The big lift — First dish of world’s biggest radio telescope in South Africa going up soon

The first of 133 new parabolic dishes being installed at the South African part of what will be the world’s largest radio telescope is set to be completed in the next month.

Following several years of planning and development, the Square Kilometer Array (SKA) began construction in December 2022.

The multi-national $3-billion (R55.85-billion) project, to which South Africa has contributed about R1.1 billion, will aid in the search for Earth-like planets and potential life elsewhere in the universe.

It will also be used to test fundamental scientific positions such as the theory of gravity and probe the dark energy of the early universe.

The SKA will consist of two sites with advanced astronomy observation capabilities thousands of kilometres apart.

The first will be located in Western Australia’s Murchison shire and comprise 131,072 low-frequency antennas.

This site is called SKA-Low as its antennas will operate in the low frequency range of 50MHz to 350MHz.

The South African SKA-Mid site in the Karoo in the Northern Cape will consist of 197 parabolic dishes, 64 of which have already been built and form part of the MeerKAT installation.

The latter has been key in several major scientific discoveries over the past few years.

The SKA-Mid dishes will be slightly bigger than MeerKAT’s and feature a curved hexagonal shape instead of the rounder design of the MeerKAT dishes.

The square kilometre in the SKA’s name refers to the original size of the collection site that was believed to be necessary several years ago.

When completed, the distance between the two dishes that are furthest from each other will now be around 150km but the fully-steerable dishes will have a combined collection area of 33,000m².

At 0.033km², this is significantly less than the size of the initial planned collection site.

Institutions in China, Australia, Canada, France, Germany, Italy, South Africa, Spain, the United Kingdom and Sweden contributed to the SKA-Mid design.

A prototype of the parabolic dishes funded by the Max Planck Society was already installed in the Karoo in 2018.

The SKA-Mid dishes will work with signals in the 350MHz to 15.4GHz frequency range.

They’re major components comprise the following:

• Main reflector with a 15-metre diameter, made up of 66 three-metre curved panels.
• The sub-reflector offset towards the bottom of the main reflector.
• Multiple types of receivers on the sub-reflector.
• A feed indexer below the receivers to move them around for signal capturing based on observed frequencies.
• A pedestal to support the reflectors and receivers.
• Optical fibre connections for sending data to off-site processing facilities.

Each dish weighs about 50 tonnes and stands six storeys tall.

The various components are being made all over the globe before being shipped to South Africa for assembly.

The SKA Observatory (SKAO) told MyBroadband that the components for the first two dishes featuring the final design were already on site, and assembly was underway.

“The pedestal for dish one has already been installed, and we are anticipating the ‘big lift’ of its reflector onto the pedestal later in April or early May,” the SKAO said.

The precise timing of the big lift will depend on the weather, as it cannot be done when it is too windy.

There are currently around 140 people working on the site. The SKAO said this would change month-on-month as activities ramped up.

By the end of the year, the goal is to have the first four dishes and their associated systems installed.

The SKAO explained a construction of this magnitude was always a logistical challenge but that its teams were prepared for the potential issues.

“Some aspects are of course beyond our control, such as the weather and global shipping,” it said.

The parts for the dishes are arriving in South Africa through the port of Cape Town, which has been unusually busy due to many shipping companies diverting traffic around the South African coast as Houthi militants have attacked ships passing through the Suez Canal.

Nevertheless, the pace of construction is expected to pick up, with the aim of installing three to four dishes every month starting next year. That would work out to between 36 and 48 dishes annually.

The entire SKA-Mid project is expected to be completed in 2029, seven years after construction began.

However, because the installation has an interferometer, early scientific activities can begin even when the array is still only partially complete.