  Starlink and alike have attracted a lot of attention recently, however, the
inner working of these low-earth-orbit (LEO) satellite networks is still
largely unknown. This paper presents an ongoing measurement campaign focusing
on Starlink, including its satellite access networks, gateway and
point-of-presence structures, and backbone and Internet connections, revealing
insights applicable to other LEO satellite providers. It also highlights the
challenges and research opportunities of the integrated space-air-ground-aqua
network envisioned by 6G mobile communication systems, and calls for a
concerted community effort from practical and experimentation aspects.
