PARIS — Astronauts on the international space station (ISS) spend nearly one-quarter of the time they allot to conducting experiments to repairing or performing routine maintenance on the payload canisters that house the scientific gear, European and Japanese space station officials said Sept. 29.

Data are still preliminary, but indications are that between 20 and 25 percent of the time astronauts devote to scientific experiments is spent performing preventive or corrective maintenance on the payload racks.

More than a year after the orbital complex reached its full permanent-crew complement of six astronauts, officials said they have noticed the sharp increase in astronaut time given over to conducting the experiments that are one of the station’s principal reasons for being.

Martin Zell, head of the station utilization department at the European Space Agency (ESA), said the agency has seen a healthy demand for experiment time on the station and is now booked for many kinds of experiments until 2015 or 2016. A recent call for proposals to use the station as a platform for Earth observation sensors has yielded a large crop of ideas for what will be a new branch of science performed onboard.

Russia’s Roskosmos space agency, which organizes the use of the Russian segment of the station, has a well-defined program of more than 170 experiments that should be completed by 2015, said Boris V. Zagreev of Russia’s TsNIIMASH organization. Zagreev told the 61st International Astronautical Congress that 38 of these experiments have been completed, with 64 more onboard the station and the remaining 70 on the ground in various stages of prelaunch preparation. Ten new experiments are started on board each year, he said.

The station’s orbit does not permit it to view the whole of Russian territory, making Earth observation a less-valuable area to pursue, Zagreev said. That makes life sciences and fluid-physics experiments, along with experiments on human physiology, the principal focus areas, he said. Zagreev said Roskosmos is still struggling with strategies on how to evaluate experiments that will make the best use of astronauts’ time and the station’s resources.

Russia is adding experiment space to the station that by 2014 will bring to nine the number of modules — 24 cubic meters of volume — available for experiments.

Roskosmos, he said, is concerned that too many experiments begun on the station are not brought to completion, for many reasons. He said he hoped the addition of new laboratory space will reduce the problem.

He did not spell out the causes of the premature abandonment of experiments. But a paper written by Nobuyoshi Fujimoto of the Japan Aerospace Exploration Agency said some 10 percent of astronaut time in the Japanese experiment module is devoted to repairing experiment modules.

Carlo Mirra, space station mission integration manager at Astrium, a major space station contractor, said European astronauts spend 23 percent of the time they devote to science experiments performing maintenance on experiment racks between experiment regimes, or repairing the racks.

“We live in the real world,” Mirra said. “Things work, and things fail.” He said an analysis of the rack-maintenance and rack-repair cycles gives no reason to believe that astronauts in the future will be able to spend any less time on these chores.

He said ESA has performed 71 experiments between 2008 and mid-2010 and has seen “an incredible boost in utilization” of the experiment capacity since the station has reached six permanent members. Mirra said he had not seen updated figures from NASA but that the data from Japan appear to be similar to those of ESA and he would be surprised if NASA’s experiments required much less, or much more, astronaut upkeep.


Peter B. de Selding was the Paris bureau chief for SpaceNews.