From soliver at tuc.nrao.edu Wed Jan 2 14:16:39 2002 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Wed, 2 Jan 2002 12:16:39 -0700 Subject: [asac] [almanews] ALMA Memo 401 Released Message-ID: ALMA Memo #401 Saturation by Noise and CW Signals in SIS Mixers A. R. Kerr (NRAO/Charlottesville, VA) 14 December 2001 Keywords: Superconductor-Insulator-Superconductor mixers, saturation, gain compression, dynamic range. In ALMA Memo 321, Plambeck points out that saturation (gain compression) is likely to be a significant factor limiting the calibration accuracy of ALMA observations. In this memo, saturation by broadband noise and CW signals is analyzed for representative SIS receivers operating at different frequencies. Many SIS mixers in current use are expected to exhibit a significant degree of gain compression when connected to a room-temperature source. Previous analyses of saturation in SIS mixers have applied only to CW signals. To analyze saturation by noise, the statistics of the output voltage are derived from those of the input signal. A single constant, applicable to all SIS mixers, is determined experimentally by fitting the predicted CW gain compression curve to measured data. View a pdf version of ALMA Memo 401. http://www.alma.nrao.edu/memos/html-memos/alma401/memo401.pdf _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From soliver at tuc.nrao.edu Wed Jan 2 16:24:41 2002 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Wed, 2 Jan 2002 14:24:41 -0700 Subject: [asac] [almanews] ALMA Memos 403 and 404 Released Message-ID: ALMA Memo #403 Fast Switching Phase Correction Revisited for 64 12 m Antennas M.A. Holdaway (NRAO/Tucson) 2001/12/17 Fast switching phase calibration has not been investigated for the ALMA telescope since ALMA has been defined as 64 12 m antennas. Furthermore, the logic chain which picked the optimal calibrator in past investigations was approximate. In order to better understand the requirements which are placed on the current ALMA design by fast switching, we have rewritten the fast switching simulation code in AIPS++, including a more complete optimization with fewer assumptions, using updated sensitivity, antenna slewing, and atmospheric information. We find that when the observing frequency is matched to the phase stability (ie, high frequency observations are always carried out during the most stable phase conditions), the Chajnantor site is good enough to permit fast switching observations of the expected frequency range (ie 30 to 950 GHz) to succeed with high efficiency. Typical observing efficiencies, including both time lost to the phase calibration cycle and decorrelation losses, range between 0.80 and 0.90 for sources above 45 deg elevation angles. The observing efficiency decays very gently at lower elevation angles, with a typical efficiency of 0.70 at 20 deg elevation. The extra sensitivity provided by 64 12 m antennas does not help as much as might be expected with fast switching because the time spent integrating on the calibrator is very small compared to the entire cycle and is a moderately small portion of the calibration phase of the cycle. The 1.5 s delay due to changing frequencies is pretty well matched to the slew times for typical objects. The slew profiles provided by Vertex are sufficient. The residual phase errors resulting from fast switching will cause baseline-dependent decorrelation. Some minor algorithmic work should proceed on fixing this decorrelation. It seems likely that the phase information gleaned from observing the calibrator will be sufficient to accurately estimate the decorrelation correction on a per baseline basis. View a pdf version of ALMA Memo 403. http://www.alma.nrao.edu/memos/html-memos/alma403/memo403.pdf Download a postscript version of ALMA Memo 403. http://www.alma.nrao.edu/memos/html-memos/alma403/memo403.ps ____________________________________________________________________________ ____________________ ALMA Memo #404 Atmospheric Dispersion and Fast Switching Phase Calibration M.A. Holdaway (NRAO/Tucson) and J.R. Pardo(Inst. Estructura de la Materia Dpto. Fsica Molecular Serrano) 2001/12/19 The differential atmospheric phase of an interferometer has an approximate linear variation with frequency up to about 300 GHz. However, near absorption lines, and especially in the sub-millimeter wavelength atmospheric windows where the absorption lines are very strong and always near, the assumption of a non-dispersive atmosphere breaks down markedly. We present simulations performed with the ATM atmospheric transmission model (Pardo et. al, 2001), tailored to the specific observing conditions at the Chajnantor site and we propose specific observing strategies to employ for the ALMA telescope. While the *absolute* wet and dry dispersive phase (ie, the part of the phase which deviates from the phase which is linear with frequency) can be very large through the atmosphere, the *differential* dispersive phases (ie, the difference in the dispersive phases above two antennas paired in an interferometer) are much smaller. We find that the differential dry atmospheric dispersion is essentially zero at all frequencies of relevance to the ALMA for the expected pressure fluctuations within the area covered by the interferometer. The differential wet dispersion can be large enough to be of concern in the 350, 400-500, 650, and 850 GHz windows. In fast switching, we expect to observe a calibrator source at 90 GHz and scale the phase solutions to the target frequency. If time dependent wet and dry phase errors occur, ALMA has a potential problem because the wet and dry phases will scale differently with frequency in the sub-millimeter windows. Separation of the phases into wet and dry components may be possible, but this sounds very messy and uncertain, requiring multi-frequency calibrator observations or associated radiometric measurements and good atmospheric modeling. If dry phase errors are negligible and the phase errors can be split between electronic and atmospheric components, then the frequency-dependent phase scaling factor can be determined by a model such as ATM to accurately account for the dispersion. As we do not have a good handle on the magnitude of dry phase errors, we cannot estimate the success of such a strategy. A worst case scenario would be to assume that the dry phase errors are larger than the dispersive phase. By using the ratio of the frequencies to scale the phase solutions to the target frequency, we correct for the dry errors, but miss the differential wet dispersive phase. The differential wet dispersive phase will manifest itself as some fraction of the phase errors which are just not calibrated. These residual phase errors will be larger during unstable atmospheric conditions, at the edges of the transmission windows, and on longer baselines. During the 10th percentile atmospheric stability conditions, on baselines of 1000 m, the fast switching residual phase will be dominated by the uncompensated dispersive phase at the edges of the sub-millimeter windows (ie, at frequencies where the transmission is less than 50% of the peak transmission for that window). This will markedly affect the ability of fast switching to correct atmospheric phase errors for sub-millimeter observations. Longer baselines could be accommodated by observing during better conditions or by observing near the window center where the dispersive phase is close to zero. If dry phase fluctuations are smaller than the dispersive phase, as will almost certainly occur far from the window centers, the dry phase can be ignored and a correct accounting for the dispersive phase from a transmission model such as ATM can be applied. If radiometric phase correction were used, a differential dry delay could be quite damaging for sub-millimeter observations. However, if the dry phase were very small, the differential dispersive phase could be calculated from transmission models and applied to correct the phase more perfectly, just as in fast switching with a negligible dry term. View a pdf version of ALMA Memo 404. http://www.alma.nrao.edu/memos/html-memos/alma404/memo404.pdf Download a postscript version of ALMA Memo 404. http://www.alma.nrao.edu/memos/html-memos/alma404/memo404.ps _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From soliver at tuc.nrao.edu Mon Jan 7 16:33:42 2002 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Mon, 7 Jan 2002 14:33:42 -0700 Subject: [asac] [almanews] ALMA Memo 405 Released Message-ID: ALMA Memo #405 Unaddressed Issues for ALMA Configurations M.A. Holdaway (NRAO) 2002/01/07 I am reminding the configuration designers about a few issues which have apparently been put aside while more important issues were being addressed. These include the requirement of multiple compact configurations to adequately cover the entire observable declination range, the design of other N-S stretched configurations for extreme declination sources, and possibly a global N-S elongation factor for the base configurations. Address- ing the need of multiple compact configurations for extreme declination sources, which is required for the observation of about 30% of the sky visible from Chajnantor, will likely add more antenna stations to the configuration design. Download a postscript version of ALMA Memo #405 http://www.alma.nrao.edu/memos/html-memos/alma405/memo405.ps View a pdf version of ALMA Memo #405. http://www.alma.nrao.edu/memos/html-memos/alma405/memo405.pdf _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From awootten at NRAO.EDU Fri Jan 11 14:55:29 2002 From: awootten at NRAO.EDU (Al Wootten) Date: Fri, 11 Jan 2002 14:55:29 -0500 (EST) Subject: [asac] Minutes; January Meeting Message-ID: <200201111955.OAA19888@polaris.cv.nrao.edu> Dear ASAC Member: Happy New Year! I append Peter's minutes of last month's meeting. Please send any corrections or additions to me. The agenda for next Wednesday's meeting is under construction. The next ASAC teleconference will take place on Wednesday 16 January at 14:30 UT. In particular, we should discuss the next face-to-face meeting. Clear skies, Al ALMA Science Advisory Committee Teleconference, 5 December 2001 Draft Minutes Participants: R. Bachiller, G. Blake, L. Bronfman, P. Cox, R. Crutcher, N. Evans, S. Guilloteau, M. Ishiguro, R. Kawabe, J. Mangum, M. Rafal, J. Richer, S. Sakamoto, P. Schilke, P. Shaver, K. Tatematsu, E. van Dishoeck, M. Walmsley, C. Wilson, A. Wootten, M. Yun The proposed agenda was adopted, and the minutes of the previous meeting were accepted. 1. Results of AEC Meeting M. Rafal summarized the recent AEC meeting in Grenoble. A formal document from the AEC is due to the ACC by 1 February, taking into account budget constraints. He said that the scope remains essentially that of the bilateral project, as given in the Project Book. J. Richer asked whether ASAC input will be required, and M. Rafal replied that the AEC will approach the ASAC if required. 2. Status of ASAC Charter It was noted that the ASAC charter is on the ACC agenda for its teleconference of 11 December. A. Wootten asked whether there are any changes to be suggested by the ASAC. Various possible issues were raised, including the frequency of meetings, the size of the ASAC, the possibility of rotation, and the status of Japanese representation, but on all issues it was agreed to leave the charter at present as it is, and wait to see the ACC reactions. 3. U.S. Funding Status A. Wootten mentioned that the various necessary milestones for U.S. funding of the construction phase (including acceptance by the President) have been passed successfully. 4. Next ASAC Face-to-Face Meeting The next face-to-face meeting will take place on 19-21 March. A. Wootten will contact Y. Fukui about plans. 5. Configuration Plans A. Wootten reported that a group is presently at Chajnantor looking at the site with different configuration plans. Next week a group of engineers will assess the feasibility of these plans. A Design Review will take place in Socorro on 24-25 January. 6. AOB P. Shaver reported the good news that UK entry into ESO has now been formally agreed, to go into effect on 1 July 2002. S. Guilloteau said that news about the European prototype antenna would soon be available. M. Ishiguro said that there was no news on the Japanese 12-m prototype antenna. 7. Next teleconference The next ASAC teleconference will take place on Wednesday 16 January at 14:30 UT. From soliver at tuc.nrao.edu Mon Jan 14 16:26:12 2002 From: soliver at tuc.nrao.edu (Stacy Oliver) Date: Mon, 14 Jan 2002 14:26:12 -0700 Subject: [asac] [almanews] ALMA Memo 400 Released Message-ID: ALMA Memo #400 A Proposal of Optimized Configurations for the ALMA Frederic Boone (Observatoire de Paris) 2002/01/14 Keywords: configurations A set of optimized configurations is presented. It results from the application of two previous papers dedicated to the design of interferometer arrays in general: the optimization of the locations of the antenna pads is performed using the Antenna Position Optimization software introduced in Boone (2001) and conforming to the analysis developed in Boone (2002). The constraints and the specifications are taken from the recommendations made at the Preliminary Design Review of February 2001. The feasibility of a design based on an inverse approach is demonstrated. The locations of the pads are determined by the scientific goals translated in terms of target distributions of samples. The method used allows, at the same time, to control the quality of the distribution of samples (shape and mininimum density of samples) and to take into account the constraints and specifications (topography, number of pads, range of resolutions). The computing time required to get a complete array is of about 3 hours on a 1 GHz PC. Rather than a fixed geometrical concept the design can therefore be seen as a numerical solution that can be re-computed for any change in the specifications or constraints. Download a zipped postscript version of ALMA Memo 400. http://alma.aoc.nrao.edu/memos/html-memos/alma400/memo400.ps.gz View a pdf version of ALMA Memo 400. http://alma.aoc.nrao.edu/memos/html-memos/alma400/memo400.pdf ****Please note that this pdf is a large file. If you have difficulties opening the file, download the file to your local machine and open it from there. To download a PDF file to your computer, go to http://alma.aoc.nrao.edu/memos/html-memos/abstracts/abs400.html, and right click on the "view a pdf" link. When the drop box appears, select "Save Target As..." (Explorer) or "Save Link As..." (Netscape). When prompted, identify the location and file name where you want to save the PDF file. You can then open the PDF file directly from your hard drive, using Adobe Acrobat or Acrobat Reader. _______________________________________________ Almanews mailing list Almanews at listmgr.cv.nrao.edu http://listmgr.cv.nrao.edu/mailman/listinfo/almanews From awootten at NRAO.EDU Tue Jan 15 09:03:09 2002 From: awootten at NRAO.EDU (Al Wootten) Date: Tue, 15 Jan 2002 09:03:09 -0500 (EST) Subject: [asac] The ALMA Observing Tool: Concept and Prototype Message-ID: <200201151403.JAA26281@polaris.cv.nrao.edu> The draft document: "ALMA Observing Tool: Concept and Prototype" by Scott and Bridger has been posted for comment at: http://www.alma.aoc.nrao.edu/development/computing/docs/memos/computdrafts.h tml (The above line might have been wrapped by a mailer - it must be a single line in your browser). All comments on this document are welcome - and all comments will receive a written response. Since this document will be revised before final review, it is OK if you only have time to make "big picture" comments for this revision. Note that the observing tool will be the major software point of contact between observers and ALMA, so it is particularly important that we get comments from potential users of ALMA. Please send your comments directly to Steve Scott (scott at ovro.caltech.edu) by February 8. It is a convenience if your comments are in the form: p.16 An interesting comment about something on page 16. Cheers, Brian Glendenning From awootten at NRAO.EDU Tue Jan 15 14:30:19 2002 From: awootten at NRAO.EDU (Al Wootten) Date: Tue, 15 Jan 2002 14:30:19 -0500 (EST) Subject: [asac] Agenda etc for 16 Jan telecon Message-ID: <200201151930.OAA23679@polaris.cv.nrao.edu> For complete agenda with hyperlinks to critical documents please see: http://www.cv.nrao.edu/~awootten/mmaimcal/asac/asacjan02agenda.html ALMA Science Advisory Committee Agenda for ASAC Telecon Weds 16 January 2002 Conference Date: 16 January 2002 (Wednesday) Here's the dial-in information for the telecon: CALL TIME: 09:30 AM EASTERN Daylight TIME 1430 Universal Time CALL DATE: 16 Jan 2002 (Wednesday) DURATION: 1 hr USA Toll-free Number 888-390-0867 USA Toll Number: +1-630-395-0147 PASSCODE: 14799 LEADER: Al Wootten Agenda items so far include: Old Business (1) Please approve the minutes of the December Meeting. New Business (1) Project Definition to be Presented to ACC (Rafal, Kurz) (2) Prototype antennas: progress New funding from MEXT (Ishiguro) Vertex antenna status (ATF webcam) (Rafal) ACE antenna status (Kurz) (3) Plans for Configuration Design Review (Wootten, Guilloteau) Please see announcement. Also note that the project plans an ALMA Week in Granada 23-27 April; details are under discussion. (4) Status of ASAC Charter (Blake, Evans) This came up at the ACC meeting . (5) Chile Status (Brown) Letter referred to in Chile Status text. (6) Discussions on the Regional Science Centers (Cox, Evans) (7) Results from PdBI AIPS++ tests (Kemball) (8) Next ASAC face-to-face meeting (Fukui, Blake) 19-21 March in Japan, with a science day on 21 March. Please see message from Japan. (9) Next teleconference (Blake) The next teleconference is nominally 6 February at 1430 UT. From tetsuo.hasegawa at nao.ac.jp Wed Jan 16 07:22:57 2002 From: tetsuo.hasegawa at nao.ac.jp (Tetsuo Hasegawa) Date: Wed, 16 Jan 2002 21:22:57 +0900 Subject: [asac] March ASAC Meeting - Hotel Booking Message-ID: Dear ASAC members, As you know, the next ASAC face-to-face meeting will be held on March 19 - 20 at the National Astronomical Observatory (NAO) headquarter in Mitaka. March 21 is a Japanese holiday, celebrating the equinox, and we will have a "ALMA Science Day" event at the National Museum of Emerging Science and Innovation located at the waterfront of Tokyo. For the participants of the meeting, we have made a block reservation of hotel rooms near the JR Mitaka station. ROYNET HOTEL MUSASHINO Phone +81-422-36-0022, FAX +81-422-36-0020 Room rate JPY 9,000 per night (breakfast not included) + Tax From Narita, you can take JR Narita Express (NEX) to Tokyo (60 min), and change to JR Chuo Line to Mitaka (30 min). The hotel is 5 min walk north from JR Mitaka station. To get NAO, you can take a bus or taxi from the station. ALMA-J office is happy to make the logistical support. For this purpose, we would like to ask you about your plan for the Tokyo ASAC meeting. Please fill in the form below and send it to Ms. Sachiyo Ueshiba by February 4. With best, Tetsuo Hasegawa, ALMA-J Office -------Please cut here and send by Monday, February 4 ---------- To: Ms. Sachiyo Ueshiba, ALMA-J Office e-mail: sachiyo at nro.nao.ac.jp FAX: +81-422-34-3764 Name (Family, First): e-mail: Institute: <<>> Do you plan to attend the ASAC meeting in Tokyo? March 19: Yes/No/TBD March 20: Yes/No/TBD March 21: Yes/No/TBD <<< Hotel Booking Request >>> Do you need booking at Roynet Hotel Musashino?: Yes/No Arrival Date and Approximate Time: Departure Date: Preference: smoking / non smoking (limited availability) -- _______________________________________________________________ Tetsuo HASEGAWA, D. Sc. ALMA-J Project Scientist Professor, National Astronomical Observatory of Japan 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Phone +81-422-34-3780 / FAX +81-422-34-3764 _______________________________________________________________ From tetsuo.hasegawa at nao.ac.jp Wed Jan 16 07:30:34 2002 From: tetsuo.hasegawa at nao.ac.jp (Tetsuo Hasegawa) Date: Wed, 16 Jan 2002 21:30:34 +0900 Subject: [asac] ASAC Meeting in Tokyo Message-ID: Dear Geoff and Pierre, The entire plan of the next ASAC face-to-face meeting was discussed in the national committee yesterday based on Hasegawa's plan as attached below. Please give us comments to our current plan. Before the next ASAC telecon, we will circulate the travel information (hotel bookings, etc.). ASAC may need to nominate one or two persons from Europe and US to organize the Science day. From our side, we two will join them. With our best regards, Yasuo and Tetsuo ******************************************************** date: March 19 (Tue) - 20 (Wed) venue: NAOJ Mitaka headquarter agenda: We would like to raise the following two items: 1. Transition from 2-way to 3-way and the final form of ALMA in scientific perspective With the inclusion of the prototype antenna and other ALMA developments in the Japanese FY2002 budget, now we have a firmer prospect for the Japanese formal participation in 2004 (or sooner). In this circumstance, ASAC should play an important role in guiding the project so that the final form of 3-way ALMA is optimized based on the global discussion of scientists. We think the forthcoming ASAC meeting in Tokyo is a good opportunity to start this. For example, 2G correlator and ACA are among the obvious topics discussed in this context. For us to do this process, we need an up-to-date information of the 2-way project sent to the participants beforehand, which we examine and discuss. Based on our global discussion, we may want to give advice if necessary. We, as scientists, should discuss our strategy toward the successful construction of the most powerful instrument. It should accord with the strategy of continued funding for construction in the North American and European sides and the official approval of the project and getting sufficient funding in the Japanese side. This would meet our goal of achieving the best instrument through the politically complicated transition of the project from 2-way to 3-way. 2. Scientific operation At the last ASAC meeting in Santiago, we identified the comparative study of single and multiple TAC systems as one of the agenda items for the next meeting. With the bilateral project starting, Japanese scientists are anxious about to what extent the way of scientific operation are decided before Japan joins officially. We would like to include this in the discussion. date: march 19 (Tue) evening venue: NAOJ Mitaka headquarter Japanese newspapers are interested in the ALMA project and the Japanese status in it. A brief (<60 min) meeting with some ASAC members and the press may be set right after the first day's ASAC and before dinner. We can state that ALMA is starting now, with Japan having a delay. Good words from European and north American members on the expectation for the Japanese participation would be very helpful. After the meeting, the press can join the ASAC dinner buffet. We may enjoy friendly atmosphere and exchanging information. date: afternoon of March 21 (Thu) - Japanese holiday to celebrate equinox venue: A hall with 300 seats in the National Museum of Emerging Science and Innovation has been tentatively reserved. This new museum opened in July 2001 at the Tokyo waterfront will co-host the Lecture session. http://www.miraikan.jst.go.jp/ The main goal of the session is to convey the exciting forefront of astronomical research and the prospect of more exciting science with ALMA to the general public with interest in science, with ages ranging from ~15 to 60 or up averaging at high school students. Families visiting the museum on that day can drop in if they get interested. We will send out invitations to people in MEXT (although not many of them may attend), in order to call attention by them. It is important to make MEXT people feel that ALMA is and will be well supported by the Japanese people and that Japan has a good role to play in it. Press are also invited of course. The session may be composed of two parts. 1. Lectures on Astronomy and ALMA (100 min total) A brief description of the ALMA project will be given. After that, scientific talks are given by European, North American, and Japanese speakers. The European and North American speakers give lecture in English followed by Japanese translation page by page (of viewgraphs/PowerPoint). We need to nominate the speakers. 2. Discussion (60-90 min) After a short break, we will have a discussion session. It can be in a panel discussion style with the former speakers and a few more (e.g., the director of the museum, Dr. Mouri, who is an astronaut himself, if we succeed to persuade him to come) on stage, exchanging discussions on ALMA in terms of science, technology, and society. In the course of the discussion, we pick up the questions from the audience written in question sheets and collected during the break. (The discussion will be made mainly in Japanese. We will assign graduate students to give a minimum of interpretation to follow the discussion. Picked questions from the audience are translated. ) The balance between the two parts may have to be adjusted as the preparation goes. If we can have Dr. Mouri (he is famous) or someone else on stage, some weight may be put on the discussion part. If not, we can spend more time in talks. (the end of the text) _______________________________________________________________ -- _______________________________________________________________ Tetsuo HASEGAWA, D. Sc. ALMA-J Project Scientist Professor, National Astronomical Observatory of Japan 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan Phone +81-422-34-3780 / FAX +81-422-34-3764 _______________________________________________________________ From awootten at NRAO.EDU Wed Jan 16 13:29:36 2002 From: awootten at NRAO.EDU (Al Wootten) Date: Wed, 16 Jan 2002 13:29:36 -0500 (EST) Subject: [asac] ALMA Conference Proceedings Message-ID: <200201161829.NAA15366@polaris.cv.nrao.edu> Folks, The Volume of Proceedings from a conference on Science With A Large Millimeter Array held 6-8 October 1999 at the Carnegie Institution of Washington was published in December 2001 and is available now! Several folks have reported receiving their copies. Many thanks to all who contributed to this effort, and my apologies for the length of time it has taken to bring the publication to reality. This is No. 235 in the ASP Conference Proceedings series; a copy has been mailed to invited speakers at the conference. The submitted manuscripts (unedited) may be found by clicking on the image of the cover at my home page, which takes one to http://www.alma.nrao.edu/conference Some articles are available only in the book, as not all were submitted via the recommended means. Clear skies, Al +--------------------------------------------------------+ | Alwyn Wootten (http://www.cv.nrao.edu/~awootten/) | | Project Scientist, Atacama Large Millimeter Array/US | | Astronomer, National Radio Astronomy Observatory | | 520 Edgemont Road, Charlottesville, VA 22903-2475, USA | | (804)-296-0329 voice Help us build The ALMA| | (804)-296-0278 FAX {> {> {> {> | +----------------------------------^-----^-----^-----^---+ From awootten at NRAO.EDU Wed Jan 16 14:11:00 2002 From: awootten at NRAO.EDU (Al Wootten) Date: Wed, 16 Jan 2002 14:11:00 -0500 (EST) Subject: [asac] "ALMA Observing Tool: Concept and Prototype" Message-ID: <200201161911.OAA18209@polaris.cv.nrao.edu> From: "Brian Glendenning" To: Sent: Wednesday, January 16, 2002 11:51 AM Subject: Re: [alma-sw-announce] DRAFT ALMA Observing Tool document The draft document: "ALMA Observing Tool: Concept and Prototype" by Scott and Bridger has been posted for comment at: http://www.alma.aoc.nrao.edu/development/computing/docs/memos/computdrafts.h tml (The above line might have been wrapped by a mailer - it must be a single line in your browser). [...] Please send your comments directly to Steve Scott (scott at ovro.caltech.edu) by February 8. It is a convenience if your comments are in the form: In order to try to cut down the cycle time until we have the final version of this document we are moving the comment deadline up to February 1 - sorry for any inconvenience. Again, if you only have time to make big-picture comments at this point that is fine (detailed comments are also welcome of course). Cheers, Brian From pmurphy at NRAO.EDU Fri Jan 18 13:07:22 2002 From: pmurphy at NRAO.EDU (Patrick P Murphy) Date: Fri, 18 Jan 2002 13:07:22 -0500 Subject: [asac] Please ignore; testing Message-ID: <15432.25690.176187.42643@orangutan.cv.nrao.edu> Sorry for the interruption. I'm seeing if the list is functional. Al Wootten and Marc Rafal: if you get this, please let me know (call x372). Thanks. - Pat Murphy Division Head, NRAO/CV Computing From awootten at NRAO.EDU Fri Jan 18 17:34:08 2002 From: awootten at NRAO.EDU (Al Wootten) Date: Fri, 18 Jan 2002 17:34:08 -0500 (EST) Subject: [asac]ALMA configuration CDR information (agenda, etc...) Message-ID: <200201182234.RAA17746@polaris.cv.nrao.edu> Folks, The updated information for the ALMA configuration CDR is now at: http://www.aoc.nrao.edu/~bbutler/work/alma/configurations/CDR/ including a link to the (relatively final) agenda. Thanks to Bryan Butler for his work on this. Clear skies, Al From soliver at nrao.edu Mon Jan 21 15:58:47 2002 From: soliver at nrao.edu (Stacy Oliver) Date: Mon, 21 Jan 2002 13:58:47 -0700 Subject: [asac][almanews] ALMA Memo 407 Released Message-ID: ALMA Memo # 407 Bandslope Effects On Sensitivity In Interferometers With Digital Correlators James W Lamb (Caltech) 2002/01/15 Keywords: Digitizers, samplers, correlators, interferometers, sensitivity In an interferometer with a digital correlator, sensitivity will be reduced by receiver and IF bandpass slopes. Numerical calculations have been carried out to estimate these losses for developing a flatness specification for the ALMA receivers and IF system. For the 3-level digitizer studied here a 2-dB slope across the band gives an efficiency reduction of about 4 % in the frequency channels where the gain is least. There is also an increase of efficiency of a similar magnitude in the high-gain channels. For continuum observations the channels are weighted according to the channel signal-to-noise and averaged, resulting in an efficiency reduction of ~1 %.