The Interplanetary Scintillation Array (IPS Array or Pulsar Array) was built at the Mullard Radio Astronomy Observatory in 1967 and originally covered four acres (16,000 m²). It was extended in 1978 to nine, and re-furbished in 1989. It operates at 81.5 MHz (3.7 m wavelength), and is made up of 4096 dipoles in a phased array. 14 beams can map the northern sky in one day. Sheep are used to keep grass away from the aerials as a lawnmower would not fit. It was designed by Antony Hewish to measure the high-frequency fluctuations of radio sources, originally for monitoring interplanetary scintillation. Antony Hewish received a Nobel prize after the high time-resolution of the array allowed the detection of pulsars by Jocelyn Bell in 1967. The IPS has more recently been used to track and help forecast interplanetary weather, and specifically to monitor the solar wind. It is now essentially retired, and has lost significant fraction of its area. The telescope was operated by the Cavendish Astrophysics Group. Mullard Radio Astronomy Observatory is home to a number of large aperture synthesis radio telescopes, including the One-Mile and 5km instruments. ... 1967 was a common year starting on Sunday of the Gregorian calendar. ... This article is about the unit of measure known as the acre. ... 1978 was a common year starting on Sunday (the link is to a full 1978 calendar). ... 1989 is a common year starting on Sunday of the Gregorian calendar. ... Binomial name Ovis aries Linnaeus, 1758 A sheep is any of several woolly ruminant quadrupeds, but most commonly the Domestic Sheep (Ovis aries), which probably descends from the wild moufflon of south-central and south-west Asia. ... Antony Hewish (born Fowey, Cornwall, May 11, 1924) is a British radio astronomer who won the Nobel Prize for Physics in 1974 (together with fellow radio-astronomer Martin Ryle) for his role in the discovery of pulsars. ... Antony Hewish (born Fowey, Cornwall, May 11, 1924) is a British radio astronomer who won the Nobel Prize for Physics in 1974 (together with fellow radio-astronomer Martin Ryle) for his role in the discovery of pulsars. ... Photographs of Nobel Prize Medals. ... Composite Optical/X-ray image of the Crab Nebula pulsar, showing surrounding nebular gases stirred by the pulsars magnetic field and radiation. ... Jocelyn Bell Burnell (born Jocelyn Bell, 15 July 1943), British astrophysicist who discovered the first radio pulsars with her thesis advisor Antony Hewish. ... 50 cm refracting telescope at Nice Observatory. ... The Cavendish Astrophysics Group (formerly the Radio Astronomy Group) is based at the Cavendish Laboratory at Cambridge University. ...