I am pleased to announce that Al Wootten has agreed to serve as Project Scientist for the MMA. Al's breadth of experience in millimeter wavelength, and submillimeter wavelength, spectroscopy brings an important perspective and emphasis to the MMA. His long involvement in these fields will allow him to transmit effectively to the project the views and expertise of the U.S. community and to communicate to that community project goals and progress.
I am grateful to Frazer Owen for the dedication he brought to the MMA for many years as Project Scientist. Much of the definition of the capabilities now incorporated in the design of the MMA were the result of Frazer's insight and perseverance. All of us, together with the future users of the MMA, owe him a debt of gratitude.
---R. L. Brown
NAO/NRAO Memorandum of Agreement
On March 23, 1998, the NRAO renewed its Memorandum of Agreement (MOA)
with the National Astronomical Observatory of Japan
(NOAJ) regarding collaboration between the MMA and
LMSA projects. A copy of the MOA follows this article.
The NRAO and Nobeyama Radio Observatory (NRO), a facility within the NOAJ, began discussions on ways the observatories might cooperate in the construction of a large millimeter-wave synthesis radio telescope over ten years ago. Other projects kept those discussions on the back burner for NRAO, the Very Long Baseline Array and the Green Bank Telescope; for NRO, the Subaru Project. In 1995, an MOA between the observatories established a framework for cooperation in site studies. Data obtained by both groups on Mauna Kea and at sites in Chile were to be shared, and the work itself done jointly when appropriate. A joint effort was conducted in configuration studies, with Mark Holdaway joining the NRO group for an extended visit.
The 1998 extension of this MOA continues the site study cooperation, recognizes the importance of sharing developments in technology, pledges cooperation in adherence to safety procedures on the site in Chile, and begins a series of three-way conversations on modes of cooperation between the LMSA and the merger of the MMA and LSA that is now being discussed by the NRAO and ESO.
Funding has been provided by the NSF International Division and by the Japan Society for the Promotion of Science to hold a series of workshops. Two have already been held, the first in Tokyo, March 16-19, 1997, "Millimeter and Submillimeter Astronomy at 10 Milli-Arcseconds Resolution." The second a small technical workshop on identifying compatibility issues, held in the Subaru Project offices in Hilo, Hawaii, December 9-10, 1997, "LSA/LMSA/MMA Technical Collaboration". As the title indicates, this workshop included participants from the European LSA project. The third and final workshop is to be held in conjunction with the URSI General Assembly in Montreal, August 1999, and will also include LSA participants.
New Whitepaper
Accurate Amplitude and Flux Calibration of the MMA
M. S. Yun, J. Mangum, T. Bastian, M. Holdaway
National Radio Astronomy Observatory
J. Welch
University of California, Berkeley
Abstract: The 10% amplitude calibration accuracy achievable with the current standard calibration techniques may be sufficient to produce images with dynamic range of less than or equal to 103, but achieving a dynamic range of 104 or higher with the MMA requires better than 1% accuracy in amplitude calibration. A self-calibration technique may be applied to improve images, but it may not be possible in all cases. Therefore, an emphasis is given to achieving accurate initial calibration. Multi-transition spectroscopic studies and multi-array synthesis also require high accuracy in absolute sense as well.
The conventional ``chopper wheel" and a two temperature load method for amplitude and flux calibrations are examined. The two temperature load calibration offers a potential to achieve the 1% accuracy in amplitude and flux calibration, but it is technically challenging. In comparison, the chopper wheel gain calibration and astronomical flux calibration cannot provide better than 5% accuracy. Whether the more complex two temperature load system is justifiable for the MMA may ultimately dependent on how well the radiometric phase correction will work. Several other relevant issues including establishment of astronomical flux standards are discussed, and engineering goals are identified.
You can view an HTML version of this whitepaper, also MMA Memo 211,
at
http://www.alma.nrao.edu/memos/html-memos/alma211/memo211.html
or a PostScript version at
http://www.alma.nrao.edu/memos/html-memos/alma211/mma211.ps.gz
MMA Site Recommendation
You can view a PDF version of this document at
http://www.mma.nrao.edu/library/management/siterec/brown598.pdf
Project Recruitment
New MMA Memos
This report has been submitted to the NSF by AUI.
It is a 52 page report describing in detail site
evaluation process, the atmospheric testing program,
and ancillary considerations that led to the site
recommendation.
or a PostScript version at
http://www.alma.nrao.edu/library/management/siterec/brown598.ps
Now that funding as been awarded, the MMA is seeking to hire
an additional fourteen people to work on the project.
You can find advertisments for these positions on the NRAO
Web pages at
http://www.cv.nrao.edu/~tschlemm/public/job.html.
Since the last MMA Newsletter, the following MMA Memos
have been posted. You can find a list of all of the
MMA memos at:
http://www.alma.nrao.edu/memos/index.html
| 214 | Hybrid arrays: the design of reconfigurable aperture-synthesis interferometers | A. Webster | 6/98 |
| 213 | Frequency Band Considerations and Recommendations | A. Wootten, L. Snyder, E. van Dischoeck, F. Owen | 5/98 |
| 212 | Optimization of an Array Configuration with a Donut Constraint | L. Kogan | 5/98 |
| 211 | Accurate Amplitude and Flux Calibration | M.S. Yun, J. Mangum, T. Bastian, M.Holdaway, J. Welch | 5/98 |
| 210 | Radiometric Phase Calibration | C.L. Carilli, O. Lay, E.C. Sutton | 5/98 |
| 209 | 183 GHz radiometric phase correction for the Millimeter Array | O.P. Lay | 5/98 |
| 208 | Polarization Calibration of the MMA: Circular versus Linear Feeds | W.D. Cotton | 5/98 |
| 207 | Wide Bandwidth, YIG-Based Sources and Modern Frequency Multipliers for the MMA Local Oscillator System | R.F. Bradley | 5/98 |
| 206 | AN INTEGRATED SIDEBAND SEPARATING SIS MIXER FOR 200-280 GHz | A. R. Kerr, S.-K. Pan, H. G. LeDuc | 3/98 |
| 205 | A Tunerless SIS Mixer for 200 - 280 GHz with Low Output Capacitance and Inductance | A. R. Kerr, S.-K. Pan, A.W. Lichtenberger, H. H. Huang | 3/98 |
| 204 | Digital Filtering in the MMA | Ray Escoffier, John Webber | 3/98 |
| 203 | Forced Air Cooling at High Altitude | Jingquan Cheng | 3/98 |
| 202 | Optimization of an Array Configuration with a Topography Constraint | L. Kogan | 3/98 |