Hisaki, also known as the Spectroscopic Planet Observatory for Recognition of Interaction of Atmosphere (SPRINT-A) is a Japanese

ultraviolet astronomy Ultraviolet astronomy is the observation of electromagnetic radiation at ultraviolet wavelengths between approximately 10 and 320 nanometres; shorter wavelengths—higher energy photons—are studied by X-ray astronomy and gamma-ray astr ...

satellite operated by the

Japan Aerospace Exploration Agency The is the Japanese national air and space agency. Through the merger of three previously independent organizations, JAXA was formed on 1 October 2003. JAXA is responsible for research, technology development and launch of satellites into orb ...

(JAXA). The first mission of the Small Scientific Satellite program, it was launched in September 2013 on the maiden flight of the

Epsilon Epsilon (, ; uppercase , lowercase or lunate ; el, έψιλον) is the fifth letter of the Greek alphabet, corresponding phonetically to a mid front unrounded vowel or . In the system of Greek numerals it also has the value five. It was der ...

rocket. It remains operational as of 2022 and is used to for

extreme ultraviolet Extreme ultraviolet radiation (EUV or XUV) or high-energy ultraviolet radiation is electromagnetic radiation in the part of the electromagnetic spectrum spanning wavelengths from 124 nm down to 10 nm, and therefore (by the Planck– ...

observations of the Solar System planets.

Launch and naming

Hisaki was launched with an

rocket, which was its first flight. The four-stage Epsilon rocket flew from the Mu rocket launch complex at the

Uchinoura Space Center The is a space launch facility in the Japanese town of Kimotsuki, Kagoshima Prefecture. Before the establishment of the JAXA space agency in 2003, it was simply called the (KSC). All of Japan's scientific satellites were launched from Uchino ...

. The launch occurred at 05:00 UTC on 14 September 2013, following a scrubbed launch attempt on 27 August 2013. Following its successful insertion into orbit and deployment of its

solar arrays A photovoltaic system, also PV system or solar power system, is an electric power system designed to supply usable solar power by means of photovoltaics. It consists of an arrangement of several components, including solar panels to absorb and c ...

, the satellite was renamed ''Hisaki'', having been designated SPRINT-A until that point. Hisaki was named after a cape used by local fishermen to pray for safe travels in the eastern part of

Kimotsuki, Kagoshima is a town in Kimotsuki District. It is located in the eastern part of the Ōsumi Peninsula in Kagoshima Prefecture, Japan. The town was formed on July 1, 2005 from the merger of the towns of Kōyama and Uchinoura, both from Kimotsuki Distric ...

near the

, but has the additional meaning of "beyond the Sun". An old name for the mission was EXCEED (Extreme Ultraviolet Spectroscope for Exospheric Dynamics).

Observations

Hisaki carries an

spectrometer A spectrometer () is a scientific instrument used to separate and measure spectral components of a physical phenomenon. Spectrometer is a broad term often used to describe instruments that measure a continuous variable of a phenomenon where the ...

, which is used to study the composition of the

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A s ...

s and the behavior of the

magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior dynam ...

s of the planets of the Solar System. Designed for a one-year mission, Hisaki has been operated in a

low Earth orbit A low Earth orbit (LEO) is an orbit around Earth with a period of 128 minutes or less (making at least 11.25 orbits per day) and an eccentricity less than 0.25. Most of the artificial objects in outer space are in LEO, with an altitude never mor ...

with a

perigee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

of , an

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

of , 31 degrees of

inclination Orbital inclination measures the tilt of an object's orbit around a celestial body. It is expressed as the angle between a Plane of reference, reference plane and the orbital plane or Axis of rotation, axis of direction of the orbiting object ...

and a

period Period may refer to: Common uses * Era, a length or span of time * Full stop (or period), a punctuation mark Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (or rhetorical period), a concept ...

of 106 minutes. In October 2020 it performed joint observation with the

BepiColombo BepiColombo is a joint mission of the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) to the planet Mercury. The mission comprises two satellites launched together: the Mercury Planetary Orbiter (MPO) and ''Mio'' ...

probe which performed a flyby of Venus en route to Mercury. Hisaki remains operational as of 2022, and e.g. is performing joint observations with ''Juno'' orbiter.Response of Jupiter's inner magnetosphere to the solar wind derived from extreme ultraviolet monitoring of the Io plasma torus
Go Murakami, Kazuo Yoshioka, Atsushi Yamazaki, Fuminori Tsuchiya, Tomoki Kimura, Chihiro Tao, Hajime Kita, Masato Kagitani, Takeshi Sakanoi, Kazunori Uemizu, Yasumasa Kasaba, Ichiro Yoshikawa, Masaki Fujimoto. ''Geophysical Research Letters''. 20 December 2016, doi: 10.1002/2016GL071675

References

{{2013space Spacecraft launched in 2013 2013 in Japan Satellites of Japan Extreme ultraviolet telescopes Satellites orbiting Earth