Collaboration of Australia and Nippon (Japan) for a GAmma Ray Observatory in the Outback aims to study the existence and properties of very high energy (VHE) gamma-ray sources by utilizing the atmospheric Cherenkov technique with large aperture telescopes located near Woomera, South Australia (136.786 degree E, 31.099 degree S, 160m a.s.l.). Gamma-ray observation by ground-based telescope covers higher energies than observation by satellites at low and medium energies.
The collaboration has observed various targets, such as pulsars, their nebulae, SNR's, and AGN's in the southern sky since 1992. (Here is the CANGAROO observation history.)
Among the increasing numbers of Cherenkov telescopes, CANGAROO-I
telescope of 3.8m reflector has been
one of the pioneers in the VHE gamma-ray astronomy with its good
quality mirror and high resolution camera of 256 small PMT's (see some photos).
A new telescope of larger mirror, called CANGAROO-II, has been constructed in Woomera, and started operation in 1999 March. This 7m-diameter telescope has been expanded to 10m in March 2000 to increase light collection. It will extend the CANGAROO observations down to multi-hundred GeV energy region, which remains untouched because it is beyond both reaches of the satellites and the Cherenkov telescopes so far.
Even more sensitive observation will be possible with our new array of four 10m telescopes, called CANGAROO-III. The upgrade of the 7m telescope to 10m in March 2000 was the first step of this project. The second, third and fourth telescopes were completed in 2002, 2002 and 2003, respectively. The full operation has started in March 2004 and observations of gamma-ray candidate objects are going on.