Summary & Conclusions of the First E-ALFA Meeting

Summary & Conclusions of the First E-ALFA Meeting Draft Version 1.4
March 15-17, 2003 21Mar03
Arecibo Observatory  
  1. The final program was modified to accomodate last minute changes including ones necessitated by late arrivals. Karen Masters, Kristine Spekkens and Martha Haynes agreed to take minutes which will be posted on the E-ALFA web page after editting. Where possible, presentation materials will also be posted.
  2. ALFA will be a 7 pixel multifeed array operating over the frequency range (1.225 to 1.525 GHz).The central pixel will have a gain of 11 K/Jy while the others will achieve 8.5 K/Jy. The central pixel is expected to have a system temperature of about 25K rising to close to 35K at the lower frequency edge (28-31 K at 1375 MHz, 34-26 K at 1225 MHz). The Tsys may be reduced by the planned addition of a spillover-reducing tertiary skirt. The outer pixels will have slightly worse performance.
    The E-ALFA workshop participants strongly encourage NAIC to reduce Tsys as much as possible, particularly via the tertiary skirt.
    A significant issue for E-ALFA is the coma lobe/sidelobe structure associated with each of the offset feeds. The beams will vary from 3.5 to 4 arcmin, with the sky footprint showing a center-to-center separation of ~2 beam widths. Contamination from these structures will have to be taken into account in data analysis software.
    More info on the ALFA hardware can be obtained at:
  3. The ALFA front end is being constructed by the CSIRO. The NAIC is working on antenna controls, the IF/LO system, backend(s), data acquisition and archiving. It is anticipated that the front end will be delivered in April 2004, and that, following a period of integration and commission, ALFA will be ready for astronomical observations in early 2005.
    NAIC indicated that a call for proposals was likely to take place towards the end of this year (2003).
  4. Where telescope motions might be similar for separate projects, the possibility of piggybacking exists, if separate backend systems are available. Current capability for spectral line observing relies on the WAPPs and will offer 100 MHz with 4K channels and 3-level sampling for each polarization and beam. A proposed enhancement would add additional WAPPs to offer another separate 100 MHz, which might be overlapped to give ~180 MHz required for searches to higher redshift, or to provide the additional velocity resolution that might benefit piggyback observations with G-ALFA in the periphery and vicinity of the Milky Way.
    The WAPPs may constitute an acceptable set of spectral processors. The E-ALFA workshop strongly urges NAIC to provide the enhanced WAPP capability delivering ~200 MHz spectral coverage and higher than three-level sampling. It is important that each backend spectrometer have its own LO capability, and that a full range of bandwidth/channel number options be available for each.
  5. RFI will pose a significant challenge to the E-ALFA surveys. Methods both to mitigate and excise it need to be vigorously pursued. Of particular note, the Galileo satellite constellation will be fully operational in the 1260-1300 MHz range by 2008. One approach to RFI identification might include construction of extra WAPPs and employing additional feeds (say horizon pointing) for cross-correlation purposes. Higher N-level sampling is an effective means of combatting RFI and is thus also desirable in the spectrometer.
  6. The ALFA surveys discussed by the group are intended to address science problems covering a wide range of topics, including those which: The workshop participants identified 5 broad survey catagories:
    1. Galaxies in different environments, (e.g., Virgo, CVn)
    2. Ultra deep survey (e.g., small area, several 100 ksec)
    3. Deep strip survey (e.g., 1 deg X 300 deg Decl. strip)
    4. Shallow all-sky survey (dubbed "ALFALFA")
    5. ZOA survey
    Considerable discussion focussed on outlining the science case for the different surveys since the requirements should be driven by the science.
  7. The amount of telescope time required for any one of these surveys is substantial, and it was thus recognized that this effort is necessarily multi year/long term. At some time in the future, some group will have to prioritize the projects, but it was agreed that it is too early to tackle that now. NAIC requested input from the E-ALFA participants on anticipated hardware & software needs, survey strategies and other requirements as well as the development of a clear assignment of tasks and responsibilities.
  8. Since these surveys will be legacies of the Arecibo Observatory and should be of broad use and interest, the final data products must be of high quality and readibly accessibly by the entire astronomical community for correlative and spin-off studies. Furthermore, data analysis tools developed for the surveys should be contributed back to NAIC for use by smaller ALFA projects. This paradigm will require significant coordination between the community and NAIC; NAIC will maintain an oversight function. It is planned that NAIC will take responsibility for initial stages of data processing (Phase I data products), such as bandpass calibrated spectra. NAIC will archive all data at several stages (raw, Phase I, Phase II). The survey teams themselves will take responsibility for further processing and product production (Phase II data products) such as cleaned maps, spectra at any position, source catalogs, final archival products and access tools (made available through NAIC). Since it is recognized that involved teams have a distinct edge already, proprietary time will be minimized and may be no longer than the time to validate data quality. At the same time, provisions must be developed to protect student thesis projects. It was recognized that there is a need to specify uniform standards across the surveys to maximize their combined scientific return.
  9. It was agreed that the next step was the drafting of a white paper which would lay out the basics of the surveys, their science justification and strategies, and other details in order to provide advice/input to NAIC on requirements from this group. A draft table of contents for this white paper was developed along with a preliminary list of volunteers who will take initial responsibility both for drafting the sections and for eliciting input from others. Specific sections were identified as follows: 1. Science justification, survey Lister Staveley-Smith, Jessica Rosenberg, strategies, and requirements Trish Henning, Steve Schneider and Liese van Zee 2. Phase I data products Riccardo Giovanelli, Christian Bruens 3. Detection algorithms, source Jon Davies, Erwin de Blok, Martha Haynes, and Steve Schneider 4. Phase II data products Martha Haynes and Lyle Hoffman 5. Archiving and Data Access Martha Haynes 6. Follow-up Observations Noah Brosch and Wim van Driel 7. Synergies with other surveys Riccardo Giovanelli, Trish Henning, Karen (both ALFA and other) O'Neil and Mary Putman 8. Organization & Outreach Martha Haynes, Karen O'Neil and Alison Peck 9. Funding support (NSF & Euro) Martha Haynes, Wim van Driel and Liese van Zee
  10. An interim steering committee consisting of Riccardo Giovanelli, Steve Schneider, and Lister Staveley-Smith was elected and charged with editting the individual sections to produce a draft white paper to be presented to NAIC by 1 Jul 2003. The mechanisms for establishing a longer term organizational structure will be developed as part of this white paper, and a vote by the current membership will be held on adoption of these mechanisms. The need for openness in the writing of this document was emphasized. The development of a final version of the white paper will be an interative process between the E-ALFA committee and NAIC.
    Chris Salter will serve as interim NAIC Point-of-Contact for E-ALFA.
  11. It was agreed that the next meeting of this group would be targetted for fall 2003 at a location to be determined. The meeting will be held over a weekend, somewhere where expenses can be minimized. NAIC indicated the possibility of providing some travel support to US participants for this next meeting.