ISRO's heaviest rocket LVM3 to launch second batch of OneWeb satellites on March 26

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The Indian Space Research Organization (ISRO) will carry out the launch of its heaviest and largest rocket LVM3, at 9 AM on Sunday, March 26. Aside from being the second commercial mission of the LMV3 rocket, the launch will also mark the completion of the first generation constellation of UK-Based LEO satellite communications firm OneWeb. OneWeb has been utilising the launch services of SpaceX, Arianespace and ISRO to place all its first-generation constellation satellites in orbit. OneWeb satellites have flown 17 times to date and ISRO will be carrying the 18th set. Placing the entire constellation in orbit would enable the firm to initiate global coverage in 2023. 

Just like it had done in October 2022, ISRO's rocket would be carrying 36 OneWeb satellites into low earth orbit, roughly 600 km above the earth's surface. The launch is scheduled to take place from ISRO's second launch pad at the Satish Dhawan Space Centre in Sriharikota.

"Across India, OneWeb will bring secured(internet communications) solutions not only to enterprises but also to towns, villages, municipalities and schools, including the hardest-to-reach areas across the country," said the firm backed by India's Bharti group. 

OneWeb had signed a pact with ISRO's commercial arm NewSpace India Limited (NSIL) for placing a total of 72 satellites in orbit (in batches of 36). This deal has raked in more than $120 million (Rs 1000 crore) in revenue for the Indian Government-run space agency. It also provides an opportunity for ISRO to demonstrate the capability and reliability of their largest rocket for offering commercial launch services. Until October 2022, ISRO's LVM3 or GSLV Mk3 rocket was being used only for fulfilling India's national missions such as Chandrayaan-2 and launching heavy satellites. Notably, the LVM3 has performed successful launches in all its missions to date. The March 26 launch of LVM3 will be the rocket's sixth mission.

When quizzed about the number of satellites in their Gen1 constellation, OneWeb recently told WION that "the first generation (Gen 1) LEO constellation is comprised of 648 satellites in total, which is inclusive of spare satellites that will be deployed on an as-needed basis.” ISRO's launch will take the constellation numbers up to 618.

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Why LEO-based satellites for internet communications?

Traditionally, communications satellites and those used for TV broadcasting purposes have been placed in Geostationary orbits, roughly 36,000 km above the earth's surface. From that high above, a single satellite would be able to view one-third of the Earth's surface and provide services over a vast area - be it communications or TV broadcast or internet or radio and even military applications. As the name suggests, in a geostationary orbit, the satellite will appear stationary when viewed from Earth, as the satellite's orbital movement is in sync with the Earth's rotation. With satellites in this orbit, all DTH antennas, ground-based antennas can simply focus in a single direction towards the sky and can perpetually receive signals. 

However, in modern-day use cases, there are many disadvantages to using Geostationary satellites for providing connectivity. Geostationary orbit satellites are large, heavy, and expensive and there is a considerable lag in the signal as it has to travel a vast distance. The signal delay is estimated at 477 milliseconds for Geostationary orbit satellites and in the case of LEO satellites it is 27 milliseconds. Lesser delays or latency can enable real-time functions such as online gaming, HD video conferencing, remote operations of machines and other strategic uses.

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Given that the LEO satellites are closer to earth (roughly 160-2000kms above the earth), the signals can travel faster. However, to provide constant coverage, a large number of satellites working in unison are required. That's why firms like OneWeb, Starlink and Amazon's Project Kuiper are putting in place constellations. Owing to the smaller size, proven capabilities and low-cost, firms prefer to install LEO constellations to provide global internet connectivity, irrespective of challenges posed by the terrain. However, the satellites in LEO have a short lifespan when compared to those in GEO, thus necessitating the entire constellation to be replaced every five years or so. 

(With inputs from agencies)

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