Beginning with only cast-offs and hand-me-downs, University researchers have endured to become the world authorities on water vapor in the upper atmosphere. Soon they will even be able to take these measurements from a space shuttle.

According to Charles L. Croskey, research associate in electrical engineering in the communications and space sciences laboratory, researchers here will join with scientists from around the world in developing part of an instrument pallet which, beginning in May 1991, will fly on several missions of the space shuttle Atlas I.

"(Water vapor) is one of the key components of the chemical reactions of the . . . atmosphere," said Croskey.

The University is the only place which takes water vapor measurements on a daily basis, although sporadic measurements have been taken at the Jet Propulsion Laboratory in California. and at the Haystack facility in Massachusetts. Croskey said few places are taking these measurements because the equipment is expensive and the technology is advanced.

When planning for the water vapor research began in the l970s there was not much funding available, according to John J. Olivero, professor of meteorology. "We really scrounged," Olivero said.

It is hard to get backing for research unless the research has been done before and has shown results, he said.

The original piece of equipment University researchers used to measure water vapor was a sun tracker which operated on the principle of microwave radiometry. According to Olivero, it picked up and focused the weak radiation signals of the sun.

"Imagine the weakest station you tried to tune in on a radio - that would be a very strong one," Olivero said.

Because water vapor absorbs the sun's radiation, scientists are able to determine the amount of water vapor at any given time by comparing the amount of solar radiation to an expected control value of radiation above the atmosphere, he said.

According to Croskey, the sun tracker had some disadvantages because it could only operate in the daytime and the dish which focused the signal was susceptible to wind.

Recently, the researchers have acquired a new piece of equipment called the MASER (Microwave Amplification by Stimulated Emissional Radiation). The MASER is a more sensitive receiver than the sun tracker, according to Olivero, because it operates at a very low temperature, minus 269 degrees Celsius, which allows for less noise interference while still amplifying the signal.

Croskey said the MASER operates on essentially the same principles as a laser, but it also has a few drawbacks. The MASER is big and bulky and maintaining the extreme temperature is expensive. Olivero also added because it is not portable, researchers can take measurements from only one area of the atmosphere.

Once the data has been collected, Olivero said the researchers look for properties like the concentration of water vapor, its distribution according to altitude and how the concentration varies over time.

"Water vapor is one of the principle chemicals of the upper atmosphere that controls ozone," said Olivero.

By studying the effects of water vapor on ozone, scientists gain a better understanding of ozone properties, said Croskey.

Noctilucent clouds, very thin clouds seen in the polar regions only under certain illumination conditions, and high altitude ice particles could also be studied through this research, Croskey said. The measurements are also used to examine the planetary hydrogen budget for signs of instability or fluctuation.