# High Performance Computing in Satellite SAR Interferometry: A Critical Perspective
## 3 Operational SAR Systems and Applications
### InSAR Applications and Products  
InSAR products are primarily used to monitor the ground stability and perform analyses related to the potential risk in zones subjected to ground displacement. Over the last two decades, the InSAR techniques have been widely applied in different scenarios to detect and analyze ground deformations related to natural and anthropogenic causes. InSAR studies permitted to assess ground deformations associated with several natural phenomena. Applications to seismic events include (among others) the analysis of large earthquakes [114; 115], detection and modeling of aseismic deformations [116; 117; 118], as well as modeling of short sequences of small earthquakes [119]. Active volcanoes are also widely analyzed by using InSAR data; this includes, for instance, the study and modeling of deformation before, during, and after an eruption [120; 121; 122; 123], or volcano flank instability triggered by eruptive or tectonic activity [124; 125]. The study of landslides is another field in which InSAR data can give an excellent insight [126; 127]. Particularly tricky is the analysis of landslides in large areas covered by forests, as small ground displacements do not result in significant forest changes. Advantages and limitations of InSAR techniques in vegetated regions have been widely discussed in [128; 129]. The applications to glacier movements are also worth mentioning [130; 131]. \begin{table}
\begin{tabular}{c|c c c c c c c c c} \hline \hline
**Sensor** & **Frequency** & **Agency/ Country** & **Access** & **Revisit-Time** & **Resolution** & **Polarization** & **Frame Size** & **Year** \\ \hline \multirow{3}{*}{**TanDEM-L**} & L-band & German & & & & & & dual-pol mode & \\  & (1275 GHz, & Aerospace & Free and open & 16 days & 7 m & Single, dual, quad & 30 km & \(\geq\)2024 \\  & \(\lambda\simeq\)24.6 cm) & Centre (DLR) & & & & & & 175 km & \\ \hline \multirow{3}{*}{**BIOMASS**} & P band & European & & & & & & & \\  & (435 MHz, & Space & Free and open & 17 days & 60 \(\times\) 50 m & quad-pol & 50 \(\times\) 50 km & \(\geq\)2023 \\  & \(\lambda=70\) cm) & Space & Free and open & & & & & & \\ \hline \multirow{6}{*}{**NISAR**} & S-band & & & & & & Single: HH,VV & \\  & (32 GHz, & \(\lambda=9\) cm) & & & & & & & Compact: RH/HV, & \\  & & & & & & & & & \\  & & NASA & Free and open & 12 days & 3–10 m & Quasi-Quad: & & \\  & & ISRO & & & & & & & \\  & L-band & & & & & & & & \\  & (1.26 GHz, & & & & & & & Compact: RH/HV, & \\  & \(\lambda=24\) cm) & & & & & & & & & \\  & & & & & & & & HH/HV/VH & \\ \hline \multirow{6}{*}{**RCM**} & C band & Canadian & & & Satellite: 12 days & & Single: HH, VV & & \\  & (5.4 GHz, & Space & Congency & Congestion: & 3-100 m & Quasi-H/HV, VV/VH, HH/VV & 20 \(\times\) 20-500 \(\times\) & 2019- \\  & \(\lambda=5.6\) cm) & Space & & & 4 days & Compact & & & \\  & & & & & & & & Compact & \\ \hline \multirow{6}{*}{**PAZ SAR**} & X band & Space & & & & & & & & \\  & (9.65 GHz, & Agency of & & Commercial & 11 days & Stripmap: 3–6 m & HH/VV/HV/VH & \\  & \(\lambda=3.5\) cm) & Space & & & & ScanSAR: 16 \(\times\) 6 m & High (single or dual) & Semi-GR: & 2018- \\  & \(\lambda=3.5\) cm) & Spain & & & & spotlight: 1–2 m & & spotlight: 10 \(\times\) & 10 km \\ \hline \multirow{6}{*}{**Cosmology-SkyMed**} & X band & German & & & & & & & & \\  & (9.65 GHz, & Agency of & & Commercial; & & & & & \\  & (9.65 GHz, & Aerospace & limited & & 1.0–17 \(\times\) 3.5 m & Subgrid: & 0.2 \(\times\) & Subgrid: & 3–10 km \\  & \(\lambda=3.5\) cm) & Centre & proposal- & & & 1.0–17 \(\times\) 3.5 m & Dual: HH/VV, VV/VH & 30 km & 2007– \\  & \(\lambda=3.5\) cm) & Centre & & & & Stripmap: 3 \(\times\) 3 m & Twin: HH/VV, & & SensSAR & 2010– \\  & X band & Space & & scientific & & ScanSAR: 18–40 m & HH/VH,VV/VH & & & & \\  & & & &More specific applications relying on advanced MT-InSAR techniques can also be found [132; 133].