Orbital decays/Re-entry/Disposals of Indian spacecraft and debris

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Let's keep thread for summarising same from next time on instead of ISRO general news thread.
 
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Controlled Re-entry Experiment of Megha-Tropiques-1
Mar 05, 2023
ISRO is gearing up for a challenging experiment of controlled re-entry of a decommissioned low Earth orbiting satellite, namely Megha-Tropiques-1 (MT1), on March 7, 2023. MT1 was launched on October 12, 2011, as a joint satellite venture of ISRO and the French space agency, CNES for tropical weather and climate studies. Although the mission life of the satellite originally was to 3 years, the satellite continued to provide valuable data services for more than a decade supporting regional and global climate models till 2021.
UN/IADC space debris mitigation guidelines recommend deorbiting a LEO (Low Earth Orbit) object at its end-of-life, 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.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 1000 kg, would have been more than 100 years in its 20 deg 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 left-over 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 end-of-life. 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 sub-system design teams across the ISRO centres, who worked in synergy to surmount these challenges.
An uninhabited area in the Pacific Ocean between 5°S to 14°S latitude and 119°W to 100°W longitude was identified as the targeted re-entry zone for MT1.Since Aug 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 IST to 19:30 IST on March 7, 2023. Aero-thermal 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 re-entry experiment of MT1 has been undertaken as a part of the ongoing efforts as this satellite with sufficient left-over 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.
 

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Megha-Trqopiques-1 (MT1) Controlled Re-entry Successful and impacted on the Pacific Ocean
Mar 07, 2023
The controlled re-entry experiment for the decommissioned Megha-Tropiques-1 (MT-1) was carried out successfully on March 7, 2023. The satellite was launched on October 12, 2011, as a collaborative effort between ISRO and the French space agency CNES for carrying out tropical weather and climate studies. Since August 2022, the satellite's perigee was progressively lowered through a series of 20 manoeuvres spending about 120 kg of fuel. Multiple Manoeuvres including the final de-boost strategy were 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 constraint on thrusters. All manoeuvre plans were screened to ensure that there would be no post manoeuvre close approaches with other space objects, especially with the crewed space stations like International Space Stations and the Chinese Space Station.
megha_tropiques.png

MEGHA-TROPIQUES

The final two de-boost burns were executed at 11:02 UTC and 12:51 UTC respectively on 7th March 2023 by firing four 11 Newton thrusters on-board the satellite for about 20 minutes each. The final perigee was estimated to be less than 80 km indicating that the satellite would enter the denser layers of the Earth's atmosphere and subsequently undergo structural disintegration. The re-entry aero-thermal flux analysis confirmed that there would be no surviving large debris fragments.
final_ground_traces_MT1.png

Final ground traces of MT1
From the latest telemetry, it is confirmed that the satellite has re-entered the Earth's atmosphere and would have disintegrated over the Pacific Ocean, the final impact region estimated is in the deep Pacific Ocean within the expected latitude & longitude boundaries. The entire sequence of events was carried out from the Mission Operations Complex in ISTRAC.
In recent years, ISRO has taken up proactive measures to improve the compliance level with the internationally accepted guidelines on space debris mitigation. Efforts are underway to build indigenous capabilities for tracking and monitoring space objects to safeguard Indian space assets. ISRO System for Safe and Sustainable Space Operations Management (IS4OM) has been established to spearhead such activities. The controlled re-entry exercise bears yet another testimony to India's continued efforts towards ensuring the long-term sustainability of outer space activities.
 

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A0218/23 - TEMPORARY DANGEROUS AREA DUE TO SATELITE DEBRIS REENTRY.
AIRSPACE DEBRIS REENTRY IN NO FIR WITHIN AN AREA BOUNDED BY THE
FOLLOWING POINTS: 0500S11900W 0500S10000W 1400S10000W
1400S11900W 0500S11900W.
ATS ROUTE UN789 IS IMPACTED IN NO FIR.
AIRSPACE USERS ARE ADVISED OF THE PARTICULARLY DANGEROUS NATURE
OF THE ACTIVITY, AND ARE STRONGLY INVITED TO AVOID THE AREA
DURING THE ACTIVITY TIME SLOT.
OPERATORS ARE INVITED TO FILE THEIR FLIGHT PLAN WITH A TRAJECTORY
THAT ENSURES THAT THE AREA IS CIRCUMNAVIGATED. SFC - UNL, 1000-1400, 07 MAR
10:00 2023 UNTIL 08 MAR 14:00 2023.
 

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A0218/23 - TEMPORARY DANGEROUS AREA DUE TO SATELITE DEBRIS REENTRY.
AIRSPACE DEBRIS REENTRY IN NO FIR WITHIN AN AREA BOUNDED BY THE
FOLLOWING POINTS: 0500S11900W 0500S10000W 1400S10000W
1400S11900W 0500S11900W.
ATS ROUTE UN789 IS IMPACTED IN NO FIR.
AIRSPACE USERS ARE ADVISED OF THE PARTICULARLY DANGEROUS NATURE
OF THE ACTIVITY, AND ARE STRONGLY INVITED TO AVOID THE AREA
DURING THE ACTIVITY TIME SLOT.
OPERATORS ARE INVITED TO FILE THEIR FLIGHT PLAN WITH A TRAJECTORY
THAT ENSURES THAT THE AREA IS CIRCUMNAVIGATED. SFC - UNL, 1000-1400, 07 MAR
10:00 2023 UNTIL 08 MAR 14:00 2023.
Map of area for which NOTAM was ishueed
Screenshot_2023-03-08-09-25-53-70_3d9111e2d3171bf4882369f490c087b4.jpg
 

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ISRO completes post-mission disposal operation of GSAT-12 satellite
The Indian Space Research Organisation (ISRO) recently completed the post-mission disposal (PMD) operation of the communication satellite GSAT-12. The satellite carrying 12 extended C band transponders was launched in 2011 and served for more than a decade. However, after the launch of its replacement satellite CMS-01 in 2020, the GSAT-12 was relocated to 47.96°E longitude from 83° E longitude where it was located till March 2021.
The PDM was successfully completed on March 23.
ISRO said that the Geosynchronous Earth Orbital (GEO) regime is one of the most populated and highly utilised regions and that the internationally accepted space debris mitigation guidelines by the UN and IADC recommend disposing of an object away from the GEO region at its end-of-life.
“The recommended practice is to re-orbit the object to a nearly circular graveyard orbit sufficiently above the GEO region so that the orbit would not decay back into the GEO-protected zone under the influence of perturbation forces, such as non-uniformity of Earth shape, Sun’s Moon’s gravity, solar radiation pressure, etc., within another 100 years,” ISRO said.
For GSAT-12, the required minimum raise in perigee altitude was estimated to be 261 km.
As a result of meticulous operations management by the Master Control Facility (MCF) in Hassan, the available fuel of GSAT-12 was more than sufficient to meet this goal, the space agency said.
A series of seven manoeuvres were carried out to raise the orbit above the GEO altitude of 35786 km and four inclination changing manoeuvres of GSAT-12 were carried out during March 20-22 to spend the remaining propellant.
“On March 23, the final passivation manoeuvre was carried out to vent out the remaining fuel by firing the oppositely mounted thrusters, cancelling the net thrust without affecting the orbit. As part of electrical passivation, all rotating mechanisms, such as the momentum wheels, reaction wheels and gyros, were turned off, and batteries were disconnected from the solar panels and discharged. Finally, the transmitters were switched off to avoid any potential RF interference. The passivation activities were completed on March 23, 2023,” ISRO said.
GSAT-12 is the 23rd GEO satellite to undergo PMD before decommissioning. The space agency added that the PMD operation is fully compliant with the IADC and UN space debris mitigation guidelines, as well as the UN guidelines for the long-term sustainability of outer space activities.
 

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Cross-post
🇮🇳PSLV-C56/🇸🇬DS-SAR Mission:

The PS4 stage de-orbiting experiment is successful.

The stage is purposefully manoeuvred to a 295 km x 300 km orbit. It now spends significantly less time in space, reducing its duration from over two decades to less than two months, before re-entering the Earth's atmosphere.

Reduced time in Space = Less risk of debris!

ISRO, 🇮🇳India remains committed to reduced space debris and sustainable use of space for the benefit of all.
 

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Atmospheric Re-entry of Cartosat-2
Cartosat-2, ISRO's first satellite in the second generation of high-resolution imaging satellites, launched on January 10, 2007. It weighed 680 kg at launch and operated in a sun-synchronous polar orbit at an altitude of 635 km. Until 2019, it provided high-resolution imagery for urban planning.
Initially, Cartosat-2 was expected to take about 30 years to naturally de-orbit. However, ISRO opted to lower its perigee using leftover fuel to comply with international guidelines on space debris mitigation. This involved reducing collision risks and ensuring safe end-of-life disposal, following recommendations from organizations like the United Nations Committee on the Peaceful Uses of Outer Space (UN-COPOUS) and the Inter-Agency Space Debris Coordination Committee (IADC).
ISRO's System for Safe and Sustainable Space Operations (IS4OM) team at ISRO Telemetry Tracking and Command Network (ISTRAC) predicted Cartosat-2's atmospheric re-entry for February 14, 2024. Electrical passivation was completed on February 14th, and tracking continued until re-entry. The final telemetry frames confirmed successful passivation, with the satellite reaching about 130 km altitude.
1708359790305.png

This provided an opportunity to assess indigenous tracking capabilities, with the Multi-object tracking radar at Shriharikota utilized for tracking. The final prediction placed Cartosat-2's re-entry over the Indian Ocean at 10:18 UTC / 3:48 pm IST on February 14, 2024. Analysis indicated that all major spacecraft components would demise during atmospheric re-entry.
Cartosat-2's successful de-orbiting at its end-of-life represents a significant step for ISRO in ensuring the long-term sustainability of outer space activities.
1708359817372.png

Final re-entry ground traces of Cartosat-2 (NORAD id 29710) showing impact point over the Indian Ocean
 

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Sorry, forgot to post earlier.

PSLV accomplishes zero orbital debris mission
Another milestone was achieved by ISRO on March 21, 2024, when the PSLV Orbital Experimental Module-3 (POEM-3) met its fiery end through a re-entry into the Earth’s atmosphere. The PSLV-C58/XPoSat mission has practically left zero debris in orbit.

The PSLV-C58 Mission was accomplished on January 1, 2024. After completing the primary mission of injecting all satellites into their desired orbits, the terminal stage of PSLV was transformed into a 3-axis stabilized platform, the POEM-3. The stage was de-orbited from 650 km to 350 km, which facilitated its early re-entry, and was passivated to remove residual propellants to minimize any accidental break-up risks.

POEM-3 was configured with a total of 9 different experimental payloads to carry out technology demonstrations and scientific experiments on the newly developed indigenous systems. Out of these, 6 payloads were delivered by NGEs through IN-SPACe. The mission objectives of these payloads were met in a month.

The orbital altitude of the upper stage continued to decay under the influence of natural forces, primarily atmospheric drag with the module (NORAD ID 58695) expected to have impacted the North Pacific Ocean (Lat 6.4 N & Long 158.7 W) on March 21, 2024, at 14:04 UTC (19:34 Hrs. IST).

Through the POEM, which serves as a very cost-effective platform for carrying out short-duration space-borne experiments, ISRO has opened up new vistas for academia, startups, and NGEs to experiment with their new payloads. This novel opportunity has been effectively utilized by numerous startups, universities, and NGEs for carrying out experiments in space, which included electric thrusters, satellite dispensers, and star-tracking. POEM also incorporates new features such as total avionics in single-chain configuration, industrial-grade components in avionics packages including Mission Management Computer, standard interfaces for electric power, telemetry & telecommand, and new in-orbit navigation algorithms making use of rate-gyro, sun sensor, and magnetometer. For the effective conduct of experiments onboard in POEM-3, the body rates were stabilized to less than 0.5 deg/s throughout, and innovative schemes like controlled dumping of residual propellant after the main mission were introduced for minimizing disturbances due to passivation.
The Vikram Sarabhai Space Centre (VSSC) has taken the lead in conceptualizing and realizing the POEM by augmenting the 4th stage of PSLV. PSLV-C58/XPoSat is the third such mission in the series, with POEMs being successfully scripted each time. The payload operations were carried out effectively by the spacecraft operations team from the mission operations complex (MOX) at ISTRAC and ISRO's System for Safe and Sustainable Spacecraft Operations Management (IS4OM) has been monitoring and analyzing the orbital decay all through. Till near re-entry, POEM-3 was tracked by ISTRAC ground stations. The Multi-Object Tracking Radar (MOTR) at Shriharikota also tracked the PS4 stage till the morning of March 21. POEM-3 was also supported by other Centres like URSC, LPSC and IISU.
ISRO will continue its commitment to providing a cost-effective orbital experiment platform. As the growing menace due to space debris, especially with multiple small satellite constellations coming up, poses a significant threat to space activities, including satellite launches, human spaceflight, and space exploration missions, ISRO, being a responsible space agency, is committed to mitigating this threat through the development and implementation of advanced debris tracking systems, space-object deorbiting technologies, and responsible satellite deployment practices, thus safeguarding orbital environments for present and future space endeavors.

1712318063928.png

PSLV Orbital Experimental Module-3 (POEM-3)

1712318073840.png

Impact location of POEM-3
 

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