A team of scientists led by Amy Parker have proposed combining images of Earth’s remote sensing satellites with radio telescope data, which will create a global map of the planet’s surface with reference to a reliable reference system. The idea is to use high-brightness telescopes on radar images, as well as knowing their coordinates in the global system. As a result, the available information will be integrated into a single set of data.
The Earth’s surface is constantly being modified due to natural and man-made processes such as earthquakes or mining. These changes can be tracked by artificial satellites that constantly record the state of the surface in different ranges. However, the problem with such measurements is to link their coordinates to random points, which makes it impossible to combine images of remote places, such as different continents, for receiving consistent global maps.
The main instrument of tracking the height of the Earth’s surface is interferometric radar with synthesized aperture, which allows receiving data with accuracy up to a meter regardless of weather conditions, light and objects on the surface, such as trees. This method is similar to the aperture synthesis used in radio astronomy, only in this case the satellites themselves are the sources of radio waves, which after reflection allow restore the relief.
At the moment there is an extensive grouping of satellites exploring the Earth by this method. In particular, the Copernicus program of the European Space Agency is engaged in this. As a rule, the images overlap partially, and the coordinates are counted from the conditional zero, for example, from the average level of the first frame. As a result, you can create extensive maps, but the areas separated by water will not be aligned, as the scattering from the water changes rapidly.
To solve this issue, a team of scientists from Australia and Sweden, led by Amy Parker from School of Earth and Planetary Sciences, Curtin University of Technology, Perth, WA, Australia, have proposed a new solution to the problem. It is based on the inclusion in the observations of satellites on a regular basis of ground-based radio telescopes, especially those included in the global interferometry system with an extra-long base. This will allow using the knowledge of the coordinates of the instruments in the global coordinate system to normalize radar maps. However, this will require adjustments to astronomical observation programmes, as telescopes will have to be pointed at satellites from time to time rather than from them, as what’s happening now.
The existing system of radio interferometers includes about 30 instruments that regularly conduct joint observations. With the help of these data, the International Celestial Reference System (ICRS) began to be formed about 30 years ago, which allows determining the coordinates of all telescopes involved in observations with respect to several hundred remote quasars, whose own movements are negligible.
The authors tested the proposal with the help of two radio telescopes included in the network and came to the conclusion that the necessary program adjustments are moderate changes. Connecting all available radio telescopes will allow you to create global maps of deformations of the continents and tectonic plates, which will allow you to assess the distribution and rate of accumulation of mechanical stresses. This, in turn, will significantly improve earthquake predictions.