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Register a new userOn the Impact of Satellite Constellations on Astronomical Observations with ESO telescopes in the Visible and Infrared Domains
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The effect of satellite constellations on observations in the visible and IR domains is estimated, considering 18 constellations in development by SpaceX, Amazon, OneWeb, and others, with over 26,000 satellites, constituting a representative distribution. This study uses a series of simplifications and assumptions to obtain conservative, order-of-magnitude estimates of the effects. The number of illuminated satellites from the constellations above the horizon ranges from ~1600 right after sunset, decreasing to 1100 at the end of astronomical twilight, most of them (~85%) close to the horizon (< 30deg). The large majority of these satellites will be too faint to be seen with the naked eye: at astronomical twilight, 110 brighter than mag 5. Most of them (~95%) will be close to the horizon. The number of naked-eye satellites plummets as the Sun reaches 30-40 deg below the horizon, depending on the latitude and season. The light trails caused by satellites would ruin a small fraction (below the 1% level) of exposures using narrow to normal field imaging or spectroscopic techniques in the visible and near IR during the first and last hours of the night. Similarly, the thermal emission of the satellite would affect only a negligible fraction of thermal IR observations. However, wide-field exposures, as well as long medium-field exposures,would be affected at the 3% level during the first and last hours of the night. Furthermore, ultra-wide imaging exposures on a very large telescope (eg NSFs Rubin Observatory, LSST), would be significantly affected, with 30 to 40% of such exposures being compromised during the first and last hours of the night. Coordination between the astronomical community, satellites companies, and government agencies is therefore critical to minimise and mitigate the effect on astronomical observations, in particular on survey telescopes.
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Up to 100,000 satellites could be launched into Low Earth Orbit (LEO) in the coming decade. Assuming the two most advanced companies plans are realised, close to 80,000 satellites will be present at a variety of altitudes between 328 - 1,325 km. At Paranal, more than 5,000 satellites will be over the horizon at any given time. Of these, depending on the hour of night and season, a few hundred to several thousand will be illuminated by the sun and potentially detectable. Satellites show a very strong concentration towards the local horizon, with over 50% of the satellites below 20 degrees elevation. This report informs ESOs Council of the impacts on ESO facilities, mitigation measures that ESO could adopt in the future, and the various community efforts in which ESO is involved.
The number of satellites in low-Earth orbit is increasing rapidly, and many tens of thousands of them are expected to be launched in the coming years. There is a strong concern among the astronomical community about the contamination of optical and near-infrared observations by satellite trails. We analyze the impact analysis of such constellations on optical and near-infrared astronomical observations in a rigorous and quantitative way, using updated constellation information, and considering imagers and spectrographs and their very different characteristics. We introduce an analytical method that allows us to rapidly and accurately evaluate the effect of a very large number of satellites, accounting for their magnitudes and the effect of trailing of the satellite image during the exposure. We use this to evaluate the impact on a series of representative instruments, including imagers (traditional narrow field instruments, wide-field survey cameras, and astro-photographic cameras) and spectrographs (long-slit and fibre-fed), taking into account their limiting magnitude. As already known (Walker et al. 2020), the effect of satellite trails is more damaging for high-altitude satellites, on wide-field instruments, or essentially during the first and last hours of the night. Thanks to their brighter limiting magnitudes, low- and mid-resolution spectrographs will be less affected, but the contamination will be at about the same level as that of the science signal, introducing additional challenges. High-resolution spectrographs will essentially be immune. We propose a series of mitigating measures, including one that uses the described simulation method to optimize the scheduling of the observations. We conclude that no single mitigation measure will solve the problem of satellite trails for all instruments and all science cases.
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 SpaceXs 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 presents a short summary of the simulations of impacts on ESOs optical and infrared facilities and ALMA, as well as the conducted observational campaigns to assess the brightness of satellites. It also discusses several activities to identify policy solutions at the international and national level.
Lucky Imaging combined with a low order adaptive optics system has given the highest resolution images ever taken in the visible or near infrared of faint astronomical objects. This paper describes a new instrument that has already been deployed on the WHT 4.2m telescope on La Palma, with particular emphasis on the optical design and the predicted system performance. A new design of low order wavefront sensor using photon counting CCD detectors and multi-plane curvature wavefront sensor will allow virtually full sky coverage with faint natural guide stars. With a 2 x 2 array of 1024 x 1024 photon counting EMCCDs, AOLI is the first of the new class of high sensitivity, near diffraction limited imaging systems giving higher resolution in the visible from the ground than hitherto been possible from space.
This article is a second analysis step from the descriptive arXiv:2001.10952 preprint. This work is aimed to arise awareness to the scientific astronomical community about the negative impact of satellites mega-constellations and put in place an approximated estimations about loss of scientific contents expected for ground based astronomical observations when about 50,000 satellites will be displaced in LEO orbit. The first analysis regards the impact on professional astronomical images in optical windows. Then the study is expanded to other wavelengths and astronomical ground based facilities (radio and higher energies) to better understand which kind of effects are expected. Authors also try to perform a quantitative economic estimation related to the loss of value for public finances committed to the ground based astronomical facilities armed by satellites constellations. These evaluations are intended for general purposes, can be improved and better estimated, but in this first phase they could be useful as evidentiary material to quantify the damage in subsequent legal actions against further satellites deployments.
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