working satellites, Iridium flares were visible quite often (2 to 4 times per night). Flares of brightness −5 magnitude occurred 3 to 4 times per week, and −8 magnitude were visible 3 to 5 times per month for stationary observers. Flares could also occur from solar panels, but they were not as bright (up to −3.5 magnitude). Such flares lasted about twice as long as those from the main mission antennas (MMA), because the so-called "mirror angle" for the solar panels was twice that for the MMAs. There were also rare cases of flares from MMAs and solar panels, or two MMAs (front and either right or left) of one satellite in a single pass. The flares were bright enough to be seen at night in big cities where light pollution usually prevents most stellar observation. When not flaring, the satellites were often visible crossing the night sky at a typical magnitude of 6, similar to a dim star. Mega-constellations Planned low-orbit satellite constellations such as Starlink are a concern for astronomers, stargazers, and indigenous communities because of light pollution. In February 2020, the Russian Academy of Sciences said it would send a letter to the United Nations complaining that Starlink's satellites will damage "30-40% of astronomical images." Numerous satellite operators have criticized SpaceX for attempting to overwhelm the FCC with paperwork as a means to gain approval to launch 42,000 satellites, which has raised questions about which aspects of space law pertain to light pollution from satellites. In normal dark sky conditions, the naked eye can see objects as dim as +6.5m, which means about 5,600 stars or about one star for every seven of the planned Starlink satellites. In perfect dark sky conditions about 45,000 stars brighter than +8m can be visible to the naked eye, or about one-to-one with the proposed Starlink satellites. Ground based telescopes are even more sensitive, so astronomers have raised concerns about the persistent brightness of Starlink. SpaceX and Elon Musk have asserted in meetings with the National Academy of Sciences and in FCC filings that "SpaceX is committed to reducing satellite brightness to allow enjoyment of the skies and not thwart scientific discovery" and that its objectives are (1) to "make the satellites generally invisible to the naked eye within a week of launch," and (2) to "minimize Starlink's impact on astronomy by darkening satellites so they do not saturate observatory detectors."