In the latest Quest

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Building MeerKat

MeerKAT is about a lot more than theoretical astronomy. Tracey Cheetham gives Quest some idea of the infrastructure that is involved in this huge project.

 ‘The infrastructure team of the SKA SA project is making excellent progress with the development of the Karoo MeerKAT site. Progress with power systems, as well as roads, civil works, landing strip, electrical and fibre reticulation and construction camps is on schedule. The clearing and grubbing of all internal roads has been completed and layering works has started. Test results have been received for the aggregate material, and the layering works have started for the all-weather landing strip. Trenching for the fibre and power reticulation has commenced and the first long-haul power cables have been laid.’ SKA newsletter, July 2012.

This excerpt from the SKA newsletter, July 2012 has a sense of excitement – and it is about more than the esoteric astronomy. The sheer scale of the project means that there are enormous numbers of people involved. The project has so far generated 164 local jobs in an area where work is scarce – with a wage bill of R2.4 million by the end of July.

Putting together all this infrastructure involves civil engineers, electrical engineers, project managers and scientists and technicians of all types.

Power: the Karoo substation upgraded

The Karoo substation that is 10 km outside Carnarvon is being upgraded from 5MVA to 10MVA capacity for MeerKAT. This work is divided into:

* Supply, delivery, installation and acceptance of two new 5MVA transformers, and

* civil works for the extension of the existing substation.

The should be completed by December 2012. Once completed, the substation will once again become the responsiblity of Eskom. The existing power line that was constructed by the SKA SA will be switched over from 22kV and operated at 33kV once the substation has been completed.  This will provide for the full power requirement for MeerKAT.

MeerKAT infrastructure will include roads, civil works, all-weather landing strip, electrical and fibre reticulation and construction camps. The contract to provide this includes bulk infrastructure:

* The construction of 35 km of internal farm roads on the MeerKAT site between the site complex and each MeerKAT antenna

* A new all-weather landing strip on site to enhance accessibility to site for SKA staff and scientists

* Civil works which includes earthworks, piling, sewers, pumping equipment, chlorination plants and sewer package treatment plants

* Electrical works which includes the provision of transformers, mini-substations, ring-main units, 35 km of electrical cabling and optic fibre ducting between the site complex and each MeerKAT antenna.

Construction of the civil works contract started March this year and is expected to be finished by the end of March 2013.

MeerKAT buildings

MeerKAT will need new buildings and extensions to existing buildings as the project progresses. There will be extensions to the existing dish assembly shed where the MeerKAT dishes will be assembled. A new pedestal integration shed where the dish components will be integrated is needed and the Karoo Array Processor building and its power facility, need to be built. This is the building in which all on-site data processing is done.

This building will be constructed 5 m underground in a bunker to protect the on-site radio telescope instruments from radio frequency interference (RFI) generated by equipment located in the centre. The underground construction is also to prevent the building from becoming too hot or too cold in the variable Karoo climate. All the centralised telescope equipment for the Karoo Array Telescope- (KAT-) 7 and MeerKAT will be housed in this building.

The data generated on site will be sent from the array processor to the science and engineering office in Pinelands, Cape Town using a long-haul fibre-optic link, which is already in place.

This section of the building requires RFI shielding with effectiveness better than 100 dB between 70 MHz and 10 GHz and better than 80 dB between 10 GHz and 15 GHz. The shielding will include shielded doors and screened penetrations for power, cooling, fibre connections and interface plates for additional penetrations such as global positioning system cables.

The hydrogen maser room, containing an extremely precise atomic clock, will be located in a separately partitioned room within the data rack area.

An atomic clock is the most accurate time and frequency standard known and atomic clocks are used as the primary standards for international time distribution services, such as global navigation satellite systems (GPS). This type of clock is based on atomic physics and uses the microwave signal that electrons in atoms emit when they change energy levels.

The soil that will be excavated for the bunker will be used as a berm next to the site complex to improve shielding between the MeerKAT radio telescope and the site complex.

Power supply

The power facility next to the data centre will also be in a bunker. It will supply 640 kVA of power to the building. A project such as this obviously needs a continuous power supply and this is provided for through the provision of rotary uniterrunptable power supplies (UPSs). The power supply design, as well as the distribution system and the building will allow for growth up to 128 racks. The total maximum capacity of the power facility is 5 MVA but it will initially supply 2.5 MVA to KAT-7 and MeerKAT.

Cooling

Cooling will be provided through a hot aisle/cold aisle concept and cold aisles will maintain a dry bulb temperature of between 18 °C and 27 °C. Hot aisle/cold aisle is a specific layout design for server racks and other computing equipment in a data centre. The idea behind this concept is to conserve energy and lower cooling costs by managing air flow.

At its simplest, a hot aisle/cold aisle design involves lining up server racks in alternating rows, with cold air intake facing one way and hot air exhausts facing the other way. The rows that are made up of rack fronts are called cold aisles and these usually face air conditioner output ducts. The rows that the heated exhausts pour into are calle hot aisles and usually face the air conditioner return ducts.

The cooling capacity for each rack is 5 kW.

Earthing, cabling and acoustics

The earthing design and cabling strategy of the building and the power facility has been carefully designed – particularly because of the problem of RFI. A mesh screen has been included in the design of the power facility to prevent RFI leaking out over the top of the bunker walls.

Environmental noise control was a particular factor in the design of the power facility and sound attenuators were installed on all air inlets and outlets of the mechanical plant rooms, as well as silencers for the generator exhausts, anti-vibration mountings for all vibration equipment, appropriately rated acoustic doors and noise-break panels in the cable trenches.

The Karoo Array Processor Building and power facility are fitted with a fire-detection and suppression system, building management system and an access control and security system.

MeerKAT antenna foundations

This contract includes the provision of 64 foundations for the MeerKAT positioners and detailed designs are in progress.

Tracey Cheetham is the Manager, Infrastructure, for MeerKAT.