Abstract
FACT is the first imaging Cherenkov telescope based on a camera using solid state photosensors (Geigermode Avalanche Photodiodes G-APD aka SiPM). Since October 2011, it has been taking data regularly. Apart from commissioning and calibration measurements, it has already started regular operation, where the main goal is to do long-term monitoring of bright TeV blazars. In June 2012, a flare of Mrk 501 was observed. Thanks to the robustness of the G-APDs, observations can be carried out during strong moon light without aging of the sensors. This improves the duty cycle of the instrument and provides better statistics for long-term light curves. The telescope, situated on the Canary Island of La Palma, is operated, already now, remotely from central Europe. For the future, robotic operation is planned. We report on our experiences during the commissioning, and we present first results from the first 1.5 years of observations.
Highlights
The telescope, situated on the Canary Island of La Palma, is operated, already remotely from central Europe
G-APDs [1] were chosen as photosensors which has provided the opportunity to show that Si-based photodetectors are suitable for Cherenkov telescopes
The G-APD camera was mounted on the refurbished HEGRA CT3 mount which was equipped with a new drive system, basically a down-scaled version of the MAGIC drive system [3], and the re-coated mirrors of the former HEGRA CT1 telescope, providing a mirror area of 9.5 m2
Summary
With the aim to monitor bright active galactic nuclei (AGN) in the very high energy (VHE) range, the First G-APD Cherenkov Telescope (FACT) was designed for stable and robust operation. G-APDs [1] were chosen as photosensors which has provided the opportunity to show that Si-based photodetectors are suitable for Cherenkov telescopes. The G-APD camera was mounted on the refurbished HEGRA CT3 mount which was equipped with a new drive system, basically a down-scaled version of the MAGIC drive system [3], and the re-coated mirrors of the former HEGRA CT1 telescope, providing a mirror area of 9.5 m2. The camera was mounted on the telescope in October 2011. Since it has been taking data regularly. FACT is the first telescope of its kind that is remotely operated
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