2 spacecrafts will create 'solar eclipses on demand.' No, you can’t see them from Earth.

On Earth, total solar eclipses are relatively rare celestial phenomena. Months often pass between them, and even then, astronomers and stargazers have to travel around the globe to witness them.

For spectators, total solar eclipses – such as the one that dazzled millions in April across North America – represent moments to be awed by the majesty of our solar system. For scientists, eclipses offer fleeting opportunities to unravel the mysteries of our sun.

Now, dual spacecraft set to launch Thursday from India are about to embark on a multi-year mission in hopes of creating what the European Space Agency is calling, "solar eclipses on demand."

By becoming the first spacecraft to ever fly in a precise formation, the Proba-3 vehicles will be able to study the sun's elusive outermost layer, known as the corona. While in formation, one of the satellites will block the fiery face of the sun from the other, creating an artificial eclipse that allows the second to observe the ghostly surrounding atmosphere for a prolonged period of time.

No, the human-made eclipse won't be visible to us on Earth. But with luck, images and even video of the stunning display may one day beam its way back down.

Here's what to know about the ESA's eclipse-making Proba-3 mission.

How to watch the Proba-3 launch

The Proba-3 satellites will hitch a ride on India's four-stage PSLV-XL rocket, which is scheduled to launch Thursday from Satish Dhawan Space Centre, located on India's barrier island of Sriharikota.

A launch window has not yet been announced. Liftoff was delayed from Wednesday due to a technical issue with the spacecraft's propulsion systems.

The launch will be covered by the Indian Space Research Organization, ISRO, and can be watched via ESA Web TV and on ISRO’s YouTube channel. The ISRO broadcast is expected to begin around 5 a.m. Thursday EST.

When will the Proba-3 satellites create a solar eclipse?

The Proba-3 satellites will take about four months to reach their orbital destination, which is about 60,000 kilometers (37,282 miles) above Earth.

Then, while flying about 150 kilometers apart (93 miles,) the pair of spacecraft will align themselves in such a way in front of the sun as to cast a shadow from one to other, blocking the blinding light and mimicking a natural solar eclipse that occurs when the moon passes between the sun and Earth.

The eclipse effect will open up sustained views of the sun's faint surrounding corona, allowing for the second craft to use a suite of onboard sensors to collect data and photograph the inner region of the corona, according to the ESA.

While terrestrial solar eclipses last for mere minutes, the cosmic artificial eclipses will allow for six hours of uninterrupted study time during every orbit throughout a mission the ESA expects to last two years.

What is the ESA hoping to learn?

Veiled by the massive star's bright light, the sun's corona only becomes visible during total eclipses, which is among the only times astronomers can conduct observations normally impossible.

The difficulty in observing the corona is why the atmospheric layer to this day carries a high degree of mystery.

Astronomers, for instance, still don't understand why the corona is significantly hotter than the sun itself. The outermost layer is able to reach a temperature of 1.8 million degrees Fahrenheit compared to the 10,000 degrees measured on the surface of the sun itself.

The Proba-3 satellites will also study coronal mass ejections (clouds of plasma and charged particles,) which drive much of the space weather that is increasingly impacting Earth amid the peak of the 11-year solar cycle.

Proba-3 is just to latest in a series of missions under the Proba banner from the ESA.

Proba-1, an Earth observation satellite, launched in 2001, followed by the sun observing Proba-2 in 2009. Earth-imaging Proba-V (for "vegetation") launched in 2012.

Eric Lagatta covers breaking and trending news for USA TODAY. Reach him at [email protected]

This article originally appeared on USA TODAY: 2 spacecraft hope to create 'solar eclipses on demand': Here's why