SDL Sensor to be Installed on International Space Station

July 31, 2006

Logan, Utah— After more than a three-year wait, Utah State University’s Space Dynamics Laboratory (SDL) will be celebrating as its sensor is installed in the International Space Station during an Extra Vehicle Activity (EVA) on August 3.

SDL’s Floating Potential Measurement Unit (FPMU) was originally scheduled to ride on the Space Shuttle launch after the Columbia and subsequently was on hold until it was launched on July 4 aboard the Space Shuttle Discovery.

“I am really excited to see the sensor installed and to start receiving data,” said Charles Swenson, Ph.D., FPMU principal investigator and USU professor. “During the three-year wait we have launched similar sensors on sounding rockets, but the data from the ISS will be unique.”

FPMU was developed in response to an urgent need to address vehicle charging on the ISS. NASA discovered that the solar panels aboard the Space Station collect electrons faster than they can be emitted. This drives the Station to a negative potential relative to its surrounding space environment, creating a possible dangerous environment for crew members during EVA.

“A similar situation is created when a person walks across a carpet, building up a static electrical charge,” said Swenson. “When the person touches an object that is at a different charge, such as a doorknob, there will be a discharge – producing a shock.”

If the voltage difference between the astronaut and the Station becomes severe enough, there is a potential for a discharge that could upset spacecraft electronics, damage surface coatings, and burn holes in thermal blanketing. These occurrences could lead to the failure of the astronaut’s space suit. The FPMU sensors will allow NASA to obtain additional data on static electrical charge buildup as the ISS moves through the ultra-vacuum environment of space.

FPMU is the first task scheduled during the EVA and is expected to take approximately two hours to complete. Swenson said his only concern is the amount of time that has gone by as SDL has waited for NASA to work through safety issues concerning the Shuttle.

In 2001 NASA's Johnson Space Flight Center awarded SDL the contract worth $2.5 million to build FPMU for the ISS. Within two years, SDL developed, built, integrated, tested and delivered four FPMU units and a ground station.