Interstellar Boundary Explorer

The IBEX satellite was mated to its Pegasus XL rocket at Vandenberg Air Force Base, California, and the combined vehicle was then suspended below the Lockheed L-1011 Stargazer mother airplane and flown to Kwajalein Atoll in the Central Pacific Ocean.[8] Stargazer arrived at Kwajalein on Sunday, October 12, 2008.[7]

The IBEX satellite was carried into space on October 19, 2008, by the Pegasus XL rocket. The rocket was released from Stargazer, which took off from Kwajalein, at 17:47:23 UTC.[3] By launching from this site close to the Equator, the Pegasus rocket lifted as much as 16 kg (35 lb) more mass to orbit than it would have with a launch from the Kennedy Space Center in Florida.[9]

The IBEX satellite, initially launched into a highly-elliptical transfer orbit with a low perigee, used a solid fuel rocket motor as its final boost stage at apogee, in order to raise its perigee greatly and to achieve its desired high-altitude elliptical orbit.

IBEX is in a highly-eccentric elliptical terrestrial orbit, which ranges from a perigee of about 86,000 km (53,000 mi) to an apogee of about 260,000 km (160,000 mi).[2] Its original orbit was about 7,000 by 320,000 km (4,300 by 198,800 mi)[5]—that is, about 80% of the distance to the Moon—which has changed primarily due to an intentional adjustment to prolong the spacecraft's useful life (see Orbit adjusted below).

This very high orbit allows the IBEX satellite to move out of the Earth's magnetosphere when making scientific observations. This extreme altitude is critical due to the amount of charged-particle interference that would occur while taking measurements within the magnetosphere. When within the magnetosphere of the Earth (70,000 km or 43,000 mi), the satellite also performs other functions, including telemetry downlinks.[10]

In June 2011 IBEX shifted to a new orbit that raised its perigee to more than 30,000 kilometres (19,000 mi). The new orbit has a period of one third of a lunar month, which, with the correct phasing, avoids taking the spacecraft too close to the Moon, whose gravity can negatively affect IBEX's orbit. Now the spacecraft uses less fuel to maintain a stable orbit, increasing its useful lifespan to more than 40 years.[6]

IBEX Lo sensor

The heliospheric boundary of the Solar System is being imaged by measuring the location and magnitude of charge-exchange collisions occurring in all directions. The satellite's payload consists of two energetic neutral atom (ENA) imagers, IBEX-Hi and IBEX-Lo. Each consists of a collimator that limits their fields-of-view, a conversion surface to convert neutral hydrogen and oxygen into ions, an electrostatic analyzer (ESA) to suppress ultraviolet light and to select ions of a specific energy range, and a detector to count particles and identify the type of each ion. Both of these sensors are a single-pixel camera with a field-of-view of roughly 7° x 7°. The IBEX-Hi instrument is recording particle counts in a higher energy band (300 eV to 6 keV) than the IBEX-Lo energy band (10 eV to 2 keV). The scientific payload also includes a Combined Electronics Unit (CEU) that controls the voltages on the collimator and the ESA, and it reads and records data from the particle detectors of each sensor.[11]

Compared to other space observatories, IBEX has a low data transfer rate due to the limited requirements of the mission.[12]

... IBEX data transfer rates are slow compared with other telescopes due to the nature of the data it collects. IBEX does not need a "high speed" connection, since it only has the opportunity to collect up to a few particles per minute. Communication from the satellite to the ground is 20 times slower than a typical home cable modem (320,000 bits per second [is the satellite's transfer speed[13]]), and from the ground to the satellite only 2,000 bits per second, which is 250 times slower! Once the signal is collected by the receivers on Earth it is carried over the internet to Mission Control Center in Dulles, VA and to the IBEX Science Operation Center in San Antonio, TX."

— NASA's IBEX Q and A[12]

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High-energy map of the heliosphere

The ribbon of ENA emissions seen in the IBEX map

IBEX is collecting energetic neutral atom (ENA) emissions that are traveling through the Solar System to Earth that cannot be measured by conventional telescopes. These ENAs are created on the boundary of our Solar System by the interactions between solar wind particles and interstellar medium particles.[14]

On the average IBEX-Hi detects about 500 particles per day, and IBEX-Lo, less than 100.[15] By 2012, over 100 scientific papers related to IBEX were published, described by the PI as "an incredible scientific harvest".[15]

As the IBEX data is validated, the IBEX data is made available in a series of data releases on the SWRI IBEX Public Data website (see External Links below). In addition, the data is periodically sent to the NASA Space Physics Data Facility (SPDF), which is the official archive site for IBEX data. SPDF data can be searched at the Heliophysics Data Portal (see External Links below).