The National Metrology Institute of South Africa (NMISA) has agreed to massively improve its time reference precision in order to support the South African element of the international Square Kilometre Array (SKA) radio telescope. This agreement was embodied in a memorandum of understanding (MoU) signed with SKA South Africa (SKA SA) on Friday.

In terms of the MoU, NMISA will refine its time reference by a factor of more than 1 000, from about 5 000 nanoseconds (ns) today to only about 4 ns. A nanosecond is a billionth of a second and 4 ns represents cutting-edge accuracy.

NMISA is responsible for the maintenance of the country’s national measurement standards, including those for time and frequency. SKA SA is the organisation responsible for South Africa’s participation in the SKA and for the country’s MeerKAT radio telescope array, which will be a precursor to the SKA.

“Cutting-edge science must be based on cutting-edge measurement accuracy,” highlighted NMISA Electricity and Magnetism Division director Natasha Nel-Sakharova. “One cannot claim what you cannot measure. This cooperation between NMISA and SKA South Africa will enhance South Africa’s position as the best time keeping facility in Africa and make it one of the best in the world.”

“Time and frequency is a critical [factor] in the observation of celestial bodies via radio techniques,” noted SKA SA Time and Frequency Systems manager Dr Johan Burger. As both MeerKAT and the SKA are arrays of antennas, the signals from each antenna will reach the telescope data processing centre at slightly different times, because of the different distances from the antennas to the centre. These signals have to be correlated to allow the creation of a single image. This correlation requires precise “time tagging” of all of the signals. The frequencies of all the antennas have also to be precisely aligned. The final result will be a single high resolution image.

Implementing the MoU will require NMISA to invest in new equipment and carry out research. It will, for example, have to acquire additional caesium atomic clocks and also obtain active hydrogen maser atomic clocks. Research will have to be done on techniques to transfer time signals from the NMISA clock room through commercial telecommunications fibres to the MeerKAT/SKA in the Karoo.