An astro-helmet was headgear of unknown purpose and origin.
There was a Wadi booth on Tulgana IV in 2381 that had an astro-helmet on display along with other objects. (LD: "Reflections")
In the real world, the Astro-Helmet was a children's toy released in 1967 by Remco Industries. It came with non-shattering bulbous lenses tinted green and an elastic chin strap with chin protector. A decal sticker with the words "Star Trek" was placed above the lenses. There were decorative stickers on either side of the helmet. Other than the decal saying "Star Trek", the Astro-Helmet had absolutely nothing to do with the franchise whatsoever – that is, until its "official" appearance fifty-five years later, in Star Trek: Lower Decks. [1]