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Oh The The United States is the world. Hello and welcome. This is Michael Annas, and you are listening to episode number 383 of the Space Rocket History podcast.

And now, Ariel 4, Prospero X-3, Shinsie, ISIS 2, and it's our 9th anniversary.

We have a bunch of satellites to talk about today, and each of them was unique in its own way,

and all of them were launched in 1971.

First of all, we have Ariel 4.

The UK United Kingdom Research Satellite 4, also known as Aerial 4, was a small observatory

designed to investigate the interaction between electromagnetic waves, plasmas, and energetic particles present in the upper ionosphere.

It was operated by the Science and Engineering Research Council.

Aerial 4 leveraged both the design and hardware of Aerial 3 to reduce cost.

Aerial 4 used pieces of its predecessors' flight backup unit and spare parts.

The satellite only cost about 1.25 million pounds.

It was the first satellite of the aerial program to have a mission-oriented payload.

This is the case when all of the experiments were designed to research one scientific objective.

The scientific objective was to study the interaction between high-energy charged particles

and electromagnetic radiation in the upper ionosphere and magnetosphere.

Three of the five experiments on aerial three were to determine a single scientific objective.

So those three were improved for use on aerial four, and an additional experiment was added.

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