Energy company Eon has put up a 360ft (110m) meteorological mast 12 miles south east of Brighton and Hove.
The mast will measure wind speeds, wave heights, sea currents and other offshore environmental data.
It has been put up as part of the preparations by Eon to try to win planning permission for the proposed Rampion wind farm.
Eon wants to build a wind farm of up to 195 turbines between 8 and 15 miles off the coast of Brighton and Hove.
The turbines would be expected to generate enough electricity to supply about 450,000 homes.
Work on the mast started on Monday 2 April but was delayed because of the weather.
Chris Tomlinson, Eon’s project development manager, said that more than 4,500 people had attended a dozen exhibitions in Brighton and Hove and surrounding towns and villages.
The exhibitions formed part of the biggest consultation exercise undertaken by the energy company.
The current round of consultation ends on Monday 6 May and will be followed by formal consultation with politicians, regulators and various statutory bodies.
The consultation document and questionnaire are still available on the project website www.eon-uk.com/rampion.
Mr Tomlinson said: “I’ve been surprised and delighted by the level of response we’ve had for the Rampion project so far.
“I’ve spoken to hundreds of people at our exhibitions and the majority feel positive about the proposed development.”
Norman Baker, the Liberal Democrat MP for Lewes, said: “I congratulate Eon for the way they have approached the community consultation process for the Rampion Offshore Wind Farm.
“They have set a very good example of best practice for others to follow and I look forward to seeing the final proposal Eon puts forward.
Is there any point in objecting the the off shore wind farm? I’m sure many other residents are as unhappy as us about this blot on the seascape – but it looks like it’s going to happen whatever we think. All the evidence is that wind energy is inconsistent and expensive, not to mention ruining our areas of natural beauty. If anyone is starting an e-partition, please send us a link.