On Wednesday, June 3 at 9:25 p.m. EDT, SpaceX launched its eighth Starlink mission aboard Falcon 9, which lifted off from Space Launch Complex 40 (SLC-40) at Cape Canaveral Air Force Station, just days after SpaceX and NASA made history amid coronavirus pandemic last weekend, launching two astronauts into space on board a Falcon 9 rocket to join the International Space Station (ISS).
Astronauts Robert Behnken and Douglas Hurley were launched into space on board a SpaceX Falcon 9 rocket, marking the first time humans have been launched from the US since 2011.
Falcon 9’s first stage previously supported the Telstar 18 VANTAGE mission in September 2018, the Iridium-8 mission in January 2019, and two separate Starlink missions in May 2019 and in January 2020. Following stage separation, SpaceX landed Falcon 9’s first stage on the “Just Read the Instructions” droneship, which was stationed in the Atlantic Ocean.
On this mission, SpaceX launched the first Starlink satellite with a deployable visor to block sunlight from hitting the brightest spots of the spacecraft. NASA’s Kennedy Space Centre said: “The goal of Starlink is to create a network that will help provide internet services to those who are not yet connected, and to provide reliable and affordable internet across the globe.”
Explaining the Starlink satellite design, SpaceX said on its website that it was driven by the fact that they fly at a very low altitude compared to other commmunication satellites. “We do this to prioritize space traffic safety and to minimize the latency of the signal between the satellite and the users who are getting internet service from it. Because of the low altitude, drag is a major factor in the design.”
During orbit raise, the satellites must minimize their cross-sectional area relative to the wind, otherwise drag will cause them to fall out of orbit. High drag is a double-edged sword—it means that flying the satellites is tricky, but it also means that any satellites that are experiencing problems will de-orbit quickly and safely burn up in the atmosphere. This reduces the amount of orbital debris or “space junk” in orbit.
This low-drag and thrusting flight configuration resembles an open book, where the solar array is laid out flat in front of the vehicle. When Starlink satellites are orbit raising, they roll to a limited extent about the velocity vector for power generation, always keeping the cross sectional area minimized while keeping the antennas facing Earth enough to stay in contact with the ground stations, said SpaceX.
When the satellites reach their operational orbit of 550 km, drag is still a factor—so any inoperable satellite will quickly decay—but the altitude control system is able to overcome this drag with the solar array raised above the satellite in a vertical orientation that we call “shark-fin.” This is the orientation in which the satellite spends the majority of its operational life.
A recent study, published in arXiv, researchers led by Stefano Gallozzi, wrote: “Depending on their altitude and surface reflectivity, their contribution to the sky brightness is not negligible for professional ground based observations. With the huge amount of about 50,000 new artificial satellites for telecommunications planned to be launched in Medium and Low Earth Orbit, the mean density of artificial objects will be of >1 satellite for square sky degree; this will inevitably harm professional astronomical images.”