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 specifically for observatories and satellite operators in collaboration. These are the focus of the SATCON2 Observations Working Group.

Recommendation 8. Support an immediate coordinated effort for optical observations of LEOsat constellation members, to characterize both slowly and rapidly varying reflectivity and the effectiveness of experimental mitigations. 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.

Recommendation 9. Determine the cadence and quality of updated positional information or processed telemetry, distribution, and predictive modeling required to achieve substantial improvement (by a factor of about 10) in publicly available cross-track positional determination.

Recommendation 10. Adopt a new standard format for publicly available ephemerides beyond two-line-elements (TLEs) in order to include covariances and other useful information. The application noted in Recommendation 2 should be compatible with this format and include the appropriate errors.

In this report, we outline implementation steps for SATCON Recommendations 8, 9, and 10. We take the liberty of expanding the scope beyond SATCON1’s focus on mid-latitude optical/NIR astronomy, because LEOsat proliferation impacts observers worldwide at all latitudes. We recognize that a successful outcome will necessarily be supported by new policies governing the use of the sky across multiple jurisdictions, including the national and international level. For more details, please see the Policy Working Group Report.

We endorse the findings of the Dark and Quiet Skies for Science and Society Report and Recommendations (Walker et al., 2020b; hereinafter the D&QS Report), in particular Chapters 6 and 7 that pertain to satellite constellations and radio astronomy, respectively. This report is designed to build on the conclusions from the D&QS Report, not supersede it. To that end, we structure our implementation plan into three main areas: a new coordinated satellite observation hub (Section 1), building a training curriculum (Section 2), and establishing minimum best practices for all satellite constellation operators to share data with the astronomical community and the public (Section 3). We conclude with a few additional considerations (Section 4).

One likely avenue for implementation as described in this report may be through the establishment of a new International Astronomical Union (IAU) Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference1 (hereinafter the IAU Centre). The Observations Working Group would like to emphasize that the implementation steps in this report require significant overall resources on as fast a timescale as possible. It is one thing to write down what must be done, and it is another to secure funding and direct appropriately skilled individuals to carry it out.

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