[asac] [almanews] ALMA Memos No. 369, 373, and 375 Released

[Carolyn White]

ALMA Memo No. 369

Seasonal and Diurnal Variation of Upper Soil Resistivity in the Cerro
Chasc´on Science Preserve

Seiichi Sakamoto

2001-May

We monitored seasonal and diurnal variation of upper soil resistivity in
the Cerro Chasc ´on Science Preserve in the Wenner method with a .xed
electrode spacing of 2 m.The resistivity shows a factor ~3 seasonal
variation with the lowest values during austral summer.The resistivity in
summer is ~300 .m in the Pampa La Bola area while it is ~1000 .m in the
Llano de Chajnantor area.Throughout the year,the resistivity at Pampa La
Bola is systematically a factor ~3 lower than at Llano de Chajnantor.This
means that worked area needed to realize a certain ground resistance will
be a factor ~10smaller at Pampa La Bola than at Llano de
Chajnantor.Although diurnal variation also exists with the lowest values
near the sunsets,the peak-to-peak variation is less than 3%of the mean
value of the day.

View a PDF version of ALMA Memo #369 at
     http://www.alma.nrao.edu/memos/html-memos/alma369/memo369.pdf

Download a postscript version of ALMA Memo #369 from
     http://www.alma.nrao.edu/memos/html-memos/alma369/mma369.ps

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ALMA Memo No. 373

Relative Pointing Sensitivity at 30 and 90 GHz for the ALMA Test
Interferometer

M.A. Holdaway and Jeff Mangum

2001-May

We compare the relative sensitivity of conducting pointing measurements at
30 and 90 GHz with the ALMA Test Interferometer (TI) at the VLA site. If
pointing is performed interferometrically, the 90 GHz system will actually
be 2.3 times more sensitive than the 30 GHz system due to very similar
system temperatures but a smaller beam at 90 GHz. If pointing is performed
in single dish mode, the system will be subject to sky brightness
fluctuations, which are worse at 90 GHz than at 30 GHz. Even so, the sky
fluctuations will usually not dominate the system noise. There are no
compelling reasons not to do the test interferometer pointing at 90 GHz.

View a PDF version of ALMA Memo #373 at
     http://www.alma.nrao.edu/memos/html-memos/alma373/memo373.pdf

Download a postscript version of ALMA Memo #373 from
     http://www.alma.nrao.edu/memos/html-memos/alma373/mma373.ps

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ALMA Memo No. 375

Coordinates of Roads, Pipelines, and Landmarks Near the ALMA Site

Seiichi Sakamoto

2001-May

We measured coordinates of roads, pipelines, and landmarks near the ALMA
site with handheld GPS receivers, and present the locations of this
information on the web.


View a PDF version of the ALMA Memo #375 at
     http://www.alma.nrao.edu/memos/html-memos/alma375/memo375.pdf

Download a postscript version of ALMA Memo #375 from
     http://www.alma.nrao.edu/memos/html-memos/alma371/mma375.ps


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