SpaceX's experimental Starlink DarkSat shows brightness reduction

Featured Image Source: @Marco_Langbroek via Twitter.

SpaceX, the rocket company founded by Elon Musk, plans to fund Mars missions by offering broadband internet services worldwide. SpaceX is in the process of building a constellation of internet-beaming satellites in low Earth orbit. 360 Starlink satellites have already been deployed into orbit out of the 12,000 that will make-up the constellation. The initial plan, consists of deploying 1,584 satellites into 72 orbits with 22 satellites per orbital ring, into an altitude of 550 kilometers above Earth. Starlink satellites are launched in clusters of 60 satellites per mission. They are especially bright soon after launch, like a fleet of bright lights moving across the night sky. The satellites reduce visibility once they reach a higher altitude, an operational orbit of approximately 550 kilometers above Earth. Each satellite is equipped with an ion thruster propulsion system powered by Krypton to move along orbits. It does take several weeks until they all move into a higher orbit after deployment. Astronomers have voiced their concerns about Starlink satellites appearing too bright in the night sky. SpaceX assures it will find solutions to reduce the impact of Starlink satellite's on astronomical observations. In response to their concerns, SpaceX deployed an experimental satellite, known as 'DarkSat,' which features an anti-reflective coating at the bottom which aims to reduce its brightness. DarkSat was deployed in January 6, engineers are testing if the coating's anti-reflective properties affect the satellite's performance due to possible thermal changes. During a broadcast of a previous Starlink mission, SpaceX manufacturing engineer Jessica Anderson said that DarkSat has demonstrated a "notable reduction" in its brightness:

"Preliminary results show a notable reduction."

On March 22, Marco Lanbroek, an amateur astronomer photographed a set of satellites in the Starlink constellation alongside the experimental DarkSat. The images clearly show a notable reduction in the DarkSat's brightness (shown below), it appears dimmer than the rest.


Source: @Marco_Langbroek via Twitter.

"I am confident that we not cause any impact whatsoever in astronomical discoveries," Musk said at the Satellite 2020 conference earlier this month, "Zero. That’s my prediction. We will take corrective action if it’s above zero." Though, he did assure that SpaceX is cooperating with astronomers to ensure less visibility. Musk stated:

"We are working with senior members of the science community and senior astronomers to minimize the potential for reflection from the satellites. We’re running a bunch of experiments. [...] To minimize the potential for any impact."

He also shared that engineers are in the process of developing a "sunshade." Anderson gave more details during last Starlink mission, "We have a couple other ideas that we think could reduce the reflectivity even further, the most promising being a sunshade that would operate in the same way as a patio umbrella, or a sun visor but for the satellite,” she said.

Same but with video: 4 @SpaceX Starlink satellites including #Starlink-1030 DARKSAT on 22 March. DARKSAT clearly somewhat fainter. Video camera pointed on fixed alt/az. Frames of 4 video sequences stacked. Brightest stars are Capella and epsilon Aur.@planet4589 pic.twitter.com/aYjIU8JYkF

— Dr Marco - Stay At Home! - Langbroek (@Marco_Langbroek) March 24, 2020

SpaceX engineers are working alongside astronomers to observe and measure the effectiveness of the DarkSat anti-reflectivity coating, "We’ve had good discussions with leading astronomers. One way or another, we’ll make sure Starlink doesn’t inhibit new discoveries or change the character of the night sky," Musk assured. He previously mentioned via Twitter that Starlink satellites' "albedo will drop significantly on almost every successive launch."

SpaceX aims to conduct as many as two Starlink dedicated missions per month. Each mission will carry 60 satellites atop a Falcon 9 rocket. The company will roll out Starlink internet service before the year ends in parts of Northern United States and Canada and hopes to expand into a global network by 2021.