[asac][almanews] ALMA Memos 448, 449 and 450 Released

[Stacy Oliver]

ALMA MEMO #448

UV intensity near AOS and OSF

Seiichi Sakamoto (NAOJ)

2003/03/23

Keywords:site testing, ultraviolet (UV), safety

UV intensity near the AOS and OSF sites in northern Chile was measured with handheld UVA and UVB radiometers and was compared with
that taken at Socorro AOC, Nobeyama, and Mitaka. Typical UVA opacity was about 0.4 at Pampa La Bola near the AOS site, about 0.6
both at San Pedro de Atacama near the OSF site and at Nobeyama, and about 0.7 at Mitaka (best conditions), respectively. The UVA
intensity toward the Sun measured at Pampa La Bola near the sunset (elevation ~20 degrees) was still comparable with the highest
value recorded at Mitaka. The difference becomes even more outstanding in UVB. The UV Index, which chiefly reflects UVB intensity,
measured with a handheld UVB radiometer is in reasonable agreement with that predicted with the satellite data, and both
consistently indicate that the UVB is extremely high at the AOS and OSF sites. The UV Index typically exceeds 7 (high) for 6 hours
near the AOS site.

View a pdf version of ALMA Memo #448.
http://www.alma.nrao.edu/memos/html-memos/alma448/memo448.pdf

Download a postscript version of ALMA Memo #448.
http://www.alma.nrao.edu/memos/html-memos/alma448/memo448.ps

--------------------------------------------------------------------------------
ALMA MEMO #449

Noise Evaluation of Hybrid Photonic Local Oscillator at 500 GHz

Y. Sekimoto, A. Ueda, T. Okuda (NAOJ), E. Bryerton (NRAO),
M. Sugimoto, H.Matsuo, S. Yokogawa, T. Noguchi, M. Ishiguro (NAOJ),
H. Ito, T. Nagatsuma, A. Hirata (NTT), and J. Payne (NRAO)

2003/03/20

Keywords: Photonic LO, hybrid option, SIS noise, multiplier

A hybrid photonic local oscillator, which consists of a multiplier, a W-band power amplifier, a W-band photomixer, and a laser
system, has been demonstrated to be sufficiently powerful to pump a superconducting-insulator-superconducting tunneling junction
(SIS) mixer at 490 GHz.
The noise temperature at 490 GHz was 135 K, which is comparable with that pumped by Gunn oscillator + multipliers. Wideband spectrum
of the multiplier is also measured.

View a pdf version of ALMA Memo #449.
http://www.alma.nrao.edu/memos/html-memos/alma449/memo449.pdf

Download a postscript version of ALMA Memo #449.
http://www.alma.nrao.edu/memos/html-memos/alma449/memo449.ps

--------------------------------------------------------------------------------

ALMA MEMO #450

Heterogeneous Imaging with the ALMA Compact Array
Melvyn Wright (University of California, Berkeley)

2003/03/21

Keywords: Heterogeneous Imaging, ALMA Compact Array, ACA.

The ALMA Compact Array will be a powerful telescope at sub-millimeter wavelengths for imaging the large scale structures which are
not well sampled by ALMA. In this memo, we propose an observing mode for the ACA as a heterogeneous array of 7 and 12 m antennas. We
compare three compact configurations: the ACA (12 x 7 m), a heterogeneous ACA with 4 x 12 m antennas, and the most compact ALMA
configurations with 60 x 12 m antennas. We present tables of the synthesised beam FWHM, brightness sensitivity and sidelobe levels
for source declinations +30, 0 and --30 degrees. Using the ACA as a heterogeneous array with four 12 m antennas doubles the
collecting area of the ACA and provides synthesised beams and brightness sensitivities which fill a useful parameter space between
the ACA alone and the most compact configurations of the ALMA telescope. Heterogeneous observing provides more short spacings and a
good cross calibration of the 7 and 12 m antennas. Calibration of the bandpass and polarization characteristics can be improved by
scheduling a few more 12 m antennas for the ACA at times when these calibrations are needed. The location of the ACA in relation to
the ALMA array, and the correlator configuration should be considered with these possibilities.

View a pdf version of ALMA Memo #450.
http://www.alma.nrao.edu/memos/html-memos/alma450/memo450.pdf

Download a postscript version of ALMA Memo #450.
http://www.alma.nrao.edu/memos/html-memos/alma450/memo450.ps

_______________________________________________
Almanews mailing list
Almanews at listmgr.cv.nrao.edu
http://listmgr.cv.nrao.edu/mailman/listinfo/almanews