Proba-3 mission, a European Space Agency (ESA) mission consisting of two satellites, is designed to study the solar corona—the outer layer of the Sun’s atmosphere. It is devoted to the demonstration of technologies and techniques for highly-precise satellite formation flying.
It consists of two small satellites launched together that will separate apart to fly in tandem, to prepare for future multi-satellite missions flying as one virtual structure.
Proba-3 Mission
1. The Proba-3 mission is developed at an estimated cost of 200 million euros with an expected mission life of two years. The ISRO will launch both the satellites stacked together in a highly elliptical orbit of 600 x 60530 km. Later, the satellites will be separated and put in a parallel orbit.
2. The mission is designed with two satellites that will be launched together, separate from each other, and then fly in tandem. This will be the first-ever attempt at “precision formation flying”, where two satellites will fly together and maintain a fixed configuration in space.
3. This is the latest solar mission in ESA’s Proba suite of missions. Its predecessors Proba-1 (also launched by ISRO) and Proba-2 were launched in 2001 and 2009, respectively. PSLV-C59, the launch vehicle, is an initiative led by NewSpace India Limited (NSIL) and supported by ISRO’s expertise.
4. The two satellites — Occulter Spacecraft (weighing 200 kg) and the Coronagraph Spacecraft (weighing 340 kg) — will mimic a natural solar eclipse. They will manoeuvre precisely in Earth’s orbit so that one satellite casts a shadow onto the other.
5. A naturally occurring solar eclipse allows solar physicists to observe and study the Sun’s corona for 10 minutes, across an average of about 1.5 eclipse events per year. Proba-3 will give six hours, equivalent to 50 such events annually, which will help deepen understanding of the Sun’s corona like never before.
6. Both the Occulter and the Coronagraph will face the Sun at all times. They will maintain a formation of a few millimetres and then move to a position where they will be 150 metres apart for six hours at a time.
7. One satellite will act as a viewing telescope, kept at the centre of a shadow cast by the other satellite positioned 150 metres away. This positioning will facilitate observing the Sun’s corona and will be autonomously achieved through precise flight formation.
8. If done successfully, the Occulter will create an artificial yet stable eclipse, by masking large parts of the Sun. As a result, the Sun’s blinding light will get blocked and only the solar corona will be visible to the coronagraph, which will photograph and facilitate studies of the lesser-known features.
Instruments on the Proba-3 mission
The Association of Spacecraft for Polarimetric and Imaging Investigation of the Corona of the Sun (ASPIICS) or the coronagraph. Its field of view is between the Sun’s outer and inner corona, a circular belt normally observable during solar eclipse events. The instrument has a 1.4-metre diameter occulting disk mounted on it, to block the Sun’s light and facilitate a close-up view of this belt.
The Digital Absolute Radiometer (DARA) will maintain a continuous measurement of the Sun’s total energy output, known as the total solar irradiance.
The 3D Energetic Electron Spectrometer (3DEES) will measure electron fluxes as it passes through Earth’s radiation belts, providing data for space weather studies.
Significance of the Study of the Sun
All space weather and its associated turbulences like solar storms, solar winds, and Coronal Mass Ejection (CME) originate from the corona. These phenomena influence space weather and can potentially interfere with the smooth operations of all satellite-based communications, navigation, and power grids on Earth.
The PROBA-3 Mission is the 61st flight of PSLV and the 26th using PSLV-XL configuration which is set to launch the spacecraft into a highly elliptical orbit as a Dedicated commercial mission of NewSpace India Limited (NSIL).
PSLV
The Polar Satellite Launch Vehicle (PSLV) is the third generation of Indian satellite launch vehicles, first used in 1994. More than 50 successful PSLV launches have taken place to date. It has also been called “the workhorse of ISRO” for consistently delivering various satellites into low earth orbits (less than 2,000 km in altitude) with a high success rate.
PSLV-XL can lift 1,750 kg of payloads to the sun-synchronous polar orbit (spacecraft here are synchronised to always be in the same ‘fixed’ position relative to the Sun), and much more — 3,800 kg — to a lower Earth orbit (normally located at an altitude of less than 1,000 km but could be as low as 160 km above the planet).
PSLV has successfully launched two spacecraft Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013. The launch of PSLV-C48 marks the 50th Launch of PSLV. Aditya-L1 mission, weighting 1,472 kg, was launched by PSLV-C57.
