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Radio telescopes observe extremely faint emission from astronomical objects, ranging from compact sources to large scale structures that can be seen across the whole sky. Satellites actively transmit at radio frequencies (particularly at 10±20 GHz, but usage of increasing broader frequency ranges are already planned for the future by satellite operators), and can appear as bright as the Sun in radio astronomy observations. Remote locations have historically enabled telescopes to avoid most interference, however this is no longer the case with dramatically increasing numbers of satellites that transmit everywhere on Earth. Even more remote locations such as the far side of the Moon may provide new radio astronomy observation opportunities, but only if they are protected from satellite transmissions. Improving our understanding of satellite transmissions on radio telescopes across the whole spectrum and beyond is urgently needed to overcome this new observational challenge, as part of ensuring the future access to dark and quiet skies. In this contribution we summarise the current status of observations of active satellites at radio frequencies, the implications for future astronomical observations, and the longer-term consequences of an increasing number of active satellites. This will include frequencies where satellites actively transmit, where they unintentionally also transmit, and considerations about thermal emission and other unintended emissions. This work is ongoing through the IAU CPS. 

The protection of the dark and (radio) quiet sky is a key aspect of the European Space Agency Zero Debris Charter. The International Astronomical Union Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS) is one of the partners working to develop and implement technical and policy recommendations. In this contribution, we summarize and discuss existing recommendations and guidelines that are aimed at enabling the coexistence of satellite constellations and ground based astronomy. Many individuals and groups, including astronomers and industry partners, are working on strategies for more effectively sharing access to space. As a result, the IAU CPS recommendations touch on a variety of subjects ranging from satellite constellation design, to operational modes, to establishing standards for information sharing. The IAU CPS uniquely enables development of publicly accessible tools and services alongside these recommendations, and we endeavor to engage all parties in an open and constructive manner.