SpaceX Doubles Up: Another Starlink Batch and the Sentinel-6 Ocean Satellite
SpaceX flew two missions in two days last week, launching more Starlink satellites and then the Sentinel-6 Michael Freilich sea-level satellite.
Last week gave a good reminder of just how much cadence SpaceX has built up. On November 20th, a Falcon 9 lifted off from Cape Canaveral carrying the 16th batch of Starlink satellites, roughly 60 more flat-packed broadband satellites headed for low Earth orbit. Less than 24 hours later, on November 21st, a different Falcon 9 launched from Vandenberg Air Force Base in California with a much different kind of payload: the Sentinel-6 Michael Freilich satellite, built to track global sea-level rise.
Two launches from two coasts in about a day is the kind of thing that would have been remarkable for the entire launch industry a few years ago. Now it is just SpaceX’s normal week.
The Starlink side of things
At 60 satellites per launch and 16 batches now flown, SpaceX’s Starlink constellation is somewhere north of 900 satellites in orbit, though not all of those are still active or in their final operational shells. The pattern for these launches has become routine: reused first stage, droneship landing, satellites deployed a little over an hour after liftoff. Routine is actually the interesting part here. Nobody blinks anymore at a rocket landing on a boat, which says a lot about how quickly reusability has gone from experimental to boring-in-a-good-way.
Sentinel-6 is the more scientifically interesting mission
The Sentinel-6 Michael Freilich satellite, named after the former director of NASA’s Earth Science division, is a joint effort between NASA, ESA, NOAA, and EUMETSAT. Its job is to continue a decades-long record of measuring sea-level height across the world’s oceans using radar altimetry. This isn’t a new measurement program starting from scratch; it extends a dataset that stretches back to the early 1990s through a series of prior altimetry satellites (Topex/Poseidon, then the Jason series). Sentinel-6 is meant to keep that continuity going with better precision.
Sea-level measurement sounds like a simple thing, bounce radar off the ocean, measure the return, but the value is entirely in the consistency of the long record. A single reading doesn’t tell you anything. Decades of consistent readings from consecutive satellites are what let researchers see a millimeter-scale trend and be confident it isn’t instrument noise. That’s the real point of Sentinel-6: not to discover something new in one shot, but to keep an irreplaceable dataset alive and improve its accuracy going forward.
Putting these two missions next to each other is a nice illustration of the range SpaceX now operates across. One launch is about deploying commercial infrastructure at volume, the other is about supporting long-term international climate science. Same rocket, same company, wildly different payload types, launched back to back. Worth keeping an eye on how quickly Sentinel-6 starts returning data now that it’s in orbit.