The Virtual Telescope for X-Ray Observations (VTXO) is an Astrophysics SmallSat mission being developed to demonstrate 10-milliarcsecond X-ray imaging using a Phase Fresnel Lense (PFL) based space telescope. PFLs promise to provide several orders of magnitude improvement in angular resolution over current state of the art X-ray optics. However, PFLs for astronomical applications require a long focal length, for VTXO the focal length is estimated to be in the range of 0.5 km to 4 km. Since these focal lengths are not feasible on a single spacecraft, the proposed solution is to use two separate spacecraft, one with the lense(s), and the second with an X-ray camera. These two spacecrafts will then fly in a formation approximating a single rigid telescope. In order to achieve this configuration, the two spacecraft must maintain the formation a focal length distance apart, with centimeter level control, and sub-millimeter level knowledge requirements. Additionally, the system must keep the telescope axis pointed at a fixed target on the celestial sphere for extended durations. VTXOs system architecture calls for two CubeSats to operate in a highly eccentric Earth orbit with one of the spacecrafts traveling on a natural keplarian orbit. The second spacecraft will then fly on a pseudo orbit maintaining a fixed offset during observations. Observations with this system will occur near apogee where differential forces on the spacecrafts are minimal which in turn minimizes fuel consumption. This paper overviews VTXOs system architecture, and looks in depth at the formation flying techniques, including fuel consumption, and methods maintaining the formation. Beyond its use in X-ray astronomy, these formations flying techniques should eventually contribute to the development of distributed aperture telescopes, with imaging performance orders of magnitude better than the current state of the art.
The ASPIICS solar coronagraph aboard the Proba-3 formation flying mission. Scientific objectives and instrument design
Centre Spatial de Liège, Université de Liège（列日大学空间中心）；European Space Research and Technology Centre, European Space Agency（欧洲航天局欧洲空间研究与技术中心）；Laboratoire Atmosphéres et Observations Spatiales（大气与空间观测实验室）；National Institute for Astrophysics, Astrophysical Observatory of Torino（国家天体物理研究所都灵天文台）；Astronomical Institute of the Czech Academy of Sciences（捷克科学院天文研究所）；Max Planck Institute for Solar System Research（马克斯·普朗克太阳系统研究所）；Institute of Geodynamics of the Romanian Academy（罗马尼亚科学院地球动力学研究所）；Astronomical Institute, University of Wrocław（弗罗茨瓦夫大学天文研究所）
在过去40年中，空间天文学主要是由低地球轨道航天器完成的，低地球轨道航天器的技术已得到验证，运载机制也很容易获得。然而，随着商业航空航天飞行任务的激增，新的机会正在出现。我们在这里描述这样一种可能性：在月球上部署一个小型仪器。这可以通过搭载印度参加Google Lunar X PRIZE竞赛的Indus团队任务来实现，该任务预计将向月球运送近30公斤的有效载荷，其中火星车作为其主要有效载荷。我们建议安装一个宽视场远紫外（130- 180纳米）成像望远镜作为印度队着陆器上的有效载荷。我们的基线操作是一个固定的天顶指向，但有一个机制，允许不同的态度观测选项。指向中间黄道纬度（50度或以上）确保太阳在任何时候都至少偏离视线40度。在这个位置，望远镜可以覆盖银河系的高纬度地区以及部分银河系平面。这种前景的科学目标进行了划定和讨论。
Optical frequency comb integration in radio telescopes: advancing signal generation and phase calibration
Korea Advanced Institute of Science and Technology (KAIST)（韩国科学技术院）；Korea Astronomy and Space Science Institute (KASI)（韩国天文学与空间科学研究所）；University of Science and Technology (UST)（科学技术联合大学院大学）；Max-Planck Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；Korea Research Institute of Standards and Science (KRISS)（韩国标准与科学研究院）
Using U-Nets to Create High-Fidelity Virtual Observations of the Solar Corona
NASA Frontier Development Lab（NASA前沿发展实验室）；IQVIA（艾昆纬）；Rosseland Center for Solar Physics（罗瑟兰太阳物理中心）；University of Oslo（奥斯陆大学）；IACS - The Catholic University of America（美国天主教大学计算科学研究所）；NASA - Goddard Space Flight Center（NASA戈达德太空飞行中心）；Lockheed Martin Solar and Astrophysics Laboratory（洛克希德·马丁太阳与天体物理实验室）；Stanford University（斯坦福大学）；Institut d’Astrophysique Spatiale, Université Paris-Sud（巴黎南大学空间天体物理研究所）；University of Oxford（牛津大学）；SETI（搜寻地外文明研究所）
