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首页> 外文期刊>The Astrophysical journal >THE SUBMILLIMETER WAVE ASTRONOMY SATELLITE: SCIENCE OBJECTIVES AND INSTRUMENT DESCRIPTION
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THE SUBMILLIMETER WAVE ASTRONOMY SATELLITE: SCIENCE OBJECTIVES AND INSTRUMENT DESCRIPTION

机译：子弹头天文学卫星：科学目的和仪器描述

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摘要

The Submillimeter Wave Astronomy Satellite (SWAS), launched in 1998 December, is a NASA mission dedicated to the study of star formation through direct measurements of (1) molecular cloud composition and chemistry, (2) the cooling mechanisms that facilitate cloud collapse, and (3) the large-scale structure of the UV-illuminated cloud surfaces. To achieve these goals, SWAS is conducting pointed observations of dense [n(H_2) > 10~3 cm~(-3)] molecular clouds throughout our Galaxy in either the ground state or a low-lying transition of five astrophysically important species: H_2O, H_2~(18)O, O_2, C Ⅰ, and ~(13)CO. By observing these lines SWAS is (1) testing long-standing theories that predict that these species are the dominant coolants of molecular clouds during the early stages of their collapse to form stars and planets and (2) supplying previously missing information about the abundance of key species central to the chemical models of dense interstellar gas. SWAS carries two independent Schottky barrier diode mixers—passively cooled to ～175 K—coupled to a 54 x 68 cm off-axis Cassegrain antenna with an aggregate surface error ～11 μm rms. During its baseline 3 yr mission, SWAS is observing giant and dark cloud cores with the goal of detecting or setting an upper limit on the water and molecular oxygen abundance of 3 x 10~(-6) (relative to H_2). In addition, advantage is being taken of SWAS's relatively large beam size of 3:3 x 4.5′ at 553 GHz and 3.5′ x 5.0′ at 490 GHz to obtain large-area (～1° x 1°) maps of giant and dark clouds in the ~(13)CO and C Ⅰ lines. With the use of a 1.4 GHz bandwidth acousto-optical spectrometer, SWAS has the ability to simultaneously observe either the H_2O, O_2, C Ⅰ, and ~(13)CO lines or the H_2~(18)O, O_2, and C Ⅰ lines. All measurements are being conducted with a velocity resolution less than 1 km s~(-1).
机译：亚毫米波天文学卫星（SWAS）于1998年12月发射升空，是NASA的一项任务，致力于通过直接测量（1）分子云的成分和化学成分，（2）促进云塌陷的冷却机制以及（3）紫外线照射的云表面的大规模结构。为了实现这些目标，SWAS正在对整个银河系中处于基态或低空过渡的五个天体重要物种的密集[n（H_2）> 10〜3 cm〜（-3）]分子云进行有针对性的观察： H_2O，H_2〜（18）O，O_2，CⅠ和〜（13）CO。通过观察这些线，SWAS正在（1）测试长期的理论，这些理论预测这些物种在其坍缩形成恒星和行星的早期是分子云的主要冷却剂，并且（2）提供以前缺少的有关丰度的信息。密星际气体化学模型中心的关键物种。 SWAS带有两个独立的肖特基势垒二极管混频器（被动冷却至175 K），并耦合至54 x 68 cm离轴卡塞格伦天线，总表面误差rms约为11μm。在其基准的3年任务中，SWAS正在观测巨云和暗云核，其目的是检测或设定水和分子氧丰度的上限（相对于H_2）为3 x 10〜（-6）。此外，利用SWAS相对较大的光束尺寸（在553 GHz时为3：3 x 4.5'，在490 GHz时为3.5'x 5.0'）来获得大面积图（约1°x 1°）的巨大和黑暗图〜（13）CO和CⅠ线云。通过使用1.4 GHz带宽的声光光谱仪，SWAS能够同时观察H_2O，O_2，CⅠ和〜（13）CO线或H_2〜（18）O，O_2和CⅠ的能力线。所有测量均以小于1 km s〜（-1）的速度分辨率进行。

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