VLBI in AfricaVLBI in Africa

Michael BietenholzHartebeesthoek Radio Observatory

Current Status of VLBI in Africa: HartRAO

Picture: Thomas Abbott

Current Status of VLBI in Africa: HartRAO

Picture: Thomas Abbott

• HartRAO 26-m dish is fully operational again – bearing has been replaced

• Regularly taking part in VLBI sessions with EVN and LBA (1.7 - 22 GHz)

• Monthly e-VLBI sessions with EVN at 1 Gbps• XDM, a 15-m composite dish, will take over

some geodetic observations

Current Status of VLBI in Africa: MeerKAT

Current Status of VLBI in Africa: MeerKAT

• KAT-7, engineering prototype for MeerKAT. All 7 dishes operating with uncooled receivers, cryogenic receivers being installed

• MeerKAT will have– 64 dishes, ~13 m diameter, – total collecting area equivalent to ~100 m diameter: most sensitive

radio telescope in the Southern hemisphere– 70% of dishes within a 1-km core, remainder out to ~10 km – Frequencies: 0.5-2 GHz and 8-14 GHz – 1 → 2 → 4 GHz instantaneous bandwidths

• First VLBI fringes have been obtained between HartRAO and KAT-7: ~900 km , 3C 273, 1.7 GHz

• VLBI observations hopefully by the end of 2011

HartRAO – MeerKAT Baseline

~900 km

J. Horrell, S. Ratcliffe, L. Schwardt

VLBI with MeerKAT

TAC response: “We are convinced that there is a strong case for MeerKAT to pursue VLBI observations … We will ensure that in due time, MeerKAT becomes affiliated to international VLBI networks in line with time allocation, scheduling and time commitments to these networks”

Status of VLBI in Africa: SKA South Africa

Re-use of Satellite Ground Stations for Radio Astronomy

• There are a considerable number of satellite ground stations in Africa

• Fully steerable 20 - 32 m dishes• Surfaces accurate enough for use at

least 10 GHz• These stations are rapidly becoming

redundant due to the proliferation of undersea optical fibre links, which have much higher bandwidth

• There is therefore a possibility to re-use some of these stations for radio astronomy, particularly for VLBI

Satellite Earth Stations in Africa

Google Earth

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Estimated Conversion Costs

Upgrade to angle encoders etc $140 K

Uncooled, dual polarization receivers & feed horns; C, X and K bands

$300 K

VLBI phase calibration, LO & IF systems $180 K

Backends: VLBI DBBC + MkV + digital multi-channel (e.g., Roach)

$280 K

Time and Freq. standard (H maser) $240 K

Other costs (test equipment, telescope control system, SCADA)

$200 K

Commissioning team: 3 engineers & 3 technicians * 1 year

$400 K

Total $1740 K

Data: M. Gaylard, HartRAO

Operations Cost

• Including 2 on-site operation technician/scientists, 1 on-site maintenance technician, 2 off-site scientists

• Power, water, disk-pack shipping costs, internet and security

• $310 K per year

Data: M. Gaylard, HartRAO

Status of Conversions and New Antennas

• A dish is to be constructed in Mozambique (~13-m) in cooperation with SKA South Africa

• Negotiations are underway for HartRAO to use one (or more) of the 32-m redundant dishes at the nearby Telkom site for radio astronomy

• A 25-m dish is also planned in Nsukka, Nigeria in collaboration with NIAOT from China

• There is in-principle approval from the minister of science in South Africa to develop the African VLBI network, although co-funding from the individual nations is required

uv-Coverage: with HartRAO, MeerKAT + EVN

uv-Coverage: adding 4 Africa Array

uv-Coverage: with 4 Africa Array

uv-Coverage: adding 4 more Africa Array

uv-Coverage: HartRAO, MeerKAT + LBA

uv-Coverage: adding 4 Africa Array

uv-Coverage: adding 4 more Africa Array

Satellite Earth Stations in Africa

Google Earth