The International Space Station approaches 15 years in orbit later this year. During the first 14 years researchers conducted more than 1,500 investigations, advancing science, technology and education. Investigations on the station began almost as soon as the first component launched in 1998, and the pace and volume of research increased steadily with each milestone.

The most recent International Space Station Utilization Statistics, published on May 2, are a look back at station data from December 1998 to September 2012. This includes 32 crew expeditions to the complex, with an expedition referring to a 3 to 6 month timeframe based on crew rotation. The statistics focus on research and technology investigations, along with education activities conducted in orbit.

"It's really exciting to see the numbers of experiments and investigators that we are carrying through on the International Space Station, and we definitely feel that energy," said NASA's International Space Station Program Scientist Julie Robinson, Ph.D.

"But what's most important is what's going on underneath -- the research discoveries, the hundreds of scientific publications, the publications in key journals, we're really starting to see the space station come into its own."

During an average 6-month period on the station, as many as 200 investigations operate, with between 70 and 100 of them being new studies. Close to 600 journal articles have published on this research, reflecting the growth in scientific findings from space station investigations. Journals that have published articles include Nature, Proceedings of the National Academy of Sciences of the United States of America and Physical Review Letters, among others.

This is the second publication of space station utilization statistics. The first released in 2011 after station's assembly phase completed. The effort to compile the data is worldwide, with inputs submitted to NASA's International Space Station Program Science Office by the five station international partners: Russia, Canada, Japan, Europe and the U.S.

"One thing that really surprises people is how many countries have participated," said Robinson. "What actually happens is that those nations then go out and collaborate with others. There are educational activities that are open to nations around the world, there are research collaborations because science is so international, and because of that we've had a total of 68 countries that have participated so far and that number keeps going up."

The goal of the space station statistics publication is to reach a broad audience with the numbers that tell the story of what microgravity research and the station platform can and have accomplished. Within the physical sciences, a cool flame discovery was made with the Flame Extinguishing Experiment (FLEX).

Vaccine development is under way for salmonella thanks to station biology research. The unique vantage point of the space station continues to provide important Earth observations. These are just a few examples of the work in orbit these statistics represent.

Political leaders, partner agencies and the public all have a stake in the results of and benefits from research performed on the space station. "We compile these statistics to keep a standard baseline across the program," said Robinson.

"People wonder what are you doing and it always helps to have a few numbers to say we are doing these active investigations, these are the disciplines that they are in, this is how much we are flying and this is how much we are doing for our scientific community."