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1.
太阳系探索和地外生命搜索 总被引：1，自引：0，他引：1
综述了国际上进行太阳系空间探测的现状，着重介绍了探测月球，火星，不星和外行星的意义，目的，手段和成就，择要介绍了美国宇般局，欧洲空间局，俄罗斯和日本近年来和下世纪初的空间计划，论及地外生命搜索，主要介绍了火星上水和生命搜索进展，地外生命搜索的的SETI计划及其发民菜，物理学家与生物学家有关搜索成功的可能性的争论，以及太阳系外行星系统的发现，太阳系外行星系统的发现是当代天文学最时髦的，也将是未来21世纪成果最丰富的研究领域之一，目前，已经发现了大约50个太阳系外行星系统，太阳系外行星系统的发现与地外生命搜索研究是密不可分的，这项研究近20年来发展较快，它的研究也促进了航天学，宇宙化学，天文生物学乃至哲学等其化学科的发展。 相似文献
2.
本研究了中子星的热演化，自转演化和磁场演化的相互影响，考虑了一个自洽模型，中子星因磁偶极辐射而自转减慢，在内部产生某些加热过程，中子星磁场通过壳层的欧姆耗散来衰减。结果表明，磁场衰减提高了加热过程的重要性，相反，加热效应减慢了磁衰减，因此可以得出，中子星的热，自转和磁场也许不是独立演化的，不仅如此，这些演化与初始条件有关，因此，人们也许可以从射电和Ｘ射线观测对脉冲星年龄，初始磁场和周期给出某些限 相似文献
3.
针对薄板玻璃的刚度差，在研磨中容易产生变形这一特点，提出了一种新的加工方法。以加工薄施密特校正板（厚径比小于1／40）为例，用传统的上盘粘接固定工件进行加工，工件在下盘前的面形精度较好，但下盘后产生的变形使其面形精度下降，不能满足要求。采用真空模具法，吸附工件从而使工件固定产生预期的变形，面形精度易于控制，使加工非球面转变为加工平面，降低了加工难度，消除了工件在粘接过程中温度所引起的变形，降低了加工时的不均匀压应力，从而减少了变形，使得加工后的面形与加工过程中的面形接近，最终保证了工件的面形精度。 相似文献
4.
TDMA／SS系统同步技术 总被引：1，自引：0，他引：1
目前，通信卫星系统普遍采用星上信号处理技术，为了满足高容量系统的要求，近几年发展了许多新的技术，其中为了解决多个点波束区域的通信，被称为时分多址／星上交换（TDMA／SS）技术便应运而生。因为使用TDMA时，一方面需要所有地球站的时间系统与同一参考源保持同步，另一方面，参考源也必须与卫星上的同步窗相关。二十世纪七十年代，许多学提出了各种各样的TDMA／SS同步解决方案，在此详细论述了TDMA／SS系统同步中的一些主要问题，对解决同步的方案作了比较，并分析了各种方案的特点。 相似文献
5.
本文对36颗不同质量、不同演化阶段的年轻星体进行了J，H，K波段测光，并结合其它光学、近红外、IRAS、亚毫米、毫米波段的观测结果，计算了它们的红外色指数、能谱分布指数、红外光度等参量，得到近红外和远红外双色图，比较了不同类别源的参量分布．最后，在前人工作的基础上，改进了低质量主序前星的辐射模型，对一些源进行了计算并分析其星周状况． 相似文献
6.
这里叙述的新发现仅指某一特殊类型的发现（如新星，超新星和小行星等）及某一特殊类型天体的认证（如X射线源证认为类星体等），而不包括某一类天体的某种天象及未知性质源的列表（如深度成像观测得到的前人没有纪录过的一般天体，如恒星，但一些特殊天体亦列入），由于收集不全面和所谓“发现”定义的困难，向有发向而未列入者先歉意。从80年代后期开始，我国的观测设备有了很大垢发展，所以有一批重的的天文发现，为天文提供了很好的机会，它包括下面几方面，层系层次天体：（1）用X射线源和射电源证认了一批包括类星体，BL Lac天体，赛弗特天体在内的活动星系核；（2）用IRAS源证认了一批W－R星系；（3）BATC巡天在一个星系周围发现了一个“环”。恒星层次天体：（1）河外星系中发现了一批超新星的一个新星，（2）发现了和用ROSAT源证认了一批激变变星，（4）BATC和超新星巡天发现了一批变星，（4）发现了若干新的δSct变星，（5）发现了一批Herbig-Haro天体，（6）发现了一批水脉泽。行星层次天体：（1）发现了大批小行星，特别是有些是近地不行星，（20发现若干彗星。 相似文献
7.
脉冲星γ射线辐射光度的分析 总被引：1，自引：0，他引：1
本文作者在脉冲星γ射线辐射的极冠模型的基础上，考虑光子在磁层中的级联过程，提出了级联过程中能量转化效率的概念并得出了转化效率公式，分析表明，能量转化效率只和磁场强度有关，与周期无关，考虑能量转化效率，我们计算了极冠模型的γ射线辐射光度，得出了可以和观测值比较的结果，本文结果倾向于支持脉冲星γ射线辐射的极冠模型。 相似文献
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第一次观看哈雷彗星追记１９８５年１０月２８日，对我来说，是一个值得纪念的日子。这一天过去快十年了，但那天晚上的一切，我还记忆犹新。那年暑假参加省天文夏令营时，我就得知了一些关于哈雷彗星的信息，得以及时汇款邮购了《哈雷彗星观测手册》；开学后，我又作了一... 相似文献
11.
Rajmal Jain Anil K. Pradhan Vishal Joshi K. J. Shah Jayshree J. Trivedi S. L. Kayasth Vishal M. Shah M. R. Deshpande 《Solar physics》2006,239(1-2):217-237
We present the first results from the low-energy detector payload of the solar X-ray spectrometer (SOXS) mission, which was
launched onboard the GSAT-2 Indian spacecraft on May 08, 2003 by the GSLV-D2 rocket to study solar flares. The SOXS low-energy
detector (SLD) payload was designed, developed, and fabricated by the Physical Research Laboratory (PRL) in collaboration
with the Space Application Centre (SAC), Ahmedabad and the Indian Space Research Organization (ISRO) Satellite Centre (ISAC),
Bangalore. The SLD payload employs state-of-the-art, solid-state detectors, viz., Si PIN and Cadmium-Zinc-Telluride (CZT) devices that operate at near room temperature (−20 °C). The energy ranges of the Si PIN and CZT detectors are 4 – 25 and 4 – 56 keV, respectively. The Si PIN provides sub-keV
energy resolution, while the CZT provides ~1.7 keV energy resolution throughout the energy range. The high sensitivity and
sub-keV energy resolution of the Si PIN detector allows measuring the intensity, peak energy, and the equivalent width of
the Fe-line complex at approximately 6.7 keV, as a function of time in all ten M-class flares studied in this investigation.
The peak energy (E
p) of the Fe-line feature varies between 6.4 and 6.7 keV with increase in temperature from 9 to 58 MK. We found that the equivalent
width (w) of the Fe-line feature increases exponentially with temperature up to 30 MK and then increases very slowly up to 40 MK.
It remains between 3.5 and 4 keV in the temperature range of 30 – 45 MK. We compare our measurements of w with calculations made earlier by various investigators and propose that these measurements may improve theoretical models.
We interpret the variation of both E
p and w with temperature as being to the changes in the ionization and recombination conditions in the plasma during the flare, and
as a consequence, the contribution from different ionic emission lines also varies. 相似文献
12.
Rajmal Jain Vishal Joshi S. L. Kayasth Hemant Dave M. R. Deshpande 《Journal of Astrophysics and Astronomy》2006,27(2-3):175-192
We present the first results from the ‘Low Energy Detector’ pay-load of ‘Solar X-ray Spectrometer (SOXS)’ mission, which was
launched onboard GSAT-2 Indian spacecraft on 08 May 2003 by GSLV-D2 rocket to study the solar flares. The SOXS Low Energy
Detector (SLD) payload was designed, developed and fabricated by Physical Research Laboratory (PRL) in collaboration with
Space Application Centre (SAC), Ahmedabad and ISRO Satellite Centre (ISAC), Bangalore of the Indian Space Research Organization
(ISRO). The SLD payload employs the state-of-the-art solid state detectors viz., Si PIN and Cadmium-Zinc-Telluride (CZT) devices
that operate at near room temperature (-20°C). The dynamic energy range of Si PIN and CZT detectors are 4–25 keV and 4–56
keV respectively. The Si PIN provides sub-keV energy resolution while CZT reveals ∼1.7keV energy resolution throughout the
dynamic range. The high sensitivity and sub-keV energy resolution of Si PIN detector allows the measuring of the intensity,
peak energy and equivalent width of the Fe-line complex at approximately 6.7 keV as a function of time in all 8 M-class flares
studied in this investigation. The peak energy (E
p) of Fe-line feature varies between 6.4 and 6.8 keV with increase in temperature from 9 to 34 MK. We found that the equivalent
width (ω) of Fe-line feature increases exponentially with temperature up to 20 MK but later it increases very slowly up to
28 MK and then it remains uniform around 1.55 keV up to 34 MK. We compare our measurements ofw with calculations made earlier by various investigators and propose that these measurements may improve theoretical models.
We interpret the variation of both Epand ω with temperature as the changes in the ionization and recombination conditions in the plasma during the flare interval
and as a consequence the contribution from different ionic emission lines also varies. 相似文献
13.
本文描述了用旋转调制器对天空X、γ射线源成象并兼测能谱的方法。它可以对大视场内的天空源测定位置、大小和强度。与常规准直器相比,它显示出多种优点。在硬X、γ射线波段,它不仅能对天空源成象,而且能测量其能谱和较强的谱线。 相似文献
14.
M. Favre P. Silva H. Chuaqui E. Wyndham P. Choi C. Dumitrescu-Zoita 《Astrophysics and Space Science》1997,256(1-2):473-478
We report on experimental observations in PFP-I, a small 3.8 kJ plasma focus, which is operated in Hydrogen-Argon mixtures to investigate the effect of parameter modifications on the overall performance of the device. An extensive array of diagnostics is been used, which includes voltage and current probes in the external circuit, a novel small magnetic probes array located along the cathode rods, filtered PIN diodes located side and end on, and filtered multi-pinhole and slit-wire X-ray camera. Extended operating range from below 0.2 Torr upwards has been achieved. Hot spot formation has been investigated as a function of H2-Ar mixing ratio. Hot spot sizes around 150 m in the soft X-ray region, have been inferred from the slit-wire measurements. Pin-hole time integrated X-ray pictures and time resolved PIN diode measurements have been used to determine characteristic hot-spot temperatures in the 350 to 450 eV range. 相似文献
15.
Narrow-band (NB) events in dynamic spectra and their relation with short (S-) bursts are an unresolved enigma of the jovian decametric emission. This paper is focused on the S/NB-structure with timescales between 0.03 s and 0.3 s. It is shown that the characteristic dash-line appearance of such narrow-band radiation in the dynamic spectrum could be considered as a result of superposition of numerous shadows events. To reproduce such shadows, the concept of the modulator is proposed. The modulator is an activating or amplifying agent, which drifts in the dynamic spectrum toward lower frequencies to stimulate the generation process in the radio source. After the source interaction, the modulator is shielded; one cannot stimulate the emission afterwards. Hence, the S/NB-emission shadows a certain region of the spectrum. This ‘shadow effect’ regularizes the random S-bursts or NB-oscillations into realistic structures in the synthetic spectrum. The resemblance between the real and the synthetic spectra is shown with 2D-correlation analysis. 相似文献
16.
We have evaluated several solid state detectors which offer excellent energy resolution at room temperature for soft X-rays. For soft X-rays (< 1 keV to 20 keV), silicon P-intrinsic-N (PIN) and avalanche-mode photodiodes (APD's) have been studied. Using commercially available charge sensitive pre-amplifiers, these photodiodes provide 1 keV resolution without cooling. Their detection efficiencies are limited to about 20 keV and 15 keV, respectively. To overcome this constraint, we have studied thick (1.5 mm) PIN detectors made by Micron Semiconductor Ltd., U.K., as well as compound semiconducting materials with high Z constituents such as CZT and PbI2. PbI2 allows high detection efficiencies of photons up to 100 keV with detectors 100–300 microns thick. These new detectors offer the capability to study the low-energy spectral evolution of Gamma ray bursts (GRBs). A matrix of these detectors could be used as an image plane detector with moderate spatial resolution for imaging. 相似文献
17.
Doing space Astronomy on lunar surface has several advantages. We present here feasibility of an All Sky Monitoring Payload for Spectro-photometry
in X-rays (SPHINX) which can be placed on a lander on the moon or in a space craft orbiting around the moon. The Si–PIN photo-diodes
and CdTe crystals are used to detect solar flares, bright gamma bursts, soft gamma-ray repeaters from space and also X-ray
fluorescence (XRF) from lunar surface. We present the complete Geant4 simulation to study the feasibility of such an instrument
in presence of Cosmic Diffused X-Ray Background (CDXRB). We find that the signal to noise ratio is sufficient for moderate
to bright GRBs (above 5 keV), for the quiet sun (up to 100 keV), solar flares, soft gamma-ray repeaters, X-ray Fluorescence
(XRF) of lunar surface etc. This is a low-cost system which is capable of performing multiple tasks while stationed at the
natural satellite of our planet. 相似文献
18.
S. Gburek J. Sylwester M. Kowalinski J. Bakala Z. Kordylewski P. Podgorski S. Plocieniak M. Siarkowski B. Sylwester W. Trzebinski S. V. Kuzin A. A. Pertsov Yu. D. Kotov F. Farnik F. Reale K. J. H. Phillips 《Solar System Research》2011,45(3):189-199
The goals and construction details of a new design Polish-led X-ray spectrophotometer are described. The instrument is aimed to observe emission from entire solar corona and is placed as a separate block within the Russian TESIS X- and EUV complex aboard the CORONAS-PHOTON solar orbiting observatory. SphinX uses silicon PIN diode detectors for high time resolution measurements of the solar spectra in the range 0.8–15 keV. Its spectral resolution allows for discerning more than hundred separate energy bands in this range. The instrument dynamic range extends two orders of magnitude below and above these representative for GOES. The relative and absolute accuracy of spectral measurements is expected to be better than few percent, as follows from extensive ground laboratory calibrations. 相似文献
19.
The polarimetric Littrow Spectrograph POLIS is designed for vector polarimetry at high angular and spectral resolution. It measures the magnetic field simultaneously in the photosphere and the chromosphere of the sun. Both branches of the polarimetry unit are dual beam systems with a single rotating modulator for both wavelengths and polarizing beam splitters in front of each CCD camera. POLIS has been installed at the VTT on Tenerife and has seen First Light on 17 May 2002. A modified version of POLIS will be developed for the balloon mission Sunrise . That version will have UV capabilities down to 200 nm. 相似文献
20.
J. Sylwester S. Kuzin Yu. D. Kotov F. Farnik F. Reale 《Journal of Astrophysics and Astronomy》2008,29(1-2):339-343
The scientific goals and construction details of a new design, Polish X-ray spectrophotometer are given. It will be incorporated within the Russian TESIS X and EUV complex aboard the forthcoming CORO-NAS solar mission. SphinX (Solar Photometer in X-rays) will use PIN silicon detectors for high time resolution (0.01 s) measurements of the solar spectra of quiet and active corona in the range 0.5–15 keV. A new filter-fluorescence target concept will be employed to allow for a fast photometry of the solar X-ray flux variations in selected, well defined narrow spectral bands including the Fe XXVI and Fe XXV iron line groups. 相似文献