Science IPT Report to JAO dd. Nov. 1, 2002 ========================== October 2002 Overview: -------- During October, Science IPT activity again centered on final definition of the ALMA Configuration, and on the Site Infrastructure Review and Transporter Review held in Tucson. There was also much activity on the calibration memo review process. Most of the NA Science IPT, along with Conway from the EU Science IPT, met in Tucson for a face-to-face meeting to refine Level 3 milestones. This meeting was attended by Guilloteau and Japanese Project Scientist Hasegawa. Several NA Science IPT staff telecons were held, and a Project Scientists telecon as well as a joint NA/EU Science IPT telecon was initiated. Van Dishoeck and Wootten, together with Guilloteau, continued to develop the science IPT organization. They also attended the ASAC telecon, and commented upon the ASAC report to the ACC. Anticipated problems: --------------------- With a workshop on receiver specifications occurring during late November, the Science IPT will be preparing to defend specifications it (and the ASAC) have contributed, particularly that on receiver stability. There is concern whether the Level 2 milestone of "Review of tests of calibration strategies on prototype interferometer complete" can be met by December 2004. Although most elements of the prototype interferometer will be in place at the ATF by early 2004, the prototype receivers may not arrive until mid 2005 for testing later that year. The Science IPT believes that this must be done earlier, if these calibration tests are to involve the actual ALMA receivers. Differences between the evaluation receiver interfaces and those of the prototype receiver suggest that substantial work would be required to implement the evaluation receivers for the prototype interferometer. The project should construct a plan for component verification at the prototype interferometer as soon as possible. Configuration: ------------- During this period, the JAO approved the plan delivered by Conway for configurations covering less than 4km in extent to the JAO. Holdaway continued designing the interface from the largest Conway array to the more extended Y+ configurations. A new detailed map of the site, accurate to a few meters, was delivered and Conway began taking into account new details of the terrain to mate the array configuration to it. The required precision on the station coordinates for uv coverage/beam constraint purposes has been quantified, which is needed to convert the JAO report into an engineering specifications document. Conway has also started to address queries in the comments on his report to the JAO, including reconfiguration schemes for 4 antenna moves at a time rather than 3, and accomodation of observations at extreme declination (e.g North of +35 degrees). New visualization tools for the array design have been developed. Calibration: ----------- Butler, as leader of the Calibration Group, organized and moderated an ALMA Calibration Group telecon. Reviews of memos were discussed; minutes of the meeting are available. Several memos will be revised. In particular, Mangum revised ALMA Memo 434 on "Load Calibration at Millimeter and Submillimeter Wavelengths" in light of the reviewers comments. Bacman, together with Guilloteau, has started working on the bandpass calibration. They are considering separating the bandpass calibration into "large scale bandpass calibration" (atmosphere+antenna+receivers) and "fine scale bandpass calibration" (downconverter+digitizers+filters). This way, three steps would be needed for the calibration: a wide-band calibration with one receiver, a wide band calibration with a second receiver (so that the contribution of the common acquisition system can be eliminated by taking the difference), and a narrow (i.e., in user configuration) band calibration. The ATM atmospheric modeling package, written by Pardo, Cernicharo and Sempere, is currently being transformed and cleaned by Pardo for specific use in the ALMA project. The current version performs forward radiative transfer calculations in user-defined bands, providing atmospheric brightness temperatures, opacities and H2O phase factors (deg/mm) for phase correction. It also allows to retrieve water vapor columns from radiometric data from devices like WVR's. The package is being installed in an array simulator, written by Viallefond et al., where it is tested for many different ALMA uses. Improvements suggested after a meeting of the software ADACE group in Grenoble are being implemented. Van Dishoeck started planning a joint ALMA/HIFI calibration meeting in December in Leiden. Site Characterization: ---------------------- A new map of the site, much more accurate than those previously available, was delivered. Rantakyro and Nyman, together with Perez and Rivera, are continuing Delgado's work on atmospheric phase correction by means of the differential analysis of PWV data and by correlating these results with the residual phase noise measured with the site testing interferometer. Holdaway and Otarola have started to investigate whether current models can predict weather and atmospheric conditions at the site at different timescales sufficiently accurate to help planning more efficient and safe site operations. Butler and Holdaway held discussions on site data analysis, particularly on water vapor scale height and on the hygrometer data. Science Software Requirements: ----------------------------- Myers continued to work with the Science Software Requirements group on audit requirements for AIPS++. Mangum also works with this group, as well as project scientists. See computing IPT report for more details. Outreach and Public Education: ----------------------------- Guilloteau, Wiesemeyer, Gueth, van Dishoeck and others organized the third millimeter interferometry school held at IRAM Grenoble September 30-October 5. This school was attended by 52 PhD students and postdocs from many different countries and nationalities. Lectures were provided by Guilloteau and several science IPT members (Gueth, Hills, Dutrey, Lucas, Pety, Pardo, and van Dishoeck), and included talks on ALMA. Van Dishoeck and Shaver continued preparations for the European ALMA Science Operations day on November 8 at ESO. They also continued to investigate possibilities for ALMA EU support within the Framework 6 program, which included a visit to meet with representatives of the program at the European Commission in Brussels, together with Richer, Booth and Cox. Wootten visited with scientists at the Arizona Radio Observatories during his trip to Tucson. Science IPT ALMA Papers: ----------------------- Revised ALMA Memo 434 on "Load Calibration at Millimeter and Submillimeter Wavelengths"