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Zpectrometer

• Status
• Strategic Value
• Personnel
• Scope and Overall Work Plan
• Detailed plans
• Current UMd Software documentation (Oct 17, 2005)
• Zpectrometer Meeting Minutes
• Budget Responsibilities
• Documents:
• Links

Status

During summer 2007 work was being done on two fronts - the Ka receiver was worked on to improve is correlation architecture, and a number of different pieces of the Zpectrometer software were worked on.

Work on the Ka receiver is captured on the Ka receiver page.

Work on the software issues is captured in the Plans for 2007

Strategic Value

We will construct the Zpectrometer, an ultra-wideband radio spectrometer for the Green Bank Telescope (GBT). Observations with this instrument are key to understanding the star formation, metal production, and structure formation histories of the Universe. The Zpectrometer covers the full 14 GHz-wide Ka-band with a set of analog lag correlation spectrometers in a multi-channel correlation radiometer architecture. The zpectrometer's bandwidth and stability, combined with the GBT's collecting area, enable sensitive and efficient spectral searches for molecules in high redshift galaxies. The instrument is optimized for observations of low-excitation spectral lines from the carbon monoxide (CO) molecule at redshifts of 1.88 < z < 3.43 and 4.76 < z < 7.87. This range of redshifts is of intense current interest because it may correspond to the era when most of the stars in the Universe formed and galaxies assembled.

All high-redshift radio molecular detections to date have started from optical redshifts. Zpectrometer's wide bandwidth bypasses this selection effect and enables it to detect new classes of sources. In addition to finding precise redshifts, its spectra with velocity resolution of approximately 150 km s^-1 probe kinematical signs of interaction and derive dynamical mass estimates. Both cold and warm gas emit low-J lines, and these observations are critical constraints on radiative transfer models of physical conditions

Personnel

• GB Project Manager: KarenONeil
• GB Project Engineer: AmyShelton
• Project Scientist: Andy Harris (UMd)
• GB Project Team: KarenONeil, AmyShelton, Galen Watts, Roger Norrod, Ray Creager, Bob Garwood, Paul Marganian
• UMd Project Team: Andy Harris (PI), Andrew Baker, Stephanie Zonak, Kevin Rauch

Scope and Overall Work Plan

This project has three main areas of responsibility, and each proposer will take lead responsibility for one: Harris (UMd) for spectrometer package fabrication and test, Baker (UMd) for data analysis software, and the GBT project group for interfaces with the GBT.

Fabricating the WASP2 correlators is largely a replication effort, and we will continue our collaboration with the University of Maryland's Physics department's Electronic Development Group and Mechanical Shop. The professional shops again will be responsible for the bulk of the fabrication. Harris' group will be responsible for microwave module fabrication and overall testing. The four-channel downconverter is a good project for a budding instrumentalist and will be a UMD student project with Harris' supervision. The UMD instrument team will also take responsibility for modifying the instrument software for the specific calibration cycles and header information at the GBT.

Baker will lead the data analysis software effort with the assistance of a UMD student. Baker, who will spend about a quarter of his time on this project, is supported as an external NRAO Jansky Fellow at the University of Maryland and receives no support from this grant.

The project team (described above and incorporating the UMd team) will ensure that the physical, electronic, and software interfaces match on the GBT and Zpectrometer. NRAO Green Bank will be responsible for the physical accommodation, including machine shop work and material for mounting, and will modify the Kaband front-end for the spectrometer. NRAO will not receive any funds from this proposal; scientist, engineer, and mechanic time will come from its operating budget.

The project timeline is an 18-month fabrication period followed by a number of test observing runs. The timeline is driven in part by an estimate of a reasonable funding profile [which was granted], but the current plan will have the zpectrometer on the telescope without delay in the winter 2006/2007 observing season. (Atmospheric water vapor is low in the winter, the best season for Ka-band observations.) A limited amount of engineering time will be available, but the bulk of the observing time will come from proposals to the normal GBT Proposal Selection Committee.

In detail, the project timeline is:

Year 1: Start all long-lead correlator items, principally the correlator boards and microwave modules. Test items with existing equipment and test setups as they become available throughout the year. Fabricate and test the downconverter, which contains long-lead items and whose student work benefits from a schedule off the critical path. Connect an existing WASP2 correlator to the Ka-band receiver for lab tests in Green Bank. Remeasure and if needed mitigate internal RFI. Use the lab data to test the new data processing software.

Year 2: Procure and modify chassis, design and fabricate correlator backplanes and phase-switch timing cards, fabricate or purchase ancillary electronics, and assemble the spectrometers. The spectrometer package should arrive in Green Bank in time for lab tests with the receiver in Fall 2006. The software groups have also requested a two-week period of concentrated joint interface work some 4-6 months before the spectrometers arrive in Green Bank. Install Zpectrometer on the GBT for first observations in Winter 2006-2007.

Year 3: After finishing the observing season, evaluate hardware and software performance with astronomical results. Modify Zpectrometer as needed and return to the GBT in Fall 2007 for the winter observing season. Prepare relevant documentation and support equipment for GBT staff.

Detailed plans

• Plans for 2007
• Original Project Schedule
• Original schedule of GB tasks:
  • 10 Feb 2006 : Determine placement of Zpectrometer machine (R. Norrod - 2005 Oct, Nov) [ DONE ]
  • 17 Apr, 2006 : Fit Dummy zpectrometer to turret for tests (Egan/Cromer) [ DONE ]
  • 31 May, 2006 : Microcode & controller deliveredd to GBT software group
  • 01 Jun, 2006 : Ship Zpectrometer rack to UMd (Egan/Cromer - 2006 April - May)
  • 15 August, 2006 : Ka receiver software manger changes (Creager/A. Shelton - 2006 May - Aug)
  • 15 August, 2006 : GBT software control manager built (Creager/A. Shelton - 2006 May - Aug)
  • 15 August, 2006 : SDFITS keyword/GBTIDL index changes made to accomodate zpectrometer data
  • 15 August, 2006 : Ka-band receiver modifications complete (G. Watts - 2006 Jun - Aug)
  • 14-18 August, 2006 : Zpectrometer in GB for RFI and software testing. (Will be hooked up to KA receiver iff possible)
  • 5-8 September, 2006 : Zpectrometer/Ka Lab tests
  • 1 October, 2006 : GBT config requirements, modifications, and scheduling blocks designed and built (SDD TBD - 2006 May - Oct)
  • 09 Oct, 2006 : Install Ka Receiver
  • 16 Oct, 2006 : Install Zpectrometer
  • 31 Nov, 2006 : 10-20 hours of Zpectromter Functional tests (2006 17 Oct - 17 Nov)

Current UMd Software documentation (Oct 17, 2005)

• http://www.astro.umd.edu/~harris/docs/waspmath.pdf is a memo that explains the signal processing for the WASP spectrometers in autocorrelation mode. No major differences for cross-correlation mode, results for which are summarized in http://www.astro.umd.edu/~harris/kaband/rsi05.pdf. These document the algorithms that produce amplitude calibrated spectra. Another document of less direct interest is http://www.astro.umd.edu/~harris/docs/freq_setup.pdf, which describes how to assign values to the FITS keywords to provide the right velocity scales for CLASS FITS files, given the data available from the Caltech Submillimeter Observatory's telecope computer. We would need to modify this for the GBT, but at least it's a start.
• http://www.astro.umd.edu/~mpound/wasp/dict.html is a dictionary of the SDFITS keywords we use. Marc Pound generates these with a script that writes this html file as well as template header files and so on, which makes it easy to update and modify the list. He would be happy to share it -- he's mpound "at" astro.umd.edu. (There are a few unusual items here: for instance the telescope's altitude, latitude, longitude, heading and speed are dynamic variables since we also support observations from NASA's SOFIA airborne observatory...)
• The command language, options, and engineering tools, along with timing calculations for the spectrometer's internal micros is covered in http://www.astro.umd.edu/~harris/microc_223.ps. This will change in detail when we switch to new micros, but gives a flavor of that interface.

Zpectrometer Meeting Minutes

• Zpectrometer Kick-off Meeting (14 October, 2005) - ZpectKickoffSched
• Zpectrometer Face-to-face meeting 2 (4 Feb, 2006) - ZpectMeeting2
• Zpectrometer Face-to-face meeting 3 (10 Apr, 2006) - ZpectMeeting3
• Zpectrometer Face-to-face meeting 4 (15 May, 2006) - ZpectMeeting4
• Zpectrometer meeting 5 (14 June, 2006) - ZpectMeeting5
• Zpectrometer meeting 6 (12 July, 2006) - ZpectMeeting6
• Zpectrometer meeting 7 (09 Aug, 2006) - ZpectMeeting7

Budget Responsibilities

• GBT: Receiver modifications, rack, installation, travel for NRAO people
• UMd: Everything including RFI sheilded chasis, short cables (within one room), downconverter, power supplies, communications, phase cal system, travel for all UMd folks
• If the decision is made to place the zpectrometer in the Jy lab and not in the turret house, GB would be responsible for the cost of the fiber cables. Hoewever, UMd will provide all monies available due to the much cheaper chasis, etc (which may even be built by GB in this case) which would be needed, to help defray the cable costs.

Documents:

• zpectrometer_prop.pdf: Zpectrometer Proposal

• zpect_fab2.mpp: Project Plan for Zpectrometer (12 August, 2005)

• GBT Interfaces and Form Factors

• http://www.astro.umd.edu/~harris/docs/waspmath.pdf : is a memo that explains the signal processing for the WASP spectrometers in autocorrelation mode.

• http://www.astro.umd.edu/~harris/kaband/rsi05.pdf : is a memo that explains the signal processing for the WASP spectrometers in cross-correlation mode.

• http://www.astro.umd.edu/~harris/docs/freq_setup.pdf : describes how to assign values to the FITS keywords to provide the right velocity scales for CLASS FITS files, given the data available from the Caltech Submillimeter Observatory's telecope computer. We would need to modify this for the GBT, but at least it's a start.

• http://www.astro.umd.edu/~mpound/wasp/dict.html : dictionary of the SDFITS keywords we use. Marc Pound generates these with a script that writes this html file as well as template header files and so on, which makes it easy to update and modify the list.

• http://www.astro.umd.edu/~harris/microc_223.ps : The command language, options, and engineering tools, along with timing calculations for the spectrometer's internal micros. This will change in detail when we switch to new micros, but gives a flavor of that interface.

• http://www.norenproducts.com/Heat_Pipes/what_is.html : Heat dissipation device

• user_instrument_policy.doc: NRAO User Instrument Policy

• phaseswitch.pdf: UMd Phase Switch information

• max353.pdf: Maxim analog switches

• hmc136.pdf: HMC 136 biphase modulator

• Zpect_interfaces_r1.pdf: First draft of zpectrometer interfaces doc

• zspecFinalcopy.doc: zpectrometer placment doc (from GBT)

• ZpectSoftwareDevelopment: Discuss/Document software development issues related to the Zpectrometer

• zpectrometer-earlyobs-2006.04.24.pdf: memo on early observations with Zpectrometer

• intermed-levdataacqint.pdf: intermediate level data acquisition interface

• zpec-data-2006.05.14.pdf: First draft of data/calibraiton memo (A. Baker)

• 26t40BlockDiagZpec-Model.jpg: Ka RX Block Diagram

• zpectrometer-idl-2006.06.13.pdf: IDL routines expected to needed

• Info on the Zpectrometer Shielded Rack

• ZpectrometerGbtidlUsage

Links

• UMd Zpectrometer website

• Email exploder page

• Zpectrometer Rack Pages

• Pictures of Zpectrometer being removed from the GBT on Dec. 8, 2006