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Sun-watching Proba-3 formation flyers tested for take-off

Proba-3 is made up of two satellites that launched together into orbit for a single mission.

What will Proba-3 Flyers Observe?

Stacked Proba-3 satellites
Stacked Proba-3 satellites

The pair will fly in precise formation relative to one another to cast a sustained shadow. This shadow will be from the disk-faced ‘Occulter spacecraft to the ‘Coronagraph spacecraft.

Due to this, it will be possible to take the observation of the inner layers of the Sun’s faint corona, or atmosphere. These are normally concealed by the brilliance of the solar disc.

Completion & Testing Details of Proba-3 Flyers 

In the spring, we completed the satellites and subsequently shipped them to IABG for testing. IABG one of a trio of European satellite test centers, possesses facilities capable of simulating every aspect of the space environment.

Alexandru Vargalui, Proba-3 structural engineer at ESA explained:

“To ensure the pair’s ability to endure launch stresses,we placed the Coronagraph spacecraft on top of the Occulter spacecraft and subjected the combined stack to ‘sine’ testing. During this testing, we placed them on a shaker table and gradually increased the frequency of vibrations to identify any resonant frequencies that could potentially cause damage.”

He added;

“Next came acoustic testing, where the spacecraft stack is blasted with noise levels representative of a launcher take-off.”

Proba-3 satellites form artificial eclipse
Proba-3 satellites form artificial eclipse

Deployment Mechanism Testing on Proba 3 Flyers 

After establishing the fitness of Proba-3, the next step involved conducting testing of the deployment mechanisms. The testing will involve trying out the systems that will separate the pair from their upper stage and each other. Additionally, the crucial arrangement of the solar drive mechanisms, which will turn their solar panels towards the Sun to allow them to charge up in orbit, will also be performed.

The next test stage will be unique to this mission, explains Damien Galano, Proba-3 project manager:

“For the Proba-3 pair to maintain their positions relative to each other down to millimeter-level precision, they employ a range of guidance, navigation, and control systems. We are taking advantage of the large space available at IABG to test Proba-3’s vision-based sensor system. This combines cameras on the Occulter spacecraft with bright LEDs on the Coronagraph spacecraft. That in turn allows them to find each other and estimate their distance apart.”

Proba-3 Preparing for acoustic testing
Proba-3 Preparing for acoustic testing

Furthermore, he said:

“The system designed to operate across up to 250 m between the two satellites requires a wide space for testing – so we’ve previously made use of the main corridor of ESA’s ESTEC technical centre in the Netherlands.”

Thermal Vacuum Testing of Proba-3

Following that test, Proba-3 will undergo more traditional ‘thermal vacuum’ testing. It involves the satellites operations occurring in a space-quality vacuum for a sustained period.

While also being exposed to orbital-style temperature extremes.

Space is a place where it is possible to be hot and cold at the same time. It happens when parts of your structure are illuminated by sunlight while others are in shadow.

Proba-3's pair of satellites
Proba-3’s pair of satellites

When will Proba 3 will be Flown?

Once the environmental campaign is complete, the satellite pair will return to Belgium for functional verification.

Proba-3 will be flown by a PSLV launcher from India next year.

fact sheet
Proba-3 fact sheet

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