Report for ALMA Calibration and Imaging November 2002 NA Progress Report Overview Milestones Achieved During November, the Science IPT delivered the ICD for the inner 172 antenna pads of the ALMA Configuration. This was considerably altered from the design approved by the JAO on 1 October and met a Level 2 Milestone for delivery of the iner configuration. Work commenced on design of a long baseline part of the plan compatible with this new inner portion, A Level 3 Milestone for December 2002 will produce a draft of requirements document ready for reviews. Final testing for one of the two amplitude calibration devices being considered for ALMA, the subreflector dual load device, commenced at BIMA. A plan for initial testing of the other device, incorporating a semi-transparent vane, was discussed at a calibration telecon, at which progress on the memo review process (particularly that on the theory of the semitransparent vane system) and other issues was also discussed. The Science IPT arranged the agenda, minutes and telecon for the ASAC on 6 November. Several Science IPT staff telecons were held, regular Science IPT leaders telecon continued, and a further joint NA/EU Science IPT telecon was held. Guilloteau and Wootten attended the ALMA Front-end specifications and requirements meeting and the Back End LO design meeting in Charlottesville. Further small changes in the list of Level 3 and 4 milestones were made. Anticipated activity in the next quarter Calibration Milestones There is one Level 3 scheduled for completion in December 2002. A draft of the calibration requirements document will be produced for reviews. This is a modification of chapter 3 of the Project Book, complete with scientific examples for drivers. The Project Scientist issued a call to the ASAC during November to provide some examples for this exercise. A Level 2 Milestone will be reached during February 2003. This will follow the results of the Level 3 Milestone above to include completion of a review of calibration requirements with science examples complete. This includes: phase, amplitude, bandpass, polarization, antenna location, illumination offset, pointing, focus, delay, opacity, and decorrelation correction. Two milestones during this quarter lead to the expected June 2003 Level 2 Milestone of the review of how calibration requirements trickle down to instrumental specifications, including special calibration devices. The first Level 3 Milestone to be achieved in January will deliver to the project the ATM atmospheric modeling software being developed by Juan Ramon Pardo. This activity is in its final stages now. A related Level 3 Milestons dur in March 2003 will deliver draft specifications for calibration devices for reviews. There will be separate specs for devices to be tested on the ATF interferometer. Other Level 3 and 4 Milestones lead toward the completion of the calibration strategy for ALMA, a Level 2 Milestone scheduled for September 2003. In March 2003, a draft of the bandpass calibration plan will be presented, following publication and review of an ALMA Memo describing limitations of bandpass calibration using astronomical sources scheduled for February 2003. Also in March, a draft of the phase calibration plan will be produced (Level 3). A further March milestone will be the production of the amplitude calibration plan, including total power calibration of ALMA. A further Level 3 milestone will review the SSR plan for all phase calibration techniques, for completion in March. Other items scheduled for March include a draft of the antenna location determination plan, a draft of the delay calibration plan, a draft of global antenna pointing plans, reference pointing plans, focus calibration plans, and a draft of an operational model for calibration, including ideas on sequence of moves and calibrations, dynamic scheduling, and number of antennas needed in 'calibration subarrays' Leading to the September 2004 report on WVR strategies (Level 2), a December 2002 Level 3 Milestone will present a draft document on technical aspects of the WVR, along with the Front End IPT. By March 2003, the Science IPT will prepare a draft plan on how to achieve ACA goals (flux-recovered imaging at all ALMA bands). Configuration New data on the terrain at Chajnantor spurred revision of the array configuration to better conform to the landforms on the site. The site characterization group received the new aerial photographs and an autocad file of the site contours from the Chilean company Aerotop. However, no digital elevation model (DEM) was included in the materials provided. Otarola and Holdaway worked to turn the contour information into a DEM which could later be turned into a mask for pad placement in the array optimization algorithms. Also, Angel and Holdaway studied the details of the new DEM and determined it was of far superior quality to the old one, but that the coordinates showed a systematic offset from the UTM frame. Communications with Aerotop indicated that the coordinates were in fact not UTM and that the coordinate offset changes slightly over the image. This resulted in a clear understanding of site topography. Large offsets (>100 m) which were coherent over 1 km scales, but which varied over the 5 km x 5 km DEM, were found between the new and old DEM. These offsets are attributed to errors in the old DEM. As the extended Y+ configuration has only the old DEM to guide its antenna placement, pad misplacement (ie, onto the sides of gullys or other steep terrain) of the order of 100 m is expected to be common, and this must be sorted out in the surveying process. Status of Y+ Configuration Holdaway worked on finalizing the Y+ configuration, adjusting the mask for terrain shadowing, inserting the new DEM mask in the center of the old Y+ mask, and removing some hard-to-access regions. The Y+ configuration now has 42 antennas moved out from Conway's largest configuration, the highest resolution configuration is optimized first, and the intermediate configurations are figured out after the fact by moving 4 antennas each day. More attention is being paid to the high resolution capabilities of the array. Calibration Wootten, temporarily backing up Butler, on family leave, organized and moderated a ALMA Calibration Group phone telecon. Discussion focussed on the current planning for deployment of a semitransparent vane at the IRAM 30m duriing the summer of 2003 and tests which will be made there. Reviews of Memos were discussed; no review has yet been received of Memo No. 423 on the theory of the semitransparent vane, so a call for reviews was urgently renewed. Wootten provided Minutes of the meeting. Site Characterization Radford and Nyman held an organizational meeting and constructed a proposed plan for construction phase activities. Radford spent much of the month at the site upgrading, repairing and testing equipment--this included replacement computers for the 225 GHz tipper and the Site Testing Interferometer, installation of two new surveillance cameras, reinstallation of the seismometer, restarting the lightning detector, installing updated radiosonde software and diagnosing and repairing submillimeter tipper at Sairecabur. Radford also observed with the SAO team at Sairecabur. Imaging Holdaway has added 1/f noise to the total power atmsopheric simulations, which observe in both beam switched and on-the-fly modes. Holdaway has made a preliminary study of a fast switching decorrelation correction, in which the atmospheric phases measured on the calibrator are used to estimate not only the mean phase correction to apply to the target source visibilities, but also the degree of decorrelation to correct the amplitudes by. This work indicated that the correction worked well to correct the flux scale and recover the correct peak flux, but that it increased the image noise level. More detailed studies will follow. Science Software Requirements Myers worked on responding to comments on his work with the Science Software Requirements group on audit requirements for aips++. Mangum also works with this group, as do the project scientists. Science IPT ALMA Papers Appendix A to the ASAC Report presented October 2002 was 'Report of the ASAC Subcommittee on Site and Stringency' which included efforts of the Science IPT Site Characterization Group, including undergraduate summer student Selby Cull. Science IPT Meetings during November, along with topics discussed: 5 November 2002 News-- ACC Meeting, ASAC Meeting and Report, FE/BE Reviews, Milestones v?. Science IPT Telecon 19 November 2002 News-- Science IPT Organizational Chart, Milestones, Subgroup Reports, Upcoming Meetings 26 November 2002 News-- FE/BE Reviews, Total Power on ALMA, Calibration discussion ASAC Telecon 6 November 2002 (ASAC Report to ACC distributed to Project and to the Public)