Starlink, SpaceX's internet connectivity constellation, may be about to tackle one of the biggest pet peeves highlighted by the astronomical community.
The company is scheduled to launch the eighth batch of 60 Starlink satellites from Space Launch Complex 40 at Cape Canaveral. The window for launch opens at 8:55 p.m. Eastern time on Wednesday and lasts for 61 minutes. After this mission, SpaceX will have sent 480 non-test Starlink satellites into space – bringing the company a step closer to its goals of high-speed, low-latency internet from practically anywhere with a view of the sky.
At least one satellite on this launch is set to offer a new feature that could help reduce the constellation's visibility in the sky. The "VisorSat" is an advanced sun shade that stops light from hitting the antennas and reduces the amount that reaches the main bodies. Less light means a darker satellite, and that makes it harder to spot from Earth. SpaceX reiterated in an April 2020 update that the firm's next launch would send up the first VisorSat prototype. It's a problem SpaceX has been trying to solve for months, and this shade could offer the solution.
It sounds like it could ruin amateur stargazers' fun – after all, spotting Starlink in the night sky has become a fun past time for SpaceX fans – but it's a move that could answer some serious concerns from astronomers. Reports emerged after the first non-test launch in May 2019 that Starlink satellites were showing up as strangely bright in the sky. The International Astronomical Union went as far as to declare in February 2020 that astronomical observations would be “severely affected” by Starlink.
This problem was quantified when researchers looked into these satellites' brightness, measured in magnitude. On this scale, a higher number means a dimmer light. Researchers from the University of Antofagasta in Chile said in March that the newer satellites had reduced brightness compared to earlier launches, but they still measured 7.57. That's dimmer than the five-magnitude craft from earlier generations, but not dim enough to avoid detection by telescopes, which can spot things at magnitudes of eight or higher.
SpaceX explained in its April 2020 update that the problem comes from a series of components that are white to try and keep temperatures down. These components, including the antenna, diffuse light and scatter it in all directions. While it sounds like the light would be dimmer than a shiny object, the shiny components reflect light in a specular fashion. That means it's focused in one direction, typically toward space.
The firm has been holding regular meetings with astronomical groups to understand how to reduce this diffused light. In the six months covering June to November 2019, for example, SpaceX held eight conference calls with the American Astronomical Society. Based on these meetings, the firm has gradually tweaked its satellites.
One solution that launched earlier this year was called "DarkSat," which reduced brightness by painting certain white components black instead. That reduced light by 55 percent, but the paint causes the satellites to heat up. The paint also still reflects some light, making it a less-than-ideal solution. If all goes to plan, SpaceX will favor VisorSat over DarkSat for future launches.
The firm also looks set to employ other techniques to reduce brightness. These include rolling the satellite to avoid it reflecting light toward the Earth. This technique is designed for when the satellite is not at its intended altitude and is not in operation, at which point the antenna's positioning doesn't matter so much.
The Inverse analysis – SpaceX's next launch could resolve this major problem with the Starlink constellation, but it could take some time for the results to emerge. Astronomers will need to wait until the new satellite has reached its intended altitude, which could take a couple of months. They will then need to evaluate whether the craft is still visible with powerful telescopes, and SpaceX will need to decide whether there are any flaws with the new design.
The satellite may launch this week, but its effects may not become clear for a while.