ASTRO-F Q and A

♦ What is ASTRO-F?
♦ What is infrared light? What can you see through the infrared light?
♦ What sort of satellite is ASTRO-F?
♦ Why is ASTRO-F going to space?
♦ What will ASTRO-F perform in space?
♦ What do you study by ASTRO-F?
♦ Who is making ASTRO-F?

Q. What is ASTRO-F?
A. ASTRO-F is an astronomical satellite to observe the Universe in the infrared light. The Institute of Space and Astronautical Science and collaborators developed it. The ASTRO-F was given a nickname of "AKARI" after the launch. "AKARI" means a "light" in Japanese.

Q. What is infrared light? What can you see through the infrared light?
A. Infrared light is an invisible light with a longer wavelength than normal visible light.

The human eye can see the several colors of the rainbow, but there are other invisible lights outside them. The infrared light is next to the red of the rainbow.

As a rainbow can be divided into some colors, there are several kinds of infrared light. They are called near-infrared, mid-infrared, and far-infrared in order of distance from red color in a rainbow. When you look into the Universe in an appropriate infrared light, you can see a star and a galaxy beyond an opaque dust cloud, or you can see the dust cloud (temperature of less than -200C) itself.

The Milky Way seen at various wavelengths of light (photo by NASA). There are black belts which are the areas hidden by dust clouds, when you see it with visible light (bottom). Many stars can be seen through the clouds when you see with near-infrared light (middle). Stars disappear but dust clouds radiate brightly at far-infrared wavelengths (top).

You can observe an aspect of the Universe which cannot be seen with visible light, and investigate the mysteries of the birth, death, and evolution of stars and galaxies.

Q. What sort of satellite is ASTRO-F?
A. ASTRO-F has a height of 3.7 m and a weight of 950 kg (at launch time). It is equipped with a telescope of 68.5 cm primary mirror and two sets of instruments for infrared observations.

The entire telescope and observation instruments are cooled down to around -270 ℃ in order to detect faint infrared rays from the distant Universe.

ASTRO-F assembled temporally for tests. Telescope and observation instruments are inside the upper cylinder (a cryostat) and cooled down to around -270 ℃. The lower (golden) part is called the bus module. It controls the entire satellite.

Scientific instruments of ASTRO-F. The FIS is for far-infrared and the IRC is for near- and mid-infrared.

The telescope of 68.5 cm diameter. The surface is coated with gold so as to reflect infrared rays efficiently.

Q. Why is ASTRO-F going to space?
A. Most of the infrared light do not reach the ground due to absorption by the atmosphere. ASTRO-F is a satellite for thorough studies in the infrared which cannot be made from the ground.

Wavelength of electro-magnetic wave and Observations

Q. What will ASTRO-F perform in space?
A.

IRAS satellite which was launched by the U.S., U.K., and the Netherlands in 1983 made a infrared map of the Universe. ASTRO-F will make observations in a similar way and investigate the more distant Universe.

ASTRO-F will make catalogues of infrared objects by observing all over the sky. The catalogues are going to be published for the benefit of astronomers in the world and will be used for astronomical studies by them.

ASTRO-F will make detailed observations toward selected regions as well as an all-sky (survey) observation.

Q. What do you study by ASTRO-F?
A. It is expected that the catalogue made by ASTRO-F will include approximately ten million objects. Astronomers will research how stars and galaxies are born and grow with the catalogue statistically. In addition to these studies, ASTRO-F observational data will be used by astronomers around the world for many purposes.

Selected objects requested by astronomers vary greatly. For example, very distant newborn galaxies, neighbour galaxies, nascent stars, stars which are forming planets, stars near its life's end, or asteroids.

Q. Who is making ASTRO-F?
A.

ASTRO-F has been developed by the Institute of the Space and Astronautical Science in collaboration with members in universities and other institutes. Korean and European members have also joined the ASTRO-F project. Of course, many companies contribute to the development of the satellite and instruments.