Sentinel-6A, Starlink Missions Primed for Weekend Launch Double-Header

Inside SpaceX’s Payload Processing Facility at Vandenberg Air Force Base in California, the U.S.-European Sentinel-6 Michael Freilich ocean-monitoring satellite is being encapsulated in the SpaceX Falcon 9 payload fairing on Nov. 3, 2020. Photo Credit: NASA

SpaceX stands ready to make personal-best-beating history this coming weekend, with a pair of back-to-back missions from the West Coast at Vandenberg Air Force Base, Calif., and the East Coast at Cape Canaveral Air Force Station, Fla. NASA’s long-awaited Sentinel-6A Michael Freilich ocean-monitoring satellite is set to launch atop a brand-new Falcon 9 from Space Launch Complex (SLC)-4E at Vandenberg at 9:17 a.m. PST (12:17 p.m. EST) on Saturday, with another batch of 60 Starlink low-orbiting internet communications satellites due to follow on a seven-times-flown core from SLC-40 at the Cape just ten hours later at 10:17 p.m. EST.

Video Credit: AmericaSpace

If both missions fly as planned, new records will be set for SpaceX’s greatest number of flights in a single calendar year, the largest number of missions by a single orbital-class booster and the shortest interval between two Falcon 9 launches.

To put it mildly, despite the trauma that this year has brought for us all, it has been a triumphant 2020 for SpaceX. With Saturday’s launch of Sentinel-6A, it will log its 22nd mission, surpassing 2018 as its most-flown year on record. Since January, the Hawthorne, Calif.-headquartered launch services provider has executed 13 Starlink missions—lifting a total of 773 satellites in “batches” of 57-60 at a time—as well as a number of “rideshare” customers.

Seen here during its third launch in May 2019, B1049 looks set to become the first Falcon 9 to fly as many as five Starlink batches. Photo Credit: John Studwell/AmericaSpace

Additional flights included the last Dragon cargo mission to the International Space Station (ISS) under the first-round Commercial Resupply Services (CRS1) contract with NASA, a pair of Block III Global Positioning System (GPS) navigation and timing satellites for the U.S. Space Force, South Korea’s ANASIS-II military communications satellite and Argentina’s SAOCOM-1B Earth-imaging satellite.

And that is not to forget, of course, a spectacular year for the Commercial Crew Program, which kicked off in January with a successful In-Flight Abort Test, followed by the 64-day Demo-2 mission by Dragon Endeavour crewmen Doug Hurley and Bob Behnken and last week’s transition to “operational” ISS crew-rotation services with the launch and arrival at the space station of Crew-1 astronauts Mike Hopkins, Victor Glover, Shannon Walker and Soichi Noguchi aboard Dragon Resilience.

B1049 last flew in August 2020, becoming the first Falcon 9 core to log six launches. On Sunday, it will also become the first to log seven. Photo Credit: SpaceX

But 2020 has been special in other ways, since the 21 launches so far have been conducted on only ten Falcon 9 cores, four of which made their maiden flights this year. The other six cores have contributed impressively to SpaceX’s reusability statistics, with individual Falcon 9s logging record-setting fifth (in March), sixth (in August) and—assuming Sunday’s mission goes well—seventh launches.

And just last month, B1051 became the first Falcon 9 to fly four missions in a single calendar year. That achievement is set to be matched by her sister core B1049 on Sunday, as she gears up for her own fourth flight of 2020.

Starlink launch, ascent and deployment flight profile. Image Credit: SpaceX

B1049 entered service way back in September 2018, when she lofted the heavyweight Telstar 18V communications satellite to geostationary altitude from Cape Canaveral. She was then transported cross-country to Vandenberg to launch the eighth and final ten-strong load of Iridium NEXT global mobile communications satellites in January 2019, before returning to the Space Coast to lift the first “production batch” of Starlinks the following May.

This was followed by three more Starlink missions in January, June and August 2020. Assuming an on-time launch at 10:17 p.m. EST Sunday, B1049 will return to land on the Autonomous Spaceport Drone Ship (ASDS), “Of Course I Still Love You”, which put to sea on Thursday, bound for a location about 395 miles (635 km) offshore in the Atlantic Ocean.

Weather conditions on the Space Coast for Sunday night’s launch are expected to be 70-percent-favorable, remaining the same in the event of a 24-hour scrub to Monday. A slight chance of violating the Cumulus Cloud Rule and Liftoff Winds Rule exists, as a ridge of high pressure pushes out over the Atlantic and scattered showers move onshore.

B1049 launches the final batch of Iridium NEXT satellites on its second mission in January 2019. This was the core’s only flight out of Vandenberg Air Force Base, Calif. Photo Credit: Brian Sandoval / AmericaSpace.com

Ten hours before B1049 lofts its own personal-best-beating fifth batch of Starlinks, another Falcon 9 is due to launch from SLC-4E, more than 2,700 miles (4,300 km) to the west at Vandenberg Air Force Base. Yet this booster (tail-numbered “B1063”) will be quite different, in that it will be embarking on its very first mission. Delivered to Vandenberg in August, B1063 was expected to launch the Sentinel-6A Michael Freilich ocean-monitoring satellite on 10 November, but was postponed in response to a last-second abort suffered by the GPS III-04 mission last month.

As investigators dug into the root cause of the abort, several elements of Merlin 1D+ first-stage engine hardware on the B1061 and B1063 boosters was removed, replaced, tested and inspected. This conspired to push the Sentinel-6A launch to the 21st. Assuming an on-time launch tomorrow, B1063 is expected to alight on the ground pad at Landing Zone (LZ)-4, becoming only the third Falcon 9 core to achieve a Return to Launch Site (RTLS) at Vandenberg since October 2018.

Sentinel-6 Michael Freilich team members from European Space Agency pose with the spacecraft during processing. Photo Credit: NASA

“Upon the re-entry of the vehicle, spectators and local residents from Santa Barbara, Ventura and San Luis Obispo counties can anticipate to hear multiple sonic booms,” noted Vandenberg Air Force Base in a 30th Space Wing update, “as the vehicle breaks the sound barrier.”

As for the payload, Sentinel-6A itself, the 2,600-pound (1,190 kg) satellite was airlifted from Germany’s Munich Airport to Vandenberg via Antonov An-124 transport aircraft in September. Upon arrival in California, the containers bearing the spacecraft and its critical support equipment were offloaded onto trucks and transported 15 miles (25 km) to the SpaceX Payload Processing Facility.

Video Credit: AmericaSpace

Last month, Sentinel-6A was fueled and pressurized in just a single day, ahead of encapsulation into the Falcon 9 payload fairing in early November. The mission wrapped up its Flight Readiness Review (FRR) last Tuesday and B1063 demonstrated its muscle with a brief Static Fire Test of its nine Merlin 1D+ first-stage engines at SLC-40 on Wednesday.

Assuming both Sentinel-6A and Starlink fly within ten hours of each other this weekend, the dual missions will establish a new record for the shortest interval between a pair of SpaceX launches. The current record is held by the SSO-A SmallSat Express and CRS-16 Dragon missions, launched a little less than 48 hours apart back in December 2018. Hopes of eclipsing that record earlier this summer with another weekend double-header came to nothing due to weather concerns.

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