Proc. SPIE. 10707, Software and Cyberinfrastructure for Astronomy V
KEYWORDS: Observatories, Digital signal processing, Spectroscopy, Computing systems, Field programmable gate arrays, Control systems, Data processing, Signal processing, Software development, Servomechanisms
The software model of the Robert C. Byrd Green Bank Telescope (GBT) is a collection of instruments that are frequently modified or updated. Subsets of these instruments are combined for monitor and control, realtime servo control, or data processing. To better manage the complexity of this dynamic system, Green Bank Observatory (GBO) software developers created a dataflow application framework, called Matrix, which allows them to use common code for disparate activities. This paper describes Matrix application components, provides several examples of how the framework is used at the GBT, and details how others can obtain the framework.
We present the design, commissioning, and initial results of the Green Bank Earth Station (GBES), a RadioAstron data downlink station located at the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. The GBES uses the modernized and refurbished NRAO 140ft telescope. Antenna optics were refurbished with new motors and drives fitted to the secondary mirror positioning system, and the deformable subreflector was refurbished with a new digital controller and new actuators. A new monitor and control system was developed for the 140ft and is based on that of the Green Bank Telescope (GBT), allowing satellite tracking via a simple scheduling block. Tools were developed to automate antenna pointing during tracking. Data from the antenna control systems and logs are retained and delivered with the science and telemetry data for processing at the Astro Space Center (ASC) of the Lebedev Physical Institute (LPI) of the Russian Academy of Sciences and the mission control centre, Lavochkin Association.
The Green Bank facility of the National Radio Astronomy Observatory is spread out over 2,700 acres in the Allegheny Mountains of West Virginia. Good communication has always been needed between the radio telescopes and the control buildings. The National Radio Quiet Zone helps protect the Green Bank site from radio transmissions that interfere with the astronomical signals. Due to stringent Radio Frequency Interference (RFI) requirements, a fiber optic communication system was used for Ethernet transmissions on the site and coaxial cable within the buildings. With the need for higher speed communications, the entire network has been upgraded to use optical fiber with modern Ethernet switches. As with most modern equipment, the implementation of the control of the newly deployed Green Bank Telescope (GBT) depends heavily on TCP/IP. In order to protect the GBT from the commodity Internet, the GBT uses a non-routable network. Communication between the control building Local Area Network (LAN) and the GBT is implemented using a Virtual LAN (VLAN). This configuration will be extended to achieve isolation between trusted local user systems, the GBT, and other Internet users. Legitimate access to the site, for example by remote observers, is likely to be implemented using a virtual private network (VPN).
This paper presents the Green Bank Telescope (GBT) antenna control system architecture, describes the tracking options available to the observer, and details the GBT pointing, focus tracking and active surface control systems, as well as approaches to vibration reduction by use of minimal jerk trajectory generation. A description of the phased approach to improve telescope performance through the use of laser metrology range finders is given.
The Green Bank Telescope (GBT) is under construction in Green Bank, West Virginia. The GBT is expected to be operational in mid 1999. Networking the GBT will require innovative application of network technologies. Distribution of data from the originating source to large groups of consumers can be accomplished in at least two ways. The first is to 'unicast' or communicate individually with each consumer on the net. The second is to 'multicast' to a group of consumers. Multicasting is a technology which seems to have merit for distribution of information, but it is inherently unreliable. In some cases, such as observational data, packets must be delivered reliably, while in other cases such as informational displays, reliable delivery is not essential. This paper introduces the basic concepts of multicasting, and also discusses the design approaches of reliable multicast protocols.
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Advanced Global Communications Technologies for Astronomy