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VLBI

What is VLBI?

VLBI (Very Long Baseline Interferometry) is a method that combines observational data from multiple radio telescopes into a single observational datum. Combining the observational data from 20-m radio telescopes erected in four locations in Japan (Oshu City, Iwate Prefecture; Satsumasendai City, Kagoshima Prefecture; Ogasawara Village, Tokyo Metropolis; and Ishigaki City, Okinawa Prefecture), NAOJ formed VERA (VLBI Exploration of Radio Astrometry), an observation network with an effective diameter of 2300 kilometers, and is observing continuously with it. The four radio telescopes of VERA are remotely operated from Mizusawa Campus. These observed data are processed at the VLBI Correlator in Mizusawa Campus.

The Mizusawa 10-m antenna at Mizusawa Campus is used for VERA’s performance evaluation, technology development, and collaborative observation with domestic VLBI stations. In addition, Mizusawa VLBI Observatory collaborates with other antennas and universities: the Yamaguchi 32-m antenna, Takahagi and Hitachi 32-m antennas, Gifu University’s 11-m antenna, the National Institute of Information and Communications Technology’s Kashima 34-m antenna, and Japan Aerospace Exploration Agency’s (JAXA) Usuda 64-m antenna. Through these collaborations, we are promoting the Japanese VLBI Network (JVN).

We are promoting international collaboration with countries in East Asia. Observations combining VERA and three Korean VLBI Network (KVN) radio telescopes located in South Korea are ongoing (KaVA: KVN and VERA Array). Furthermore, we are working to complete the East Asia VLBI Network (EAVN) through cooperation with multiple Chinese telescopes such as in Shanghai, Urumqi, and Kunming, and also with a Thai telescope which is going to be built. To this end, we are investing in the Japan-Korea Joint VLBI Correlator at the Korea Astronomy and Space Science Institute. It is playing an important role as the main correlation center for VLBI observations in the East Asia region.

VLBI

Research

We aim to measure the precise distances to masers, which are celestial bodies with very strong radio wave intensity, like lighthouses in space, to make a map of the entire Milky Way Galaxy and to measure its movement. We also promote research on high-precision observation of active galactic nuclei which exist in the centers of galaxies.

VERA receives dual beams with an angular difference of up to 2.2 degrees apart with one radio telescope to observe two celestial objects at the same time. In this way, VERA is the first radio telescope in the world to be able to correct for fluctuations in the radio wave propagation caused by the equipment and Earth’s atmosphere and measures the precise positions of celestial bodies. We measure the position change of celestial bodies (annual parallax) caused by the Earth revolving around the Sun and measure the precise distances to the celestial bodies.

Specifications

VERA Mizusawa Station

LocationNAOJ Mizusawa (Hoshigaoka, Mizusawa, Oshu, Iwate, Japan)
Prime manufacturerMitsubishi Electric Corporation
Aperture20 meters
Dual beam wavelengths22 gigahertz, 43 gigahertz

VERA Iriki Station

LocationUranomyo, Iriki, Satsumasendai, Kagoshima, Japan
Prime manufacturerMitsubishi Electric Corporation
Aperture20 meters
Dual beam wavelengths22 gigahertz, 43 gigahertz

VERA Ogasawara Station

LocationAsahiyama, Chichijima, Ogasawara, Tokyo, Japan
Prime manufacturerMitsubishi Electric Corporation
Aperture20 meters
Dual beam wavelengths22 gigahertz, 43 gigahertz

VERA Ishigakijima Station

LocationTonoshirotakeda, Ishigaki, Okinawa, Japan
Prime manufacturerMitsubishi Electric Corporation
Aperture20 meters
Dual beam wavelengths22 gigahertz, 43 gigahertz

Mizusawa Station: Mizusawa 10-m Antenna

LocationNAOJ Mizusawa (Hoshigaoka, Mizusawa, Oshu, Iwate, Japan)
Prime manufacturerMitsubishi Electric Corporation
Aperture10 meters

Ibaraki Station: Takahagi 32-m Antenna

LocationKuretsubo, Ishitaki, Takahagi, Ibaraki, Japan
Prime manufacturerMitsubishi Electric Corporation
Aperture32 meters

Ibaraki Station: Hitachi 32-m Antenna

LocationKakozawa, Ishi, Juo, Hitachi, Ibaraki, Japan
Prime manufacturerMitsubishi Electric Corporation
Aperture 32 meters

Yamaguchi Station

LocationNihonakago, Yamaguchi, Yamaguchi, Japan
Prime manufacturerMitsubishi Electric Corporation
Aperture32 meters

History

1979Yamaguchi University’s 32-m antenna constructed (used for satellite communications by KDDI)
1992Mizusawa 10-m antenna constructed.
1993Mizusawa 10-m antenna started operation.
2001VERA Mizusawa 20-m antenna, VERA Ogasawara 20-m antenna, and VERA Iriki 20-m antenna were constructed.
2002Yamaguchi University’s 32-m antenna was placed under the control of NAOJ and started operation as a radio telescope.
2002VERA Ishigakijima 20-m antenna was constructed.
2009Ibaraki Hitachi 32-m antenna was placed under the control of NAOJ and started operation as a radio telescope.
2010Ibaraki Takahagi 32-m antenna was placed under the control of NAOJ and started operation as a radio telescope.