The Low Frequency Array (LOFAR) is Europe’s largest radio telescope, originally designed, built and operated by ASTRON. It consists of an interferometric array of low band and high band antennas, distributed among 52 stations. Since 2018, a considerable upgrade of the main infrastructure has taken place both on the hardware and on the software side, the so-called LOFAR 2.0. The monitor and control software system of each LOFAR 2.0 station is based on the open-source TANGO-Controls framework, which manages the device architecture and the various functionalities of the station, including its states and transitions. Since each hardware device of the station is implemented as a software module, the startup of the station and its states transitions until a full operative state implies a non-trivial interaction and communication among the different device classes. The proposed design solution places each one of these devices in a specific hierarchical structure, which defines the parent-child relations and the allowed operations for its nodes. Besides that, the device hierarchy can be different according to the two main sequences that are involved in the station states transition: the power sequence and the control sequence. The whole set of sequential operations are entirely managed by the TANGO framework, in particular from a root device called Station Manager, which controls the children devices and the hierarchical sequences. In order to adhere to the TANGO architecture, the operations are mainly developed exploiting device attributes and properties, such that a potentially complex process is handled in a very straightforward, lightweight and maintainable way. The aforementioned software architecture has been already deployed and successfully tested on the LOFAR2 Test Station (L2TS) located in the Netherlands. Therefore, it is proving to be a primary feature for the whole LOFAR2 infrastructure, in view of a forthcoming fully operational phase within the next few years.
KEYWORDS: Telescopes, Data archive systems, Data modeling, Radio telescopes, Visualization, System integration, Telescope instrument control software, Efficient operations
The Low Frequency Array (LOFAR) is Europe’s largest radio telescope, designed, built and operated by ASTRON and international LOFAR partners. It is a complex instrument which had an expensive active human workflow and became difficult to adjust. The new Telescope Manager Specification System (TMSS) solves this by the introduction of a dynamic scheduler, a data-quality assessment workflow and a specification system that allows easy versioned specification of known observing setups but also detailed adjustments of observations and processing pipelines. In this presentation we will show the new optimized operations workflow and dynamic scheduling with TMSS.
Centralised solutions for Video-on-Demand (VoD) services, which stream pre-recorded video content to multiple clients
who start watching at the moments of their own choosing, are not scalable because of the high bandwidth requirements of
the central video servers. Peer-to-peer (P2P) techniques which let the clients distribute the video content among themselves,
can be used to alleviate this problem. However, such techniques may introduce the problem of free-riding, with some peers
in the P2P network not forwarding the video content to others if there is no incentive to do so. When the P2P network
contains too many free-riders, an increasing number of the well-behaving peers may not achieve high enough download
speeds to maintain an acceptable service. In this paper we propose Give-to-Get, a P2P VoD algorithm which discourages
free-riding by letting peers favour uploading to other peers who have proven to be good uploaders. As a consequence,
free-riders are only tolerated as long as there is spare capacity in the system. Our simulations show that even if 20% of
the peers are free-riders, Give-to-Get continues to provide good performance to the well-behaving peers. In particular, they
show that Give-to-Get performs very well for short videos, which dominate the current VoD traffic on the Internet.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
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.