MEGHA TROPIQUES-1

1. Context

2. About Megha Tropiques

• Megha- Tropiques is an Indo-French Joint Satellite Mission that studies the water cycle and energy exchanges in the tropics.
• Its objective is to comprehend the life cycle of convective systems that influence tropical weather and climate, as well as their role in the associated energy and moisture budget of the tropical atmosphere.
• It provides scientific data on the contribution of the water cycle to the tropical atmosphere, including information on condensed water in clouds, water vapor in the atmosphere, precipitation, and evaporation.

Image Source: The Indian Express

3. What is the Re-entry of satellite?

• Due to the increasing number of objects in space (Space debris), the international aerospace community has adopted guidelines and assessment procedures to reduce the number of non-operational spacecraft and spent rocket upper stages orbiting the Earth.
• One method of post-mission disposal is to allow the re-entry of these spacecraft, either from natural orbital decay (uncontrolled) or controlled entry.

4. How was the satellite brought down?

• The Megha Tropiques satellite was launched aboard a PSLV by the space agency in 2011. And, although the planned mission life of the satellite was only three years, it continued providing data on the water cycle and energy exchanges in the tropics for nearly a decade.
• With over 120kgs of fuel remaining in the satellite even after being decommissioned, the space agency determined that there was enough to attempt a controlled re-entry, where a series of 20 maneuvers over eight months lowered the orbit of the satellite such that it re-entered the dense atmosphere and burned up. 
• This was the first time that the space agency attempted such a maneuver to clear out space debris despite the satellite not being built to do so.
• The re-entry was not really planned as part of the mission; there was fuel left so Isro attempted it. Usually, satellites are left in their orbit and because of the gravitational pull of the earth, they come down to the atmosphere over years and years.
• When the satellites re-enter the atmosphere, the friction causes them to heat up to extremely high temperatures of thousands of degrees Celsius.
• Without a heat shield, 99% of a satellite gets burnt up whether in a controlled re-entry or an uncontrolled one.
  

5. Why did ISRO attempt a controlled Re-entry?

• Other than extra fuel conveniently remaining in the satellite after the mission life ended, ISRO attempted the controlled re-entry to demonstrate and understand the process of doing so.
• With several space-fairing nations and private entities launching satellites, mostly in low earth orbits, it has become imperative to keep space clean.
• There are thousands of objects flying around in these orbits; not just old satellites and their parts but also the last stages of the rockets that take them there.
• Moving at extremely high speeds even the smallest debris can destroy active satellites.
• In fact, the space agency set up a department last year to monitor space debris and mitigate the risks posed.
• The space agency was also following the guidelines of the UN and the Inter-Agency Space Debris Coordination Committee (IADC) that say satellites should be deorbited after mission life either through controlled entry over a safe impact zone as was attempted by ISRO with Megh Tropiques-1 or by bringing it down to reduce the orbital lifetime to less than 25 years.

6. Space Debris

• Space Debris encompasses both natural meteoroid and artificial (human-made) orbital debris. Meteoroids are in orbit about the sun, while most artificial debris is in orbit about the Earth (hence the term "orbital" debris).
• Orbital debris is any human-made object in orbit about the Earth that no longer serves a useful function. Such debris includes nonfunctional spacecraft, abandoned launch vehicle stages, mission-related debris, and fragmentation debris.

Image Source: NASA