Time reference system of the VLT

Martin Ravensbergen; Krister Wirenstrand

doi:10.1117/12.211435

8 June 1995 Time reference system of the VLT

Martin Ravensbergen, Krister Wirenstrand

Proceedings Volume 2479, Telescope Control Systems; (1995) https://doi.org/10.1117/12.211435
Event: SPIE's 1995 Symposium on OE/Aerospace Sensing and Dual Use Photonics, 1995, Orlando, FL, United States

Abstract

The generation and distribution of an accurate time signal has been the cause of some technical difficulties in the past. Modern telescopes with their distributed computer architecture have increased this problem even more. Since the availability of the Global Positioning System (GPS), the generation of an accurate time signal of isolated telescope sites is not a problem any more. However, distribution of a time signal with a high accuracy to all computers is still an issue. The IRIG-B code, which is commonly used, is not adequate if accuracy requirements are in the 10 microsecond range. Also, synchronization of software processes in one computer and in different computers must be solved. This paper presents the design that is adopted for the ESO Very Large Telescope (VLT). An overview of the requirements of the time reference system (TRS) is given. These requirements have been defined on the basis of experiences with the timing system of the ESO NTT telescope. The hardware components are described with the emphasis on the distribution and the decoding module in the computers. As timing is vital in a `real time' software environment, the operating system and application software requirements have driven the TRS requirements from the beginning of the definition. This has led to a TRS system that supports the software needs on time synchronization between processes, even in different computers. A description is given about the software implementation.

Citation Download Citation

Martin Ravensbergen and Krister Wirenstrand "Time reference system of the VLT", Proc. SPIE 2479, Telescope Control Systems, (8 June 1995); https://doi.org/10.1117/12.211435

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available