HartRAO instrumental in the successful adoption of the Third realisation of International Celestial Reference Frame (ICRF-3)


SARAO News #02 2018

The South African Radio Astronomy Observatory, through its Hartebeesthoek Radio Astronomy Observatory in Gauteng, has been instrumental in the adoption of the Third realisation of the International Celestial Reference Frame (ICRF-3), adopted at the International Astronomical Union (IAU) General Assembly held in Vienna, Austria last month.

HartRAO provided essential geometric coverage and is one of only two observatories in the Southern Hemisphere covering two of the three wavelengths (“colours”) for the ICRF-3.

“South Africa constantly tries to profile the utilitarian value of radio astronomy and the ICRF-3 provides such an opportunity where geophysicists can use the improved celestial positional grid to understand a number of phenomena such as plate tectonics, earthquakes, sea level rise, and processes that affect our planet’s orientation in space,” says Dr Alet de Witt, a member of the IAU working group for the ICRF-3.

Climate change is a major concern to society. In particular, current projections predict alarming rises in sea levels caused by climate change. The ICRF-3 provides the long term stability needed to monitor and understand sea level rise with its potential to affect millions of people.

Chris Jacobs, NASA Deep Space navigation Engineer and first chair of the ICRF-3 says: “The ICRF-3 provides the stable platform from which we can monitor the dynamic changes of the Earth with unprecedented levels of accuracy of a few parts in 10 billion – about the size of a tennis ball at the moon. This is achieved by using quasars powered by supermassive black holes to provide radio beacons which do not change their positions even after decades.”

This also allows the ICRF-3 to monitor plate tectonics with extreme accuracy and thus better understand the natural hazards from earthquakes and other geological processes.

It enables radio astronomers to provide the data on the Earth’s rotation which is essential for stabilizing global navigation satellite systems (GPS, GLONASS, Galileo) which are widely used by the public for navigation and hundreds of related uses. A GPS device gets its stability by connecting people to the stars.

Read more about the ICRF-3



For more information contact Dr Alet de Witt on alet@hartrao.ac.za