  The growth of megaconstellations is rapidly increasing the number of rocket
launches. While Low Earth Orbit (LEO) broadband satellites help to connect
unconnected communities and achieve the Sustainable Development Goals (SDGs),
there are also significant environmental emissions impacts from burning rocket
fuels. We present sustainability analytics for phase 1 of the three main LEO
constellations including Amazon Kuiper (3,236 satellites), Eutelsat Group`s
OneWeb (648 satellites), and SpaceX Starlink (4,425 satellites). We find that
LEO megaconstellations provide substantially improved broadband speeds for
rural and remote communities, but are roughly 6-8 times more emissions
intensive (250 kg CO2eq/subscriber/year) than comparative terrestrial mobile
broadband. In the worst-case emissions scenario, this rises to 12-14 times more
(469 kg CO2eq/subscriber/year). Policy makers must carefully consider the
trade-off between connecting unconnected communities to further the SDGs and
mitigating the growing space sector environmental footprint, particularly
regarding phase 2 plans to launch an order-of-magnitude more satellites.
