The Global Oscillation Network Group (GONG) project is a community-based activity to develop and operate a six-site helioseismic observing network for at least three years, to do the basic data reduction and provide the data and software tools to the community, and to coordinate analysis of the rich data set that should result. The project is currently looking forward to an operational network and data management and analysis center in 1994. GONG data will be available to any qualified investigator whose proposal has been accepted, however active membership in a GONG Scientific Team will allow early access to the data and the collaborative scientific analysis that the Teams have already initiated. The GONG Newsletter provides status reports on all aspects of the project and related helioseismic science.
GONG continues to make good progress towards full scientific operations with the Data Team moving into the AURA building on Warren Avenue, the Instrument Team in the process of moving the six field stations to the integration site on the shores of Lake Rillito, the Management Team preparing for a peer review of the Production and Deployment Plan, and members of the international GONG community having concluded a very successful week-long tutorial workshop hosted by the Physical Research Laboratory at Ahmedabad, India. The Annual GONG meeting will take place in Tucson this year, 19-21 April.
The Instrument Team continued work on the production of the final field instruments, testing and debugging hardware and software at the prototype site, and observing with the prototype. The latter activities share the prototype on a six week/two week schedule respectively. This winter's heavy rains delayed a planned move of the six field instrument shelters from their present location near the NOAO shops and offices to a good-horizon site a few kilometers away on the University of Arizona Agriculture Department's farm. This move should take place in a few weeks, weather permitting. Interior fitting of the shelters (electrical and carpentry work) is finished.
On the optics front, the major current production activity is assembly of the ten Lyot filters. Several front entrance windows were delivered by the vendor, and two were tested using the prototype instrument. The results showed no detectable fringes or irregularities which were problems that affected calibration quality with earlier windows. Some of the windows have a large number of pinhole defects, and the effect of these is being tested and evaluated. The 5 A prefilters were a production challenge for the vendor. For stability reasons, an ion-assisted coating was specified, but it turned out to be hard to deposit uniformly on Schott filter glass. The design has been changed to put the coating on clear glass and to mount the Schott filter glass separately in place of what was originally a clear glass window. Production of the interferometers continues to run behind schedule. The vendor experienced trouble contacting together the two halves of the polarizing beam splitter cube with sufficient alignment precision. A fixture has been built which has solved this alignment problem, but now the contacting is not working well. The solution will probably be to use an optical epoxy to join the cube halves. The project has always been nervous about this from the standpoint of long term stability, but the interferometer that has been in use for more than a year was joined this way and shows no sign of change. The waveplates manufactured for the interferometer have been tested by both the vendor and us with good agreement.
Good progress has been made toward final software for instrument control and data collection. Comparison of ephemeris calculations of the solar position with actual pointing coordinates has allowed alignment errors to be located and quantified, and the instrument may be pointed at the Sun with an accuracy of better than one pixel without the guider being active.
While it is not necessary to do any flat field corrections to measure velocities, it is helpful to have a good intensity flat field calibration when defining scattered light and locating the limb. A procedure has been developed that works using a small-angle scatter plate in front of the objective to define high spatial frequency components of the instrument response function, while low spatial frequency components are determined from an image of the entrance pupil. Either of these approaches alone did not work well, but together the results are very good. We also settled on a magnetograph observing scheme that gives results quite comparable with daily magnetograms from Kitt Peak (except for spatial resolution).
The Data Management Analysis Center (DMAC) Team is working on the preparation of a new version of GRASP that is to be released in February. Significant progress was made in extracting the scattering point spread function from intensity images and in understanding how this correction can be efficiently applied to the GONG data. The development of the multi-site merging capability continued with the evaluation of alternative merge strategies and the generation of a new artificial dataset.
Seven members of the DMAC team moved from the main NOAO building to the AURA building on 19 November (about ten days ahead of schedule!). The move went well with many computers up and on the network the next day. Prior to the move, the interior of the building was redecorated: ceiling insulation and ceiling tiles were replaced; walls were painted; carpets were replaced with floor tiles; FDDI and Ethernet networks were installed.
Late in the summer of 1992, the instrument team resolved many of the outstanding optical problems. Since then the volume of calibratable data produced by the instrument has increased dramatically as has the production of data products from the raw data. During the last quarter, the following prototype data days were calibrated: 31 August; 25, 30, 31 October; 1-8, 21, 24-27 November. Ten-minute averages of calibrated velocity, modulation, and intensity images were produced for 21 July; 30, 31 August; 5, 6 September; 30 October; 3-8, 21 November. l- spectra were produced from the calibrated velocity images for 30, 31 August; 25 October; 1-8 November.
A prototype implementation for most aspects of the DSDS has been assembled; many components are functional including the cartridge library and the cartridge catalog which are used routinely to support the prototype data reduction activities. The development of the file catalog, the DSDS operator interface, various report generators, and the distributable catalog and associated query software is proceeding rapidly.
The second meeting of the Data Management Analysis Committee Users Committee (DUC) was held on 2 October. The meeting was attended by Tuck Stebbins, Tim Brown, and Todd Hoeksema and by several members of the GONG project, and topics included the prioritization of DMAC development tasks, low frequency and steady flows reduction, magnetograms and rectangular pixels, m-averaged peak finding, the interface to the DSDS, and GONG/SOI interoperability. The third meeting took place on 29 January.
GONG project management recently produced an update of the detailed plan for the production and deployment of the six field stations. This plan calls for the full field network to begin operations in December 1994. The effort remaining has been broken down into small enough work packages to accurately model the problem, totaling approximately 1500 tasks. On 20 November a group of five NOAO managers, familiar with the practical realities of project management in the local environment, reviewed the planning process and tools, the resulting production strategies and tactics, the conclusions reached, and strengths and weaknesses of the draft plan itself. The project will use this feedback in its ongoing management efforts and in its presentation of the updated plan to a formal management review in early February 1993 to be chaired by Bob Noyes.
The Physical Research Laboratory, at Ahmedabad, Indiathe parent organization for GONG's Udaipur sitehosted an international tutorial workshop 4-8 January, organized by Arvind Bhatnagar, Kumar Chitre, and Juri Toomre. There were 39 participants from thirteen institutions, and the lecturers included Tim Brown, Jrgen Christensen-Dalsgaard, Douglas Gough, Frank Hill and Juri Toomre.
The annual GONG meeting will be held in Tucson this year, at the Ramada Downtown, located at 475 North Granada, 19-21 April. Hotel registration forms will be enclosed with the forthcoming GONG Newsletter. Reservations must be received by the hotel no later than 19 March 1993. The hotel telephone number is (602) 622-3000, and their facsimile number is (602) 623-8922.