On December 5, at 10:34 UTC, an ISRO PSLV-XL rocket lifted off from India’s Satish Dhawan Space Centre, launching ESA’s Proba-3 Mission.
A minute and ten seconds later solid ground-lit boosters separation occurred, followed by the air-lit solid boosters separation. At T +1:49 the first stage separation occurred and the second stage began its burn. The launch proceeded with second and third stage separation. Nearly nineteen minutes into flight the fourth stage deployed Proba-3 satellites.
The launch was performed in nominal conditions and delivered the payload into a highly elliptical orbit (600 x 60530 km at around 59-degree inclination).
LIFTOFF of #Proba3 on PSLV-XL rocket from Satish Dhawan Space Centre in Sriharikota, India a on 5 December 2024! pic.twitter.com/wyT53jzAkn
— European Space Agency (@esa) December 5, 2024
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A multi-satellite mission
ESA’s competence in formation flying has been proven in previous years. Automated Transfer Vehicle has demonstrated high precision when docking with the ISS while Sweden’s Prisma mission successfully performed formation flying for brief periods.
These missions achieved centimeter-level accuracy but current technological challenges require even more precision and smaller features. Larger apertures and longer focal lengths for the detection of ever-fainter signals can’t be obtained by a single spacecraft.
Proba-3 aims to explore multi-satellite system capabilities, which would behave as a single virtual structure. It consists of two smaller satellites, the Coronagraph spacecraft, and the Occulter spacecraft.
They have been deployed in a stack configuration, and after a preparatory period, they will separate to perform tandem flights. Due to fuel consumption restraints, they will demonstrate formation flight for six hours during each orbit, and spend the rest of the time passive drifting.
They will autonomously maintain formation to a few millimeters and arc second precision at distances around 150 meters during the maneuvering period which will take place around the apogee of each orbit, where gravitational, atmospherical, and magnetic perturbations are minimized. Collision Avoidance Manoeuvre testing, acquisition, rendezvous, and proximity operations are included in the mission objectives.
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Artificial Solar Eclipses
The precision of such a system of coordinated satellites is not an end in itself. Solar Corona is a region of scientific interest but it’s rarely observable due to the low rate at which solar eclipses occur.
In 1975 a cylindrical Apollo capsule attempted to produce an artificial eclipse to be observed by a soviet Soyuz vehicle during the test Apollo-Soyuz. Proba-3 aims to produce artificially inducted solar eclipses regularly.
To obtain an undisturbed observation of the Solar Corona it’s necessary to move the occulting disk much further away from the observing coronagraph, but practical spacecraft size limitations have made this solution impractical for space. Therefore, the Occulter and Coronagraph will try to position themselves to a relative distance of approximately 150 meters while acting as a single giant observer.
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About PSLV-XL
ESA selected the PSLV-XL rocket for its ability to deliver the mission’s 550kg payload to a highly elliptical orbit. ESA’s Vega-C launcher could not meet these requirements, while Ariane-6 would be too expensive for a tightly budgeted technology demonstration mission.
PSLV-XL is a four-stage launcher, it has an overall height of 44,4 meters and a 2,8 meters diameter. It can take up to 1750 kg of payload to Sun-Synchronous Polar Orbits at 600 km altitude and up to 1425 kg of payload to Geosynchronous and Geostationary orbits.
The first stage is powered by six solid strap-on boosters alongside an S139 solid rocket motor. The second stage uses the Vikas liquid engine while the third is propelled by a solid rocket motor. Lastly, the fourth stage uses two liquid engines.
The Polar Satellite Launch Vehicle (PSLV), India’s third-generation launch vehicle, is the first in the country to feature liquid-propellant stages. Since its maiden successful flight in October 1994, PSLV has proven to be a dependable and versatile workhorse for Indian space missions.
It has launched numerous satellites for both Indian and international customers. Notably, the PSLV successfully deployed two groundbreaking spacecraft: “Chandrayaan-1” in 2008, which journeyed to the Moon, and the “Mars Orbiter Spacecraft” in 2013, which traveled to Mars.
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