[Paper Review] FACT: Towards Robotic Operation of an Imaging Air Cherenkov Telescope

A. Biland, H. Anderhub+52 more|arXiv (Cornell University)|Jul 30, 2013

Opportunistic and Delay-Tolerant Networks1 references3 citations

TL;DR

FACT demonstrates the first successful remote, near-robotic operation of an imaging air Cherenkov telescope using solid-state G-APD sensors. With minimal manual intervention, the telescope operates reliably since 2012, achieving stable remote data acquisition and paving the way for fully autonomous robotic operation through redundant safety systems and remote diagnostics.

ABSTRACT

The First G-APD Cherenkov Telescope (FACT) became operational at La Palma in October 2011. Since summer 2012, due to very smooth and stable operation, it is the first telescope of its kind that is routinely operated from remote, without the need for a data-taking crew on site. In addition, many standard tasks of operation are executed automatically without the need for manual interaction. Based on the experience gained so far, some alterations to improve the safety of the system are under development to allow robotic operation in the future. We present the setup and precautions used to implement remote operations and the experience gained so far, as well as the work towards robotic operation.

Motivation & Objective

• To enable remote, crewless operation of an imaging air Cherenkov telescope using solid-state G-APD sensors.
• To identify and resolve operational challenges in a prototype telescope to ensure long-term stability and reliability.
• To develop automated systems for critical functions such as telescope parking, power management, and fault detection.
• To implement robust safety protocols to protect personnel and equipment during unattended operation.
• To prepare for fully robotic operation by designing independent monitoring systems for telescope position and system health.

Proposed method

• Equipped the refurbished HEGRA CT3 telescope with a 1440-pixel G-APD camera using Hamamatsu MPPC S10362-33-50C sensors with light concentrators.
• Integrated trigger and data acquisition electronics using the DRS4 chip, enabling real-time signal processing and Ethernet-based data transfer.
• Implemented a centralized control system using the DIM environment to coordinate drive, slow control, trigger, bias, and DAQ subsystems.
• Enabled remote operation via command-line, full GUI, and smartphone-accessible reduced GUI, allowing remote monitoring and control.
• Deployed redundant safety systems including physical fencing, emergency power cutoffs, and independent environmental monitoring (e.g., temperature, power, brightness).
• Developed a prototype for a fully independent smartphone-based system to monitor telescope position and send alerts in case of failure, ensuring remote verification of parking status.

Experimental results

Research questions

• RQ1 Can a Cherenkov telescope using G-APD sensors be operated reliably without an on-site crew?
• RQ2 What automated systems are required to ensure safe and stable remote operation of a robotic telescope?
• RQ3 How can telescope parking be verified remotely when standard communication and sensor systems fail?
• RQ4 What are the key failure modes in a remote telescope system, and how can they be mitigated through software and hardware redundancy?
• RQ5 How can documentation and system state be preserved and accessed reliably in a robotic, crewless operation model?

Key findings

• FACT has operated continuously since October 2011 with minimal downtime, achieving stable remote operation since summer 2012.
• Over 90% of hardware issues were resolved remotely via software commands or resets, eliminating the need for on-site intervention.
• Only rare manual tasks were required—such as refilling cooling water, greasing camera lid hinges, and replacing a RAID disk—demonstrating high system reliability.
• The telescope’s drive system overheated twice, prompting the development of improved cooling and the installation of additional thermal monitoring.
• A DRS4 initialization failure caused a power surge that blew a fuse, leading to the addition of real-time power and temperature monitoring to prevent recurrence.
• A prototype smartphone-based system is being developed to provide independent, self-powered monitoring of telescope position and environmental conditions, enabling remote verification of parking status in case of system failure.