Two vehicles developed by the European Space Agency (ESA) as part of the Proba-3 mission were launched yesterday at 13:34 Moscow time on the Indian Polar Satellite Launch Vehicle (PSLV). It placed the vehicles into an elongated orbit with a low point of about 573 km and a high point at an altitude of 60,563 km with an inclination of 59° to the equator. These devices will create artificial solar eclipses for a more detailed study of our star.
Image source: esa.int
After initial checks, the two Proba-3 mission satellites will separate and experimental work with them will begin early next year. The larger satellite is called Coronagraph and is equipped with instruments to take images of the corona, or outer atmosphere of the Sun. The smaller Occulter spacecraft is equipped with navigation sensors and low-impulse engines that will help it position itself at a distance of about 150 m from the Coronagraph, the distance necessary for the Occulter’s 1.4 m diameter screen to hide the sun’s disk. It will block the star’s glare and cast an 8cm shadow on the Coronagraph, allowing it to study the heated gases that make up the corona.
Under natural conditions, the solar corona is hidden by the bright light of the star, and it can be observed from Earth only during total solar eclipses, which last a few minutes. Attempts to replicate this effect have been made using coronagraphs, spacecraft used in previous missions. However, they were placed on the same devices as the surveillance equipment, which reduced efficiency due to diffraction and other optical effects. Therefore, it was decided to place the artificial eclipse disk on a separate satellite, which became the basis of the Proba-3 mission.
Launching a single 150-meter-long spacecraft would be prohibitively expensive, so ESA, with Canadian support, developed a mission with two satellites and a budget of about €200 million, designed for the next ten years. About three-quarters of the mission’s cost was financed by Spain and Belgium, which are not ESA members. The devices will maintain a stable distance from each other using radio links, navigation receivers and cameras on the Occulter. The small satellite will be guided by LED lights on board the Coronagraph, and for more precise positioning will use a laser beam transmitted from the Occulter and reflected by the Coronagraph. As a result, the distance between the devices will be controlled with an error of less than 1 mm and maintained for up to 6 hours – this is 50 times longer than the maximum duration of a total solar eclipse. Artificial eclipses will be created when the Proba-3 satellites are at the farthest point from Earth in their 20-hour orbit. The Proba-3 main mission will last two years, during which scientists expect to conduct 1,000 hours of observations under artificial eclipse conditions.
Coronagraph will take images every two seconds, allowing scientists to study the fast plasma waves that are thought to be causing the corona’s temperature to soar. Another object of research will be the glow of plasma jets, which, according to scientists, play an important role in accelerating the solar wind – a stream of particles carried away from the Sun at speeds of up to 2 million km/h. Finally, Proba-3 will help confirm the ability to maintain a fixed distance between the two vehicles for a long time, which will become the basis for future missions to return samples of Martian soil and clear Earth orbit of space debris.