Optical Ground Station
What is the Optical Ground Station for Space Laser Communications?

Our information-intensive society demands high-performance communication technologies, which makes space communications essential for the 21st century. Having the ability to transmit a large volume of data at high data rates, to reduce satellite size and weight, and to operate free from interference, space laser communications are now becoming a major communication technology. Many countries are eagerly working on research and development in this area.

In order to collaborate with other countries and participate in international research, the "Space Optical Ground Station Center" was established in 1988 as a center for Japanese research in optical communications. This center has a telescope of 1.5 m in diameter with a main mirror having a 1.5 m aperture. Its tube is short and can be rotated quickly, allowing it to track satellites even at very low altitudes. It is the largest telescope in Japan capable of tracking satellites.

Using this telescope, we are conducting advanced research on measurement technology and on the collection and detection of very weak lights from space and satellites, for laser optical communications. Our research specifically concerns the following:


・Optical communications to and from satellites

・Measurement of the precise location of satellites and the observation of space debris

・Observation of imaged rings around infrared celestial bodies (e.g. galactic systems), employing high-space-resolution techniques

・Atmospheric observation with laser radar, observation of Earth observatory satellites using a reflector

・Laser ranging, geodetics, and positioning for satellites


Built in March, 1988
Multi-purpose and multi-focus design
(switchable among four focuses, 10-port observatory equipment) 
First class of telescopes in Japan with satellite-tracking laser sending abilities 
Several-arcsecond-level high-speed (LEO tracking) pointing jitter







Light source: Diode pumped Nd:YVO4 second harmonic 
Wavelength: 532 nm 
Power: 5 W (CW)
Beam size by 1.5 m main mirror: approx. 60 cm 
Beam divergence angle: approx. 190 μrad (FWHM) 

Laser equipment is installed on the optical bench in the coudé room.


1988. 03 Building of the 1.5 m telescope
1993.03 Addition of a preparation room and napping room for observation
1994. 03 Telescope enhancement for higher directionality and more accurate tracking, adding new functionality for satellite tracking function
1994. 03 Installation for aircraft monitoring radar
1994. 08 Re-coating on primary mirror
1996.03 Addition of the Leading Optical Technologies Research and Experimental Center Building
1999. 03 Enhancement of the telescope control system, etc.
2001. 03 Update of satellite laser ranging equipment (Key Stone SLR laser integration)
2004. 03 2 µm laser radar light source installation
2005. 08 Renewal of the opening-and-closing shutter of the dome
2006. 03 Installation of a small dome for NeLS 10 cm optical terminal