitoring: Current Insights and Future Directions
## 3 Radio Telescope Measurements with Active Transmitters
### MeerKat  
The Meer Karoo Array Telescope (MeerKAT), located in the Northern Cape of South Africa, is part of the SKA network. It comprises 64 dishes intended for radio astronomy and serves as proof of technological advancement toward constructing a Square Kilometre Array (SKA), as shown in Figure 13. The MeerKAT radar is designed to operate at 1350 MHz \begin{table}
\begin{tabular}{l l c c c c c} \hline \hline
**Target** & **Receiver** & **TAC** & **TFAC** & **STC** & **SFS** & **SIRTA** & **Average** \\ \hline \multirow{6}{*}{Delta-4} & WSRT & 164.2373 & 164.1280 & 164.2228 & 164.1748 & 164.4878 & 164.2501 \\  & JBO-KN & 164.0500 & 164.0257 & 164.0103 & 161.3476 & 164.6694 & 164.1889 \\ \cline{1-1}  & JBO-DE & 164.2581 & 164.1588 & 164.2345 & 162.1518 & 164.3632 & 164.2537 \\ \cline{1-1}  & JBO-DA & 164.2790 & 164.2472 & 164.3130 & 162.5722 & 164.9472 & 164.4466 \\ \cline{1-1}  & JBO-CM & 164.1957 & 164.2717 & 164.3948 & 166.5494 & 164.5672 & 164.3573 \\ \hline \multirow{2}{*}{Atlas 5} & WSRT & 33.6552 & 33.6567 & 33.6627 & 33.6651 & 33.6490 & 33.6577 \\ \cline{1-1}  & TIRA & 33.6388 & 33.6507 & 33.6654 & 33.6221 & 34.8242 & 33.6442 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The table shows the results of rotation period estimation using different methods: **TAC**—time–domain auto-correlation, **TFAC**—time–frequency domain auto-correlation, **STC**—slow-time cepstrum, **SFC**—slow frequency spectogram, **SIRTA**—spectrogram–inverse Radon transform-based algorithm [64]. Reprinted from IET Radar, Sonar, and Navigation, Copyright 2023, with permission from John Wiley and Sons. Figure 12: Bistatic Doppler tomography reconstructions of the Atlas 5 Centaur rocket body using L-band data with 8 MHz bandwidth, collected by WSRT. The results illustrate the target structure based on Doppler information: (**a**) PP—prime polarization channel, (**b**) OP—orthogonal polarization channel [64]. Reprinted from IET Radar, Sonar, and Navigation, Copyright 2023, with permission from John Wiley and Sons. (L-Band) frequency with a bandwidth of 10 MHz. The Radar Remote Sensing Group (RRSG) at the University of Cape Town, South Africa, laid the essential groundwork with simulations for the Mission Planning Tool (MPT), which will be used at the MeerKAT radar to perform sensor scheduling and orbit determination analysis [70,71]. [PERSON]'s PhD thesis [71] primarily concentrates on designing the comprehensive system operation and the radar signal processing for the proposed MeerKAT radar with the RRSG's Flexible Extensible Radar Simulator (FERS) [72]. In addition, different radar configurations, such as monostatic, quasi-monostatic, and single-input-multiple-output (SIMO), were analyzed to determine the best performance with MeerKAT. The results indicate that the multistatic radar configuration is the most appropriate and computationally efficient option compared with the bistatic and SIMO configurations. The research presented in this PhD thesis also focused on Inverse Synthetic Aperture Radar (ISAR) imaging, comparing simulated results with theoretical models while developing methods to correct range and Doppler ambiguities, thereby improving imaging precision [71]. Moreover, in another study, a bistatic system was proposed with a transmitter located at Denel Dynamics' Overberg Test Range in Arniston, Bredasdorp (Western Cape, South Africa) and a receiver at MeerKAT, separated by a baseline of approximately 450 km. A preliminary case study was conducted to demonstrate the operation of a bistatic passive radar system to observe the International Space Station [73]. The authors compared the capabilities of the MeerKAT radar to the BIRALES system, as described in Section 3.4, to estimate azimuth and elevation angles [70]. This comparison was necessary because the current design of MeerKAT does not include an angle of arrival estimation scheme. Nonetheless, the simulation results demonstrate the potential effectiveness of the MeerKAT radar in tracking LEO space debris.