Sam Hooke

Tour of MRAO (Part 2): HERA, MERLIN, AMI Small Array, COAST and SKA

All trips at this location:

Map §

SITE 1.ADMINISTRATIONCambridge RoadWimpoleRoadHaslingfieldRoadBarton RoadLord's BridgeStationAMI Small ArrayCOASTAMI Large Array†Pulsar Array4C Array†Half-Mile Telescope (small) & †One-Mile Telescope (large)†One-MileTelescopeTrack continues 1km eastwardse-MERLIN†CLFST†CATUnknown?Unknown?†SKA†HERAUnknown?†SKAPrototypearrayPrototypeindividualPrototypeRyle ControlRoomOne-MileControlRoom(Previously site of †Ryle Telescope)(Track is shared)Name†NameLong BrookBourn Brook𝕳𝖊𝖞 𝕳𝖎𝖑𝖑𝕽𝖔𝖒𝖆𝖓𝕭𝖆𝖗𝖗𝖔𝖜NSITE 6.SEWAGE DISPOSALSITE 2.BOMB STORESSITE 4.F.F.D.4.1 Mile1 Kilometerhttps://sam.hooke.me/mraoJune 2024Mullard Radio AstronomyObservatory (MRAO)KeyFormer railwayTelescope railwayMain roadMRAO tarmac roadMRAO trackTelescope (static)Telescope (on track)Telescope (approx. area)Telescope (active)Telescope (inactive)MRAO (approx. area)

Leaving the AMI Large Array (at the furthest east of MRAO), we drove west back along the road that follows the old east-west railway line, under the bridge, and then turned left at the fork. This gentle curve follows the line of the former railway sidings, for when this site used to be a munitions storage facility.

We carried on southwest, taking a slight right at the point of a teardrop shaped road, then pulled in just after the next road loop, where HERA is visible about 60m away to the northwest.

HERA §

HERA (Hydrogen Epoch of Re-ionization Array) is not mentioned on the MRAO Wikipedia page. Perhaps this is because it is technically a HERA prototype. Here is an article by Cavendish Astrophysics (who operate the MRAO) about the “3-dish HERA prototype” at MRAO, which can clearly be seen in the photos below:

Three mesh dishes on the ground.
The three dishes of the HERA prototype.
A receiver, a horn antenna with many holes cut in it to reduce its weight.
A close up of one of the receivers. The holes are cut strategically to reduce the weight, while also enabling it to have the correct characteristics for being an RF receiver.

There is much more information about HERA and the receiver in this paper, titled Design of the New Wideband Vivaldi Feed for the HERA Radio-Telescope Phase II.

The actual HERA radio telescope is in South Africa.

A one storey red brick building.
The building in the distance, behind HERA.

Cambridge MERLIN §

From the same spot, but turning east, is a great view of the Cambridge MERLIN radio telescope with its 32m dish. It forms part of the e-MERLIN array, which consists of seven radio telescopes across England.

The e-MERLIN array consists of:

Wikipedia omits the Darnhall telescope from its list of MERLIN telescopes for some unknown reason?

See this Wikipedia page for many more radio telescopes.

The Cambridge MERLIN telescope, with its 32m diameter dish, is the second biggest dish in England. First place goes to the Lovell Telescope, which is also part of e-MERLIN, with its whopping 76.2m diameter!

A big parabolic receiver on a tower behind a line of trees.
The e-MERLIN dish at MRAO is 32m in diameter, the second biggest dish in England.

Map §

SITE 1.ADMINISTRATIONCambridge RoadWimpoleRoadHaslingfieldRoadBarton RoadLord's BridgeStationAMI Small ArrayCOASTAMI Large Array†Pulsar Array4C Array†Half-Mile Telescope (small) & †One-Mile Telescope (large)†One-MileTelescopeTrack continues 1km eastwardse-MERLIN†CLFST†CATUnknown?Unknown?†SKA†HERAUnknown?†SKAPrototypearrayPrototypeindividualPrototypeRyle ControlRoomOne-MileControlRoom(Previously site of †Ryle Telescope)(Track is shared)Name†NameLong BrookBourn Brook𝕳𝖊𝖞 𝕳𝖎𝖑𝖑𝕽𝖔𝖒𝖆𝖓𝕭𝖆𝖗𝖗𝖔𝖜NSITE 6.SEWAGE DISPOSALSITE 2.BOMB STORESSITE 4.F.F.D.4.1 Mile1 Kilometerhttps://sam.hooke.me/mraoJune 2024Mullard Radio AstronomyObservatory (MRAO)KeyFormer railwayTelescope railwayMain roadMRAO tarmac roadMRAO trackTelescope (static)Telescope (on track)Telescope (approx. area)Telescope (active)Telescope (inactive)MRAO (approx. area)

Moving on, from HERA we turned left heading southeast down the main road, then turned left after Long Brook to park outside the front of the AMI Small Array.

According to the old map, this used to be the location of the BOMB STORES!

Plaques §

The AMI Small Array is completely enclosed within some angled walls. The only way to get in is through the adjacent building, which has a couple of interesting plaques out front:

TODO.
CAMBRIDGE UNIVERSITY MULLARD RADIO ASTRONOMY OBSERVATORY
TODO.
GROTE REBER (1911 - 2002) ELECTRICAL ENGINEER AND PIONEER ASTRONOMER

Inside §

Inside, there is a server room that contains a couple of RF signal racks:

A server rack with a dozen or so rows of rack mounted RF equipment.
AMI Small Array RF/IF Signal Rack.

Back through the main hallway, a lab space leads to an angled door, that leans inwards at about 45 degrees. As will become clearer in the next picture, that’s because this door emerges from the sloping wall that encircles the AMI Small Array.

A metal wall and door leaning towards the camera at about 45 degrees.
The door that leads back outside, to the enclosed area with the AMI Small Array.

AMI Small Array §

As the name implies, the AMI Small Array is indeed smaller than the AMI Large Array!

Each receiver is approximately 4m high from ground level, and the dishes are 3.7m wide.

There are 10 receivers in total, arranged in the following formation:

  x x
x     x
   x
x     x
 x   x
   x

Seven parabolic receivers.
Seven of the receivers (the other three are behind the camera).
Close up shot of a dish.
A closer look at a dish.
A view from behind two receivers.
A view from behind.

COAST §

Just southeast of the AMI Small Array is COAST (Cambridge Optical Aperture Synthesis Telescope). Much of COAST is inside a bunker, but some of the equipment is also contained in this white boxes on the grass outside.

A bunker covered in grass with some white boxes out front, connected to the bunker by white pipes.
The COAST bunker and nearby equipment.

SKA §

Directly in front of COAST is an individual prototype SKA antenna. Specifically, I believe this is a SKALA-2 antenna for SKA-Low. See the paper titled Evolution of SKALA (SKALA-2), the log-periodic array antenna for the SKA-low instrument.

An antenna about the size and shape of a Christmas tree.
SKALA-2 has the appearance of a Christmas tree.

While researching SKA, I found this post from Cavendish Astrophysics, which links to this YouTube video, which provides aerial drone footage of SKA!

Looking down a dirt road towards a hedge.
The array of SKALA-2 antennas is behind the hedge to the right. I did not get to take a look, but the above video shows the view from there.
The SKALA-2 antenna with one of the COAST white boxes behind.
Another view of SKALA-2 with COAST equipment in the background.

The tour guide told us that this SKA antenna was called “the final design”, but afterwards there were two more!

Next part §

To carry on with the tour, see here for part 3.

All trips at this location: