U.S.-European Sea Level Satellite Gears Up for Launch

Sentinel-6 Michael Freilich spacecraft will soon be heading into orbit to
monitor the height of the ocean for nearly the entire globe.

are ramping up for the Nov. 10 launch of the world’s latest sea level satellite.
Since arriving in a giant cargo plane at Vandenberg
Air Force Base in California last month, Sentinel-6 Michael Freilich has been
undergoing final checks, including visual inspections, to make sure it’s fit to
head into orbit.

the bone-rattling vibrations and sounds of launch atop a Falcon 9 rocket is just
the start of the mission. Once in orbit some 830 miles (1,336 kilometers) above
Earth, Sentinel-6 Michael Freilich has the task of collecting sea level
measurements with an accuracy of a few centimeters (for a single measurement) for
more than 90% of the world’s oceans. And it will be making those measurements
while repeatedly flying through an area of intense radiation known as the South
Atlantic Anomaly, which can scramble electronics.

why engineers and researchers have put Sentinel-6 Michael Freilich through a battery of tests to ensure that the spacecraft will
survive launch and the harsh environment of space. But how will the mission pull
the rest of it off? With sophisticated instruments, global navigation
satellites, and lasers – lots of lasers. They’ll all work in concert to enable
the spacecraft to carry out its task of observing the ocean.

the challenges and goals of the mission, the satellite’s moniker is appropriate:
It’s named after noted researcher Dr. Michael Freilich, the former director of
NASA’s Earth Science Division.

A second
spacecraft identical to Sentinel-6 Michael Freilich, Sentinel-6B, will launch
in 2025 to continue the work after its sibling’s five-and-a-half-year prime
mission ends. Together, the satellites make up the Sentinel-6/Jason-CS
(Continuity of Service) mission, which is a partnership between NASA, ESA (the
European Space Agency), the European Organisation for the Exploitation of
Meteorological Satellites (EUMETSAT), and the National Oceanic and Atmospheric
Administration (NOAA).

the satellites will add a decade’s worth of the most accurate satellite data
yet on ocean height to a nearly 30-year record documenting how our oceans are
rising in response to climate change. Both spacecraft will also collect data on
atmospheric temperature and humidity that will help to improve weather
forecasts as well as atmospheric and climate models.

is where those sophisticated instruments, global navigation satellites, and
lasers come in.

It Works

accurately measure extremely small variations in sea level, Sentinel-6 Michael
Freilich will rely on a suite of three instruments that provide scientists
information to determine the spacecraft’s exact position in orbit.

component of this positioning package is the laser retroreflector array, a set
of nine small, precisely shaped mirrors. Lasers are directed at them from ground
stations on Earth, and they reflect the (harmless) beams right back to their
point of origin. These laser-emitting ranging stations, as they’re known,
calculate how long the laser takes to bounce off the reflectors and return,
which gives the distance between the satellite and the station.

instrument, the Global Navigation Satellite System – Precise Orbit
Determination (GNSS-POD), tracks GPS and Galileo navigation signals.
Researchers analyze these signals to help determine the satellite’s position.

third instrument in the positioning package is the Doppler Orbitography and
Radioposition Integrated by Satellite (DORIS). It analyzes radio signals from
55 global ground stations, measuring the Doppler shift of the radio signals’
frequencies to determine the 3D position of the satellite over time. When used
together, these instruments provide the data needed to ascertain the precise
position of the satellite, which in turn helps to determine the height of the
sea surface.

the science side are two instruments that work in concert to determine sea
level and a third that collects atmospheric data. The Poseidon-4 radar
altimeter measures ocean height by bouncing radar pulses off the water’s surface
and calculating the time it takes for the signal to return to the satellite.
However, water vapor in the atmosphere affects the propagation of the radar
pulses from the altimeter, which can make the ocean appear higher or lower than
it actually is. To correct for this affect, an instrument called the Advanced
Microwave Radiometer for Climate (AMR-C) measures the amount of water vapor
between the spacecraft and the ocean.

is the next generation of AMR instruments, and it includes new components that
will enable more accurate measurements along coastlines and throughout the
mission,” said Shannon Statham, AMR-C integration and test lead at NASA’s
Jet Propulsion Laboratory in Southern California.

information on the atmosphere, the Global Navigation Satellite System – Radio
Occultation (GNSS-RO) instrument gathers data on temperature and humidity that
can help to improve weather forecasts. GNSS-RO analyzes radio signals from
global navigational satellites as they appear and disappear beyond the limb of
the Earth – the hazy blue edge of the atmosphere that’s visible when you look
at pictures of our planet in space. As these radio signals travel through
different layers of the atmosphere, they bend and slow by varying degrees. Sentinel-6
Michael Freilich and satellites like it use GNSS-RO technology to measure these
changes, enabling researchers to then extract atmospheric characteristics like
temperature and humidity at different altitudes.

the instruments, power systems, telecommunications – everything that makes
Sentinel-6 Michael Freilich tick – must work together to accomplish the
mission’s science goals, much like the international partners have worked together
to get this satellite ready for launch.

Sentinel-6 Michael Freilich is a great contribution to climate change,
environment monitoring, and to the Digital Twin Earth. Sentinel-6 is a reference model of the
cooperation between the U.S. and Europe on Earth Observation and represents a
good foundation for future projects,” said Josef Aschbacher, ESA director
of Earth Observation Programmes.

About the Mission

Sentinel-6/Jason-CS is being jointly
developed by ESA, EUMETSAT, NASA, and NOAA, with funding support from the
European Commission and technical support from France’s National Centre for
Space Studies (CNES).

JPL, a division of Caltech in Pasadena,
is contributing three science instruments for each Sentinel-6 satellite: the
Advanced Microwave Radiometer, the Global Navigation Satellite System – Radio
Occultation, and the Laser Retroreflector Array. NASA is also contributing
launch services, ground systems supporting operation of the NASA science
instruments, the science data processors for two of these instruments, and
support for the international Ocean Surface Topography Science Team.

Sentinel-6 Michael Freilich press kit:


learn more about Sentinel-6 Michael Freilich, visit:



News Media Contact

Jane J. Lee / Ian J. O’Neill

Jet Propulsion Laboratory, Pasadena, Calif.

818-354-0307 / 818-354-2649

jane.j.lee@jpl.nasa.gov / ian.j.oneill@jpl.nasa.gov


Source: Jet Propulsion Laboratory

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