Surface Displacement Measurement from Remote Sensing Images. Olivier Cavalie

technical specifications of some future optical missions, where available, are given in Tables 1.12 and 1.13. Some of them may be of specific interest for future 3D and surface displacement measurements:

       – Co3D: These extremely agile satellites with all-electric platforms will provide new ways of acquiring, processing and transferring images. They will provide very-high-resolution 3D data;

       – PléiadesNeo: This system corresponds to the new generation of Pléiades satellites. With a 1.5 m diameter telescope, the satellites will provide 30 cm images. The constellation will produce 40 TB of data every day;

       – EarthDaily: EarthDaily provides an alternative choice for building global world coverage for change detection activities with this satellite constellation working at a 5 m resolution. This system complements a very-high-resolution service;

       – Vivid-i: This constellation is planned with 15 satellites, with a weight lower than 100 kg, providing imagery and video capabilities at less than 1 m resolution;

       – WorldView Legion: These satellites correspond to the new generation of WorldView satellites. Launches are planned for 2021;

       – WorldView Scout: This constellation will have six or more small satellites, which will be able to revisit some key areas 40 times a day at a 0.80 m resolution.

Table 1.12. Future mission characteristics and parameters

Satellite	Nation	No. of satellites	Altitude (km)	Local time	Weight (kg)
Co3D	France	4–2	502	11:00	300
Enmap	Germany	1	653	11:00	871
PléiadesNeo	France	4	620	10:30	750
ResourceSat-3/3A	India	1	795	10:30	1,200
EarthDaily	Canada	8	-	-	340
Vivid-i constellation (Earth-i)	UK	15	500	-	100
WorldView Legion 1–6	USA	6	-	-	-
WorldView Scout 1–6	USA–Saudi Arabia	6	-	-	-

Table 1.13. Future instrument characteristics

Satellite	Year of launch	Highest spatial resolution (m)	No. of XS bands	Swath width for highest resolution (km)
Co3D	2023	0.5	4	7 x 5
Enmap	2021	30	8 + 154	30
PléiadesNeo	2021	0.3	≥4	14
ResourceSat-3/3A	2021	10	4	280
EarthDaily	2022	5	9	360
Vivid-i constellation (Earth-i)	-	0.6–1	3	5.2 x 5.2
WorldView Legion 1–6	2021	0.30	-	-
WorldView Scout 1–6	2021	0.8	-	-

1.5. Conclusion

With SAR imaging missions, free data availability, as with, for example, Sentinel-1 and future NISAR or ROSE-L missions, is of real interest for scientists in the field of displacement observations, in particular from missions with high repetitiveness and controlled orbits. For other missions, data of interest will hopefully be accessible through scientific announcements as they used to be. As for new low-cost constellations delivering X-band SAR data, the usefulness for remote sensing displacement applications is still unknown. Even if high resolution is often the highlighted improvement for these missions, the lack of systematic acquisitions over large areas reduces the potential interest of these data for ground displacements all over the Earth.

      For the optical imaging missions, nowadays, many Earth observation images are available across many spectral bands and many spatial resolutions. Thanks to the Sentinel and Landsat programs, a large number of images are freely available, allowing many new applications for scientists and commercial companies. Temporal resolution becomes as important as spatial resolution. Many satellite optical missions are commercial ones, with high competition in terms of the prices of provided images, the freshness of the data and the value-added services. With some applications, the satellite image