Featured Image Source: SpaceX
SpaceX aims to join the broadband internet provider business to fund its space program. The aerospace company calls the network Starlink – it will be a constellation of over 12,000 internet-beaming satellites orbiting Earth. Starlink’s revenue will go towards making life multiplanetary. SpaceX’s ultimate mission is to send a fleet of 1,000 Starships to Mars before the year 2050. Customers will be supporting that ambitious endeavour that will change the course of humanity’s future. Starlink will be offered on a global scale and benefit rural areas where internet connection is too expensive, unreliable, or non-existent. The latest fleet of 60 satellites was deployed on April 22nd, there is now a total of 420 satellites in low Earth orbit.
Astronomers have voiced their concerns over ‘Starlink appearing too bright.’ Days after deployment, the fleet of Starlink satellites navigate at lower altitudes making them visible to the naked eye (video below). The reflectivity is due to the sun’s light hitting the satellites’ solar panel and antenna arrays. It can take over three weeks for all satellites to reach their operational altitude(s) to reduce reflectivity. The network’s initial phase, is to deploy about 1,584 satellites into an altitude of 550-kilometers above Earth.
SpaceX is actively working with senior members of the astronomy community to minimize the potential reflection of the satellites. Today, April 29, SpaceX released a presentation which details how it aims to reduce Starlink satellites' brightness.
"SpaceX is launching Starlink to provide high-speed, low-latency broadband connectivity across the globe, including to locations where internet has traditionally been too expensive, unreliable, or entirely unavailable," the company wrote. "We also firmly believe in the importance of a natural night sky for all of us to enjoy, which is why we have been working with leading astronomers around the world to better understand the specifics of their observations and engineering changes we can make to reduce satellite brightness."
According to SpaceX, Starlink appears bright because its phased array antennas at the bottom of the satellite, parabolic antennas on the sides, and the backside of the single solar array diffuse white reflection. The surfaces are white to maintain temperature low, thermal changes may affect the satellites’ signal performance. SpaceX’s key solutions to reduce Starlink’s reflectivity are to reduce reflection on antenna during sunrise and sunset.
“The key to making Starlink darker is to prevent sunlight from illuminating these white surfaces and scattering via reflection toward observers on the ground.”
“Satellites are visible from the ground at sunrise or sunset. This happens because the satellites are illuminated by the Sun but people or telescopes on the ground are in the dark. These conditions only happen for a fraction of Starlink's 90-minute orbit.”
When satellites are deployed, they conduct an “orbit raise” operation by using integrated ion thrusters. “During orbit raise, when the solar array is in open book, sunlight can reflect off of both the solar array and the body of the satellite and hit the ground.” SpaceX explains some of the satellites “pause in parking orbit” at an altitude of 380-kilometers, as each satellite thrusts itself into designated orbital lanes. That is when the satellites are the most visible from the ground, as satellites group into position. Then, all move up into 'shark-fin' position at an operational altitude of 550-kilometers above Earth, where satellites become less visible from the ground. “Once satellites are on-station they reconfigure so the antennas face Earth and the solar array goes vertical so that it can track the Sun to maximize power generation,” SpaceX wrote, “As a result of this maneuver, the satellites become much darker because the solar array visibility from the ground is greatly reduced.”
SpaceX plans to make the satellites “generally invisible to the naked eye within a week of launch” by modifying the satellites orientation to minimize the potential of reflectivity as each satellite maneuvers through orbits in space. “We're doing this by changing the way the satellites fly to their operational altitude, so that they fly with the satellite knife-edge to the Sun. We are working on implementing this as soon as possible for all satellites since it is a software change,” SpaceX stated.
The ‘knife-edge’ of each satellite will be faced towards the sun as the satellite moves during orbit raise. This will minimize the sunlight's reflection. Though, the company says this will on occur on small instances because “rolling the solar array away from the Sun reduces the amount of power available to the satellite.”
Engineers are developing a ‘visor’ that will act as a sunshade “to block sunlight from hitting the brightest parts of the spacecraft.” The satellite visor (pictured below) is referred to as ‘VisorSat.’ VisorSats will be made up of a radio-transparent foam material. This would shield from the sun’s rays and minimize the potential for reflection on the satellites' chassis where the antennas are located. SpaceX will launch an experimental VisorSat prototype during an upcoming launch in May. The next cluster of 60 satellites will all feature a “deployable visor” on the ninth Starlink mission, scheduled for June.
SpaceX acknowledged, “it will not be possible to create satellites that are invisible to the most advanced optical equipment on Earth.” But assured that it is committed to design future satellites with less reflective surfaces. “SpaceX is committed to making future satellite designs as dark as possible,” the company stated, “The next generation satellite, designed to take advantage of Starship's unique launch capabilities, will be specifically designed to minimize brightness while also increasing the number of consumers that it can serve with high-speed internet access.” The Starship spacecraft is still in its initial phase of development; It will be capable of carrying about 400 satellites to orbit at once.