The PSLV-C59 launch was a joint effort between the European Space Agency (ESA), the Indian Space Research Organisation (ISRO), and NewSpace India Limited (NSIL).
Today, the Indian Space Agency (ISRO) successfully launched the European Space Agency’s PROBA-3 satellite. The mission took place aboard ISRO’s reliable Polar Satellite Launch Vehicle (PSLV) during its 61st commercial mission, “C-59.”
Everything You Need to Know About the European Satellite PROBA-3
PROBA, short for Project for Onboard Anatomy, is a space program developed by the European Space Agency (ESA), which has seen a series of satellite launches. Today’s launch marked the third satellite in the series, named PROBA-3.
PROBA-3 is a solar mission aimed at studying the Sun’s corona with unprecedented precision. The mission consists of two independent, three-axis stabilized spacecraft: the Coronagraph Spacecraft (CSC), weighing 310 kg, and the Occulter Spacecraft (OSC), weighing 240 kg. Both spacecraft will follow a highly elliptical orbit around Earth, with an apogee (the farthest point from Earth at the equator) of 60,500 km.
According to ESA, the mission will showcase “formation flying” as part of a large-scale scientific experiment. The two spacecraft will create a solar coronagraph about 150 meters long to study the faint corona of the Sun, closer to the solar rim than ever before.
The Occulter Spacecraft will cast a precise shadow on the Coronagraph’s telescope by flying in such close formation, blocking direct sunlight. This will allow the Coronagraph to map and image the Sun’s corona across the entire electromagnetic spectrum, including visible light, ultraviolet (UV) radiation, and infrared (IR) radiation. It will also capture images in polarized light, which includes linearly, circularly, and elliptically polarized light. The CSC will be capable of performing these observations for extended periods.
The primary scientific goal of the PROBA-3 mission is to observe the Sun’s corona at a distance of 1.1 solar radii, within the visible light wavelength range. A solar radius is a unit of distance used to describe the size of stars in relation to the Sun, equivalent to 6.95700 x 10^8 meters (695,700 km), which is approximately 109 times the radius of Earth. This makes PROBA-3 the most precise satellite to map and image the Sun’s corona.
PROBA-3 represents a significant advancement in formation flying. For the first time, its two satellites—the Coronagraph Spacecraft and the Occulter Spacecraft—will maintain a formation with millimetre and arc-second precision, staying about 150 metres apart for six hours during each 19-hour, 36-minute orbit. Essentially, the two satellites will form a virtual giant satellite. This will be achieved autonomously, without relying on ground-based guidance.
With the satellites successfully placed in orbit, a brief preparatory phase will follow, during which the European Space Agency (ESA) will conduct safety tests. Because the two satellites will operate independently while flying in close proximity, a collision avoidance test will be performed. Once these tests are complete, the satellites will be positioned in a safe relative orbit, ensuring they won’t collide or drift apart.
Throughout each orbit, the PROBA-3 satellites will continually demonstrate tasks such as acquisition, rendezvous, proximity operations, formation flying, coronagraph observations, separation, and convoy flying. According to ESA, PROBA-3 will serve as a “laboratory in space” to validate strategies for guidance, navigation, control, and algorithms like relative GPS navigation, previously tested in ground simulators.
The mission also includes a rendezvous experiment to test sensors and algorithms for cooperative and uncooperative satellite rendezvous in elliptical orbits. This advanced technology could play a crucial role in future missions, such as Mars sample return missions and de-orbiting satellites from low-Earth orbit, helping to reduce space debris around Earth.
