[asac] [almanews] ALMA Memo 374 and 376 Released

[Carolyn White]

ALMA Memo No. 374

Wide Field Imagings with the Atacama Large Millimter/Submillimeter Array

Koh-Ichiro Morita (Nobeyama Radio Observatory, NAOJ)

2001-05-29

Image quality of wide field observations with the ALMA has been studied with
imaging simulations. Results of the simulations showed that antenna pointing
errors are a serious problem for obtaining high quality images because they
make a large error in visibilities in the central (u,v) hole estimated by
mosaicing data processings. The ALMA Compact Array (ACA) with more than 10
smaller dishes (6-8m) can compensate this problem. However, a carefull
treatment of adding the data measured with the ACA to the data from the ALMA
is needed to obtain a significant improvement of imaging performances. The
ACA with 6m antennas has better imaging performances than that of the ACA
with 8 m antennas, although the difference between them is small for noisy
cases. Another option to realize high fidelity images for large objects is
to improve the pointing of some or all of the 12 m antennas.

View a pdf version of ALMA Memo 374.
http://www.alma.nrao.edu/memos/html-memos/alma374/memo374.pdf

Download a ps version of ALMA Memo 374.
http://www.alma.nrao.edu/memos/html-memos/alma374/memo374.ps

========================================================================

ALMA Memo #376

Integration of LO Drivers, Photonic Reference, and Central Reference
Generator

Eric W. Bryerton, William Shillue, Dorsey L. Thacker, Robert Freund, Andrea
Vaccari, James Jackson, Robert Long, Kamaljeet S. Saini, and Richard F.
Bradley

2001-05-18

These measurements represent the first test of a local-oscillator (LO)
driver based on a multiplied YIG-tuned oscillator (YTO) locked to a variable
frequency photonic mm-wave reference. The reference is provided as a
beatnote between two optical signals and is carried from a remote location
by 10 meters of optical fiber to a photomixer at the LO driver site. Phase
noise measurements were performed at about 80 GHz. A pre-prototype of the
Central Reference Generator (CRG) developed in Socorro was also used in the
tests as the fundamental reference from which all other sources were
synchronized.

View a pdf version of ALMA Memo 376.
http://www.alma.nrao.edu/memos/html-memos/alma376/memo376.pdf

Download a ps version of ALMA Memo 376.
http://www.alma.nrao.edu/memos/html-memos/alma376/memo376.ps
=============================================================================
ALMAnews is a broadcast service.  To unsubscribe, send an e-mail message to
majordomo at nrao.edu with "unsubscribe almanews" in the message body.