Thread by @Chethan_Dash

Here’s the first one. #Thread #Satellites #Debris

Exclusive: More than 10yrs after it was launched, #MeghaTropiques, @isro & @CNES joint weather modelling satellite that was studying water cycle & energy exchanges in the tropics has reached what’s called “end of mission”. 1/n

https://twitter.com/Chethan_Dash/status/1511935022185558017

The satellite, which was launched in October 2011 and initially estimated to have a life of five years has worked for five-years-and-six-months more than initial estimations and sent in at least 5TB of raw data which has yielded around 30TB of data sitting on various servers. 2/n

A senior Isro scientist said: “As on date, the satellite still has 120kg of fuel and end of mission is also not because of failures in communication, solar panels or any other systems or because we lost communication. All of those are still working.” 3/n

The decision to declare “end of mission” was taken because the satellite had developed an “attitude problem” which rendered the data unusable. 4/n

In layman’s terms, another scientist explained: “When my face is in front of yours and I’m seeing you, that’s my attitude to see you. Now, if my face is vibrating continuously, your image will be blurred. This is happening with the satellite; there’s no ground trace limit.” 5/n

The problem was first noticed some time in early or mid March and given that it is a scientific mission there are minimum requirements. Even if payloads are healthy, the mission won’t continue if data is not usable. 6/n

“Each day, it does 14 orbits & is expected to yield data in each orbit. For the past many months, it yielded data for about 4-5 orbits,” the first scientist said. 7/n

What Next: At present, Megha-Tropiques is in an orbit around 870km away from Earth. As is the procedure, Isro will now have to fire the engines again and reduce the altitude through orbit reduction manoeuvres. 8/n

Sources said that the plan is to bring the satellite down to an orbit that is less than 300km away from Earth. This will be controlled. After this, which is expected to be done within the next fortnight, the satellite will be monitored for more than two months. 9/n

Once the ground stations lose the telemetry connection, the spacecraft will be declared as debris and its responsibilities would be with the Directorate of Space Situational Awareness and Management (DSSAM). 10/n

“As per estimations, it could re-enter the atmosphere in two-three months, which would be as per the shortest time. Or, it could take as long as 18 months,” the source said. 11/n

@isro & @CNES are now planning another joint mission, #Trishna, meant for accurate mapping of land surface temperatures. In his last address, former chairman Sivan K had said “Trishna will be the benchmark for temperature data at best resolution and repeatability globally”. 12/n

According to @CNES, Trishna — Thermal infraRed Imaging Satellite for High-resolution Natural resource Assessment — will acquire imagery of Earth’s surface in the thermal infrared with a resolution and revisit frequency never seen before. n/n