- PROBA, short for Project for Onboard Anatomy, is a space program under the European Space Agency, or ESA. Under PROBA, a series of satellite launches have taken place. Today’s one was the third in that series, hence it was named PROBA-3.
- PROBA-3 is a solar mission. Its purpose is to study the Sun’s corona at a level of accuracy never achieved before. PROBA-3 consists of two independent, three-axis stabilized spacecraft – the Coronagraph Spacecraft or CSC, which weighs 310 kilograms, and the Occulter Spacecraft or OSC, which weighs 240 kilograms. Both spacecraft will have a highly elliptical orbit around Earth whose farthest distance from the planet’s surface at apogee or equator will be 60,500 km.
- According to the European Space Agency, the mission will demonstrate ‘formation flying’ in the context of a large-scale scientific experiment. The two spacecraft in orbit will form a solar coronagraph approximately 150 meters long to study the Sun’s faint corona close to the solar rim, something never achieved before.
- Flying so close – 150 meters – the Occulter spacecraft will cast a perfect shadow on the coronagraph’s telescope, blocking out any direct sunlight. The coronagraph will then be able to map and image the Sun’s corona across the full electromagnetic spectrum – including visible light, ultraviolet radiation (UV rays) and infra-red radiation (IR). It will also be able to image the solar corona in polarized light – which is made up of waves vibrating in the same plane and includes linear, circular and elliptically polarized light. CSC will be able to do this for several hours at a time.
- The scientific objective of the PROBA-3 mission is to observe the Sun’s corona at 1.1 solar radii in the visible wavelength range (visible light). The solar radius is a unit of distance used to describe the size of stars compared to the size of the Sun. 1 solar radius is equal to 6.95700 x 10 (power 8) meter or 695,700 km. This is approximately 109 times the radius of Earth. This will make PROBA-3 the most accurate satellite to map and image the Sun’s corona.
- PROBA-3 is the next step in construction flight. As the world’s first satellite, its two satellites – the Coronagraph spacecraft and the Occulter spacecraft – will maintain formation to a few millimeters and arc second accuracy for six hours every 19 minutes at a distance of about 150 meters from each other, 36-minute class. In effect the pair will create a virtual giant satellite. And this will be achieved autonomously, without relying on ground guidance.
- Now that both satellites have been successfully placed in orbit, there will be a short preparation period for both satellites in which some safety tests will be conducted by the European Space Agency. Since these two satellites will be independent yet will fly together in close proximity, collision maneuver testing will be conducted. Once these tests are completed, both satellites will be placed in a safe relative tandem orbit. They can then be released safely without the risk of collision or running away from each other.
- The PROBA-3 satellites will perform repeated acquisition, rendezvous, proximity operations, formation flight, coronagraph observations, separation, and convoy flight in each orbit.
- According to the European Space Agency, PROBA-3 will be a “laboratory in space” to validate strategies, guidance, navigation and control and other algorithms, such as relative GPS navigation, that were previously tried in ground simulators.
- ESA said the mission includes a rendezvous experiment. It will test sensors and algorithms for Rendezvous (cooperative and uncooperative) satellites in elliptical orbit. This cutting-edge technology could be used for future Mars sample return missions and to de-orbit satellites from low-Earth orbit – which would also help de-clutter the space around Earth.
