Tour of MRAO (Part 3): 4C Array, Flora & Fauna, and One-Mile Telescope
All trips at this location:
- Tour of MRAO (Part 1): Lord's Bridge station and AMI Large Array
- Tour of MRAO (Part 2): HERA, MERLIN, AMI Small Array, COAST and SKA
- Tour of MRAO (Part 3): 4C Array, Flora & Fauna, and One-Mile Telescope
- Tour of MRAO (Part 4): One-Mile Telescope Control Room
Map §
Walking clockwise, following the road around the AMI Small Array, we reached the 4C Array, One-Mile Telescope and Half-Mile Telescope, which all run parallel to each other.
4C Array §
Flora & Fauna §
As a brief interlude to all the radio telescopes, I thought it worth highlighting some of the flora and fauna at the MRAO. The site is typically devoid of much human activity, and unlike the surrounding farmland, countains many acreas of grassy meadows. There’s also countless hedgerows and patches of woodland. This adds up to create an oasis for certain plants and animals.
At the very start of the tour, we were meant to enter by the main entrance at the Lord’s Bridge railway station. However, when I got there at 9:30am, the facility was experiencing a power cut which prevented the electronic main gate from opening. We were advised to use the secondary entrance, a little further down the road near HERA, which is normally closed. After entering, we parked along the side of the tree lined avenue. A few minutes later I saw a Red-tailed Hawk being mobbed by crows in the nearby trees. While Red-tailed Hawks are now rather common (a rare success story, coming back from the brink of extinction in the UK), it was exciting to see one so close.

I was told that the MRAO is home to some rare wild orchids.
Here’s a quick game.
Can you spot the orchid?
The orchid was right in the center of the previous photo.
By my estimate, it might be a Dactylorhiza maculata subsp. fuchsii (perhaps better known as the Common Spotted Orchid) which is common throughout the UK. So, perhaps not one of the aforementioned rare wild orchids.
However, according to NatureSpot:
This is a difficult genus that readily hybridises, leading to many intermediate forms; the species also exhibit a wide range of variation. Other Dactylorhiza in VC55 are Heath-spotted Orchid, Southern Marsh Orchid, Early Marsh Orchid, and hybrid between Common Spotted and Southern Marsh Orchids (D x grandis); other hybrids within Dactylorhiza are possible where both parents grow together.
So perhaps it is a hybrid? Unfortunately the photo does not provide enough detail to know.
One-Mile Telescope and Half-Mile Telescope §
The last stop on the tour was a close up visit of the One-Mile Telescope and Half-Mile Telescope. Both of these impressive radio telescopes feature static and track mounted equipment.
Track mounted §
The half mile (800m) east-west track is shared between the two telescopes:
- One-Mile Telescope: A single track mounted 18m diameter dish.
- Half-Mile Telescope: Two track mounted dishes (unknown diameter).
Static §
As for the static equipment:
- One-Mile Telescope: One 18m diameter dish at the east end of the track (above the control room), and another one half a mile to the east.
- Half-Mile Telescope: Two dishes (unknown diameter) at the west end of the track.
For more details about the One-Mile Telescope, see this paper from 1966 titled THE OPERATION OF THE CAMBRIDGE ONE-MILE DIAMETER RADIO TELESCOPE.
According to Wikipedia, the far end of the track is raised by 5cm to allow for the curvature of the Earth. However, I can’t find any reliable source for this. The only non-Wikipedia reference to this I can find is from this post, which may in turn have got that information from Wikipedia.
Next part §
To carry on with the tour, see here for part 4.
All trips at this location:
- Tour of MRAO (Part 1): Lord's Bridge station and AMI Large Array
- Tour of MRAO (Part 2): HERA, MERLIN, AMI Small Array, COAST and SKA
- Tour of MRAO (Part 3): 4C Array, Flora & Fauna, and One-Mile Telescope
- Tour of MRAO (Part 4): One-Mile Telescope Control Room