NASA will launch a novel spacecraft this weekend on a mission to study the outermost boundary of the solar system where the solar wind meets the vast interstellar medium of the Milky Way galaxy. The $169 million Interstellar Boundary Explorer (IBEX) will be lofted into orbit by an Orbital Sciences air-launched Pegasus in the predawn hours off Kwajalein Atoll in the South Pacific Sunday morning.
READ: NASA IBEX FACT SHEET READ: ORBITAL SCIENCES CORP. IBEX FACT SHEET READ: PEGASUS FACT SHEET READ: IBEX LITHOGRAPH AUDIO: LISTEN TO THE IBEX PRELAUNCH MEDIA TELECONFERENCE As the Sun burns its nuclear fuel supply, it throws off super hot gases known as the solar wind. As the solar system moved through interstellar space, this wind forms a bubble around the Sun, planets and other bodied in the solar system. This bubble, called the heliosphere, protects everything in the solar system from galactic cosmic rays and the gases in the interstellar medium. The mission of IBEX is to study the boundary between the heliosphere and surrounding interstellar space, known as the termination shock, and to answer fundamental questions about how our solar system interacts with its galactic surroundings. "The interstellar boundary regions are critical because they shield us from the vast majority of dangerous galactic cosmic rays, which otherwise would penetrate into Earth's orbit and make human spaceflight much more dangerous," said David J. McComas, IBEX principal investigator and senior executive director of the Space Science and Engineering Division at the Southwest Research Institute in San Antonio. The IBEX satellite will orbit the Earth every eight days on a highly-elliptical path that takes it to an apogee of 320,000 km (approximately 80% of the distance to the Moon) to make the first comprehensive map of the boundary between our Solar System and interstellar space. Measuring this interstellar interaction is important for understanding our protection from galactic cosmic rays – energetic particles from beyond the Solar System – that could pose health risks to future astronauts exploring deep space. "The solar system's frontier is billions of miles away, so it's difficult for us to go there, but interesting things happen at boundaries, and with IBEX, we will see them for the first time," said Dr. Robert MacDowall, IBEX Mission Scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. Unlike many satellites in space that collect light, IBEX collects particles. These particles come from the boundary of the solar system and beyond — from the interstellar medium. IBEX has two sensors that collect particles as the satellite orbits the Earth. The satellite spins as it orbits so that over the course of six months, each sensor has the opportunity to collect particles from every part of the sky. As they collect the particles, the sensors and spacecraft keep track of the area the particles came from, the time they entered the sensor, the mass of the particles, and the amount of energy each particle has. This allows the science team to build a map of how many particles of each energy came from each direction in the sky. "IBEX will let us visualize our home in the galaxy for the first time and explore how it may have evolved over the history of the solar system. Ultimately, by making the first images of the interstellar boundaries neighboring our solar system, IBEX will provide a first step toward exploring the galactic frontier" says Dr. David J. McComas, IBEX principal investigator from the Southwest Research Institute (SwRI) in San Antonio, Texas. By analyzing the map, the team of scientists can determine what the interaction of the solar wind and interstellar medium is like in all of the areas of the protective bubble around the solar system. For example, scientists are trying to find out if there are some areas where the interstellar medium stops the solar wind from flowing outward more quickly (like slamming on the brakes) than other places (where a slow gradual stop may occur.) Also, scientists are trying to determine the overall shape of the bubble which may be affected by differences in density, and magnetic fields in the interstellar medium. IBEX will be launched on a Pegasus rocket dropped from under the wing of an L-1011 aircraft flying over the Pacific Ocean. Eight minutes after launch, Pegasus will release IBEX into a low Earth orbit 130 miles high. Because Earth's magnetic field generates the same kind of high-energy particles that IBEX is intended to study, the spacecraft must be placed in a very high orbit outside the magnetic field, also called the magnetosphere. IBEX's orbit will take it up to 200,000 miles from Earth. The three-stage Pegaus rocket isn't powerful enough to take IBEX all the way to its final orbit, so the final leg of its journey will be accomplished by an additional solid fuel upper stage motor attached to the base of IBEX. "What makes the IBEX mission unique is that it has an extra kick during launch," said Willis Jenkins, IBEX program executive at NASA Headquarters in Washington. "An extra solid-state motor pushes the spacecraft further out of low-Earth orbit where the Pegasus launch vehicle leaves it." Sunday's available launch window extends from 1:44:20 to 1:51:50 p.m. EDT, with the target launch time somewhere in the middle of the window. A modified L-1011 carrier aircraft, called the Stargazer, will list the Pegasus XL rocket to an altitude of 39,000 feet while flying on a predetermined "racetrack" course into the drop zone north of Kwajalein. The aircraft will take off from Kwajalein at around 12:50 p.m. EDT to begin a 58-minute flight to the drop point. The zone is 4 miles wide and 40 miles long, with the drop target being located inside the box located at 10.5 degrees North Latitude, 167.6 degrees East Longitude. After the L-1011 reaches the drop zone and the launch window opens, the pilot will be given a go for the drop at his discretion, and will push a button in the *such language*pit to release Pegasus when the aircraft is in the correct position and in stable flight with low turbulence. After the drop command, PEgaus will free-fall for 5 seconds before lighting its first stage engine approximately 300 feet below the carrier aircraft, which will have begun a 10-degree turn to get out of the way of the rocket as it ascends toward space. The first stage, powered by an Orion 50S XL solid propellant motor, will ignite at T+5 seconds and send the rocket on its way to orbit heading eastward at 81.5 degrees. The first stage burns out 78 seconds later. Burnout is followed by a short coast period and separation of the first stage. Fifteen seconds after first stage burnout, the Orion 50 solid fuel second stage will ignite to begin the third leg of IBEX's ride to orbit. 45 seconds later, the protective shroud over the spacecraft will be jettisoned, no longer necessary to protect the payload from aerodynamic stresses in the lower atmosphere. The second stage burns out two minutes, forty-seven seconds into flight. The vehicle will enter a coast phase for about 2 1/2 minutes before the second stage is jettisoned and the third stage ignited to send IBEX and its attached upper stage into a preliminary low Earth orbit 6 minutes, 22 seconds into flight. The vehicle will coast for for two minutes. At T+7 minutes, 47 seconds, the rocket and payload will be spun up to 60 rpm. Thirty-five seconds later, at T+8 minutes, 22 seconds, the spacecraft and kick stage will separate from the Pegasus third stage. The kick motor, a Star 27 motor manufactured by Alliant Techsystems, will hurl IBEX into a high looping orbit with an apoaxis, or high point, of 130,000 miles. Over the next couple weeks, IBEX will use its own hydrazine thrusters to raise itself to a final highly elliptical orbit with a high point 200,000 miles above Earth and a low point just 4,000 miles high. (the Spacearium / Space Media Corporation)
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