Screenshot from SpaceX Webcast of the launch of SWOT. No one was stirring - Not even a mouse
Mission Rundown: SpaceX Falcon 9 B5 - SWOT
Written: December 17, 2022
What lies in still waters?
SpaceX’s Falcon 9 launched the joint NASA/CNES Surface Water and Ocean Topography - SWOT satellite mission from Space Launch Complex 4E at Vandenberg Space Force Base at 03:46 PST - 11:46 UTC on Friday, December 16, 2022.
Lift-off took place from the Space Launch Complex 4E (SLC-4E), at Vandenberg Space Force Base, in California, USA. This Falcon 9 performed a massive dogleg maneuver, a course change starting its flight due southwest, to end up flying heading southeast.
Screenshot of the flightpath of Falcon 9’s second stage. Now that’s an epic NASCAR powerslide
SpaceX’s vehicle placed the satellite in a 845 km polar orbit at 77.6° inclination. From there, the spacecraft will later climb to its final destination at 891 km in altitude, where it will operate. After the booster separation, the first stage B1071-6 performed a Return to Launch Site landing at Landing Zone 4 and was redesignated as B1071-7.
SpaceX will also recover both fairing halves in the Pacific Ocean with the recovery vessel NRC Quest, leased for the fairing and booster recovery operations.
B1071-6 will have made its sixth flight after launching its next mission:
B1073-5 didn’t perform a static fire test after refurbishment while waiting for an east coast launch out of Cape Canaveral. SpaceX has omitted this safety precaution many times so far. It isn’t required to perform a static fire test on inhouse missions like Starlink as to save time. Only a few other missions have omitted the static fire test.
SpaceX is the first entity ever that recovers and reflies its fairings. After being jettisoned, the two fairing halves will use cold gas thrusters to orientate themselves as they descend through the atmosphere. Once at a lower altitude, they will deploy drogue chutes and later a parafoil to help them glide down to a soft landing for recovery.
Falcon fairings halfs have been recovered and reused since 2019. Improved design changes and overall refurbishment procedures have decreased the effects of water landings and led to an increased recovery rate of fairings.
The fairings are a new or refurbished pair with no known joint mission. Both fairings are expected to survive the landing. Active fairings are equipped with four pushrods to separate the two fairing halfs.
Fairings have evenly spaced venting ports that have been redesigned a number of times by having first ten, then eight and now having their venting ports built as close pairs along the fairing edge. This prevents saltwater from the ocean from flooding and sinking the fairing, and makes refurbishment toward the next flight easier.
The Payload
In a joint effort from the National Aeronautics and Space Administration (NASA) and the Centre National d’Études Spatiales (CNES) — France’s space agency — the Surface Water and Ocean Topography (SWOT) mission was born.
For the first time, a spacecraft will study almost the whole of the water present on the surface of the Earth. This is to say, the SWOT satellite will observe our planet, focusing on rivers, lakes, seas, and oceans, studying levels and currents.
SWOT will gather data, which will then help researchers back on Earth to better understand on a global scale the cycle — among other things — of this precious, limited resource.
Together with NASA and CNES, both the Canadian Space Agency (CSA) and the United Kingdom Space Agency (UKSA) are adding their efforts. These new partners have contributed in terms of founding, but also of components for some of the instruments flying on this mission.
Logos of the space agencies which are SWOT mission partners
SWOT will be about two scientific communities: physical oceanography and hydrology, which will benefit from the qualities of the KaRIN instrument — the main payload on this satellite. Its implementation will bring about the innovative use of swath altimeters, in contrast to the previous ones used: profile altimeters. Thus, it is possible to say that larger areas will be covered in each observation, but also with greater accuracy.
By means of this instrument, along with others that will significantly contribute, the scientists expect to carry out a series of tasks, described in the following subsections. As a clarification, it is worth stressing that from these come the satellite’s design requirements.
From the polar orbit where the Falcon 9 will drop it, SWOT will be capable of observing about 90 % of Earth’s surface water. This is due to the fact that the orbital inclination will not allow the satellite to reach the most extreme latitudes — i.e., the poles.
Additionally, some water bodies or flows will be smaller than what the eyes of the spacecraft will be able to see. Nevertheless, the scale of the global survey will still be unprecedented. In order to fulfill this job, SWOT was designed featuring systems and payloads that will ensure it is mission-capable.
SWOT is about 5 m (16.4 ft) tall with a 14.9 m (48.8 ft) span when the solar arrays are deployed. These feature a total surface area of 31 m2 (335 ft2), and the whole spacecraft masses at 2,200 kg (4,850 lb).
Structurally, it is subdivided into two main assemblies: the payload module and the spacecraft bus. The former, where all the science instruments live, was developed by the NASA Jet Propulsion Laboratory (JPL). The latter, which is tasked with hosting electronics needed for the flight, and for science, as well as attitude and orbit control systems, was entrusted to Thales Alenia Space by the CNES.
To conduct science and collect the needed data for the mission, the SWOT satellite features several instruments. These include the wide-swath Ka-band Radar Interferometer (KaRIn) which was designed by NASA’s Jet Propulsion Laboratory (JPL) with its radio frequency assembly built by Thales Alenia Space and CNES.
KaRIn can view 60-kilometer-wide strips on each side of the ground track of the satellite once in orbit, using two Ka-band synthetic aperture radar antennas on either end of a 10-meter boom. The instrument has a horizontal resolution of 50 to 100 meters.
The spacecraft is powered by a pair of solar arrays which were built by Boeing-owned Spectrolab Inc. Across all six panels, the arrays have a total of 3,360 NeXt Triple Junction (XTJ) solar cells.
SWOT’s satellite bus was built by Thales Alenia Space for prime contractor CNES. The science instruments supplied by JPL were integrated with the satellite bus at the CNES assembly facility during final assembly, which began about a year before SWOT was shipped to the United States for launch.
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