Green Bank Spectrometer

Project Number 450102


Status Update and To Do List

Project Description

The Project

  • Building on their successful collaboration on the GUPPI project, UC Berkeley and NRAO now propose to use similar technology to develop a spectrometer with 1.350 GHz of bandwidth, 16 Intermediate Frequency (IF) inputs, and X spectral channels per IF, divided into N “zoom” windows, or sub-bands, per IF, where N is ~four. These sub-bands will allow efficient use of the 32k channels for studies of multiple lines that lie in the instantaneous 1.350 GHz of bandwidth. This bandwidth and number of channels is closely coupled to both the 7-pixel dual- polarization 18-26 GHZ receiver (K-Band FPA) project and the proposed prototype 16-pixel single-polarization 3mm FPA.

    Developing the proposed spectrometer will allow the maximum value to be extracted from the science observations conducted with these new receivers. Existing GBT receivers will also benefit from the advanced capabilities of this new instrument, as they are also limited by the currently available spectrometer.

    In addition to the increased capability provided to the GBT’s observers, additional modules will be developed and added to CASPER’s open-source FPGA digital signal processing (DSP) toolset 8, allowing future spectrometers to be built with correspondingly less effort.

Instrument Design, Construction, and Commissioning

The work breakdown for this project has been divided into six distinct tasks, each of which will contain many smaller tasks. As noted below, part of the design and development phase is to create a project plan that can be tracked and followed once the major systems decisions are made and work commences.
  1. Design and Development
    • During the duration of this task, we will develop and agree on the detailed specifications of the spectrometer, and develop the work plan for the remainder of the project. We will prototype various options for doing the signal processing work, and complete the analysis to ensure a working system. We will develop the interface specifications for the mechanical envelope, including cooling, power, size, and weight. We will develop the software interface documents, and detail the support needed from the GBT observing system. The design and development task will last 9 months, with all disciplines (Electronics, Software, FPGA Programming, Microwave Engineering, and Science) involved.
  2. Detailed Engineering
    • During the Detailed Engineering task, we will design the front-end electronics, the power distribution system, racks, cabinets, and other hardware. Mounting brackets, fixtures, and cabling runs will be designed. Space in GBT fiber bundles and circuit breaker panels will be reserved. Orders for materials and supplies will be entered. Test plans for subsystem and system testing will be developed. Most of this work will be done in Green Bank by the undergraduate and graduate engineering students under the direction of Green Bank engineers.
  3. FPGA Programming
    • This task will begin concurrently with the Detailed Engineering phase. During this phase, the DSP and FPGA control logic will be developed. Most of this work will be done by the UC Berkeley group engineers and students under the direction of Werthimer and Parsons. . We expect this task to take 12 months.
  4. Software Development
    • The software development task will begin with the end of the design and development task. During this task, the Green Bank Software Development Division (SDD) will design and implement the software needed to control the instrument, acquire the data, and integrate the instrument into the GBT observing system. SDD engineers are experienced in writing control software for instrumentation, and have successfully completed control software and system integration for the Zpectrometer, the MUSTANG 64-pixel Bolometer Receiver, the Caltech Continuum Backend, and GUPPI. All four of these projects had requirements similar to this spectrometer project, but were smaller in total scope. We expect this task to take 12 months.
  5. Construction
    • Construction will be done at the Green Bank site. All machine work and custom assemblies will be built by the Green Bank shop and electronics technicians. The Project Manager will ensure that sufficient time is reserved in the shop for this effort.
  6. Commissioning
    • Commissioning will be accomplished with the instrument post-doc. The instrument post-doc will be supported by O’Neil and Frayer, along with the Green Bank science staff. Engineering and Software will be supporting commissioning as well. The commissioning plan will be developed by the science co-PI’s and the instrument post-doc during the early phases of the project.

Project Schedule

  • Timeline from proposal:

Major Project Milestones

Milestone Plan Date Actual Date Complete? Comments
Finalization of spec and design     DONE Iterative w/NRAO & Berkeley inc. science stakeholders
Finalization of all Hardware components for procurement       This sets the maximum performance spec for the system
Design Review     DONE  
Procure hardware for one spectrometer     DONE Expert mode only - includes some level of hardware "overhead"
Completion of one spectrometer     DONE (ie the spectrometer that can handle one beam data) operating in the full bandwidth mode with 2 K channels
Critical Design Review     DONE  
Completion of all 8 spectrometers     DONE  
Test/science observation with the above spectrometer     DONE  
Completion of one spectrometer in 16 subband mode with 64 K channels        
Test/science observation with the subband mode        
Completion of all 8 spectrometers        
Test/science observation with the KFPA        
Implementing all the relevant mode and testing        
Test/science observations using different modes        

Project delivery Flow Chart

Initial functionality delivery dates

Project Partners

  • Project Team:


  • While the final authority and responsibility for managing the project remain with the UC Berkeley PI Dan Werthimer and his organization, much of the day to day project management structure for this project is being provided by NRAO. This is because the instrument will be hosted at the GBT, and the NRAO’s Green Bank staff is experienced with managing projects like this that require intense coordination between the instrument builder and the GBT staff.

University of California at Berkeley - Casper Group

Project Personnel

  • NRAO
    • Randy McCullough
    • Jason Ray
    • Roger Norrod
    • David Frayer
    • John Ford
    • Anish Roshi
    • Amy Shelton
    • Patrick Brandt
    • Marty Bloss

General Specifications

Initial System Specifications (from KFPA - needs updated)

  • 16 IF's (7 pixels, dual polarizations, plus a spare pair for non-array use)
  • Sampling bandwidth Minimum of 3.0 Gs/s
  • 8 bit sampling
  • 1.35 GHz of bandwidth with 1 K channels
  • 8 to 16 Subbands to look at multiple narrow lines in each IF
  • Generate and accept up to three switching signals, plus a hardware blanking signal.
  • Accumulation for 0.5 ms to 10 seconds.
  • Needed in 2 years.
  • Useable as general purpose spectrometer for other receivers, with proper samplers/data transmission system

Detailed Specifications

Project Meetings

Preliminary Tests (December, 2011)

Tests and GC observations (March, 2012)

Tests and GC observations (Dec, 2012)

Tests August 2013

Shared Risk Science Tests Feb/March 2014


ROACH-2 notes

Trouble-Shooting Guide

Support Staff Training Schedule

eNews article

Topic revision: r48 - 2015-02-23, JasonRay

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