ISRO preps for re-entry experiment of decommissioned satellite on March 7
Bengaluru ( PTI): The Indian Space Research Organisation (ISRO) is preparing for a challenging experiment of controlled re-entry of a decommissioned low earth orbit satellite, Megha-Tropiques-1 (MT1), into the earth's atmosphere on March 7.
MT1 was launched on October 12, 2011, as a joint satellite venture of ISRO and French space agency CNES for tropical weather and climate studies.
Although the mission life of the satellite was originally three years, the satellite continued to provide valuable data services for more than a decade supporting regional and global climate models till 2021, the Bengaluru-headquartered space agency noted in a statement on Sunday.
UN/IADC (Inter-Agency Space Debris Coordination Committee) space debris mitigation guidelines recommend deorbiting a LEO (Low Earth Orbit) object at its end-of-life (EOL), preferably through controlled re-entry to a safe impact zone, or by bringing it to an orbit where the orbital lifetime is less than 25 years, according to ISRO.
It is also recommended to carry out "passivation" of on-board energy sources to minimise the risk of any post-mission accidental break-up.
The orbital lifetime of MT1, weighing about 1,000 kilograms, would have been more than 100 years in its 20 degree inclined operational orbit of 867 km altitude. About 125 kg on-board fuel remained unutilised at its end-of-mission that could pose risks for accidental break-up.
This leftover fuel was estimated to be sufficient to achieve a fully-controlled atmospheric re-entry to impact an uninhabited location in the Pacific Ocean.
Controlled re-entries involve deorbiting to very low altitudes to ensure impact occurs within a targeted safe zone.
Usually, large satellites/rocket bodies which are likely to survive aero-thermal fragmentation upon re-entry are made to undergo controlled re-entry to limit ground casualty risk. However, all such satellites are specifically designed to undergo controlled re-entry at EOL.
MT1 was not designed for EOL operations through controlled re-entry which made the entire exercise extremely challenging.
Furthermore, the on-board constraints of the aged satellite, where several systems had lost redundancy and showed degraded performance, and maintaining subsystems under harsher environmental conditions at much lower than originally designed orbital altitude added to the operational complexities.
Innovative workarounds were implemented by the operations team based on the study, deliberations, and exchanges among the mission, operations, flight dynamics, aerodynamics, propulsion, controls, navigation, thermal, and other subsystem design teams across the ISRO centres, which worked in synergy to surmount these challenges.
An uninhabited area in the Pacific Ocean between 5 degrees south to 14 degrees south latitude and 119 degrees west to 100 degrees west longitude was identified as the targeted re-entry zone for MT1.
Since August 2022, 18 orbit manoeuvres were performed to progressively lower the orbit. In between the de-orbiting, aero-braking studies at different solar panel orientations were also carried out to gain better insights into the physical process of atmospheric drag affecting the orbital decay of the satellite.
The final de-boost strategy has been designed after taking into consideration several constraints, including visibility of the re-entry trace over ground stations, ground impact within the targeted zone, and allowable operating conditions of subsystems, especially the maximum deliverable thrust and the maximum firing duration of the thrusters.
The final two de-boost burns followed by the ground impact are expected to take place between 16.30 hours to 19.30 hours on March 7.
Simulations show that no large fragments of the satellites are likely to survive the aerothermal heating during the re-entry.
"As a responsible space agency committed to safe and sustainable operations in outer space, ISRO proactively takes efforts for better compliance with the UN/IADC space debris mitigation guidelines on post-mission disposal of LEO objects," the statement said.
The re-entry experiment of MT1 has been undertaken as a part of the ongoing efforts as this satellite with sufficient leftover fuel presented a unique opportunity to test the relevant methodologies and understand the associated operational nuances of post mission disposal by direct re-entry into the Earth's atmosphere, it was stated.
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World saw valour, courage of Indian armed forces through Operation Sindoor: President
New Delhi (PTI): President Droupadi Murmu on Wednesday said the world saw the valour of Indian armed forces through Operation Sindoor when they destroyed terror camps on the strength of their own resources and asserted that any terror act will be responded with decisive action.
"India has proved that power can be used with responsibility and wisdom. The world has seen the valour and courage of Indian armed forces through Operation Sindoor," Murmu said in her address to both Houses of Parliament, marking the beginning of the Budget Session.
"Our nation, on the strength of our own resources, destroyed terror camps. My government sent a message that any act of terror will be responded to with resolute and decisive action," the President said, amid thumping of desks by Prime Minister Narendra Modi and other parliamentarians.
Murmu said the suspension of the Indus Water Treaty was part of India's fight against terror.
"We are also working on Mission Sudarshan Chakra to further strengthen national security," the President said, adding that security forces have also taken decisive action against Maoist terror.
Following Operation Sindoor, she said, the trust on Indian defence platforms has increased.
Murmu further said her government was committed to social justice in the country.
In the third term of the government, she said, work is being done to further empower the poor, and social security benefits are available to nearly 95 crore citizens now.
"My government is committed to true social justice," she said, adding that 25 crore Indians moved out of poverty in the last 10 years.
The President also said the government has been successful in tackling corruption and scams, and ensuring proper use of public funds.
"For India, the end of the first 25 years of this century has been filled with several successes, proud achievements and extraordinary experiences. In the last 10-11 years, India has strengthened its foundation in every sector," she said.
Lauding India's celebration of the 350th martyrdom day of the ninth Sikh guru, Guru Tegh Bahadur, and the country's tribute to revered tribal leader and freedom fighter Birsa Munda on his 150th birth anniversary, Murmu said, "when the country remembers the contribution of its ancestors, the new generation gets inspiration, which further speeds up our journey towards Viksit Bharat (Developed India)."
"The country celebrated the 350th Shaheedi Diwas of Sri Guru Tegh Bahadur Ji. During the 150th birth anniversary of Birsa Munda, the entire country paid him tribute and remembered his contribution to the tribal community," the President said.
"The events related to the 150th birth anniversary of Sardar Vallabhbhai Patel further strengthened the sense of Ek Bharat, Shresht Bharat (One India, Best India). The entire country became witness to how Bharat Ratna Bhupen Hazarika's birth anniversary celebrations filled the country with music and a sense of unity," Murmu said.
The President's mention of the Viksit Bharat – Guarantee for Rozgar and Ajeevika Mission (Gramin) (VB-G RAM G) scheme was met with loud protests from the Opposition benches.
Murmu said the VB-G RAM G initiative would provide guarantee for 125 days of work, would stop corruption and leakages, and provide a new impetus to rural development.
The Opposition members raised slogans demanding its rollback, even as the treasury benches thumped their desk in support of the scheme.
The President had to take a brief pause amid opposition cries of "vapas lo" (roll back) against the Act that replaced the Mahatma Gandhi National Rural Employment Guarantee Act (MGNREGA).
The Opposition parties have been demanding withdrawal of the VB-G RAM G Act and restoration of MGNREGA as a rights-based law in its original form, the right to work and the authority of panchayats.
The government has, meanwhile, claimed that the new Act will further strengthen the guarantee for rural employment.
