The Hard X-ray Modulation Telescope (HXMT) will perform an all-sky survey in hard X-ray band as well as deep imaging of a series of small sky regions. We expect various compact objects to be detected in these imaging observations. Point source detection performance of HXMT imaging observation depends not only on the instrument but also on its data analysis since images are reconstructed from HXMT observed data with numeric methods. Denoising technique plays an import part in HXMT imaging data analysis pipeline alongside with demodulation and source detection. In this paper we have implemented several methods for denoising HXMT data and evaluated the point source detection performances in terms of sensitivities and location accuracies. The results show that direct demodulation with 1-fold cross correlation should be the default reconstruction and regularization methods, although both sensitivity and location accuracy could be further imporved by selecting and tuning numerical methods in data analysis of HXMT imaging observations.
We present the calibration of the Insight-Hard X-ray Modulation Telescope (Insight-HXMT) X-ray satellite, which can be used to perform timing and spectral studies of bright X-ray sources. Insight-HXMT carries three main payloads onboard: the High Energy X-ray telescope (HE), the Medium Energy X-ray telescope (ME) and the Low Energy X-ray telescope (LE). In orbit, the radioactive sources, activated lines, the fluorescence lines and celestial sources are used to calibrate the energy scale and energy resolution of the payloads. The Crab nebular is adopted as the primary effective area calibrator …
Expectation Maximization for Hard X-ray Count Modulation Profiles
本文研究了用RHESSI（Ramaty High Energy Solar Spectroscopic Imager）太阳光谱仪获得的太阳硬X射线调制剖面数据进行图像重建的问题。我们的目标是证明一个经典的统计迭代方法适用于图像去卷积问题是非常有效的，当用于分析计数调制分布在太阳硬X射线成像的旋转调制准直器的基础上。本文所述的算法迭代求解极大似然问题，并将一个正性约束编码到迭代优化方案中。因此，结果是经典的期望最大化方法，这次不应用于图像去卷积问题，而是应用于从计数调制轮廓的图像重建。使我们的实现在这个应用程序中特别有效的技术原因是使用了一个非常可靠的停止规则，它能够正则化的解决方案，同时提供了一个非常令人满意的现金统计量（C统计量）。该方法适用于再现合成燃烧配置和重建图像从对应于三个真实事件的实验数据。在第二种情况下，与Pixon图像重建相比，期望最大化的性能显示出相当的准确性和显著降低的计算负担;与CLEAN相比，显示出更好的测量保真度和相当的计算效率。如果最佳地停止，期望最大化表示当计数调制配置文件用作输入数据时在RHESSI上下文中用于图像重建的非常可靠的方法。
Quantitative and analytical analysis of modulation process of the collimator is a great challenge, and is also of great value to the design and development of Fourier transform imaging telescopes. The Hard X-ray Imager (HXI), as one of the three payloads onboard the Advanced Space-based Solar Observatory(ASO-S) mission, adopts modulating Fourier-Transformation imaging technique and will be used to explore mechanism of energy release and transmission in solar flare activities. As an important step to reconstruct the images of solar flares, accurate modulation functions of HXI are needed. In thi…
The Cosmology Large Angular Scale Surveyor (CLASS) is a telescope array observing the Cosmic Microwave Background (CMB) at frequency bands centered near 40, 90, 150, and 220 GHz. CLASS measures the CMB polarization on the largest angular scales to constrain the inflationary tensor-to-scalar ratio and the optical depth due to reionization. To achieve the long time-scale stability necessary for this measurement from the ground, CLASS utilizes a front-end, variable-delay polarization modulator on each telescope. Here we report on the improvements in stability afforded by front-end modulation usin…
InnoPOL: an EMCCD imaging polarimeter and 85-element curvature AO system on the 3.6-m AEOS telescope for cost effective polarimetric speckle suppression
Effective collecting area, angular resolution, field of view and energy response are fundamental attributes of X-ray telescopes. The performance of state-of-the-art telescopes is currently restricted by Wolter optics, especially for hard X-rays. In this paper, we report the development of a new approach - the Stacked Prism Lens, which is lightweight, modular and has the potential for a significant improvement in effective area, while retaining high angular resolution. The proposed optics is built by stacking discs embedded with prismatic rings, created with photoresist by focused UV lithograph…
Flight Performance of an advanced CZT Imaging Detector in a Balloon-borne Wide-Field Hard X-ray Telescope - ProtoEXIST1
我们成功地进行了第一次高空气球飞行的宽视场硬X射线编码孔径望远镜ProtoEXIST 1，这是从哥伦比亚科学气球设施发射的。2009年10月9日，新墨西哥州萨姆纳。ProtoEXIST 1是我们正在进行的项目中第一次实现先进的CdZnTe（CZT）成像探测器，以建立下一代宽视场硬X射线望远镜所需的技术。ProtoEXIST 1中的CZT探测器平面由一个8 x 8阵列组成，该阵列由2 cm x 2 cm x 0.5 cm厚的像素化CZT晶体紧密平铺而成，每个晶体具有8 x 8像素，覆盖256 cm^2的有效面积，像素为2.5 mm。安装在探测器上方90 cm处的钨掩模提供30 - 600 keV波段的X射线源的阴影图用于成像，允许9度x 9度的完全编码视场，角分辨率为20 arcmin。为了减少背景辐射，探测器四周被半渐变（Pb/Sn/Cu）被动屏蔽层包围，一直到掩模。在背面，一个26 cm x 26 cm x 2 cm CsI（Na）有源屏蔽提供信号，以标记带电粒子感应事件以及来自下方的>~ 100 keV背景光子。由于在漂浮高度（38-39公里）的强风（60节），飞行持续时间仅约7.5小时。在整个飞行过程中，CZT探测器表现出色。望远镜在飞行结束时观察了Cyg X-1约1小时。尽管指向和方位系统存在一些问题，导致望远镜跟踪偏离目标约6.4度，但对天鹅座X-1数据的分析显示，在机载…
As China's first X-ray astronomical satellite, Insight-HXMT (Hard X-ray Modulation Telescope) successfully launched on Jun 15, 2017. It performs timing and spectral studies of bright sources to determine their physical parameters. HXMT carries three main payloads onboard: the High Energy X-ray telescope (HE, 20-250 keV, NaI(Tl)/CsI(Na)), the Medium Energy X-ray Telescope (ME, 5-30 keV, Si-Pin) and the Low Energy X-ray telescope (LE, 1-15 keV, SCD). In orbit, we have used the radioactive sources, activated lines, the fluorescence line, and Cas A to calibrate the gain and energy resolution of th…
As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/fa…
Hitomi (ASTRO-H) carries two Hard X-ray Telescopes (HXTs) that can focus X-rays up to 80 keV. Combined with the Hard X-ray Imagers (HXIs) that detect the focused X-rays, imaging spectroscopy in the high-energy band from 5 keV to 80 keV is made possible. We studied characteristics of HXTs after the launch such as the encircled energy function (EEF) and the effective area using the data of a Crab observation. The half power diameters (HPDs) in the 5--80 keV band evaluated from the EEFs are 1.59 arcmin for HXT-1 and 1.65 arcmin for HXT-2. Those are consistent with the HPDs measured with ground ex…
The observation of small bodies in the Space Environment is an ongoing important task in astronomy. While nowadays new objects are mostly detected in larger sky surveys, several follow-up observations are usually needed for each object to improve the accuracy of orbit determination. In particular objects orbiting close to Earth, so called Near-Earth Objects are of special concern as a small but not negligible fraction of them can have a non-zero impact probability with Earth. Telescopes are often hosted by amateur observatories. With upcoming new NEO search campaigns by very wide field of view…
We are currently developing Cadmium Zinc Telluride (CZT) detectors for a next-generation space-borne hard X-ray telescope which can follow up on the highly successful NuSTAR (Nuclear Spectroscopic Telescope Array) mission. Since the launch of NuSTAR in 2012, there have been major advances in the area of X-ray mirrors, and state-of-the-art X-ray mirrors can improve on NuSTAR's angular resolution of ~1 arcmin Half Power Diameter (HPD) to 15" or even 5" HPD. Consequently, the size of the detector pixels must be reduced to match this resolution. This paper presents detailed simulations of relative…
