X-ray pulsar navigation has attracted extensive attentions from academy and engineering domains. The navigation accuracy is can be enhanced through design of X-ray mirrors to focus X-rays to a small detector. The Wolter-I optics, originally proposed based on a paraboloid mirror and a hyperboloid mirror for X-ray imaging, has long been widely developed and employed in X-ray observatory. Some differences, however, remain in the requirements on optics between astronomical X-ray observation and pulsar navigation. The simplified Wolter-I optics, providing single reflection by a paraboloid mirror, is more suitable for pulsar navigation. In this paper, therefore, the grazing incidence X-ray mirror was designed further based on our previous work, with focus on the reflectivity, effective area, angular resolution and baffles. To evaluate the performance of the manufactured mirror, the surface roughness and reflectivity were tested. The test results show that the grazing incidence mirror meets the design specifications. On the basis of this, the reflectivity of the mirror in the working bandwidth was extrapolated to evaluate the focusing ability of the mirror when it works together with the detector. The purpose of our current work to design and develop a prototype mirror was realized. It can lay a foundation and provide guidance for the development of multilayer nested X-ray mirror with larger effective area.
X-ray pulsar telescope (XPT) is a complex optical payload, which involves optical, mechanical, electrical and thermal disciplines. The multiphysics coupling analysis (MCA) plays an important role in improving the in-orbit performance. However, the conventional MCA methods encounter two serious problems in dealing with the XTP. One is that both the energy and reflectivity information of X-ray can’t be taken into consideration, which always misunderstands the essence of XPT. Another is that the coupling data can’t be transferred automatically among different disciplines, leading to computational inefficiency and high design cost. Therefore, a new MCA method for XPT is proposed based on the Monte Carlo method and total reflective theory. The main idea, procedures and operational steps of the proposed method are addressed in detail. Firstly, it takes both the energy and reflectivity information of X-ray into consideration simultaneously. And formulate the thermal-structural coupling equation and multiphysics coupling analysis model based on the finite element method. Then, the thermalstructural coupling analysis under different working conditions has been implemented. Secondly, the mirror deformations are obtained using construction geometry function. Meanwhile, the polynomial function is adopted to fit the deformed mirror and meanwhile evaluate the fitting error. Thirdly, the focusing performance analysis of XPT can be evaluated by the RMS. Finally, a Wolter-I XPT is taken as an example to verify the proposed MCA method. The simulation results show that the thermal-structural coupling deformation is bigger than others, the vary law of deformation effect on the focusing performance has been obtained. The focusing performances of thermal-structural, thermal, structural deformations have degraded 30.01%, 14.35% and 7.85% respectively. The RMS of dispersion spot are 2.9143mm, 2.2038mm and 2.1311mm. As a result, the validity of the proposed method is verified through comparing the simulation results and experiments, which can be employed in the reliability-based design of XPT.
We have developed X-ray grazing incidence optics with a single mirror. Although t can be used to demonstrate and test on
the ground to verify the feasibility of X-ray detection system, it is unable to meet the requirements of X-ray pulsar
navigation due to small effective area and large mass. There is an urgent need to develop multilayer nested grazing
incidence optics, which consists of multilayer mirrors to form a coaxial and confocal system to maximize the use of space
and increase the effective area.
In this paper, aiming at the future demand of X-ray pulsar navigation, optimization and analysis of nested X-ray grazing
incidence optics was carried out, the recurrence relations between the layers of mirrors were derived, reasonable initial
structural parameters and stray light reduction method was given, and theoretical effective collection area was calculated.
The initial structure and stray light eliminating structure are designed. The optical-mechanical-thermal numerical model
was established using optical analysis software and finite element software for stray light analysis, focusing performance
analysis, tolerance analysis, and mechanical analysis, providing evidence and guidance for the processing and alignment of
nested X-ray grazing incidence optics.
As a promising new technology for deep space exploration due to autonomous capability, pulsar navigation has attracted
extensive attentions from academy and engineering domains. The pulsar navigation accuracy is determined by the
measurement accuracy of Time of Arrival (TOA) of X-ray photon, which can be enhanced through design of appropriate
optics. The energy band of X-ray suitable for pulsar navigation is 0.1-10keV, the effective focusing of which can be
primely and effectively realized by the grazing incidence reflective optics.
The Wolter-I optics, originally proposed based on a paraboloid mirror and a hyperboloid mirror for X-ray imaging, has
long been widely developed and employed in X-ray observatory. Some differences, however, remain in the requirements
on optics between astronomical X-ray observation and pulsar navigation. X-ray concentrator, the simplified Wolter-I
optics, providing single reflection by a paraboloid mirror, is more suitable for pulsar navigation.
In this paper, therefore, the requirements on aperture, effective area and focal length of the grazing incidence reflective
optics were firstly analyzed based on the characteristics, such as high time resolution, large effective area and low
angular resolution, of the pulsar navigation. Furthermore, the preliminary design of optical system and overall structure,
as well as the diaphragm, was implemented for the X-ray concentrator. Through optical and FEA simulation, system
engineering analysis on the X-ray concentrator was finally performed to analyze the effects of environmental factors on
the performance, providing basis and guidance for fabrication of the X-ray concentrator grazing incidence optics.
X-ray pulsar provides stable, predictable and unique signatures, which is attractive for spacecraft navigation. An X-ray
pulsar timing instrument based on semiconductor detectors is assigned to detect the X-ray photon. The time tagging error
arises from the detector and the pulse signal processing chain. Considering these factors, we find that the time tagging
error is dominated by the design parameters of the processing circuits at low count rate. The contribution of the detector
time resolution increases rapidly as the shaping time constant reduces at high count rate, which is critical for X-ray
pulsar navigation. A correction program is performed to improve the time tagging accuracy at various photon energies
and count rates, so that the random error is minimized. The signal risetime and delay time of the constant fraction
discriminator are simulated to get optimum levels. The photon time tagging error could be reduced by using a fast
shaping filter and optimum designed constant fraction discriminator.