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The Akebono satellite, known as EXOS-D previous to its launch and 1989-016A for international design code, is a satellite designed to study the Earth’s magnetosphere and aurora (polar lights). Akebono was developed by the Japanese national research organization of astrophysics: Institute of Space and Astronautical Science (ISAS). [1]The satellite operates through eight instruments on board as well as additional facilities to assist the operation of the instruments.

History

Origin

The satellite was first launched on February 22, 1989 at 8:30 (JST) by the M-3SII-4 launch vehicle from the Uchinoura Space Center (USC).The shape can be described as an octagonal cylinder with four solar-array paddles, has a height of 100cm and 126cm from face to face, weighing approximately 295kg.[2]

Akebono was launched into highly elliptical orbit, covering the region from the polar cap to the equator, and a status of:[3]

  • Inclination: 75 degrees
  • Initial apogee (highest point):10,482km
  • Initial perigee (nearest to Earth): 272 km
  • Orbital period: 211 minutes
  • Spin axis direction: Always towards sun
  • Spin-Stabilisation: 7.5rpm spin rate

Akebono, meaning “the dawn”, is the fourth satellite within the EXOS series of satellites launched by ISAS to investigate Earth’s upper atmosphere.The satellite’s purpose is to study the mechanism of auroral particle acceleration and the related physical phenomena of the magnetosphere. For maximum data coverage, four ground stations track Akebono’s path:[4][5]

Termination

Akebono's operation was terminated on April 23, 2015 at 15:59 p.m. due to build up of space radiation damaging instruments and deteriorating the electric system onboard the spacecraft. The damage reduced flight altitude and made it incapable to collect sufficient observation data for operation. 25 years past expected target life,The Japan Aerospace Exploration Agency (JAXA) stopped sending and receiving radio waves to and from Akebono.[6][2]

Mechanics

There are eight instruments contributing to the operation of Akebono including: Electric Field Detector (EFD), Magnetic Field Detector (MGF), Very Low Frequency Plasma Wave Detectors (VLF), Plasma Wave Detectors in High Frequency Range and Sounder (PWS), Low Energy Particle Spectra Analyzer (LEP), Suprathermal Mass Spectrometer (SMS), Thermal Electron Detectors (TED), and an Auroral Television Camera (ATV). The components contribute to a direct observation of particle acceleration regions above the auroral region.

Electric Field Detector (EFD)

The satellite includes two electric field detector systems, (EFD-B) and (EFD-P), to measure both the static and quasi-static vector electric field though two techniques: standard double probe and ion beam, which was developed specifically for the Akebono satellite. The electric field has three components, through the standard double probe technique (EFD-P), the field is measured as the possible differences between three orthogonal (intersecting at right angles) pairs of sensors, the sensors are separated and later divided by the distance between their separation. [7][8]

Magnetic Field Detector (MGF)

Akebono carries both triaxial [three directions] search coil and triaxial fluxgate magnetometers [a device used to measure magnetic fields]. Fluxgate is mounted on a 5-m extendable mast and used for vector magnetic fields, collecting data at an altitude of 3,000-10,000 km. Search coils are mounted on a 3-m extendable mast and measure low frequency magnetic field fluctuations and waves, the measurements are collected with a frequency response of up to 800 Hz.[9][10]

(VLF) and (PWS)

(PWS) has three sub-systems; i.e. i) a sub-system for natural plasma wave observations (NPW), ii) a sub-system for stimulated plasma wave experiments (SPW) and iii) the instrumentation for measurement of the number density of electron (NEI).

(LEP) and (SMS)

Measuring magnetospheric phenomena requires the measurement of ion components of hot plasma, (LEP) and (SMS) are utilized for these measurements. (LEP) is designed in keV energy range and (SMS) in thermal and suprathermal range.(SMS) is a radio frequency type mass spectrometer with a fast scan mode, thermal mode and a retarding potential analyzer (RPA) (sensor used to measure ion energy distribution of a plasma). The large dynamic range helps to regularly measure major and minor components of high latitude auroral plasma.[11] [12]

Thermal Electron Detectors (TED)

To support (LEP) and (SMS), Akebono carries a device, (TED) to measure the temperature and energy distribution of plasma.

Auroral Television Camera (ATV)

To improve the quality of the electric field measurement, the satellite's surface is designed conductive to decrease possible electrical disturbances surrounding Akebono.[5]


To support the operation of the instruments, the satellite contains: [subcategory]

Two sets of 60 m tip-to-tip wire antennas

One three-axial loop antenna with a 60 cm X 60cm rectangular shaped winding

5m and 3m extensible masts

A despun-mirror system

Observations

Akebono’s orbit covers a vast region of the plasmasphere. From 500 to 10,500 kilometers.[13] [1]

observed by the Akebono satellite in the altitude region around 3200–10,000 km (L= 1.5–3.4) in 1989 and 1990, which is the highest altitude where at which M/Q = 2 ion cyclotron whistlers have been observed till date. We discuss the ion concentration in the inner magnetosphere estimated from crossover frequencies of ion cyclotron whistlers observed by Akebono. [Need to work on revising this area, just have trouble with keeping it accurate]

have shown that small-scale field-aligned currents always exist in large-scale region 1, region 2, cusp and polar cap current systems. (throught the fluxgate, source 7, the science journal one)

See Also

References

  1. ^ "Akebono (satellite)", Wikipedia, 2021-01-31, retrieved 2021-10-20
  2. ^ a b "AKEBONO | Spacecraft". ISAS. Retrieved 2021-11-01.
  3. ^ Shinbori, A.; Ono, T.; Iizima, M.; Kumamoto, A.; Oya, H. (2003). "Sudden commencements related plasma waves observed by the Akebono satellite in the polar region and inside the plasmasphere region". Journal of Geophysical Research: Space Physics. 108 (A12). doi:10.1029/2003JA009964. ISSN 2156-2202.
  4. ^ Miyake, W.; Miyoshi, Y.; Matsuoka, A. (2015-12-01). "An empirical modeling of spatial distribution of trapped protons from solar cell degradation of the Akebono satellite". Advances in Space Research. 56 (11): 2575–2581. doi:10.1016/j.asr.2015.10.021. ISSN 0273-1177.
  5. ^ a b Tsuruda, K.; Oya, H. (1991). "Introduction to the EXOS-D (Akebono) Project". Geophysical Research Letters. 18 (2): 293–295. doi:10.1029/91GL00039. ISSN 1944-8007.
  6. ^ "JAXA | Aurora Observation Satellite "AKEBONO" (EXOS-D)". JAXA | Japan Aerospace Exploration Agency. Retrieved 2021-10-20.{{cite web}}: CS1 maint: url-status (link)
  7. ^ Mozer, F. S. (2016). "DC and low-frequency double probe electric field measurements in space". Journal of Geophysical Research: Space Physics. 121 (11): 10, 942–10, 953. doi:10.1002/2016JA022952. ISSN 2169-9402.
  8. ^ Hayakawa, H.; Okada, T.; Ejiri, M. (1990). "Electric field measurement on the Akebono (EXOS-D) satellite". Journal of Geomagnetism and Geoelectricity (Tokyo). 42 (4): 371–384. ISSN 0022-1392.
  9. ^ "akebono exos-d satellite: Topics by WorldWideScience.org". worldwidescience.org. Retrieved 2021-10-30.
  10. ^ Fukunishi, H.; Fujii, R.; Kokubun, S.; Hayashi, K.; Tohyama, T.; Tonegawa, Y.; Okano, S.; Sugiura, M.; Yumoto, K.; Aoyama, I.; Sakurai, T. (1990). "Magnetic Field Observations on the Akebono (EXOS-D) Satellite". Journal of geomagnetism and geoelectricity. 42 (4): 385–409. doi:10.5636/jgg.42.385.
  11. ^ Abe, T.; Whalen, B. A.; Yau, A. W.; Horita, R. E.; Watanabe, S.; Sagawa, E. (1993). "EXOS D (Akebono) suprathermal mass spectrometer observations of the polar wind". Journal of Geophysical Research: Space Physics. 98 (A7): 11191–11203. doi:10.1029/92JA01971. ISSN 2156-2202.
  12. ^ Whalen, B. A.; Burrows, J. R.; Yau, A. W.; Budzinski, E. E.; Pilon, A. M.; Iwamoto, I.; Marubashi, K.; Watanabe, S.; Mori, H.; Sagawa, E. (1990). "The Suprathermal Ion Mass Spectrometer (SMS) onboard the Akebono (EXOS-D) Satellite". Journal of geomagnetism and geoelectricity. 42 (4): 511–536. doi:10.5636/jgg.42.511.
  13. ^ Matsuda, Shoya; Kasahara, Yoshiya; Goto, Yoshitaka (2015). "M/Q = 2 ion distribution in the inner magnetosphere estimated from ion cyclotron whistler waves observed by the Akebono satellite". Journal of Geophysical Research: Space Physics. 120 (4): 2783–2795. doi:10.1002/2014JA020972. ISSN 2169-9402.
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