MMA Imaging and Calibration Group

Minutes for meeting Tuesday, 16 Apr 2002 at 4:00pm EDT.

Date: 16 Apr 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 2nd floor).

Past minutes, etc on MMA Imaging and Calibration Division Page

Agenda

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News. -Wootten

News from my point of view.
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Meetings Last Week-Wootten

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Other Items-Wootten

The Debris Disk Meeting was last week in Tucson. Jeff presented the poster. The AAS is meeting in Albuquerque in June. Some plans for the new ALMA backdrop are at stuff.
Calibration Meeting During ALMA Week
Jeff made up anagenda.
Gain Compression
Tony has made some minor revisions to ALMA Memo 401 on saturation in SIS mixers. The revised version is probably not on the ALMA Memos web page yet, so he has put it at anon ftp. He spoke about this at the THz conference; viewgraphs are available. The main change is in section 4 (Discussion), in the section on gain compression of a CW signal in the presence of broadband noise. The conclusions are still the same, i.e., that a mixer can have substantial gain compression from broadband noise but still be linear to a small CW test signal, the small signal gain depending on the broadband noise power. He has also added a paragraph on how to determine the degree of gain compression produced by broadband noise using a small CW test signal.
Stephane has 'been discussing with people around on Tony Kerr memo, and it seems we converged on a common understanding. The "bad" point is that according to the theory, it is almost impossible to avoid receiver saturation with 1 junction SIS mixers below 400 GHz. SSB mixers and slightly narrower bandwidth do help a little bit, but 2 or 3 junction arrays are required to fall below 1 % saturation on a 300 K load.
'Of course, building 2 junction arrays is more risky than a single junction element, and SIS manufacturers are reluctant to do so. Now, since the dual-load system has its own drawbacks (integration time, switching time, plus "has not been proven yet"), what do we do ?
'Bernard Lazareff suggested we might go to the "full scale" solution of implementing a rotating polarizer in front of the receiver (coupled to a load) and make a full turn and measure the receiver output as function of position angle. This would give a sinusoidal output on linear receivers, and a saturated version on receivers presenting any degree of saturation. It would allow to measure the full saturation properties...
'Any other bright idea around ?'

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Project Book Status -- Wootten

Holdway has produced a draft Chapter 13 for comment.
Baars report of Mar 2002 on status: Revisions have been received for Chapters 4, 5, 7, 9, 10 and 12 and v5.5 has been issued in a limited edition.
It is not planned to print this version. Rather, it should be considered an intermediate version towards a more complete Version 6 which we hope to issue during the summer. You are cordially invited to read the PB and in particular to scrutinise those sections which interface to the part of your own responsibility.
Please report any error you discover to Jaap, so we can make corrections.
In particular, an old version of receiver work at OSO somehow made its way into the previously reported version; this has now been fixed.
Version 6 will in particular contain updated versions of the Backend Chapter, based on the PDR during the ALMA Week, and of the Configuration and Calibration chapters.
        4 Antennas (Napier & Andersen)                 2001-02-06
        5 Front Ends (Wild, Payne et al.)              2001-08-01
           Receiver Optics (Carter & Lamb)              2000-11-28
        7 Local Oscillators (D'Addario)                2001-02-05
        9 (Sramek, Baudry, Brundage & Jackson)         2001-01-30
      10 Correlator (Webber, Escoffier, Broadwell,    2001-02-07
           Greenberg & Baudry)
      12 Computing (Glendenning, Raffi and others)    2001-01-29
           (also available as HTML )

S. Oliver is working on uniformity. Version 5.5 containing these chapters will be issued 28 Feb 2002. Version 6, with all updates, will
be out by midyear. Backend will await PDR during ALMA Week for update. Baars will redo Chapter 2.

         3 Calibration
           1. General Calibration Issues (Holdaway &
           Wootten)                                                                                 2001-02-06
1. General Calibration Issues (Guilloteau, Holdaway & Wootten) (alternative as HTML ) 2001-02-06

This chapter will be revised in the light of the June PDR last year. Mark has proposed a plan of action.

2. Calibration Hardware (Payne, Vaccari et
al.) 2001-02-02

2. Calibration Hardware (Payne, Vaccari et al.) (alternative HTML ) 2001-02-02

This needs input from IRAM on the semi-transparent vane, in my opinion. It should have something about the optical pointing telescopes also. It should also include WLM material from Cambridge, IMHO. However, I think it is inevitable that some items mentioned in 3.1 won't be addressed yet in 3.2--FTS for instance.

13 Data Analysis: Imaging Requirements 2000-04-24
(Holdaway & Wootten)
Mark has proposed changes to this chapter.

        14 Site Characterization (PDF)                           2001-08-01
                                            (Radford has revised this .)
        15   Array Configuration (Min Yun)
                                                Conway will be rewriting this.
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Meetings upcoming -- ALMA Week? -- Radford
Schedule as of 11 March

SOME INFO ON LOGISTICS
1. Additional activities
Our Spanish colleagues Jos=E9 Cernicharo and Rafael Bachiller are planning a presentation of the ALMA Project to a wider audience. A public lecture is planned in the Granada Science Museum as well as a late afternoon session for Spanish scientists, engineers and industry. Some of you might be asked to give a short presentation at this last event.
The IRAM Granada staff is helping with the local organisation. We expect to organise a diner in one of Granada's restaurants, Mirador de Morayma with a breathtaking view of the surroundings. Also we will try to arrange for a guided evening tour of the Alhambra.
3. Logistics
IPT leaders are requested to pass the following information to each participant.
The meeting will be held in Hotel Saray in downtown Granada. This is a modern hotel with sufficient conference rooms to accommodate our needs. IRAM has made a block reservation for a special price. Each participant should make his reservation directly with the hotel, mentioning the ALMA Week. The Reservation form is attached. The deadline for the special rate is 21 March.
If you encounter problems with your hotel reservation, get in touch with Javier, who will try to help you.
Hotel Saray Calle Tierno Galvan 4 Granada, Spain
fax number +34 958 12 91 61 phone number +34 958 13 00 09 email hotelsaray@h-santos.es
Prices.- Double room 128,74 EUR ( breakfast buffet included ) single room 103,49 EUR ( breakfast buffet included ) Plus 7% VAT.
Deadline 21th March 2002,
mention: Congreso Astronomia ALMA.
Granada is served by Iberia Airlines; there are several flights daily both from Madrid and Barcelona. =46or some (European) participants Malaga might be an attractive alternative. It is about a 1.5 hour drive from Malaga to Granada. There is also a regular bus connection from Malaga bus station to Granada .

Instituto de Radioastronomía Milimétrica (IRAM)
Avenida Divina Pastora 7, Núcleo Central
E 18012 Granada (Spain)

Granada telephones: (+34) 958 8054 54 (switchboard)
(+34) 958 8054+extension (see below)
Granada fax: Fax (+34) 958 222 363

Rainer Mauersberger +61 mauers@iram.es Station Manager
Javier Lobato +64
lobato@iram.es Administrator

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