The Indian Space Research Organisation (ISRO) recently launched the first flight of the Small Satellite Launch Vehicle (SSLV). This launch carried an Earth observation satellite, EOS-02, and a student-developed satellite called AzaadiSAT. However, due to failure in placing the satellites in their required orbits, the mission did not achieve its goals.
Description and Significance of Small Satellite Launch Vehicles (SSLVs)
A Small Satellite Launch Vehicle (SSLV) is a lightweight, three-stage Launch Vehicle configured with three Solid Propulsion Stages and a liquid propulsion-based Velocity Trimming Module (VTM) as a terminal stage. SSLVs are primarily designed to launch small satellites and have a low cost, low turn-around time, flexibility in accommodating multiple satellites, minimal launch infrastructure requirements, and high launch demand feasibility.
These vehicles have become increasingly important in recent years due to the rising demand for the launch of small satellites. This demand has grown due to the increasing need for space-based data, communication, surveillance, and commerce.
Small Satellites: The Rising Demand and Business Opportunity
Small satellites have gained significant importance in the last eight to ten years, with new players such as businesses, government agencies, universities, and laboratories joining the sector. Organizations are increasingly developing constellations of satellites in space to save on costs and reduce waiting times for launching satellites. With this rising demand, the frequent and cost-effective launch of rockets, like ISRO’s SSLV, provides significant business opportunities for space agencies.
About EOS-02 and AzaadiSAT: The Mission Satellites
The SSLV-D1/EOS-02 Mission was designed to carry two satellites. EOS-02 is an advanced optical remote sensing earth observation satellite with high spatial resolution. The secondary satellite, AzaadiSAT, is an 8U Cubesat weighing around 8 kg. This student-developed satellite carried out tiny experiments which would have measured the ionising radiation in its orbit and also operated a transponder in the ham radio frequency.
Issue with the Launch: The Problem of SSLV’s Terminal Stage
The main issue with the small satellite launch was a problem with the SSLV’s terminal stage or the Velocity Trimming Module (VTM). The VTM was supposed to have burnt for 20 seconds at 653 seconds after launch. However, it only burnt for 0.1 seconds, denying the rocket the necessary altitude boost. This resulted in the satellites being placed in an elliptical orbit, rather than a circular orbit, making it unstable.
The Difference between Circular and Elliptical Orbits
Satellites and spacecraft are often put in elliptical orbits temporarily until they can be pushed up to circular orbits at a greater height or their acceleration is increased. In contrast, satellites that orbit the Earth are mostly placed in circular orbits as it is easier to manage if the satellite is used for imaging the Earth.
Previous Year Question on India’s Satellite Launch Vehicles
A previous year question in the UPSC Civil Services Examination asked students to consider statements about India’s satellite launch vehicles. The correct answer was that PSLVs launch satellites useful for Earth resources monitoring, while GSLVs are designed mainly to launch communication satellites. The other statements considered in the question were found incorrect.
The recent SSLV-D1/EOS-02 Mission sheds light on the rising importance and challenges of small satellite launches. New developments in this sector present significant opportunities for space agencies and businesses alike.
