Abstract
The Interstellar Boundary Explorer (IBEX) is a Small Explorers (SMEX) mission that will provide the first global views of the Sun’s interstellar boundaries (see McComas et al.1,2,3). For a spacecraft in a low-Earth orbit, attempts to study this region would be drowned out by the Earth’s magnetosphere, so developing these global images requires a high-energy orbit that puts the spacecraft beyond the magnetosphere for the majority of the time. Scheduled to launch in the fall of 2008, IBEX is the first Pegasus-class spacecraft to achieve such a high energy orbit, using an innovative ascent profile that efficiently combines the performance of the Pegasus launch vehicle, an additional solid rocket motor, and the spacecraft’s hydrazine propulsion system. The Pegasus launch vehicle will target a 200 km circular orbit, and 22 seconds after Pegasus separation IBEX will fire its own solid rocket motor to boost apogee. A series of hydrazine burns then finishes the job, raising both apogee and perigee to a 7000 x 319,000 km altitude orbit. This paper begins with the initial daunting problem of finding the performance to reach a high enough orbit and steps through a series of innovations that led to a final design that could reach such an orbit with performance to spare. This ascent approach and mission orbit also present several unique challenges, such as the potential for solar eclipses lasting longer than 10 hours and lunar orbit perturbations that can reduce the orbit perigee to below the surface of the Earth. This paper discusses how those challenges were addressed, and also discusses how the IBEX ascent approach could be applied to future high-apogee – or even Earth escape – missions.
Presentation Slides
The Interstellar Boundary Explorer Mission Design: A Pegasus-Class Mission to a High Energy Orbit
The Interstellar Boundary Explorer (IBEX) is a Small Explorers (SMEX) mission that will provide the first global views of the Sun’s interstellar boundaries (see McComas et al.1,2,3). For a spacecraft in a low-Earth orbit, attempts to study this region would be drowned out by the Earth’s magnetosphere, so developing these global images requires a high-energy orbit that puts the spacecraft beyond the magnetosphere for the majority of the time. Scheduled to launch in the fall of 2008, IBEX is the first Pegasus-class spacecraft to achieve such a high energy orbit, using an innovative ascent profile that efficiently combines the performance of the Pegasus launch vehicle, an additional solid rocket motor, and the spacecraft’s hydrazine propulsion system. The Pegasus launch vehicle will target a 200 km circular orbit, and 22 seconds after Pegasus separation IBEX will fire its own solid rocket motor to boost apogee. A series of hydrazine burns then finishes the job, raising both apogee and perigee to a 7000 x 319,000 km altitude orbit. This paper begins with the initial daunting problem of finding the performance to reach a high enough orbit and steps through a series of innovations that led to a final design that could reach such an orbit with performance to spare. This ascent approach and mission orbit also present several unique challenges, such as the potential for solar eclipses lasting longer than 10 hours and lunar orbit perturbations that can reduce the orbit perigee to below the surface of the Earth. This paper discusses how those challenges were addressed, and also discusses how the IBEX ascent approach could be applied to future high-apogee – or even Earth escape – missions.
