Observatory hosts a rare absolute gravimeter January 2016

Opportunity presents to measure gravity changes over four year period.

Collaboration with Kyoto University and Japan’s National Institute of Information and Communications (NICT) led to the loan of an absolute gravimeter in early January 2016.  There are fewer than 100 of these machines in the world as cost is prohibitive and New Zealand doesn’t own one.  An absolute gravimeter works by dropping a prism down a vacuumed cylinder and measuring the time of its free fall.  It is far more accurate than relative gravimeters which are cheaper and present here.

Another absolute gravimeter was used here when it travelled from Antarctica to Australia. It measured gravity at Warkworth Observatory in February 2015, but scientists wanted to see if there had been any change in the past year.  Gravity had increased by about 3 microGals, which could be due to a sinking by about 1cm, or to increase of soil moisture content, and tidal movements of the Earth’s crust.  The machine will return to New Zealand several times over the next 3 years.

Professor Sergei Gulyaev, the Director of IRASR says of the machine, “It is very cool.  It means that we can measure vertical movements of the Earth crust using three different and independent methods at one time - radio telescopes, GPS, and the absolute gravimeter.  It is rare to have all three instruments in one site, so the readings and comparisons between them are interesting for scientists all over the world. I am pleased that in New Zealand this work is conducted in collaboration between universities (AUT and Otago) and research institutes – LINZ and GNS Science.”