Mission Summary
The European Space Agency's (ESA) Proba-3 mission is an innovative dual-spacecraft project aimed at advancing high-precision formation flying techniques to enable detailed coronagraphic studies of the Sun. As part of ESA's PROBA series, which focuses on testing cutting-edge spacecraft technologies, Proba-3’s design will allow it to explore the solar corona in unprecedented detail.

Mission Design and Operations
Proba-3 consists of two independently controlled satellites—the Coronagraph Spacecraft (CSC) and the Occulter Spacecraft (OSC)—which will operate in a carefully coordinated orbit around Earth, extending to a maximum altitude of 60,500 km. When spaced approximately 150 meters apart, the OSC will cast a shadow over the CSC’s telescope, allowing it to image the solar corona by blocking the Sun’s intense light. This precise alignment will be maintained through autonomous formation control, with the CSC held in position within the shadow cast by the OSC, enabling uninterrupted observations of solar events, like coronal mass ejections (CMEs).

Both spacecraft are equipped with advanced metrology systems that include laser and visual sensors to maintain accurate positioning. During each orbit, they will separate at perigee to safely avoid collision, then reunite at apogee, where gravitational influences are minimized. Proba-3 is expected to provide vital data on CMEs and total solar irradiance, contributing insights into solar processes that may impact Earth’s climate.

Design and Scientific Instruments
- Coronagraph Spacecraft (CSC): Weighing 300 kg, the CSC is designed with a mono-propellant propulsion system that enables it to maintain tight formation with the OSC. It houses the ASPIICS coronagraph, which will capture images of the Sun’s corona in visible and ultraviolet light.
- Occulter Spacecraft (OSC): The OSC, weighing 250 kg, is equipped with a 1.4-meter occulter disk that blocks direct sunlight. It uses a cold-gas propulsion system for precise control, ensuring the corona remains observable through the CSC’s coronagraph.

The primary scientific instrument, ASPIICS, is designed as a classical Lyot coronagraph, with an external occulter mounted on the OSC. A secondary instrument, the Davos Absolute Radiometer (DARA), on the OSC will measure total solar irradiance, aiding in the study of solar energy output fluctuations.

The Polar Satellite Launch Vehicle - XL (PSLV-XL) is the six side-mounted solid rocket booster configuration of the overall PSLV family of expendable rockets flown by India.

It is the most-used rocket of the PSLV line and is capable of launching missions to the Moon and Mars.

Its first flight occurred on October 22nd, 2008.

The rocket uses a mixture of solid and liquid propellant stages to get to orbit. The first stage, also called the core, is a solid propellant rocket, and the six side-mounted solid propellant boosters are bolted to it.

A liquid fueled second stage then takes over, followed by a third stage that is powered by solid propellant.

A liquid fueled fourth stage serves as the final part of the rocket. The engines on this stage are restartable to place satellites into their proper orbits.

Image: ISRO

Satish Dhawan Space Centre or Sriharikota Range is a rocket launch center operated by the Indian Space Research Organisation. It is located in Sriharikota in Andhra Pradesh.

Chosen for its remote location, the center became operational in 1971 and hosted its first launch that year for a suborbital mission.

The first orbital launch took place on August 10, 1979.

The spaceport received its current name in 2005 when it was named in honor of Satish Dhawan, the former head of the Indian Space Research Organisation.

The facility has two launch pads and will be the base of India's upcoming human spaceflight program.

Image: ISRO