Biting at the heels of NASA’s latest launch, the space agency is preparing to send up a rocket to probe the atmosphere of Venus.

The Venus Spectral Rocket, VeSpR for short, is scheduled to lift off in the next 12 hours to peer through the thick fog which envelopes our solar neighbour.

VeSpR is a two-stage system, combining a Terrier missile – originally built as a surface-to-air missile and later repurposed to support science missions – and a Black Brant model Mk1 sounding rocket with a telescope inside.

The new probe will look at ultraviolet (UV) light emitted from Venus' atmosphere, which can provide information about the history of the planet’s water. This kind of measurement cannot be done on Earth, as our atmosphere absorbs most UV light before it reaches terrestrial telescopes.

The sounding rocket will carry the telescope more than 110 kilometres above the surface of Earth, where the atmosphere is thin enough to capture UV light from Venus.

"Venus today has a thick atmosphere that contains very little water, but we think the planet started out with an ocean's worth of water," said John T. Clarke, the mission's principal investigator.

The key to figuring out how much water Venus once had lies in how much hydrogen and deuterium, a heavier version of hydrogen, remain in the atmosphere.

Both combine with oxygen to make water, either in the familiar H2O form or the rarer hydrogen, deuterium and oxygen form, called HDO.

Intense UV light from the sun has broken apart nearly all of the water molecules in Venus' atmosphere.

Because the hydrogen atoms in the water are lighter, they escape into space more quickly than the heavier deuterium ones.

By comparing the amount of deuterium now in the atmosphere to the amount of hydrogen, researchers can estimate how much water disappeared from Venus and how quickly it happened.

The VeSpR instrument will observe Venus for 8 minutes, with data being transmitted in real time, before the payload returns on a parachute safely to Earth. Later, the payload will be retrieved so that the instrument can be used for future experiments.