Amy L. Shelton

Launching GUPPI: the Green Bank Ultimate Pulsar Processing Instrument

The National Radio Astronomy Observatory (NRAO) is launching the Green Bank Ultimate Pulsar Processing Instrument (GUPPI), a prototype flexible digital signal processor designed for pulsar observations with the Robert C. Byrd Green Bank Telescope (GBT). GUPPI uses field programmable gate array (FPGA) hardware and design tools developed by the Center for Astronomy Signal Processing and Electronics Research (CASPER) at the University of California, Berkeley. The NRAO has been concurrently developing GUPPI software and hardware using minimal software resources. The software handles instrument monitor and control, data acquisition, and hardware interfacing. GUPPI is currently an expert-only spectrometer, but supports future integration with the full GBT production system. The NRAO was able to take advantage of the unique flexibility of the CASPER FPGA hardware platform, develop hardware and software in parallel, and build a suite of software tools for monitoring, controlling, and acquiring data with a new instrument over a short timeline of just a few months. The NRAO interacts regularly with CASPER and its users, and GUPPI stands as an example of what reconfigurable computing and open-source development can do for radio astronomy. GUPPI is modular for portability, and the NRAO provides the results of development as an open-source resource.

TWiki as a platform for collaborative software development management

The software development process in Green Bank is managed in six-week development cycles, where two cycles fall within one quarter. Each cycle, a Plan of Record is devised which outlines the teams commitments, deliverables, technical leads and scientific sponsors. To be productive and efficient, the team must not only be able to track its progress towards meeting commitments, but also to communicate and circulate the information that will help it meet its goals effectively. In the early summer of 2003, the Software Development Division installed a wiki web site using the TWiki product to improve the effectiveness of the team. Wiki sites contain web pages that are maintainable using a web interface by anyone who becomes a registered user of the site. Because the site naturally supports group involvement, the Plan of Record on the wiki now serves as the central dashboard for project tracking each development cycle. As an example of how the wiki improves productivity, software documentation is now tracked as evidence of the software deliverable. Written status reports are thus not required when the Plan of Record and associated wiki pages are kept up to date. The wiki approach has been quite successful in Green Bank for document management as well as software development management, and has rapidly extended beyond the bounds of the software development group for information management.

RRI-GBT multi-band receiver: motivation, design, and development

We report the design and development of a self-contained multi-band receiver (MBR) system, intended for use with a single large aperture to facilitate sensitive and high time-resolution observations simultaneously in 10 discrete frequency bands sampling a wide spectral span (100-1500 MHz) in a nearly log-periodic fashion. The development of this system was primarily motivated by need for tomographic studies of pulsar polar emission regions. Although the system design is optimized for the primary goal, it is also suited for several other interesting astronomical investigations. The system consists of a dual-polarization multi-band feed (with discrete responses corresponding to the 10 bands pre-selected as relatively radio frequency interference free), a common wide-band radio frequency front-end, and independent back-end receiver chains for the 10 individual sub-bands. The raw voltage time sequences corresponding to 16 MHz bandwidth each for the two linear polarization channels and the 10 bands are recorded at the Nyquist rate simultaneously. We present the preliminary results from the tests and pulsar observations carried out with the Robert C. Byrd Green Bank Telescope using this receiver. The system performance implied by these results and possible improvements are also briefly discussed.

Advanced multi-beam spectrometer for the Green Bank Telescope

A new spectrometer for the Green Bank Telescope (GBT) is being built jointly by the NRAO and the CASPER, University of California, Berkeley. The spectrometer uses 8 bit ADCs and will be capable of processing up to 1.25 GHz bandwidth from 8 dual polarized beams. This mode will be used to process data from focal plane arrays. The spectrometer supports observing mode with 8 tunable digital sub-bands within the 1.25 GHz bandwidth. The spectrometer can also be configured to process a bandwidth of up to 10 GHz with 64 tunable sub-bands from a dual polarized beam. The vastly enhanced backend capabilities will support several new science projects with the GBT.

Autonomous quality assurance and troubleshooting

To improve operational availability (the proportion of time that a telescope is able to accomplish what a visiting observer wants at the time the observation is scheduled), response time to faults must be minimized. One way this can be accomplished is by characterizing the relationships and interdependencies between components in a control system, developing algorithms to identify the root cause of a problem, and capturing expert knowledge of a system to simplify the process of troubleshooting. Results from a prototype development are explained, along with deployment issues. Implications for the future, such as effective knowledge representation and management, and learning processes which integrate autonomous and interactive components, are discussed.

A standard python environment for software applications at the Robert C. Byrd Green Bank Telescope (GBT)

Since 2003, the monitor and control software systems for the Robert C. Byrd Green Bank Telescope (GBT) have been substantially redesigned to make the telescope easier to use. The result is the release of the Astronomers Integrated Desktop (Astrid), an observation management platform used to create and submit scheduling blocks, monitor their progress on the telescope, and provide a real time, quick look data display. Using Astrid, the astronomer launches one application and has access to all of the software, documentation, and feedback facilities that are required to conduct an interactive observing session. These systems together provide a common look and feel for GBT software applications, enable offline observation preparation, and facilitate dynamic scheduling and remote observing.

An Enterprise Software Architecture for the Green Bank Telescope (GBT)

The enterprise architecture presents a view of how software utilities and applications are related to one another under unifying rules and principles of development. By constructing an enterprise architecture, an organization will be able to manage the components of its systems within a solid conceptual framework. This largely prevents duplication of effort, focuses the organization on its core technical competencies, and ultimately makes software more maintainable. In the beginning of 2003, several prominent challenges faced software development at the GBT. The telescope was not easily configurable, and observing often presented a challenge, particularly to new users. High priority projects required new experimental developments on short time scales. Migration paths were required for applications which had proven difficult to maintain. In order to solve these challenges, an enterprise architecture was created, consisting of five layers: 1) the telescope control system, and the raw data produced during an observation, 2) Low-level Application Programming Interfaces (APIs) in C++, for managing interactions with the telescope control system and its data, 3) High-Level APIs in Python, which can be used by astronomers or software developers to create custom applications, 4) Application Components in Python, which can be either standalone applications or plug-in modules to applications, and 5) Application Management Systems in Python, which package application components for use by a particular user group (astronomers, engineers or operators) in terms of resource configurations. This presentation describes how these layers combine to make the GBT easier to use, while concurrently making the software easier to develop and maintain.