2. Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array FPGA Spectrometer for the GBT - Risks NRAO and U.C. Berkeley Joint Conceptual Design Review January 31, 2011

3. GBT The main items that have any remaining R&D component are Hardware speed I/O between FPGA and GPUs Both are also being addressed as project risks R&D Items

4. GBT 4 Project Risks & Mitigation Project risks are largely mitigated because - Well established science case Detailed, prioritized specifications Teams have extensive experience in similar systems Three GUPPI-style systems built by NRAO [UC-B experience outside NRAO] Proven technology Broad use in astronomy and other scientific systems Large industry group Open architecture, open source

5. GBT Identified Risks - Performance Specification is incomplete or incorrect Mitigation: Multiple internal reviews with entire NRAO Science Staff and overall review in the Conceptual Design Review and a Critical Design Review System performance is insufficient to meet speed requirements of the science case Mitigation: Identified as a risk early on, much of the early work focused on characterizing the performance of the system components and system architecture. Calculated system benchmarks to date, show the system will meet requirements

6. GBT Roach board development – Availability of Roach 2 boards for production spectrometer. Mitigation: Three GUPPI systems have been deployed on Roach 1 boards by the NRAO/Berkeley team. The spectrometer is being developed and benchmarked so that if the performance, reliability, or availability of the Roach 2 becomes a problem, a fully operational spectrometer can be built using Roach 1 boards. Hardware speed. Mitigation: Specific Berkeley resources have focused on FPGA issues and is nearing completion of work to verify the necessary speeds for various spectrometer modes are supported in the design. I/O Speeds. Mitigation: As above, specific resources at Berkeley are dedicated to optimizing I/O speeds on-board the ROACH board and throughout the system. A dedicated system integration resource joins the Berkeley team in March 2011. Identified Risks – Development

7. GBT Identified Risks – Outside Reqs. What requirements are ‘embedded’ in the Virtual Astronomy Observatory (VAO)? Would these affect the GB Spectrometer archiving plans and policies? Mitigation: Since the timeline of the spectrometer development grant require these decisions to be made before VAO requirements are finalized, no assurance of compliance with VAO requirements is guaranteed.

8. GBT Identified Risks – Staffing Will resources be available for the duration of the spectrometer project? Mitigation: While drastic budgetary actions in future years could have a devastating effect on the development and deployment. All members of the NRAO staff are full-time staff with varying, but generally long tenure with NRAO. The Berkeley team is comprised of a combination of staff positions and students, mostly post-graduate and post-doc positions with well defined project tenure.

9. GBT There is risk that early science demands will drive schedules and design decisions in ways that are not necessarily best for the long-term operations (e.g. Roach1 v. Roach2 decision). Mitigation: The project will monitor science requests and commitments along with NRAO management to assess the effect of taking on any aggressive science cases before the designs and implementations are ready. Early Science Demands