用于引力波关键技术验证的近地低成本商业卫星设计

地面引力波探测由于受到地表振动、重力梯度等噪声以及试验尺度的限制,探测频段被限制在10Hz以上,而对于更大特征质量和尺度的波源,探测频段主要在中低频段(0. 1 mHz～1 Hz)。因此,为避免地面干扰,需要在空间进行探测。由于引力波信号微弱,探测精度极高,针对空间引力波探测,国际上提出了以LISA为代表的空间引力波探测计划,国内中国科学院也提出了太极计划。然而,国内外的引力波探测卫星计划,对卫星的技术指标、设计复杂性和成本均提出了极高要求,短期之内难以实现。针对这一现实情况,本文参考LISA pathfinder的设计思路,设计一颗近地低成本商业卫星,针对引力波探测关键技术的验证需求,进行卫星任务需求分析及结构、热控、姿态控制等关键技术分析,提出商业化的低成本技术验证初步设想,希望能对空间引力波探测卫星总体设计提供一定借鉴。     

英国开发出一部引力波探测光学观测仪器

据国外媒体报道,近日英国牵头开发出了一部引力波探测光学观测仪器系统。据悉,该仪器系统在英国进行关键试验顺利,对于探测引力波至关重要的太空技术已经为搭乘火箭进行空天超重试验做好了准备。据介绍,这项新仪器技术指的是“激光干涉仪太空天线”（LISA）,LISA航天器旨在验证未来用于观测引力波的必要关键技术。该光学装置由位于格拉斯哥大学的引力研究所（IGR）建造和试验,现已被运送到德国阿斯特里姆公司,与其他科学模块集成。     

S-dual模型产生的原初黑洞和次级引力波

在S-dual暴涨模型中通过在非正则动能项中引入峰值函数,可产生丰度可观的原初黑洞和次级引力波.该模型分别在10¹²,10⁸和10⁵ Mpc^-1对原初密度扰动的功率谱进行放大,产生了质量量级分别为10^-13太阳质量、地球质量、行星质量的原初黑洞,以及峰值频率分别为毫赫兹、微赫兹、纳赫兹的次级引力波.其中在10^-13太阳质量附近的原初黑洞可以解释全部的暗物质,产生的次级引力波能被未来的空间引力波探测器探测到.     

面向空间引力波探测的低噪声稳频激光器

基于未来卫星间激光干涉任务的需求,介绍了一种基于迈克耳孙光纤干涉仪稳频的1064 nm激光稳频系统,该系统采用全光纤器件,结构紧凑、体积小、可靠性强。通过拍频测试,得到该系统的频率噪声在30 mHz～1 Hz范围内小于30 Hz/Hz1/2,频率稳定度在积分时间为1 s和1000 s时分别为1.2×10-14和3×10-13。该系统的性能满足LISA任务对稳频激光的需求,有望应用于未来的空间引力波探测任务。     

通向天基引力波探测器

正来自LISA探路者任务的初步结果表明,对于处于自由落体状态的两个测试立方体,它们之间的相对加速的噪声很小,满足天基引力波探测的要求。2016年2月,激光干涉引力波天文台(LIGO)探测到由两个黑洞合并引发的引力波。这一结果的公布使很多物理和天文学领域的科学家感到震惊和兴奋。当所有的眼光转向LIGO时,LISA探路者(LPF)正静悄悄但信心十足地为引力波天文学的下一场革命铺平道路。LPF是激光干涉空     

空间引力波探测望远镜初步设计与分析

引力波的直接观测已开启引力波天文学的新篇章,爱因斯坦的百年预言终获证实。空间引力波探测器使得探测0.1 m Hz~1 Hz频段丰富的引力波源成为可能,与地面引力波探测器互为补充,才可实现更加宽广波段的引力波探测,揭开宇宙早期的更多秘密。空间激光干涉引力波探测采用外差干涉测量技术,测量间距百万公里的两自由悬浮测试质量间10 pm量级的变化量。望远镜是激光干涉测量系统的重要组成部分,1 pm的光程稳定性及苛刻的杂散光要求,不同于传统的几何成像望远镜。本文根据空间太极计划任务需求,对望远镜的功能及技术要求进行了分析,并完成了原理样机的初步方案设计,针对百万公里远场波前分布,分析了望远镜系统的敏感性,同时完成了在轨光机热集成仿真,为后面原理样机的研制奠定了技术基础。     

聆听天籁

一般认为,宇宙中充满了者听到。特鲁迪·E．贝尔以前所未有规模探测引力波的测器。LISA最初是作为欧洲空ESA）“视野2000＋”计划的一未获批准,后来于2004年正式（NASA）的合作项目,美方负制系统及深空通讯网络。欧洲测器将于2018年升空,在此之“LISA探路者”以验证实验技术的可靠性。     

可调谐的低频连续引力波接收天线的研究

我们设计制造了共振频率在47.3Hz到60.5Hz之间连续可调谐的低频引力波四极天线。天线的重量为498kg,室温时在空气中加上调谐系统后Q值为4.4×10³。木文把天线的振动简化为在自由端附有—刚性质量的悬臂梁的振动。代替弹性力学的繁复计算,用材料力学的简单方法得到了可以满足要求的结果。本文对用机械方法调整频率的可能方案作了比较,并对把四极天线用于探测更低频的引力波的可能性进行了探讨。 关键词：     

星上剩磁对惯性传感器的影响

空间引力波探测对剩余加速度的要求极高,达到了10~(-15)ms~(-2)Hz~(-1/2)量级,然而在空间引力波探测时,惯性传感器所在位置的环境磁场会带来磁场力和洛伦兹力。为保证引力波的正常探测,必须将环境磁场及磁场梯度控制在一定范围内。本文主要针对星上剩磁对惯性传感器的影响,从星际磁场、卫星部件剩磁和时变磁场探测等几个方面探讨了剩磁与加速度之间的关系,也对卫星磁场源模拟以及磁场探测方法进行了讨论。结果表明,通过对磁场源位置和方向进行优化可以降低直流剩磁,通过弱磁探测装置对星际磁场和时变磁场进行实时监控以排除磁场噪声影响,对于得到高精度的引力波探测数据是必不可少的。本文研究说明实施星上剩磁对惯性传感器的影响分析是有必要的,并且可以发展一套卫星平台剩磁评估方案和弱磁探测方法。     

面向天基引力波探测的时间延迟干涉技术

时间延迟干涉技术(Time-delay?Interferometry,TDI)对中国引力波探测项目及其它天基激光精密测量任务具有重要的参考价值.在天基引力波探测任务中,需利用激光干涉仪对无拖曳检验质量块间实现十皮米量级的位移测量精度.其中,激光源频率噪声和时钟频率噪声是两项主要噪声.在欧洲主导的LISA(Laser?I...     

Gravitational wave detection by laser interferometry – on earth and in space

The space project LISA is approved by ESA as a cornerstone mission in the field of ‘fundamental physics’, sharing its goal and principle of operation with the ground-based interferometers currently under construction: the detection and measurement of gravitational waves by laser interferometry. Ground and space detection differ in their frequency ranges, and thus the detectable sources. At low frequencies, ground-based detection is limited by seismic noise, and yet more fundamentally by ‘gravity gradient noise’, thus covering the range from a few Hz to a few kHz. On five sites worldwide, detectors of armlengths from 0.3 to 4 km are being built, two of them in Europe (GEO and VIRGO). They will progressively be put in operation between 2001 and 2003. Future improved versions are being planned, with data not until 2008, i.e. near the launch of the space project LISA. It is only in space that detection of signals below, say, 1 Hz is possible, opening a wide window to a different class of interesting sources of gravitational waves. The project LISA consists of three spacecraft in heliocentric orbits, forming a triangle of 5 million km sides.     

Atomic Interferometric Gravitational-Wave Space Observatory(AIGSO)

We propose a space-borne gravitational-wave detection scheme, called atom interferometric gravitationalwave space observatory(AIGSO). It is motivated by the progress in the atomic matter-wave interferometry, which solely utilizes the standing light waves to split, deflect and recombine the atomic beam. Our scheme consists of three drag-free satellites orbiting the Earth. The phase shift of AIGSO is dominated by the Sagnac effect of gravitational-waves, which is proportional to the area enclosed by the a√tom interferometer, the frequency and amplitude of gravitational-waves.The scheme has a strain sensitivity 10~(-20)/Hz~(1/2) in the 100 mHz–10 Hz frequency range, which fills in the detection gap between space-based and ground-based laser interferometric detectors. Thus, our proposed AIGSO can be a good complementary detection scheme to the space-borne laser interferometric schemes, such as LISA. Considering the current status of relevant technology readiness, we expect our AIGSO to be a promising candidate for the future space-based gravitational-wave detection plan.     

Achieving geodetic motion for LISA test masses: ground testing results

The low-frequency resolution of space-based gravitational wave observatories such as LISA (Laser Interferometry Space Antenna) hinges on the orbital purity of a free-falling reference test mass inside a satellite shield. We present here a torsion pendulum study of the forces that will disturb an orbiting test mass inside a LISA capacitive position sensor. The pendulum, with a measured torque noise floor below 10 fN m/square root of Hz from 0.6 to 10 mHz, has allowed placement of an upper limit on sensor force noise contributions, measurement of the sensor electrostatic stiffness at the 5% level, and detection and compensation of stray dc electrostatic biases at the millivolt level.     

Temporal extent of surface potentials between closely spaced metals

Variations in the electrostatic surface potential between the proof mass and electrode housing in the space-based gravitational wave mission Laser Interferometer Space Antenna (LISA) is one of the largest contributors of noise at frequencies below a few mHz. Torsion balances provide an ideal test bed for investigating these effects in conditions emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near a Au coated Si plate pendulum suspended from a thin W wire. We have measured a white noise level of 30 microV/sqrt Hz above approximately 0.1 mHz, rising at lower frequencies, for the surface potential variations between these two closely spaced metals.     

Gravitational Wave Science with Laser Interferometers and Pulsar Timing

Within this decade, gravitational wave detection will open a new observational window on the Universe. Advanced ground-based interferometers covering the kilohertz frequency range will be online by 2016, and the announcement of a first detection within 5 years is foreseeable. At the same time, a worldwide effort for detecting low-frequency waves (in the nanohertz regime) by timing ultra-precise millisecond pulsars is rapidly growing, possibly leading to a positive detection within this decade. The millihertz regime, bridging these two windows, is the realm of space-based interferometers, which might be launched in the late 1920s. I provide here a short overview of the scientific payouts of gravitational wave astronomy, focusing the discussion on the low-frequency regime (pulsar timing and space-based interferometry). A detailed discussion of advanced ground-based interferometer can be found in Patrick Brady’s contribution to this proceeding series.     

Sources and technology for an atomic gravitational wave interferometric sensor

We study the use of atom interferometers as detectors for gravitational waves in the mHz–Hz frequency band, which is complementary to planned optical interferometers, such as laser interferometer gravitational wave observatories (LIGOs) and the Laser Interferometer Space Antenna (LISA). We describe an optimized atomic gravitational wave interferometric sensor (AGIS), whose sensitivity is proportional to the baseline length to power of 5/2, as opposed to the linear scaling of a more conservative design. Technical challenges are briefly discussed, as is a table-top demonstrator AGIS that is presently under construction at Berkeley. We study a range of potential sources of gravitational waves visible to AGIS, including galactic and extra-galactic binaries. Based on the predicted shot noise limited performance, AGIS should be capable of detecting type Ia supernovae precursors within 500 pc, up to 200 years beforehand. An optimized detector may be capable of detecting waves from RX J0806.3+1527.     

Stochastic Background of Gravitational Waves Generated by Compact Binary Systems

Binary systems are the most studied sources of gravitational waves. The mechanisms of emission and the behavior of the orbital parameters are well known and can be written in analytic form in several cases. Besides, the strongest indication of the existence of gravitational waves has arisen from the observation of binary systems. On the other hand, when the detection of gravitational radiation becomes a reality, one of the observed pattern of the signals will be probably of stochastic background nature, which are characterized by a superposition of signals emitted by many sources around the universe. Our aim here is to develop an alternative method of calculating such backgrounds emitted by cosmological compact binary systems during their periodic or quasiperiodic phases. We use an analogy with a problem of statistical mechanics in order to perform this sum as well as taking into account the temporal variation of the orbital parameters of the systems. Such a kind of background is of particular importance since it could well form an important foreground for the planned gravitational wave interferometers DECI-Hertz Interferometer Gravitational wave Observatory (DECIGO), Big Bang Observer (BBO), Laser Interferometer Space Antenna (LISA) or Evolved LISA (eLISA), Advanced Laser Interferometer Gravitational-Wave Observatory (ALIGO), and Einstein Telescope (ET).     

Gravitational-wave stochastic background from cosmic strings

We consider the stochastic background of gravitational waves produced by a network of cosmic strings and assess their accessibility to current and planned gravitational wave detectors, as well as to big bang nucleosynthesis (BBN), cosmic microwave background (CMB), and pulsar timing constraints. We find that current data from interferometric gravitational wave detectors, such as Laser Interferometer Gravitational Wave Observatory (LIGO), are sensitive to areas of parameter space of cosmic string models complementary to those accessible to pulsar, BBN, and CMB bounds. Future more sensitive LIGO runs and interferometers such as Advanced LIGO and Laser Interferometer Space Antenna (LISA) will be able to explore substantial parts of the parameter space.