Chandrayaan-3 propulsion module retraces steps to Earth orbit: why it matters
Context- Scientists have brought the Propulsion Module (PM) of the Chandrayaan-3 mission— which took the Vikram lander to within 100 km of the surface of the Moon before it detached and made the historic controlled descent to the lunar surface on August 23 — back into Earth orbit.
(Credits- universetoday.com)
The PM, carrying the lander, left the Earth’s orbit on August 1, and was inserted in a lunar orbit on August 5. Its successful return to Earth orbit is a significant achievement that marks a step towards bringing back samples from lunar missions in the future.
The manoeuvre, announced by the Indian Space Research Organisation (ISRO) on Monday, was not in the original mission plan.
The Propulsion Module
- Unlike Chandrayaan-2 — ISRO’s second lunar exploration mission that failed in September 2019 — the Chandrayaan-3 mission featured, instead of a full fledged orbiter, a light Propulsion Module that was essentially only a system for the lander to travel to the Moon.
- For communications with Earth stations, the mission used the Chandrayaan-2 orbiter, which was still in orbit around the Moon with functioning systems on board.
- The Chandrayaan-3 PM carried only an instrument called the Spectro Polarimetry of Habitable Planet Earth (SHAPE), an experimental payload to look back at Earth and study the signatures that make it habitable, so as to identify habitable exoplanets.
- The PM separated from the lander (which carried the Pragyaan rover in its belly) on August 17, but it was expected to continue orbiting the Moon for another six months, with SHAPE looking at Earth.
- “The main function of PM is to carry the LM [or Lander Module] from launch vehicle injection till final lunar 100 km circular polar orbit and separate the LM from PM. [The PM]…also has one scientific payload…which will be operated post separation of the Lander Module,” ISRO had said ahead of the Chandrayaan-3 mission.
Seizing the opportunity
- According to ISRO, the initial plan for the PM was to operate SHAPE for about three months, which was essentially the module’s mission life.
- However, “The precise orbit injection by LVM3 (or Launch Vehicle Mark-3, which launched the Chandrayaan-3 mission) and optimal earth/ lunar burn manoeuvres, resulted in the availability of over 100 kg of fuel in the PM after over one month of operations in the lunar orbit,” ISRO said in a release on Monday.
- “It was not a part of our mission plan. The meticulous mission planning…and precise injection orbit by launch vehicle resulted in propellant saving. This was used as a demonstration for future lunar sample return missions,” Chandrayaan-3 project director .
Return to Earth orbit
- After considering fuel availability and aspects of safety, “the optimal Earth return trajectory was designed for October 2023 month,” ISRO said.
- On October 9, the agency performed a manoeuvre to raise the orbit of the PM around the Moon to 5,112 km from 150 km (from 2.1 hrs to 7.2 hrs).
- “Later, considering the estimate of available propellant, the second manoeuvre plan was revised to target an Earth orbit of 1.8 lakh x 3.8 lakh km. The Trans-Earth injection (TEI) manoeuvre was performed on October 13,” ISRO said.
- Subsequently, the PM made four Moon fly-bys before leaving the Moon’s sphere of influence on November 10.
- Currently, the propulsion module is orbiting Earth and the orbit period is nearly 13 days with 27 deg inclination.
Way Forward- Through efforts to bring the PM back to Earth orbit, ISRO has been able to understand what is involved in the “planning and execution of trajectory and manoeuvres to return from Moon to Earth” for a small spacecraft. The experiment allows ISRO to work towards developing a software module to plan going forward.
Syllabus- GS-3; Science and Tech
Source- Indian Express
