New International Ocean Satellite Completes Testing
A team of engineers in the U.S. and Europe subjected the Sentinel-6 Michael Freilich spacecraft to a battery of trials to ready it for liftoff later this year.
Once the state-of-the-art
Sentinel-6 Michael Freilich satellite launches in November, it will collect the
most accurate data yet on sea level - a key indicator of how Earth's warming
climate is affecting the oceans, weather and coastlines. But first, engineers
need to ensure that the spacecraft can survive the rigors of launch and of
operating in the harsh environment of space. That's where meticulous testing
comes in.
At the end of
May, engineers finished putting the spacecraft - which is being built in
Germany - through a battery of tests that began in November 2019. "If it
can survive all the abuse we deliberately put it through on the ground, then
it's ready for space," said John Oswald, the mission's deputy project
manager at NASA's Jet Propulsion Laboratory in Southern California.
The Sentinel-6
Michael Freilich spacecraft is a part of the Copernicus Sentinel-6/Jason-CS
(Continuity of Service) mission, a joint U.S.-European effort in which two
identical satellites will be launched five years apart. The spacecraft will
join the Copernicus constellation of satellites that constitutes the European
Union's Earth Observation Programme. Once in orbit, each satellite will collect
sea level measurements down to the centimeter for 90% of the world's oceans. The
data will add to almost 30 years of information gathered by an uninterrupted
series of joint U.S.-European satellites, creating an unprecedented - and unbroken
- 40-year sea level dataset. The spacecraft will also measure the temperature
and humidity of Earth's atmosphere, which can be used to help improve weather
forecasts and hurricane predictions.
These measurements
are important because the oceans and atmosphere are tightly connected. "We're
changing our climate, and the clearest signal of that is the rising
oceans," said Josh Willis, the mission's project scientist at JPL. "More
than 90% of the heat trapped by greenhouse gases is going into the ocean."
That heat causes seawater to expand, accounting for about one-third of the
global average of modern-day sea level rise. Meltwater from glaciers and ice
sheets account for the rest.
"For
climate science, what we need to know is not just sea level today, but sea
level compared to 20 years ago. We need long records to do climate science,"
said Willis.
Six scientific
instruments are key to that task. Two of them will work in concert to measure
the distance from the satellite to the ocean's surface. That information -
combined with data from three other instruments that precisely establish the
satellite's position in orbit and a sixth that will measure vertical slices of the
atmosphere for temperature and humidity - will help determine sea levels around
the world.
Put Through
Their Paces
To ensure that
the scientific instruments will work once they get into space, engineers sent
the Sentinel-6 Michael Freilich to a testing facility near Munich and ran the
satellite through a gauntlet starting in November 2019.
First up: the
vibration test, where the engineers subjected the Sentinel-6 Michael Freilich satellite
to the kinds of shaking it will experience while attached to a SpaceX Falcon 9
rocket blasting into orbit. Then in December, engineers tested the spacecraft
in a big vacuum chamber and exposed it to the extreme temperatures that it will
encounter in space, ranging from 149 to minus 292 degrees Fahrenheit (65 to
minus 180 degrees Celsius).
The next two trials
took place in late April and May. The acoustics test, performed in April, made
sure the satellite could withstand the loud noises that occur during launch. Engineers
placed the spacecraft in a roughly 1,000-square-foot (100-square-meter) chamber
outfitted with enormous speakers. Then they blasted the satellite with four
60-second bursts of sound, with the loudest peaking around 140 decibels. That's
like standing next to a jet's engine as the plane takes off.
Finally, in the
last week of May, engineers performed an electromagnetic compatibility test to
ensure that the sensors and electronics on the satellite wouldn't interfere
with one another, or with the data collection. The mission uses
state-of-the-art instruments to make precise measurements, so the smallest
interference could compromise that data.
Normally, JPL engineers
would help to conduct these tests in person, but two of the trials took place
after social-distancing safety measures had been established due to the coronavirus
pandemic. So team members worked out a system to support their counterparts in
Germany remotely.
To account for
the nine-hour time-zone difference, engineers in California pulled shifts from
midnight to 10 a.m. for several weeks, consulting with colleagues in Germany
through phone calls, video conferences, chat rooms and text messages. "It
was confusing sometimes, keeping all the channels and groups going at the same
time in the middle of the night, but I was impressed with our team," said
Oswald.
The
upshot of all that effort? "The tests are complete and the preliminary
results look good," Oswald said. Team members will spend the next several
weeks completing the analysis of the test results and then preparing the
satellite for shipment to Vandenberg Air Force Base in California for launch this
fall.
About
the Mission
Copernicus Sentinel-6/Jason-CS is being
jointly developed by the European Space Agency (ESA), the European Organisation
for the Exploitation of Meteorological Satellites (EUMETSAT), NASA and the
National Oceanic and Atmospheric Administration (NOAA), with funding support
from the European Commission and support from France's National Centre for
Space Studies (CNES).
The first Sentinel-6/Jason-CS satellite that
will launch was named after the former director of NASA's Earth Science
Division, Michael Freilich. It will follow the most recent U.S.-European sea
level observation satellite, Jason-3, which launched in 2016 and is currently
providing data.
NASA's contributions to the Sentinel-6
mission are three of the science instrument payloads for each of the two
Sentinel-6 satellites, including the Advanced Microwave Radiometer, the Global
Navigation Satellite System - Radio Occultation, and the Laser Reflector Array.
NASA is also contributing launch services for those satellites, ground systems
supporting operation of the JPL-provided science instruments, the science data
processors for two of these instruments, and support for the international
Ocean Surface Topography Science Team.
To learn more about NASA's study of sea
level rise, visit:
https://sealevel.nasa.gov
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