[asac]Achievement of Sub-mm observations with ASTE 10m Antenna

[Ryohei Kawabe]

Dear Madam and Sir,

On behalf of ASTE Team, we announce the successful observations of [CI] 492
GHz line with ASTE (Atacama Sub-mm Telescope Experiment) 10m antenna on
December 9th, 2002.
 ASTE is a project to install and operate a 10-meter submillimeter telescope
at Pampa la Bola (4800 m in elevation) of the Atacama desert in the northern
Chile. The project is driven by the National Astronomical Observatory of
Japan (NAOJ) in collaboration with Universidad de Chile, and also with
Japanese astronomers from universities including the University of Tokyo,
Nagoya University, and Osaka Prefecture University. There are two main
purposes in the project. First we are aiming at the on-site testing of high
precision submillimeter antenna and high sensitivity receivers for
development toward the ALMA project. The ASTE project offers a very unique
opportunity of astronomical observations of the southern sky in the
wavelengths as well. In the latter respect, the ASTE 10 m antenna will be
the only large (i.e., 10-m class) submillimeter telescope in the southern
hemisphere that works in these wavelengths shorter than 0.7 mm (frequencies
higher than 400 GHz).



The ASTE 10m antenna was transported to Pampa la Bola in March 2002 after
assembling at San Pedro de Atacama site. From April, we started several
measurements to evaluate antenna performances. As a result, antenna blind
pointing is as accurate as 1.5” (rms), and surface accuracy is measured to
be 29 micron (rms) at this moment. First we installed ASTE evaluation
receiver composed of three receiver bands, 100 GHz, 230 GHz, and 345 GHz,
together with four sets of XF-type digital auto-correlators, one of them
covers 512 MHz with 1024 frequency channels. A 3-band bolometer system at
350 GHz, 650 GHz, and 850 GHz was also installed. Recently, we installed an
ALMA- type (i.e., cartridge type) receiver which consists of three
cartridges, that is, band-3 (100GHz), band-8 (490 GHz), and band-10 (810
GHz). The engineering evaluation of the receiver was successfully performed.
The test observations with band-8 receiver was made on Dec. 9th, 2002, and
we succeeded in detecting [CI] 492 GHz line from Orion-KL (see Fig. 4 in the
attached PDF file). The observational condition was good even in the summer
!; opacity at 492 GHz was less than one during the night. The sub-mm
observations with ALMA will be very promising. We would greatly appreciate
your kind understanding and cooperation toward this ASTE project.

 Best Wishes,

Satoshi Yamamoto (Univ. of Tokyo) and,
 Ryohei Kawabe (NAOJ)
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