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 deploying its first sites and a fully operational network and data management and analysis center should be online this Summer. 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.
The deployment of GONG has begun as this is being written! The first shipment has arrived on Tenerife, in the Canary Islands, and the "setup" team is at the IAC's Observatorio del Teide. The second instrument has left Tucson destined for the IPS's Learmonth Solar Observatory. The remainder of the instrument team is really busy trying to meet the shipping schedule for the remainder of the sites, and the data team is analyzing the data from the instruments undergoing integration and getting ready for the flood of data. On a parallel front, the NSF has announced an opportunity for community support to assure that the initial GONG data is analyzed in an expeditious manner.
Two meetings directly related to GONG are on the horizon. The 1995 GONG Annual Meeting is being hosted by our colleagues at Stanford University and will be held in conjunction with the SOHO Workshop on helioseismology at the Asilomar Conference Center, Pacific Grove, California April 2-6. On the occasion of the Golden Jubilee Celebrations of the Tata Institute of Fundamental Research ( Bombay, India ) and a total solar eclipse ( which passes within 50 kilometers of the Taj Mahal ) and the deployment of the Udaipur GONG station, a workshop entitled "Windows on the Sun's Interior" will be held October 19-22 in the TIFR.
We've had a bit of coming and going within the project team during December. Mark Trueblood left GONG to join the U.S. Gemini office. Mark had been with the Project since 1990 and played a key role in the development of the project's Data Storage and Distribution System. We are pleased to welcome Susie Davidson, a long-time NOAO employee, "upstairs" from the Electronic Supply Room as the new GONG Administrative Assistant.
The second station left Tucson for Learmonth, Western Australia on January 24th and is expected to arrive at the site about March 10th. Tom Bajerski, Rob Hubbard, Duane Miller, Ed Stover, and Jeff Vernon are poised to head "down under" when it arrives. These first two remote stations will form a three-site "mini network" with the Big Bear station operating in Tucson. This will allow engineering data to be gathered and evaluated, beginning in late March or April, while the remaining stations are deployed over the next several months. It will provide us with our first real data for merging, and science-quality data at that!
The station destined for the Udaipur Solar Observatory in India is currently in certification tests in Tucson, with the objective of completing its deployment before the Indian monsoon season gets under way - sailing schedules and certification permitting. This will be followed by Mauna Loa, CTIO and Big Bear. This would permit full six-site operation to commence in July or August.
The October 30 day was used for the common-site merge test of the Teide versus Big Bear instruments. The November 27 day was used for the common-site merge test of the Learmonth versus Big Bear instruments. These tests indicate that these instruments, sharing a common atmosphere, produce remarkably similar velocity signals in the p-mode band.
The Data Storage and Distribution System ( DSDS ) volume catalog now contains over eight hundred cartridges, and there are over three hundred thousand files in the file catalog. The cartridge count is higher ( or, alternatively, the data volume per cartridge is lower ) than anticipated during the network phase of the project since most of the calibratable data obtained from instrument development and production testing has been recorded during relatively short acquisition intervals (i.e. a few days ).
Accesses ( including `ftp` logins ) to the DSDS's users' machine by non-project GONG members is currently about 3 logins per day. These are primarily 'rlogin' or 'telnet' accesses. 'ftp' access to the anonymous 'ftp' disk has been declining as the use of the World Wide Web has increased. During November, there were over 3000 'http' requests by non-NOAO users, and it is growing rapidly. We have updated the GONG bibliography and placed it on the WWW server, with a modest search capability and links to abstracts maintained by the ADS folks at the CfA, and the SIMBAD folks in Strasbourg. The scientific programs and teams are maintained on the WWW server as well, for broad access and rapid updating.
The anonymous 'ftp' disk, the GONG member accounts, and the 'http' server are on the DSDS user's machine ( helios ). This workstation was recently upgraded to a SPARC20/61 running Solaris 2.4 with more disk space than the workstation that was replaced. The node name ( CWhelios ) and IP address (188.8.131.52) remain the same.
The next DMAC Users Committee (DUC ) meeting is scheduled for mid-March. Previous DUC meetings have lasted four to eight hours and have focused on an assortment of technical issues. In contrast, the March meeting will be a two-day session during which the DUC will perform a DMAC readiness review. This will appraise both the functional and performance aspects of the DMAC. This event is scheduled to coincide with the expected onset of network data. The project expects to have two sites operating in late February: the Big Bear instrument in Tucson and the Teide instrument.
We have completed the processing for the large-scale merge test using artificial data. Comparison of the time series of spherical harmonic coefficients shows that the baseline merge algorithm continues to work well. The merged time series is very similar to the "perfect" time series, with the largest differences appearing around changes in the number of stations observing. We are developing statistical comparisons of the time series consisting of scatter-plot comparisons of the time series amplitude, and regressions. We are also peak finding the spectra and comparing the results of the line parameters.
All of this artificial data work is necessary to develop and test the algorithm and, of course, has the great advantage that the right answer is known. However, the real question is "how does it work on actual data?". We have now used the method on actual data obtained simultaneously from the Big Bear and Teide instruments, and the Big Bear and Learmonth instruments at the farm. The answer is, "it works really well!" The most pleasant surprise is that the merging cleans up the low-l region considerably. We suspect that a large contribution to the low-l noise comes from transient objects moving through the image ( bird, planes, etc ), and these events which rarely happen in simultaneous images are efficiently removed by the merging process.
Note that this test of the merging process is not the acid one, though. These instruments were side by side, no more than 50 m apart and looking through almost identical atmospheres, zenith angles, etc... We have so far demonstrated that the merge can remove instrumental effects, but we have not yet dealt with the terrestrial atmosphere. That opportunity will not come until the instruments have been deployed. We are beginning to look at Taiwanese Oscillation Network data ( courtesy of Dean-Yi Chou ) that was obtained simultaneously with the NSO High-l Helioseismometer. BUT, before the next Newsletter appears, we should have data from the three-site GONG mini-network. Stay tuned!
The careful reader will note that over the last three Newsletters, GONG
has brought together all six instruments at the integration site in Tucson,
gotten them all put together and the first three to an operational status,
and here is the moment [ December 2, 1994 ] when the first instrument was
removed for shipment to the Tenerife site. [ It has now arrived on site,
and is undergoing assembly. ]