Testing time for MetOp Second Generation26 November 2019

MetOp Second Generation's structural and thermalmodel during testing at ESA's ESTEC Test Centre in theNetherlands during summer 2019. Credit: ESA-SJMPhotography

MetOp Second Generation (MetOp-SG) is a follow-on system to the successful MetOp satellites, thelast of which launched into its 800 km polar orbit in2018.

MetOp-SG is Europe's component of the JointPolar System, which is a collaboration with the US.Eumetsat, the European Organisation for theExploitation of Meteorological Satellites, operatesthe MetOp satellites and is responsible fordeveloping the ground segment of the system anddelivering the meteorological data to the world-wide user community. ESA is responsible fordesigning and manufacturing the space segmentof the system—the satellites themselves.

For this campaign the test item was not flighthardware but a prototype version specially built forinitial testing, known as the structural and thermalmodel (STM).

This initial MetOp-SG satellite, standing 6.5m highand weighing in at 4.4 tonnes including propellant,was shaken, shocked and placed in prolonged

vacuum under simulated sunlight to demonstratethe design's qualification for launch and readinessfor space.

The MetOp Second Generation mission is actuallymade up of two different satellites each withdifferent suites of instruments onboard.

For MetOp Second Generation testing a prototypeversion specially built, known as the ‘structural andthermal model’ (STM). This MetOp-SG STM, standing6.5m high and weighing in at 4.4 tons includingpropellant, was shaken, shocked and placed in prolongedvacuum under simulated sunlight to demonstrate thedesign’s qualification for launch and readiness for space.Credit: ESA-SJM Photography

"Our STM is actually a hybrid of these two satellitedesigns," explains Nick Goody, the mission'spropulsion and assembly integration and testingengineer.

"The two satellites have a common platform, whilethe STM is equipped with the nadir-pointinginstruments from satellite-A plus payload unit itemsfrom satellite-B, including amplifiers and powersupplies. This hybrid configuration results in the

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maximum mass and power dissipation for the STMtesting, intended for mechanical and thermalqualification. Those qualification objectives notcovered by the STM will be addressed by the SAT-A and SAT-B proto-flight models."

The test campaign began at the Toulouse facility ofAirbus Defence and Space in December 2018,where dummy units, thermal hardware andelectrical harness was integrated, together with thepropulsion module supplied by Airbus's facility inStevenage, UK. This was followed by integration oftest models of the instruments and the completionof its harness—the maze of wiring connectingeverything together—and its multi-layer insulationwrapping.

"A micro-vibration test campaign was performed tocharacterize the transfer functions between theinstruments and other microvibration exporterssuch as the reaction wheels," said MetOp-SGsatellite engineering manager Enrico Corpaccioli.

"These measurements allow us to better analyzethe effects of micro-vibrations on the instrumentsduring the operation of the satellite when it is inorbit. Alignment measurements were alsoperformed to provide a reference beforeenvironmental testing began."

MetOp Second Generation's STM being mated with itspropulsion module at the Toulouse facility of AirbusDefence and Space in December 2018. Credit: AirbusD&S

Then, in June 2019, the STM was transported tothe ESTEC Test Centre in Noordwijk. The largestsatellite test site in Europe, the center is equippedwith facilities to simulate every aspect of the spaceenvironment under a single cleanroom roof.

Here it was unpacked for vibration testing. It wasthen filled with 760 kg of demineralized water, in

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place of the hydrazine propellant it will be fueledwith before launch, for sine testing along eachaxis—undergoing a progressive sweep offrequencies and amplitudes to hunt out anypotentially harmful structural resonances.

"Qualification levels are applied to the STMstructure," adds Nick, "meaning that the amplitudesare significantly above the expected flight levelsand the durations are longer in order todemonstrate the necessary margin in the design."

A quasi-static load test was also performed.Satellites are exposed to simultaneous static anddynamic loads during the launch phase due tolauncher acceleration and aerodynamics. Thisquasi-static load test combines static and dynamicloads into an equivalent load which is applied to thesatellite in a high amplitude sine burst over a fewseconds.

A rocket launch is an extremely noisy event, soMetOp-SG was then transferred to the LargeEuropean Acoustic Facility. Here nitrogen is passedthrough massive acoustic horns within a sealedchamber, recreating the sound of a launch.

MetOp-SG's STM was transported to the ESTEC TestCentre in a protective, air-conditioned container. Credit:ESA

The next step was a 'fit check' and separation test,involving mating the satellite with a launcher

adapter provided by Arianespace, to guarantee thetwo designs fit together as intended and that thering securing the satellite to the launcher—known asthe clampband—operates correctly so that theseparation can occur without any problem.

Next came the thermal test phase, which sawMetOp-SG moved into the Large Space Simulator,the largest vacuum chamber in Europe, equippedwith a solar simulator based on an array of highpower lamps.

A number of orbits were simulated in various hotand cold conditions until thermal stability wasachieved within set levels. The results from this testallows experimental correlation of the spacecraftmathematical thermal model, used to verify thethermal control design.

Testing concluded with further alignment testing—tocheck the model had endured its test regimewithout structural deformation—and a leak checkinvolving filling the propulsion module with heliumgas.

"This test campaign has provided importantqualification data," adds Nick, "allowing correlationof the models with representative test data andconfirming the analysis performed during thedesign stage. The structural thermal model hasnow been transported back to Toulouse in France,where the instrument models, propulsion moduleand dummy units are being removed.

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MetOp-SG's STM on the Electrodynamic Shaker, used tosimulate the intense vibrations of a space launch. In thebackground can be glimpsed part of another weathersatellite, with the structural and thermal modelof Meteosat Third Generation's Infrared Sounderinstrument in the Large Space Simulator. Credit: ESA

MetOp-SG's structural and themal model being lowered

into ESA's Large Space Simulator, the largest vacuumchamber in Europe, ahead of thermal vacuum testingduring summer 2019. Credit: ESA-SJM Photography

"The satellite STM structure and propulsion modulewill be returned to their suppliers for refurbishment,as they are destined to be employed in MetOp SG-A's second flight model."

A tale of two MetOp-SGs

The two-satellite MetOp-SG system provides datafrom polar orbit for weather forecasting and climatemonitoring and the suite of instruments provideinformation on atmospheric chemistry, air quality,oceanography, hydrology, wind, sea ice,precipitation and temperature profiles in theatmosphere.

MetOp SG-A hosts IASI-NG (Infrared AtmosphericSounder Interferometer—New Generation)developed by French space agency CNES; theMETimage advanced multispectral imagingradiometer developed by German AerospaceCenter DLR; the ESA-developed CopernicusSentinel-5 for atmospheric sounding plus ESA'sMWS (Microwave Sounder); 3MI ((MultiviewMultichannel Multipolarization Imager) and RO(Radio Occultation) instruments.

MetOp SG-B includes the same RO instruments asMetOp-SG-A plus the ESA-developed SCA(Scatterometer), ICI (Ice Cloud Imager), MWI(MicroWave Imager) and the CNES-contributedArgos Data Collection Service, collectinginformation from ocean-going buoys and a SpaceEnvironment Monitor contributed by Thales AleniaSpace.

MetOp-SG is projected to enter service in 2023.

Provided by European Space Agency

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APA citation: Testing time for MetOp Second Generation (2019, November 26) retrieved 28 May 2022from https://phys.org/news/2019-11-metop.html

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