- PROBA, short for Project for Onboard Anatomy, is a space programme under the European Space Agency or ESA. Under PROBA, there have been a series of satellite launches. Today’s was the third in that series, hence the name PROBA-3.
- PROBA-3 is a solar mission. It’s aim is to study the Sun’s corona at a level of precision never done before. PROBA-3 consists of two independent, three-axis stabilised spacecraft – the Coronagraph Spacecraft or CSC, which is 310 kg and the Occulter Spacecraft or OSC, which is 240 kg. Both spacecraft will have a highly elliptical orbit around Earth whose apogee or distance farthest from the surface of the planet at the equator will be 60,500 km.
- According to the European Space Agency, the mission will demonstrate ‘formation flying’ within the context of a large-scale scientific experiment. The two spacecraft in orbit will create an approximately 150-metre-long solar coronagraph to study the Sun’s faint corona closer to the solar rim than has ever been achieved before.
- By flying in such a close formation – 150 metres – the Occulter Spacecraft will cast a precise shadow onto the Coronagraph’s telescope, thereby blocking any direct sunlight. The Coronagraph will then be able to map and image the Sun’s corona in the full electromagnetic spectrum – which includes visible light, Ultraviolet radiation (UV rays) and Infra-Red radiation (IR). It will also be able to image the solar corona in polarised light – which is made up of waves that vibrate in a single plane and include linearly, circularly, and elliptically polarised lights. The CSC will be able to do this for many hours at a time.
- The scientific objective of the PROBA-3 mission is to observe the Sun’s corona at 1.1 solar radius in the visible wavelength range (visible light). Solar radius is a unit of distance used to describe the size of stars in comparison to the size of the Sun. 1 solar radius equals 6.95700 x 10(to the power 8) meters or 695,700 km. This is roughly 109 times the radius of the Earth. This would make PROBA-3 the most precise satellite to map and image the Sun’s corona.
- PROBA-3 marks the next step in formation flying. As a world first, its two satellites – the Coronagraph spacecraft and the Occulter spacecraft – will maintain formation to a few millimetres and arc second precision at distances of around 150 metres of each other for six hours at a time per 19-hour, 36-minute orbit. In effect the pair will be forming a virtual giant satellite. And this will be achieved autonomously, without relying on guidance from the ground.
- Now that the two satellites have been successfully placed in orbit, there will be a short preparatory period for the two satellites in which some safety tests will be conducted by the European Space Agency. Because these two satellites will be independent yet flying in tandem in close proximity, a collision manoeuvre test will be conducted. Once these tests are complete, the two satellites will be placed into into a safe relative tandem orbit. They can then be left safely in with no risk of collision or running away from each other.
- The PROBA-3 satellites will repetitively demonstrate acquisition, rendezvous, proximity operations, formation flying, coronagraph observations, separation and convoy flying in every orbit.
- According to the Europan Space Agency, the PROBA-3 will be a “Laboratory in space” to validate strategies, guidance, navigation and control, and other algorithms, such as relative GPS navigation, previously tried in ground simulators.
- The ESA said that this mission includes a rendezvous experiment. It will test sensors and algorithms for satellites to Rendezvous (cooperative and uncooperative) in elliptical orbit. This cutting-edge technology could be used for a future Mars Sample return mission and for de-orbiting satellites from low-Earth orbit – which will also help declutter the Space around Earth.