RAP

RAP is an ultraviolet light detector package used to measure the amount of ozone in the stratosphere.

Ozone (O₃) is a small but essential part of Earth’s atmosphere. When hard ultraviolet photons strike an ozone molecule in the stratosphere, the molecule absorbs the energy of that photon and breaks down into diatomic oxygen (O₂, the stuff we breath) and an oxygen radical. By absorbing that hard UV photon, the ozone keeps it from striking Earth’s surface where it can do damage to living tissue.

RAP measures the amount of sunlight at various ultraviolet frequencies after it has passed through the ozone layer. When the sunlight strikes the ozone layer some of it is absorbed or scattered and the rest passes through. The amount of absorption and scattering is proportional to the amount of ozone present. The light that passes through can be measured to find out how much has been absorbed and scattered. This gives a measurement of how much ozone is present. By taking measurements throughout the flight, the data can be used to produce a continuous vertical profile of the amount of ozone present.

RAP uses four ultraviolet photo diodes each with different filters to measure the amount of light at four different ultraviolet frequencies. It is a compact package, fitting into a 15 cubic inch housing and riding inside of the skin section containing the VIRGO payload.

RAP uses an internal printed circuit board designed in APRL and manufactured by Quick Turn Circuits. The surface mount components and wiring were assembled to the board in the lab. The aluminum housing was machined at the University’s machine shop after being designed on Pro/ENGINEER in the lab.