Our historic SSO-A mission last December launched 64 satellites from more than 34 customers. The engineering feat was enormous, and required two large on orbit deployment platforms known as the Upper and Lower Free Flyers. Part of the mission includes deorbiting these platforms safely and efficiently, within 25 years as mandated by FCC. Deorbiting the deployment platforms is also just good stewardship of space and part of Spaceflight’s mission. We’re happy to report that both free flyers appear to be deorbiting on schedule, according to data from our partners Surrey Space Centre.
Dr. Ben Taylor, a Systems Engineer at the Surrey Space Centre, said: “After many months of waiting for good observing conditions, we are delighted to see observations confirming that the sails we have provided to Spaceflight are working as planned. In fact, the sails are regularly bright enough to be visible to the naked eye.”
There are multiple ways to deorbit spacecraft and bring them down to our atmosphere where they will burn up. Some spacecraft have onboard propulsion, which uses their remaining fuel to push them towards the atmosphere at the end of their life. Some use electromagnetic components that take advantage of the Earth’s magnetic poles or the Sun’s radiation to bring them down. For the task of deorbiting the large deployment platforms, Spaceflight turned to Surrey Space Centre, who has experience with drag sails for deorbiting. They constructed sails for both Free Flyers.
Within 24 hours of the last satellite deployment (a time lag is built in so there is no risk of collision), carbon fiber booms deployed from the rings and slowly pulled out an approximately 16m2 sail of reflective metal film. The sail acts like a parachute, creating drag that pulls the spacecraft down – even in Low Earth Orbit, there are small particles that hit the sail which creates drag and pushes it downward towards the atmosphere. As it descends, it collides with more particles which exponentially increases the friction (and hence temperature) that will ultimately cause both Free Flyers to burn up.
The Deorbit Sail in its deployed state
Confirming if the sails have deployed is tricky, but Surrey Space Centre uses radar, drag effect comparisons, and visual observation to determine if everything is going as planned. We were pleased to hear when they confirmed with a very high degree of certainty that the sails deployed, and that Free Flyers are on track to burn up in atmosphere. In fact, they are visible in the night sky and easily trackable. The links below provide an explanation on when they can be seen (after entering your location), and how to observe them.
The Lower Free Flyer should deorbit within approximately 5 years, and the Upper Free Flyer in less than 14, far less than the 25 years that is the requirement. We’re also hoping to get a clear image of the deployed sails from one of the satellites in the BlackSky constellation, and will share that when available. The Free Flyers executed a perfect deployment sequence for our SSO-A mission, and we’re happy that they continue to perform as planned.