“ The Orbital Solution Portal will also deliver significant value to satellite operators who wish to avoid collisions with one another, collaborate with astronomers on darkening mitigation experiments, and more easily visualize their own constellation’s present and past states. The Orbital Solution Portal provides an opportunity for operators to contribute not only data, but also funding to operate a public service which serves their data in an accessible way. ”

“ For observations to be useful to the community vis-a-vis the characterization of satellite reflectivity, timing, radio frequency magnitude, and the effectiveness of mitigation strategies, it is necessary that the data are reported accurately and in standardized, readily usable format. This module introduces learners to the different and most likely image types, the kinds of information needed a priori, and how to use SatHub to share data. ”

“ In general, the position of a satellite at a future time is forecast with a propagator algorithm that uses an orbital solution from the recent past. Orbital solutions may be in the form of either general perturbations, i.e., time-averaged Keplerian elements that include atmospheric drag computations (commonly represented in TLE format) , or ephemerides, i.e., state vectors of position and velocity data (sometimes referred to as an orbit ephemeris message or OEM) . ”

“ While we envision SatHub as a community-driven resource, creating and sustaining it will require significant funding. Funds are necessary for nearly all aspects of SatHub, most notably to pay for web hosting and key personnel to build and maintain each of five key portions shown in Figure 1. Funding is also needed to pay for telescope time, software developers, community-building experts, analysis of new and archival data, instructors, curriculum developers, forum moderators, industry liaisons, and more. ”

“ Regularly inform the community about the evolving population of satellite constellations and their potential impact to different scientific studies. Establish and sustain dialogs with satellite operators, policymakers, and other stakeholders so future satellite design and operation has less unintentional impact on astronomy and dark skies. Sustain an accessible, responsive website as an evolving resource to accommodate the present and future needs of astronomy, the space industry, and observers worldwide. Some examples of SatHub use cases follow. ”

“ Astronomers should:
conduct observations to provide feedback to LEOsat operators;
compile accurate brightness and timing information on LEOsats;
perform simulations to predict visibility, brightness, and timing of satellites and develop software and hardware tools to mitigate the impact of satellite trails in science images.
Observing satellites can be quite challenging, and requires a slightly different approach than, say, observing variable stars or galaxies or exoplanet transits. One has to anticipate or calculate, based on available data, where the satellite is expected to be in the sky. ”

“ Without revealing proprietary information, they use SatHub to share a list of experimental and control satellites for observers to target. Interested observers subsequently use SatHub to plan their observations and upload, coordinate, and analyze results from the experiment. An observer is reducing their CCD data and notices one or more satellite streaks in an image. They use SatHub as a resource for processing the image to minimize impact of the trails, uploading the image to aid in satellite brightness studies, and discussing strategies with others facing similar situations. ”

“ After working through the curriculum, a learner should be able to:
Appreciate the different kinds of satellites in orbit, and the harmful impact of satellite megaconstellations on astronomy, stargazing, and our night skies; Appreciate the purpose and importance of satellite observations; Access and use existing satellite databases; Efficiently use and contribute to SatHub; Plan satellite observations based on criteria such as location, time, hardware (telescope, camera, etc.) ; Carry out satellite observations using the hardware they have available to them ”

“ A central web portal for sharing and retrieving orbital solutions
To improve community collaboration among myriad stakeholders, especially satellite operators, we propose the Orbital Solution Portal aspect of SatHub (see Figure 1) to simplify how orbital solution data are collected and shared. The key components of the Orbital Solution Portal are ephemerides with error bars, general perturbations with error bars, and equivalent general perturbation information in “old style” TLE format for backwards compatibility. ”

“ An astronomer is planning an observing run for later in the week, and wishes to schedule high-priority observations of a certain target in a satellite-free viewing window. SatHub enables them to access PassPredict and forecast the windows when an input sky coordinate or field of view will have the fewest satellite crossings. An astronomy enthusiast enjoys participating in Zooniverse projects and wishes to help identify images with satellite streaks for a citizen science project. ”

“ Satellites are much closer to the observer than the more traditional targets and will leave a (bright) trail on the image. Tracking satellites is possible, but is quite challenging and will inevitably result in star trails.
As described in Section 1, SatHub will serve as a hub for astronomers and satellite operators to work together towards quantifying and cataloging various observational parameters (timing, satellite brightness, location, velocity, etc.) of non-classified satellite constellations. ”

“ Different sections of the website can subsequently be built out to address different goals, as illustrated in Figure 1. The SatHub umbrella will encompass a user-friendly, accessible, and responsive interface with tools for accessing public data products and satellite orbital solutions, documented open source software to plan and process (or avoid) satellite observations, a curriculum to empower observers of all backgrounds to meaningfully contribute, and a real-time collaboration center. ”

“ The population of Earth-orbiting satellites is dramatically increasing with the advent of commercial satellite constellations that form global consumer communication networks. The impact of these satellite constellations on astronomy and the night sky depends strongly on the brightness of their constituent satellites, which is a complex function of time, attitude, orbital position, and wavelength. ”

“ Photographed satellite streaks for brightness measurements should ideally have accurate timing and location data, and could use a tool such as astrometry.net to learn where it was pointed in the sky. We encourage observers with all backgrounds to use SatHub to coordinate. ”

“ A student wishes to write a report on the impacts of satellite constellations on astronomy and the night sky. They complete the SatHub core training curriculum and participate in the discussion forum to learn both the historical context and the latest developments, and produce a well-researched report. An amateur astronomer highly experienced in visual magnitude estimation has meticulously recorded unaided eye brightnesses of satellites over many nights. ”

“ A data scientist is interested in testing a new image feature detection algorithm. They use SatHub to access images from several astronomy databases in order to train and test their algorithm on streaks, point sources, extended sources, and artifacts. ”

“ Much more worryingly, extreme space weather events — which are most common during solar maximum — like coronal mass ejections and radio bursts could cause communication disruptions with LEOsats, and the high-energy charged particles could cause satellites to enter safe mode or even become fully disabled. With thousands of satellites in similar orbits that are relying on active collision avoidance, even a short window of time where many satellites are disabled or in safe mode could prove disastrous. ”

“ We propose a “one-stop shop” to enable astronomers, community members, satellite operators, other interested groups, and the public to work together more effectively. This initiative, SatHub, will serve as a central coordination hub for characterizing the LEOsat population’s reflectivity, emission properties, positions/trajectories, and other properties over time. ”

“ Darkening satellites is critical, but observers use more than just the V band. To allow forecasting models to accurately predict changes in satellite reflectivity as a function of time, operators should provide relevant metadata such as reflectivity and BRDF measurements in the optical to infrared (at least ~ 0.3–20 microns) range. This will better enable observers to assess the potential impact on their observations and/or detectors and take the appropriate action while observing or preparing to observe. ”

“ Trailblazer is being built publicly with open source tools, and will allow observational astronomers to salvage some scientific value from their satellite-streaked images, and it will give ready access to a user-friendly dataset to any group seeking to quantify scientific impacts of satellite trails.
A sustained funding source will be necessary to maintain and improve Trailblazer long-term. Nevertheless, a website with minimal functionality should exist by the end of 2021. ”

“ As the Sun approaches its next maximum activity level in 2024 or 2025, space weather events that affect the LEO environment will become more frequent. Increased solar activity will result in increased atmospheric scale height, which causes increased drag on LEOsats. In periods of greater solar activity, LEOsats will have to correct their altitudes much more frequently than they currently do in order to maintain operating altitudes. ”

“ Various proposals have been circulated to add flashing light emitting diodes, either in the optical or the NIR, to all satellites as a means of positive identification or as a form of advertising. While these might or might not be visible to the unaided eye, the impact on images obtained by modest to large-aperture astronomical telescopes could be catastrophic. ”

“ Such observations require facilities spread over latitude and longitude to capture Sun-angle-dependent effects.In the longer term, support a comprehensive satellite constellation observing network with uniform observing and data reduction protocols for feedback to operators and astronomical programs. Mature constellations will have the added complexity of deorbiting of the units and on-orbit aging, requiring ongoing monitoring. ”