SwRI-Led Team Begins Instrument Commissioning

Just over three weeks since its October 19 launch, NASA's Interstellar Boundary Explorer (IBEX) spacecraft -- the first mission designed to image the interaction at the edge of the solar system -- concluded its orbit-raising phase and is beginning instrument commissioning in preparation to start science observations.

After its launch to low Earth orbit (about 140 miles) onboard a Pegasus rocket, the spacecraft used its own solid rocket motor and hydrazine propulsion system to perform a series of burns that ultimately raised its apogee (furthest point from Earth) to about 200,000 miles and its perigee (closest point) to about 8,000 miles above the Earth — an orbit ideal for its science mission.

"Because the orbit goes so far out -- about five-sixths of the way to the Moon -- it gets pushed around significantly by lunar gravity and evolves over time in altitude and inclination," said IBEX Principal Investigator Dr. David McComas, senior executive director of the Space Science and Engineering Division at Southwest Research Institute. "We're now in an orbit that provides excellent science viewing and no long eclipses for at least the next two to three years, without the need for additional burn maneuvers."

Before the science investigation begins, the IBEX team will commission those spacecraft subsystems that weren't needed for the orbit-raising period as well as the two IBEX science instruments. During commissioning, the spacecraft spin rate will be reduced from 23 rpm to 4 rpm and pointed toward the Sun. At that point, the remaining subsystems and instruments will be turned on and tuned to ensure optimum mission performance.

When it begins its science observations in early December, IBEX will use energetic neutral atom imaging to create the first-ever all-sky maps of the interactions between the million mile-per-hour solar wind blown out by the Sun and the low-density material between the stars, known as the interstellar medium. The spacecraft will complete an all-sky map of the interstellar boundaries every six months.

IBEX is the latest in NASA's series of low-cost, rapidly developed Small Explorers spacecraft. SwRI leads the IBEX mission that includes a team of national and international partners. The NASA Goddard Space Flight Center manages the Explorers Program for the Science Mission Directorate in Washington.

FMI: www.ibex.swri.edu, www.nasa.gov/ibex