Final Orbit-Raising Manoeuvre Of Chandrayaan-3 Completed

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(Source: The Hindu, 07/26/2023)

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Why in the news?

• Recently, ISRO completed the fourth orbit-raising maneuver of the Chandrayaan-3 mission from ISTRAC, Bengaluru.
• Chandrayaan-3 is expected to complete its soft landing on the moon’s surface on 23rd August 2023.

Orbit raising maneuvers

• The Chandrayaan-3 rocket is expected to attain an orbit of 1,27,609 km x 236 km following the successful completion of the fifth and final orbit-raising maneuver.
  • As a result, the rocket is 236 km from Earth at its nearest and 1,27,609 km away at its farthest.
• The next step is the Translunar Injection which will slingshot the rocket toward the moon.
• All the orbit-raising maneuvers were performed by the ISRO Telemetry, Tracking and Command Network (ISTRAC), Bengaluru.

Other orbits

• First orbit raising maneuver (Earthbound firing-1): The spacecraft reached an orbit of 41762 km x 173 km.
• Second orbit raising maneuver (Earth-bound apogee firing): The spacecraft reached an orbit of 41603 x 226 km.
• Third orbit raising maneuver (Earth-bound perigee firing): The rocket reached an orbit of 51400 x 228 km.
• Fourth orbit raising maneuver (Earth-bound perigee firing): The rocket attained an orbit of 71351 x 233 km.

Why is Chandrayaan-3 taking so long to reach the moon?

• The Chandrayaan-3 Mission is expected to take around 41 days to reach the moon’s surface.
• In comparison, NASA’s Apollo 11 completed its flight in just 4 days in 1969.
• Trajectory:
  • Apollo 11 used the Translunar Injection method to reach the moon aboard the powerful Saturn V launch vehicle.
  • The spacecraft was propelled directly into Earth orbit and then directly sent to the moon through a single engine burn.
  • Chandrayaan-3 has used a series of Earth orbits and engine burns to gradually increase the spacecraft's speed and position it to complete lunar insertion.
  • This approach is necessary because of the use of the relatively less powerful GSLV Mark-III, which possesses a lower payload capacity compared to the Saturn V.
• Cost-effective:
  • Chandrayaan-3’s longer route has been chosen to economize the entire journey.
  • It is cost-effective in terms of the equipment(heavier rockets) and fuel expenses.

How will Chandrayaan-3 reach the moon?

• Using gravity:
  • The elliptical orbital path used by Chandrayaan-3 allows it to achieve peak speed when at the perigee.
• Each time the perigee is approached, the rocket’s engines are activated, helping it gain momentum and energy as it climbs.
  • When the module obtains the escape velocity required to escape Earth’s gravity, the orbit elongates allowing the rocket to enter into the Lunar Transfer Trajectory.
• Lunar insertion:
  • Once the module reaches the intended point in the Lunar Transfer Trajectory, lunar orbit insertion is performed.
  • This reduces the module’s speed allowing it to be pulled into a stable lunar orbit by the moon’s gravitational force.
  • The module then orbits the moon in an elliptical path, gradually reducing its altitude until it reaches a circular orbit of 100 km.
• Landing:
  • The Propulsion Module and Lander Module (Vikram) will then separate and deboost maneuvers performed before the power descent phase which involves the soft landing.

ISTRAC

• The ISRO Telemetry, Tracking, and Command Network (ISTRAC) is responsible for providing tracking support to all of ISRO’s satellite and launch vehicle missions.
• It carries out mission operations of all operational remote sensing and scientific satellites from launch vehicle lift-off to injection of satellite into orbit.
• It provides space operations support for Deep Space Missions of ISRO and undertakes radar systems development for launch vehicles.
• It is mandated to establish and operationalize the ground segment for the Indian Regional Navigational Satellite System (IRSNSS) and provide services such as Search & Rescue and Disaster Management.
• It also supports space-based services such as telemedicine, tele-education, and Village Resource Centers (VRC).

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FAQs

MCQs

Question: Consider the following statements:

1. Chandrayaan-3 has used the translunar injection method to directly reach the lunar orbit.
2. It aims to land near the south pole of the moon.

Which of the above statements is/are correct?

(a) Only 1

(b) Only 2

(c) Both 1 and 2

(d) None