The number of small satellites has grown dramatically in the past decade from tens of satellites per year in the mid-2010s to a projection of tens of thousands in orbit by the mid-2020s. This presents both problems and opportunities for observational astronomy. Small satellites offer complementary cost-effective capabilities to both ground-based astronomy and larger space missions. Compared to ground-based astronomy, these advantages are not just in the accessibility of wavelength ranges where the Earth's atmosphere is opaque, but also in stable, high precision photometry, long-term monitoring and improved areal coverage. Astronomy has a long history of new observational parameter spaces leading to major discoveries. Here we discuss the potential for small satellites to explore new parameter spaces in astrophysics, drawing on examples from current and proposed missions, and spanning a wide range of science goals from binary stars, exoplanets and solar system science to the early Universe and fundamental physics.
Private space companies are increasingly commercializing near-earth space. Some estimates show that more than 100,000 satellites may orbit the Earth by 2030. This increase in the number of satellites has many consequences for science, particularly astronomy. Satellite mega-constellations for satellite Internet connectivity are one of the main drivers behind the explosion in the number of satellites. Here, we briefly note whether such satellite mega-constellations can justify their impact on astronomy.
Small satellite platforms with high performance avionics are becoming more affordable. So far, with a few exceptions, small satellites have been mainly dedicated to earth observation. However, astronomy is a fascinating field with a history of large missions and a future of promising large mission candidates. This prompts many questions; can the recent affordability of small satellites change the landscape of space astronomy? What are the potential applications and scientific topics of interest, where small satellites could be instrumental for astronomy? What are the requirements and objective…
AstroSat is a multi-wavelength astronomy satellite, launched on 2015 September 28. It carries a suite of scientific instruments for multi-wavelength observations of astronomical sources. It is a major Indian effort in space astronomy and the context of AstroSat is examined in a historical perspective. The Performance Verification phase of AstroSat has been completed and all instruments are working flawlessly and as planned. Some brief highlights of the scientific results are also given here.
Measuring photometric brightness is a common tool for characterizaing satellites. However, characterizing satellite mega-constellations and their impact on astronomy research requires a new approach and methodology. A few measurements of singular satellites are not sufficient to fully describe a mega-constellation and assess its impact on modern astronomical systems. Characterizing the brightness of a satellite mega-constellation requires a comprehensive measurement program conducting numerous observations over the entire set of critical variables. Utilizing Pomenis, a small-aperture and wide …
In the coming decade, up to 100 000 satellites in large constellations could be launched into low Earth orbit. The satellites will introduce a variety of negative impacts on astronomy observatories and science, which vary from negligible to very disruptive depending on the type of instrument, the position of the science target, and the nature of the constellation. Since the launch of the first batch of SpaceX's Starlink constellation in 2019, the astronomy community has made substantial efforts to analyse the problem and to engage with satellite operators and government agencies. This article …
Modelling steerable beams of satellite constellations for radio astronomy impact studies
SKA Observatory（平方公里阵列望远镜观测台）；IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference（国际天文学联合会暗静天空保护中心）；Onsala Space Observatory, Chalmers University of Technology（翁萨拉空间天文台，查尔姆斯理工大学）
Electromagnetic metamaterials at microwave frequencies are well established in industry and research. Recent work has shown how a specific kind of metallic metamaterial can contribute towards improving the performance of the feedhorn antennas used in radio astronomy and satellite telecommunications. In this article, we justify this argument, finding an innovative type of meta-ring of remarkable manufacturability with a potential to improve the state of the art in these fields. A pioneering meta-horn antenna formed of meta-rings is then fabricated and characterized in the laboratory, showing an…
Tata Institute of Fundamental Research (TIFR) has a very long tradition of conducting space astronomy experiments. Within a few years of the discovery of the first non-solar X-ray source in 1962, TIFR leveraged its expertise in balloon technology to make significant contributions to balloon-borne hard X-ray astronomy. This initial enthusiasm led to extremely divergent all-round efforts in space astronomy: balloon-borne X-ray and infrared experiments, rocket and satellite-based X-ray experiments and a host of other new initiatives. In the early eighties, however, TIFR could not keep up with the…
Several post-detection approaches to the mitigation of radio-frequency interference (RFI) are compared by applying them to the strong RFI from the Iridium satellites. These provide estimates for the desired signal in the presence of RFI, by exploiting distinguishing characteristics of the RFI, such as its polarization, statistics, and periodicity. Our data are dynamic spectra with full Stokes parameters and 1 ms time resolution. Moreover, since most man-made RFI is strongly polarized, we use the data to compare its unpolarized component with its Stokes I. This approach on its own reduces the R…
Large satellite constellations in low-Earth orbit seek to be the infrastructure for global broadband Internet and other telecommunication needs. We briefly review the impacts of satellite constellations on astronomy and show that the Internet service offered by these satellites will primarily target populations where it is unaffordable, not needed, or both. The harm done by tens to hundreds of thousands of low-Earth orbit satellites to astronomy, stargazers worldwide, and the environment is not acceptable.
The Medium Energy X-ray telescope (ME) is one of the three main telescopes on board the Insight Hard X-ray Modulation Telescope (Insight-HXMT) astronomy satellite. ME contains 1728 pixels of Si-PIN detectors sensitive in 5-30 keV with a total geometrical area of 952 cm2. Application Specific Integrated Circuit (ASIC) chips, VA32TA6, is used to achieve low power consumption and low readout noise. The collimators define three kinds of field of views (FOVs) for the telescope, 1°{\times}4°, 4°{\times}4°, and blocked ones. Combination of such FOVs can be used to estimate the in-orbit X-ray and part…
We present new measurements of the vertical density profile of the Earth's atmosphere at altitudes between 70 and 200 km, based on Earth occultations of the Crab Nebula observed with the X-ray Imaging Spectrometer onboard Suzaku and the Hard X-ray Imager onboard Hitomi. X-ray spectral variation due to the atmospheric absorption is used to derive tangential column densities of the absorbing species, i.e., N and O including atoms and molecules, along the line of sight. The tangential column densities are then inverted to obtain the atmospheric number density. The data from 219 occultation scans …
A Danish computer, GIER, from 1961 played a vital role in the development of a new method for astrometric measurement. This method, photon counting astrometry, ultimately led to two satellites with a significant role in the modern revolution of astronomy. A GIER was installed at the Hamburg Observatory in 1964 where it was used to implement the entirely new method for the measurement of stellar positions by means of a meridian circle, then the fundamental instrument of astrometry. An expedition to Perth in Western Australia with the instrument and the computer was a success. This method was al…
The Ultraviolet Transient Astronomy Satellite (ULTRASAT) is a space-borne near UV telescope with an unprecedented large field of view (200 sq. deg.). The mission, led by the Weizmann Institute of Science and the Israel Space Agency in collaboration with DESY (Helmholtz association, Germany) and NASA (USA), is fully funded and expected to be launched to a geostationary transfer orbit in Q2/3 of 2025. With a grasp 300 times larger than GALEX, the most sensitive UV satellite to date, ULTRASAT will revolutionize our understanding of the hot transient universe, as well as of flaring galactic source…
Towards Genuine Coexistence: Per-Satellite Emission and Radiation Limits to Protect Radio Astronomy and Geodetic VLBI at 1-14 GHz from Satellite Constellations
With the observation of the gravitational wave event of August 17th 2017 the multi-messenger astronomy era has definitely begun. With the opening of this new panorama, it is necessary to have new instruments and a perfect coordination of the existing observatories. Crystal Eye is a detector aimed at the exploration of the electromagnetic counterpart of the gravitational waves. Such events generated by neutron stars' mergers are associated with gamma-ray bursts (GRB). At present, there are few instruments in orbit able to detect photons in the energy range going from tens of keV up to few MeV. …
The far-infrared (FIR) is one of the few wavelength ranges where no astronomical data with sub-arcsec resolution exist yet. Neither of the medium-term satellite projects like SPICA, Millimetron or OST will resolve this malady. Information at high spatial and spectral resolution in the FIR, taken from atomic fine-structure lines, highly excited CO, and especially from water lines would, however, open the door for transformative science. This calls for interferometric concepts. We present first results of our feasibility study IRASSI (Infrared Astronomy Satellite Swarm Interferometry) for a FIR …
We have been developing P-channel Charge-Coupled Devices (CCDs) for the upcoming X-ray Astronomy Satellite XRISM, planned to be launched in 2021. While the basic design of the CCD camera (Soft X-ray Imager: SXI) is almost the same as that of the lost Hitomi (ASTRO-H) observatory, we are planning to reduce the "light leakages" that is one of the largest problems recognized in Hitomi data. We adopted a double-layer optical blocking layer on the XRISM CCDs and also added an extra aluminum layer on the backside of them. We develop a newly designed test sample CCD and irradiate it with optical ligh…
The low energy (LE) X-ray telescope is one of the three main instruments of the Insight-Hard X-ray Modulation Telescope (Insight-HXMT). It is equipped with Swept Charge Device (SCD) sensor arrays with a total geometrical area of 384 cm2 and an energy band from 0.7 keV to 13 keV. In order to evaluate the particle induced X-ray background and the cosmic X-ray background simultaneously, LE adopts collimators to define four types of Field Of Views (FOVs). LE is constituted of three detector boxes (LEDs) and an electric control box (LEB) and achieves a good energy resolution of 140 eV at 5.9 keV, a…
\textit{Resolve} onboard the X-ray satellite XRISM is a cryogenic instrument with an X-ray microcalorimeter in a Dewar. A lid partially transparent to X-rays (called gate valve, or GV) is installed at the top of the Dewar along the optical axis. Because observations will be made through the GV for the first few months, the X-ray transmission calibration of the GV is crucial for initial scientific outcomes. We present the results of our ground calibration campaign of the GV, which is composed of a Be window and a stainless steel mesh. For the stainless steel mesh, we measured its transmission u…
Lessons learned from ongoing coordination between NRAO/GBO and LEO NGSO satellite constellations
National Radio Astronomy Observatory (NRAO)（美国国家无线电天文台）；Green Bank Observatory (GBO)（格林班克天文台）；NRAO Domenici Socorro Operations Center (DSOC)（NRAO多梅尼奇索科罗运营中心）
The field of gamma-ray astronomy has experienced impressive progress over the last decade. Thanks to the advent of a new generation of imaging air Cherenkov telescopes (H.E.S.S., MAGIC, VERITAS) and thanks to the launch of the Fermi-LAT satellite, several thousand gamma-ray sources are known today, revealing an unexpected ubiquity of particle acceleration processes in the Universe. Major scientific challenges are still ahead, such as the identification of the nature of Dark Matter, the discovery and understanding of the sources of cosmic rays, or the comprehension of the particle acceleration …
The Impact of Artificial Space Objects on Optical Astronomy as Determined from 32 Million Photometric Observations
IAU Centre for the Protection of the Dark and Quiet Sky（国际天文联合会保护黑暗与宁静天空中心）；Czech Academy of Sciences（捷克科学院）；Institute of Physics, Czech Academy of Sciences（捷克科学院物理研究所）
The global climate crisis poses new risks to humanity, and with them, new challenges to the practices of professional astronomy. Avoiding the more catastrophic consequences of global warming by more than 1.5 degrees requires an immediate reduction of greenhouse gas emissions. According to the 2018 United Nations Intergovernmental Panel report, this will necessitate a 45% reduction of emissions by 2030 and net-zero emissions by 2050. Efforts are required at all levels, from the individual to the governmental, and every discipline must find ways to achieve these goals. This will be especially di…
Pictorial and Documentary Guide for Research, Teaching, and Education through Astronomy, Physics, and Mathematics Pursued under the Umbrella of the United Nations (1974-2024)
The Insight-Hard X-ray Modulation Telescope (Insight-HXMT) is a broad band X-ray and gamma-ray (1-3000 keV) astronomy satellite. The High Energy X-ray telescope (HE) is one of its three main telescopes. The main detector plane of HE is composed of 18 NaI(Tl)/CsI(Na) phoswich detectors, where NaI(Tl) serves as primary detector to measure ~ 20-250 keV photons incident from the field of view (FOV) defined by the collimators, and CsI(Na) is used as an active shield detector to NaI(Tl) by pulse shape discrimination. CsI(Na) is also used as an omnidirectional gamma-ray monitor. The HE collimators ha…
A measurement-based approach to EPFD calculation, to quantify the impact of satellite mega-constellations on low-frequency radio astronomy
International Centre for Radio Astronomy Research, Curtin University（国际射电天文研究中心，科廷大学）；Cahill Center for Astronomy and Astrophysics, California Institute of Technology（加州理工学院凯尔天文学与天体物理学中心）；Owens Valley Radio Observatory, California Institute of Technology（加州理工学院欧文斯谷射电天文台）；Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology（麻省理工学院电气与计算机工程系）；Haystack Observatory, Massachusetts Institute of Technology（麻省理工学院海斯塔克天文台）；Max-Planck-Institut für Radioastronomie, Radioobservatorium Effelsberg（马克斯·普朗克射电天文研究所，埃费尔贝格射电天文台）；IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference（国际天文学联合会卫星星座干扰下暗夜与宁静天空保护中心）；SKA Observatory, Jodrell Bank（平方公里阵列射电望远镜天文台，乔德雷尔银行）；CSIRO Space and Astronomy（澳大利亚联邦科学与工业研究组织空间与天文部门）
The ESO workshop "Ground-based thermal infrared astronomy" was held on-line October 12-16, 2020. Originally planned as a traditional in-person meeting at ESO in Garching in April 2020, it was rescheduled and transformed into a fully on-line event due to the COVID-19 pandemic. With 337 participants from 36 countries the workshop was a resounding success, demonstrating the wide interest of the astronomical community in the science goals and the toolkit of ground-based thermal infrared astronomy.
Being one of the most fascinating and ancient sciences, astronomy has always played a special role in society. In 2022 ESO organised an online conference to offer the community a platform to discuss astronomical topics of sociological and philosophical relevance in a professional atmosphere. The talks touched on several crucial aspects, moving from the methodology of science to the use of metrics, to the importance of diversity in evaluation processes, and to the link between astronomy and society.
Harnessing the sheer discovery potential of gravitational wave astronomy will require bold, deliberate, and sustained efforts to train and develop the requisite workforce. The next decade requires a strategic plan to build -- from the ground up -- a robust, open, and well-connected gravitational wave astronomy community with deep participation from traditional astronomers, physicists, data scientists, and instrumentalists. This basic infrastructure is sorely needed as an enabling foundation for research. We outline a set of recommendations for funding agencies, universities, and professional s…
This contribution presents a poll undertaken at the beginning of 2012, and addressed to every doctor in astronomy who obtained his/her degree in France. Its goal is to motivate the French astronomical community to think and discuss about what should be the training of PhDs, and what should be its objective. Further discussions and reactions can be posted e.g. on http://docastro.blogspot.fr/. A worrying results from the poll is that the majority of the participants would not encourage a young student to start a thesis in astronomy. The main reasons for this fact may be the high pressure on astr…
The QueSERA Study Group (QSG) have been tasked by the RadioNet Board to produce a White Paper on the future organisation and coordination of radio astronomy in Europe. This White Paper describes the options discussed by the QSG, and our conclusions on how to move forward. We propose, that as a first step, RadioNet-work, be established as an entity that persists between EC contracts, and that takes responsibility for preparing or coordinating responses to EC opportunities specific to the field of radio astronomy research infrastructures. RadioNet-work should provide a safety net that ensures th…
The past decade has seen the rise of various radio astronomy arrays, particularly for low-frequency observations below 100MHz. These developments have been primarily driven by interesting and fundamental scientific questions, such as studying the dark ages and epoch of re-ionization, by detecting the highly red-shifted 21cm line emission. However, Earth-based radio astronomy below frequencies of 30MHz is severely restricted due to man-made interference, ionospheric distortion and almost complete non-transparency of the ionosphere below 10MHz. Therefore, this narrow spectral band remains possib…
The literature on horn antennas dedicated to radio astronomy and satellite communications applications is very extensive and at times disjointed, relevant contributions being distributed as far back as from the 60's until the present today. This work combines a compact but complete review of the different theories, methodologies and techniques used to describe corrugations and metamaterials in their application to feedhorns used in radio astronomy and satellite communications along with some new work to help explain the theory in a more practical way. Starting with the hybrid-mode condition fi…
We review the history of space mission in Korea focusing on the field of astronomy and astrophysics. For each mission, scientific motivation and achievement are reviewed together with some technical details of the program including mission schedule. This review includes the ongoing and currently approved missions as well as some planned ones. Within the admitted limitations of authors' perspectives, some comments on the future direction of space program for astronomy and astrophysics in Korea are made at the end of this review.
Why study astronomy, why teach astronomy? We give answers to these fundamental questions based on our experience with the Astronomical Camp "Beli Brezi" (White Aspens; Kardzhali, Bulgaria). It has been a place for teaching astronomy to high schools kids for nearly half a century. We describe shortly the history of the camp and draw some conclusions based on nearly five decades of experience. Major among them is that the camp has gone further than just distributing astronomical knowledge - while this is an important and worthy task, the main achievement has been the cultivation of critical thin…
The infrared astronomy group of Department of Astronomy and Astrophysics at Tata Institute of Fundamental Research has been pursuing astronomical instrumentation activities since its inception. The group has been routinely involved in balloon-borne astronomy programs from the field station at Hyderabad with indigenously developed payloads. Ground-based astronomical activities began with a single element infrared detector. Later, over time, larger format array detectors are being used in the cameras. These astronomy cameras have been routinely used at observatories across India. Recently, the g…
Africa has amazing potential due to natural (such as dark sky) and human resources for scientific research in astronomy and space science. At the same time, the continent is still facing many difficulties, and its countries are now recognising the importance of astronomy, space science and satellite technologies for improving some of their principal socio-economic challenges. The development of astronomy in Africa (including Ethiopia) has grown significantly over the past few years, and never before it was more possible to use astronomy for education, outreach, and development as it is now. Ho…
THESEUS is a medium size space mission of the European Space Agency, currently under evaluation for a possible launch in 2032. Its main objectives are to investigate the early Universe through the observation of gamma-ray bursts and to study the gravitational waves electromagnetic counterparts and neutrino events. On the other hand, its instruments, which include a wide field of view X-ray (0.3-5 keV) telescope based on lobster-eye focusing optics and a gamma-ray spectrometer with imaging capabilities in the 2-150 keV range, are also ideal for carrying out unprecedented studies in time domain …
For the first time in history, humans have reached the point where it is possible to construct a revolutionary space-based observatory that has the capability to find dozens of Earth-like worlds, and possibly some with signs of life. This same telescope, designed as a long-lived facility, would also produce transformational scientific advances in every area of astronomy and astrophysics from black hole physics to galaxy formation, from star and planet formation to the origins of the Solar System. The Association of Universities for Research in Astronomy (AURA) commissioned a study on a next-ge…
Gender equity is one of the biggest issues facing the field of astrophysics, and there is broad interest in addressing gender disparities within astronomy. Many studies of these topics have been performed by professional astronomers who are relatively unfamiliar with research in fields such as gender studies and sociology. As a result, they adopt a normative view of gender as a binary choice of 'male' or 'female', leaving astronomers whose genders do not fit within that model out of such research entirely. Reductive frameworks of gender and an overemphasis on quantification as an indicator of …
We present a concept for on-orbit radio detection of ultra-high energy cosmic rays (UHECRs) that has the potential to provide collection rates of ~100 events per year for energies above 10^20 eV. The synoptic wideband orbiting radio detector (SWORD) mission's high event statistics at these energies combined with the pointing capabilities of a space-borne antenna array could enable charged particle astronomy. The detector concept is based on ANITA's successful detection UHECRs where the geosynchrotron radio signal produced by the extended air shower is reflected off the Earth's surface and dete…
