重要性Why Study Infrared? Exploring the hidden universe 尘埃物质的消光与波长成反比，受尘埃消光影响小 ◆银河系中心，处于分子、尘埃云中刚形成的年轻恒星 Detecting Cool Objects ◆宇宙中有大量低温天体：ISM、原始星云、小质量恒星 ◆ 3000K一3K(宇宙背景辐射)，辐射的峰值处于红外阶段 Exploring the Early Universe ◆高红移天体的紫外、光学波段的辐射，红移到红外波段 Understanding physical conditions and processes ◆宇宙中有大量物质是以分子形式存在：红外波段分子谱线丰富 ◆观测红外波段谱线，研究行星大气、星际云、宇宙早期的环境
123 Why Study Infrared? u Exploring the hidden universe u bcde4f%g'E:hi-IRjbcf%klm u nopqr-st!">bc#qu9:42356 u Detecting Cool Objects u vwqxyz{HAB$ISM>|}6#>mez56 u 3000KJ3K(vw~WX)-WX4ÄÅst/0Ç( u Exploring the Early Universe u É/ÑAB4Ö0>%&'(4WX, /ÑÜ/0'( u Understanding physical conditions and processes u vwqxyzdeáà!"9âä8$/0'(!"ã`åç u <=/0'(ã`-?@é6yè>6ê#>vwëí4ìî
2.3观测困难 But there's a Challenge... a)地球大气对红外辐射的吸收：JHKLMN ◆大气中C02H20/03/CH和NO2等对红外辐射吸收强 visible CH, range N20 O2 and O Wavelength,μm C02 C0,H,0C0,01H,0 H:O CO,Co, Absorbing molecule J=1.20μm;H=1.60um;K=2.20m H20 Atmosphere 0 0.1 0.2 0.30.40.60.811.5234568102030 Wavelength(microns) 地面红外观测站大气中的水气含量要少； Paranal Observatory (ESO), 或者空间红外观测 Chile
2.3 5678 But there’s a Challenge... a) [\]^0%&78K_`6JHKLMN u ]^aCO2/H2O/O3/CHbNO2c0%&78_`d ïñ/0<=óyèq4òèôzDöõ úùûü/0<= J=1.20μm; H=1.60μm; K=2.20 μm Paranal Observatory (ESO), Chile
b)天空背景和地球存在热辐射 104 Airglow 黄道光(Zodiacal light):星际 OH 10 =10μm 尘埃对太阳光的散射 Zodiacal light λ=1000um 106 8-0.5μm CMB(2.726K) 地球温度T=300K,入=10um 10 Fai0ts减s 10 0.1 10 100 1000 10000 Wavelength um) COBE/DIRBE image of the infrared sky,in Galactic projection.The S- 银河系卷云(Cirrus):银河系星系际介质 shaped blue streak is the zodiacal light 的辐射（整个红外波段），不重要 in the plane of our Solar System. Cosmic IR background:summed emission from distant,unresolved galaxies.Traces history of star formation (CMB:T=3K,A=1000um)
b) #456789:;<=> †°% (Zodiacal light)$6ê bc¢TU%4£X nop§#(Cirrus)$nop6pê•e 4WX¶ß®/0'(©-™CD Cosmic IR background: summed emission from distant, unresolved galaxies. Traces history of star formation¶CMB$T=3K, l=1000µm© [\3JT= 300K, l= 10µm l=1000µm l= 10µm l=0.5µm COBE/DIRBE image of the infrared sky, in Galactic projection. The Sshaped blue streak is the zodiacal light in the plane of our Solar System
C)望远镜本身的热辐射 BLACK BODY CURVES pazllewJou uollelpeJ paqlw3 SUN EARTH T .1.15.2.35 11.5235 1015203050 100 WAVELENGTH Range of wavelengths of solar and Earth spectra. 天体的红外观测要尽可能的减少这些影响 ◆尽量减少红外背景辐射对观测的影响一空间红外卫星 ◆选择干燥、寒冷的高山作为红外台址一地球大气影响 ◆设计、制造适用于红外观测的望远镜一减少自身辐射
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红外望远镜特点 ◆不要封闭式镜筒，而是采用衍架式结构 ◆尽可能减少视场内的机械结构 采用较小副镜和小巧副镜支架，减小它们的红外辐射 ◆不可缺省的结构物也不能涂黑而要抛光镀亮，减少其红外发射系数 ◆ 主、副镜镀银或金，比镀铝对R反射率高，发射率小 Primary 2 mirror Instrument bay Secondary mirror Sunshield HST JWST Spacecraft control systems Souree:NASA
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