SpaceX, NASA, ESA Launch Sentinel-6 Michael Freilich Mission


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Fresh off their second crewed launch for NASA, SpaceX temporarily shifted focus on launches to the U.S. West Coast, where a Falcon 9 rocket launched the Sentinel-6 Michael Freilich oceanography satellite in cooperation with NASA, the National Oceanic and Atmospheric Administration, the European Space Agency, and various other partners.

Launch occurred from Space Launch Complex 4 East (SLC-4E) at Vandenberg Air Force Base, California, at 09:17 Pacific Standard Time — or 17:17 UTC — on Saturday, 21 November.

This mission was the 100th for SpaceX’s workhorse Falcon 9 launch vehicle (but only its 99th launch), and the 108th mission in general for the company since its creation in May 2002. This was also the 95th orbital launch attempt made by any launch provider so far in 2020.

The first stage of the Falcon 9 that will launch Saturday’s mission was core B1063.1. This designation originates from SpaceX’s internal booster naming/numbering scheme, with B1063 being the 63rd Falcon booster core built by the company at their headquarters/production facility in Hawthorne, California, and the “.1” signifying the booster’s first flight.

The Falcon 9 launched the Sentinel-6A Earth observation mission, which was named for the late NASA Earth Science division director Michael Freilich.

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The mission is also referred to as the Jason-Continuity of Service (Jason-CS) mission and was jointly developed by NASA, the National Oceanic and Atmospheric Administration (NOAA), the European Space Agency (ESA), the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT), and France’s Centre National d’Etudes Spatiales (CNES).

Sentinel-6A Michael Freilich is the latest in a series of spacecraft designed to monitor changes in sea states and aims to continue high precision ocean altimetry measurements in the 2020-2030 timeframe alongside an identical spacecraft, Sentinel-6B, which is due to launch sometime in 2025.

A secondary objective of Sentinel-6A Michael Freilich is to collect high-resolution vertical profiles of temperature using the Global Navigation Satellite System – Radio Occultation science instrument, in order to assess temperature changes in the troposphere/stratosphere and support Numerical Weather Prediction (NWP) models.

The Michael Freilich spacecraft was built by Airbus Defence and Space at their Friedrichshafen facility in Germany. It ia 5.15 meters in length, 2.35 meters in height, and 2.58 meters in width. The satellite weighs approximately 1,192 kilograms (2,628 pounds) when fully fueled for launch.

The spacecraft obtains electrical power via two 17.5-square-meter body-mounted solar arrays, which cover the top and sides of the satellite like a tent (hence its house/tent-shaped appearance). Excess energy will be stored inside a double-module lithium-ion battery, which has a total capacity of approximately 200 amp hours. Sentinel-6A’s electrical system is able to provide an average of 1 kilowatt of power while on orbit.

Communications between the satellite and ground stations is accomplished using microwave S-band and X-band transmitters and antennae, which are located on the nadir (Earth-facing) panel of the spacecraft bus.

The spacecraft is also outfitted with a series of thrusters for propulsion, with the fuel consisting of hydrazine monopropellant. This propulsion system is actually two independent sections, with four 8 Newton thrusters for each section.

The Sentinel-6A satellite’s on-orbit attitude will be managed by a system consisting of sensors, actuators, and software. Subsystems include reaction wheels, magnetic torquers, magnetometers, a rate measurement unit, an Earth and Sun sensor, a star tracker, and precise orbit determination instruments.

These subsystems will all work simultaneously to provide 3-axis stabilized Earth-pointing attitude control during all mission modes and measure spacecraft rates and orbital position.

Sentinel-6A Michael Freilich was transported to SpaceX’s facilities at Vandenberg Air Force Base in California on 24 September in order to be prepared for its launch on Falcon 9. This included final tests and checkouts, as well as fueling the satellite for launch.

The launch was originally scheduled to occur on 10 November. However, the flight was postponed for several days as SpaceX and NASA started investigating off-nominal behavior observed during several firings of Merlin-1D engines – 9 of which power the first stage of the Falcon 9 rocket.

The behavior was first noted as an issue when the launch of the GPS III SV04 spacecraft was aborted at T-2 seconds before liftoff on 2 October due to two engines experiencing early-start behavior.

The engines were subsequently removed from the booster and sent back to SpaceX’s dedicated testing facility in McGregor, Texas, for a series of tests — during which the issues were replicated. Following these tests, the engines were scanned, torn down, and inspected further.

The joint investigation concluded that the problems were attributed to a blocked relief valve in the gas generator of the engines, and that a masking lacquer (described by SpaceX Vice President of Mission Assurance Hans Koenigsmann as “sort of like nail polish”) was to blame for the blockage. This lacquer was left over from the engine building process, when part of the gas generator was anodized.

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