SpaceX currently operates the world's largest broadband constellation of approximately 4,265 Starlink satellites in Low Earth Orbit (LEO) that provide high-speed internet service to over 1.5 million subscribers globally. In the years ahead, SpaceX has plans to deploy 7,500 second-generation (V2) Starlink satellites to build a robust network with enhanced capabilities and extend service coverage. SpaceX already deployed a ‘Mini’ iteration of the V2 satellites during four Falcon 9 Starlink missions. “V2 minis include key technologies—such as more powerful phased array antennas and the use of E-band for backhaul—which will allow Starlink to provide ~4x more capacity per satellite than earlier iterations,” says the company. 

Astronomers voiced their concerns over Starlink satellites’ potential to interfere with their stellar observations, in response SpaceX engineers upgraded the satellites to diminish their visibility across the sky. “Space exploration is fundamental to SpaceX’s core mission. SpaceX has therefore taken unprecedented steps to work with the astronomy community to better understand how SpaceX – and all satellite operators – can mitigate the effect that the Sun’s reflection off of satellites can have on astronomical observations,” said SpaceX, “As a result of this deep, collaborative work, SpaceX has implemented innovative technological solutions and techniques to minimize its satellites’ effect on the night sky. In fact, SpaceX has invested more than any other satellite owner/operator to develop and deploy such technologies and techniques,” the company said.

The Starlink V2 Minis feature upgrades to mitigate brightness in order to decrease their visibility. “SpaceX continues development with additional technologies, including a combination of dielectric mirror film (developed and made by SpaceX), which reflects sunlight away from the Earth, and the SpaceX-developed, low-reflectivity black paint, which reduces lower specular peak by a factor of five compared to the darkest available space stable paint. These improvements are implemented on our V2 satellites. With several years of experience and the ability to design, test, and field mitigation strategies, mitigations were able to be ‘baked into’ the design of the V2 satellites from the start,” shared the company. This improvement can be seen with the naked eye as demonstrated in the images below, which shows the reflection of a Starlink V1 WiFi router sitting on top of the old and new mirrors. “Additionally, we’ve designed our solar arrays to allow off-pointing to reduce reflections as a satellite approaches the terminator. So, while our V2 Mini satellites are larger than earlier versions, we’re still expecting them to be as dark or darker once the full range of mitigations are implemented and the satellites reach their operational orbit.”

An independent team of astronomers, led by Raytheon Senior Engineer Anthony Mallama, performed research on SpaceX’s Starlink satellite constellation’s ‘photometric characterization’ – which is the science of measuring visible light in units that are weighted according to the sensitivity of the human eye. They measured Starlink’s visibility with cameras. The team published a new scholar article about their findings at arXiv on June 11, where they shared data stating that SpaceX’s Starlink V2 Mini satellites are already 12 times less luminous than the first-generation (V1) satellites “despite their larger size.” Mr. Mallama has previously collected photometric data of the Starlink V1 satellites in 2021/2022 and compared the new data to previous findings. 

The astronomer team reported on brightness measurements of the Starlink V2 Mini satellites obtained at visible wavelengths through June 3, 2023. The report states that besides implementing a less reflective layer on its satellites, SpaceX also adjusted the altitude and orientation of where the Starlink V2 Mini satellites operate in LEO to make the satellites less visible from the ground while each rises to their designated orbits. The astronomers characterized the satellite's brightness with the scale of ‘apparent magnitude’, which is a measure of the brightness of an object as observed from Earth. It takes into account both the object's intrinsic luminosity and its distance from us. The apparent magnitude scale is logarithmic, where smaller magnitudes represent brighter objects. For example, a star with an apparent magnitude of 1 appears brighter than a star with an apparent magnitude of 6. 

They observed the Starlink V2 Mini satellites in altitudes ranging from 370 km to 520 km (kilometers). “The peak of the apparent magnitudes for [Starlink] satellites in the brightness mitigating mode is at 6.5, making them difficult or impossible to see with the unaided eye, and the peak for the distance-adjusted magnitudes is 8.0,” the researchers said. “[...] The means are 7.06 +/- 0.10 for apparent magnitudes and 7.87 +/- 0.09 for distance-adjusted magnitudes. The adjusted mean indicates a factor of 12 reduction in luminosity relative to the corresponding mean for satellites not in brightness mitigation mode,” they wrote.

“We find that Gen 2 satellites are very luminous during their early mission phases before reaching on-station altitudes and being placed in a brightness mitigation mode. This was expected due to their large size and because SpaceX stated before launch that ‘V2 Mini satellites may be somewhat bright initially, especially during orbit raising and initial operations’,” the paper states. “On-station satellites are found to be much fainter [...]. A private communication from SpaceX explained that Gen 2 Starlinks place the solar arrays edge-on to the Earth’s limb so observers on the ground will not usually see portions of the solar array that are illuminated by the Sun. The factor of 12 reduction in brightness that we determined for on-station Mini satellites exceeds the factor of 10 dimming [...] for Gen 1 satellites in knife-edge configuration,” wrote Mallama about their findings.  “[...] For the future, more observations will be recorded when the Mini satellites have risen to their final on-station altitude of 560 km,” the paper says. Read full scholar article and see the data astronomers collected in this PDF document: Starlink Generation 2 Mini Satellites: Photometric Characterization

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All Featured Images Source: SpaceX Starlink.com