Aditya-L1 scheduled for 11.50am launch, with a 63-minute separation process explained.

Isro’s Preparations for Aditya-L1 Launch

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India’s space agency, Isro, is gearing up for the launch of Aditya-L1, the country’s first solar space observatory mission. The launch is scheduled for 11.50 am on Saturday, and it marks the culmination of years of development and preparation.

Significance of Aditya-L1 Mission

Aditya-L1 is a significant mission as it represents India’s entry into the field of solar observation in space. Until now, only the US and the European Space Agency (ESA) have independently or jointly launched solar missions, with Germany participating through NASA.

Unique Orbit and Journey

The Polar Satellite Launch Vehicle (PSLV), in its XL configuration, will place Aditya-L1 in a highly eccentric Earth-bound orbit. This orbit will have a Perigee (closest point to Earth) of around 235km and an Apogee (farthest point from Earth) of over 19,000km.

From this Earth-bound orbit, Aditya-L1 will utilize its liquid apogee motors (LAM) to perform multiple orbital maneuvers. These maneuvers will help it reach the Lagrange Point-1 (L1), which is approximately 1.5 million kilometers away from Earth, constituting just 1/100th of the distance between Earth and the Sun.

Explanation of 63-Minute Separation

Unlike typical PSLV launches, where spacecraft separation occurs within 25 minutes, Aditya-L1’s separation will take approximately 63 minutes after liftoff. This extended duration is due to specific requirements related to the spacecraft’s Argument of Perigee (AOP).

VSSC director S Unnikrishnan Nair explains that to achieve the required AOP, the final stage of the PSLV (PS4) is not fired in a single go. Instead, PS4 is fired initially for 30 seconds, allowing the rocket to reach a normal orbit. It remains in this orbit until the desired AOP is naturally achieved. Then, PS4 is fired again before the spacecraft separation, which occurs at 63 minutes, once the AOP is met.

The Significance of AOP for Aditya-L1

The Argument of Perigee (AOP) is crucial as it defines the spacecraft’s trajectory to its final destination. For Aditya-L1, the AOP is when the ascending trajectory of the spacecraft intersects with the Earth’s equator. Achieving this specific angle is necessary to reach the L1 Lagrange point.

Importance of Lagrange Point-1 (L1)

Lagrange Point-1 (L1) serves as a strategic vantage point for Aditya-L1. Satellites positioned in the halo orbit around L1 continuously view the Sun without any interruptions or eclipses. This positioning provides a unique advantage for observing solar activities and their impact on space weather in real-time.

Aditya-L1’s Journey to L1

Following its launch, Aditya-L1 will spend 16 days in Earth-bound orbits, during which it will undergo five maneuvers to gain the necessary velocity for its journey. Subsequently, it will execute a Trans-Lagrangian1 Insertion (TLI) maneuver, marking the start of its 110-day trajectory towards the L1 Lagrange point. Upon arrival at L1, another maneuver will bind Aditya-L1 to an orbit around L1.

Scientific Objectives of Aditya-L1

Aditya-L1’s primary mission is to study solar activities and their influence on space weather. Its scientific objectives include investigating coronal heating, solar wind acceleration, coronal mass ejections (CMEs), the dynamics of the solar atmosphere, and temperature anisotropy. To achieve these objectives, the spacecraft is equipped with seven scientific instruments, enhancing our understanding of the Sun’s behavior and its implications for Earth.

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