Interstellar Boundary Explorer

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IBEX (Explorer 91)
IBEX (Explorer 91)
Type: Research satellite
Country: United StatesUnited States United States
Operator: NASA
COSPAR-ID : 2008-051A
Mission dates
Dimensions: 107 kg
Begin: October 19, 2008, 17:48 UTC
Launcher: Pegasus-XL
Status: in operation
Orbit data
Rotation time : 9.1 days
Orbit inclination : 28.1 °
Apogee height :  307,961 km
Perigee height :  47,016 km

Interstellar Boundary Explorer ( IBEX ; German  Interstellar Grenzschichten- Erforscher ) is a NASA research satellite for researching the interaction of the solar wind with the interstellar medium . It registers and maps high- energy electrically neutral atoms (ENA) that are generated in the helio envelope , the outer area of ​​the heliosphere . The IBEX mission is carried out as part of the Small Explorer program . After the successful launch, the satellite was given the additional name Explorer 91 .

mission

Structure of the heliosphere and the boundary layers to the interstellar medium. (In this NASA graphic from 2008, the then suspected Bow Shock is entered.)

The only measurements from the outer solar system so far came from the space probes Pioneer 10 and 11 and Voyager 1 and 2 . Most important of all was the data from the Voyager probes, as they were still in contact when they crossed the termination shock and reached the Helio hull. In contrast to them, IBEX does not carry out any in-situ measurements, but remains in earth orbit.

Pegasus XL launcher before takeoff

IBEX was brought into space by an airborne Pegasus XL rocket with an additional Star 27H upper stage. The launch site of the L-1011 carrier aircraft was the Kwajalein Atoll in the Pacific. The L-1011 with the name “Stargazer” took off on October 19, 2008 at 16:51 UTC from the Kwajalein Missile Range for a night take-off, according to local time it was 3:51 am on October 20. The release occurred at 17:48 UTC from 39,000  ft (11,900  m ) altitude in the Kwajalein Drop Zone north of the atoll at about 167.6 ° East, 10.5 ° North

Immediately after take-off, the highly eccentric orbit had an inclination of 11.3 °, a perigee of 226 km and an apogee of 250,300 km with an orbit time of 7,921 minutes. IBEX increased the orbit height and in particular the perigee in the first 45 days of the mission with the help of its own engine, to finally an orbit with a perigee of 7000 km and an apogee of approx. 50 earth radii (approx. 317,850 km) and a period of approx 8 days to reach. In November 2011, the orbit was changed again. The period of rotation was adjusted to 9.1 days, which corresponds to exactly one third of a sidereal month. This synchronizes the movement of IBEX with that of the moon, whereby care was taken that IBEX never comes very close to the moon. In this way, gravitational influences and the necessary path corrections can be avoided.

construction

Base

The satellite, which weighs only 107 kg, is built on an octagonal structure derived from the Orbcomm communication satellites . The manufacturer is the Orbital Sciences Corporation . The satellite is spin stabilized , with the axis of rotation always pointing towards the sun. IBEX has a hydrazine propulsion system that is used to raise the perigee to 7000 km after take-off.

Instruments

There are only two simple one-pixel sensors on board IBEX. One of the instruments attached perpendicular to the axis of rotation of the satellite is used to register high and low energy electrically neutral particles (IBEX-Hi and IBEX-Lo). These are attached to opposite sides of the satellite. Both sensors are read out by shared electronics. Through the rotation of the satellite and the rotation of the axis of rotation, which is always aligned with the sun, over the course of a year, the entire sky is recorded and mapped by the detectors.

research results

Angular distribution of electrically neutral atoms (ENA), measured by IBEX. Significantly more ENA come from the band-shaped angular area.

According to research data, the Voyagers and IBEX (2012) the sun moves so slowly through the interstellar gas that there is no bow shock (bow shock) are. For the first time, evidence of a "tail" of the heliosphere of our solar system was found. However, combined long-term measurements with the space probes Voyager 1 and 2 , Cassini and IBEX suggested in 2017 that the heliosphere is more spherical.

The discovery that the neutral particles came to a greater extent from a band-shaped solid angle region was unexpected. This band structure is said to result from the flow around the heliosphere in the interstellar magnetic field.

In 2016, IBEX observed the effects of increased solar activity: in the second half of 2014, the density and speed of the solar wind had increased, increasing its pressure by 50%. Two years later, IBEX detected solar wind particles that had reached the edge of the heliosphere and were scattered back from there as neutral atoms.

Web links

Commons : IBEX  - collection of images, videos and audio files

Individual evidence

  1. ^ Orbit data according to Chris Peat: IBEX - Orbit. In: Heavens Above. September 1, 2012, accessed October 8, 2012 .
  2. ↑ NASA: IBEX Mission Pages. Retrieved April 2, 2018 . Mission Statement: The Interstellar Boundary Explorer (IBEX) mission science objective is to discover the nature of the interactions between the solar wind and the interstellar medium at the edge of our solar system.
  3. ↑ If we could see Our Heliosphere, What would our Home in the Galaxy look like? IBEX Science Overview
  4. ↑ Steve Siceloff: NASA's IBEX Launch Blog. NASA, October 19, 2008, accessed October 8, 2012 .
  5. ↑ Jonathan McDowell: Jonathan's Space Report No. 602 October 26, 2008, accessed October 8, 2012 .
  6. ↑ Space 40: 2008-051A - IBEX
  7. ^ Southwest Research Institute - Launch. In: swri.org. Archived from the original on May 18, 2014 ; Retrieved October 8, 2012 .
  8. ↑ Dave McComas: November 2011: IBEX Orbit - Raising Maneuver. NASA, November 2011, archived from the original on September 29, 2014 ; accessed on October 8, 2012 .
  9. ^ Graphics. In: swri.edu. Archived from the original on October 31, 2013 ; accessed on January 20, 2018 .
  10. ^ Pictures. In: swri.edu. Archived from the original on October 31, 2013 ; accessed on January 20, 2018 .
  11. ↑ Benjamin Knispel: Heliosphere, The discovery of slowness . In: ASTROnews, May 11, 2012; Retrieved May 16, 2012.
  12. ↑ NASA proves the tail of our solar system . heise.de, July 12, 2013 14:00
  13. ^ Sarah Frazier: NASA's Cassini, Voyager Missions Suggest New Picture of Sun's Interaction with Galaxy. In: NASA .gov. April 24, 2017, accessed September 21, 2017 .
  14. ↑ Sarah Frazier: NASA's IBEX Observations Pin Down Interstellar Magnetic Field. In: NASA.gov . February 26, 2016, accessed April 1, 2018 .
  15. ^ Miles Hatfield: As Solar Wind Blows, Our Heliosphere Balloons. In: NASA.gov. June 6, 2018, accessed September 20, 2018 .