2007-11-08 ALMA Calibration Group Telecon Agenda and Minutes


ALMA Calibration Group Telecon
  • Date: November 8, 2007 (Thursday)
  • Time: 15:00 UT
  • Duration: 1.0 hr
  • USA Toll Free Number: 1-877-919-7148
  • International: +1-203-566-1039
  • Passcode: 5 1 0 4 6 8
  • Leader: JeffMangum

Table of Contents:



Complete List of Action Items


Action Items from Last Telecon

Assigned To Due Date Description State Notify  


Agenda and Minutes

NOTE: Discussion from the telecon is shown in italic.


Attendees

  1. RobertLucas
  2. Bojan Nikolic
  3. JeffMangum
  4. Matsushita
  5. LeonardoTesti
  6. AlWootten


Calibration Examples Status

All complete. Please read and comment. See CalExamples wiki for further information. Note that Calibration Sequence information is now included in each CalExamples document.


Amplitude Calibration Subsystem Development Reports

Multi/Dual-Load (M/DL) Calibration System (Ferdinand Patt)

On October 18, 2007 JeffMangum has submitted a CRE requesting changes to the total move time and a relaxation of the requirements on the hot load (no need to be used at Bands 1 and 2).

Richard Hills notes that through discussions with the Frontend IPT the design is converging on the following:
  • Ambient load Bands 1 to 10, hot load Bands 3 through 10.
  • Effective emissivity (or reflectivity) higher than 0.998, with 0.999 as a goal.
  • Variation of the brightness temperature across the aperture: +-1K for the hot load and +-0.5K for the ambient load.
  • Total calibration uncertainty (difference between "measured" brightness temperature and the load's brightness temperature calculated from thermistors (PTRs) and knowledge of the emissivity); this includes implicitly the required accuracy and repeatability of the physical temperature measurement (present Spec sect. 4.2). That would not be specified any longer: Ambient: +-0.3 K, Hot: +-0.5 K at 90 deg C.


Berkeley Absolute Flux Calibration System (Jack Welch)

  • No report.


Ancilliary Measurement Devices

Weather Station (P,T,RH,Ws,Wd) Instrumentation

In December 2006 JeffMangum submitted weather station instrumentation (RH, P, T, and wind) RFQ documentation to NRAO procurement system. After having reviewed information received from bidders and consulted with Calibration Group (see CalAncillary for discussion), on 2007/03/21 JeffMangum submitted purchase information to RobertLaing for procurement. Leonardo Testi received first set of weather measurement devices at ESO in late September and is assembling devices for testing. Test assembly nearly complete.

ICD submitted for AOS site locations discussed during August meeting. A few kinks under discussion with computing and site include power distribution (440V needs transformer) and fiber lighting (only done when antenna occupies station).

JeffMangum has iterated with Eduardo Donoso on site installation logistics for weather stations. Eduardo has investigated proposed weather station siting (see CalAncillary) and found all proposed locations to be acceptable.

Oxygen Sounder

See CalAncillary for background discussion on this system.

AlWootten will investigate the following:
  • Feasibility/cost of a significant number (1000 or more) radiosonde launches at the ALMA site
  • Is ALMA already purchasing meteorological forecasting for the site? What data products?

Also, question remains as to whether the oxygen sounder data going to be used by any subsystem other then WVR-based atmospheric phase correction?

The requirement that the sounder needs ~1000 radiosonde launches will require some additional effort. Another option is to get an accurate site atmospheric model. Lars is working with one of the Chilean university groups to work on this modeling problem.


Frontend Requirements and Pointing

Richard continues to iterate with the Frontend IPT on this issue. Richard has confirmed that the requirement related to pointing due to FE deformation got lost - it disappeared between two versions of the Front End specifications. Obviously people are not keen to have it reintroduced but I don't think anyone has any arguments against it, except for the fact that it is too late to change anything! It has been confirmed that the FEA calculations did not attempt to calculate the relevant displacements - they only looked at the tilt of the beam, i.e. the illumination.

TICRA has offered to do the analysis of how the movements of various components affect the pointing (as well as the illumination). I do not know whether that offer has been taken up.

John Webber has agreed to try to get some measurements of the movements using the scanner at the NA FEIC.


Date of Next Phone Meeting

The next ALMA Calibration Group telecon will be 2008, January 10th 15:00 UT.

-- JeffMangum - 06 Nov 2007

This topic: ALMA > WebHome > AlmaSci > AlmaCal > CalAgendaMinutes > CalAgendaMinutes20071108
Topic revision: 2007-11-08, JeffMangum
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