MMA Imaging and Calibration Group
Minutes for meeting Tuesday, 11 June 2002 at 4:00pm EDT.
Date: 11 June 2002
Time: 4:00 pm EDT
pm EDT (2:00 pm Socorro, 1:00 pm Tucson)
Phone: (434)296-7082 (CV SoundStation Premier Conference phone 3rd floor).
Past minutes, etc on MMA
Imaging and Calibration Division Page
Agenda
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News. -Wootten
News from my point of view. Report for February-March for ALMA/US Science IPT has been submitted. Time for April-May now, so please send a report of your activities.
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Y+ Configuration - Otarola, Holdaway
Progress; discussion of how to satisfy the ALMA Board Charge.
Please review
the Mark's
proto-plan for Y+.
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Meetings Past and Future - Wootten
Report from ASAC telecon. ASAC Agenda for 5 June. The Charges from the Alma Board are of special interest. Pierre has galvanized the
ASAC into action.
The 3mm Receiver Design review was held last week. Documents may
be read at Sitescape.
The JAO meets this week in Charlottesville, Weds-Fri.
Change request for Band 7.
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Calibration--Butler, Mangum
Sideband gain ratio
ALMA MEMO #393
DSB versus SSB and Bandwith/Sensitivity tradeoff, S.Guilloteau (IRAM/ESO)
2002/05/14
Abstract: The ALMA performances will depend on the receiver design and performances. Conflicting requirements on cost, reproducibility, maintainability,
bandwidth and noise temperature affect the receiver design, and the capabilities of ALMA. This memo reviews the possible tradeoff between receiver
complexity and ALMA performances, considering DSB vs SSB and Bandwidth vs Receiver noise tradeoffs. Realistic scientific applications are
considered. This memo reproduces the numerical results obtained in memo 304 using a different approach. However, the conclusion differ because I also
account for a scheduling strategy in which high frequency observations are made only when the weather allows. Combined with a reasonable assumption
on the distribution of continuum (or dual-line) observations vs single spectral line cases, this assumption favors DSB mixers at high frequencies. DSB
receivers may provide a 10 % advantage above 500 GHz, while SSB receivers would provide a 10 % advantage below that frequency. Analysis of the
Bandwidth/Receiver noise trade-off indicate that reduction of a factor 2 in detection bandwidth can be compensated by improvement by 25 -- 30 % in
Receiver noise.
Discussion on this memo ensued with L. D'Addario.
For those not in the email loop, you can
recover the following files on Stephane's web
page
comments
which may help.
Conclusion and Recommendations
Based on the above discussions, SG suggests to change the specifications of the ALMA receivers to incorporate the following:
- 1. Receivers for band 9 and 10 should be DSB, 4-12 GHz IF mixers.
I agree with this conclusion.
- 2. Receivers for band 3 to 7 should be 2SB, 4-8 GHz IF mixers. This offers the best compromise in performance and saturation level.
I am not convinced about this conclusion.
This discards 2SB 4-12 GHz IF mixers without much
discussion, IMHO.
- 3. An upgrade path starting from DSB mixers with 4-8 GHz IF, and finishing with 2SB 4-8 GHz IF mixers is the only one providing full performance of all receivers at all time.
I agree with this conclusion.
- 4. The correlator must allow sideband separation (by Walsh functions) to be able to use DSB receivers.
I agree with this conclusion.
- 5. DSB receivers which will be upgraded to 2SB must provide a double output.
I agree with this conclusion.
- 6. There is significant sensitivity gain in Band 3 between receivers with Trec = 50 K SSB, and receivers with Trec = 6h*nu/k + 4 K. The later should be kept at least as a very serious goal for ALMA.
I agree with this conclusion.
Issues: Calibration Group Set Up
New Memo 422
(for review).
New Memo 423
(for review).
Other
Lucas' list of simulation requirements to be discussed in
Granada
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Star Wars -- Others?
Any other reviews of the movie?
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Upcoming Meetings - Wootten
May 2 ASAC agenda.
MAY 6-9 Astrophysics
of Life Space Telescope Science Institute Wootten attending
May 24 ESO Committee of Council
June 2 - 6 AAS Meeting Albuquerque
JUN 18-21 Scientific
Frontiers in Research on Extrasolar Planets at Carnegie Institution
See ALMA abstract. Program now online with two ALMA posters:
Session: Ground-based Planet Search Instruments: ALMA
Jean-Francois Lestrade, Observatoire de Paris/LERMA
"Astrometry at millimeter wavelengths with ALMA to search for extrasolar planets or to determine their orbits"
Henry Alwyn Wootten, National Radio Astronomy Observatory
"Extrasolar Planet Research with the Atacama Large Millimeter Array"
JUN 24 AMAC Meeting Munich
AUG 17/24 URSI General Assembly,
Maastricht, the Netherlands Butler attending
AUG 22/28 SPIE Symposium on Astronomical
Telescopes and Instrumentation, Waikoloa, Hawaii. Brown, Wootten attending
SEP 9-13 Winds, Bubbles
and Explosions
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Travel
Oh, always
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