Evaluate the significance of debris-mitigation measures adopted in PSLV missions in the context of long-term sustainability of outer space activities.

Q. Evaluate the significance of debris-mitigation measures adopted in PSLV missions in the context of long-term sustainability of outer space activities. (15 marks, 250-350 words)

Orbital congestion has made debris a first-order threat to space access, prompting COPUOS to adopt 21 voluntary Guidelines for the Long-term Sustainability of Outer Space Activities in 2019 [4]. Since spent PSLV rocket bodies form the single largest category of Indian debris — 40 of 129 trackable objects [3] — mitigation built into the PSLV is central to India's credibility, though its significance remains real but partial.

Merits of the measures - Post-mission disposal: PS4 upper stages are passivated and de-boosted; ISRO records that PSLV-C58 and PSLV-C60 stages were lowered to 350 km, re-entering within months [2] — directly shortening orbital lifetime. - Controlled re-entry capability: PSLV-C62 carried the KID Capsule, a re-entry prototype targeted for South Pacific splashdown [1], advancing precisely the technology that safe disposal demands. - Reuse over abandonment: the POEM platform converts the spent PS4 into an orbital testbed, hosting payloads instead of adding junk [3]. - Institutional backing: IS4OM is the nodal agency for sustainability and analysed over 53,000 close-approach alerts in 2024 [2], with the Debris Free Space Missions target of zero debris creation by 2030 binding both government and private actors [3].

Limitations - Legacy debris endures: 41 fragments from the 2001 PSLV-C3 break-up remained in orbit at end-2024 [2] — mitigation cannot undo past events. - Non-binding character: DFSM is a policy commitment and LTS guidelines are voluntary [4]; compliance rests on self-discipline. - Cost trade-off: de-boost burns propellant, trimming payload margin in a price-sensitive commercial market [1]. - Marginal effect alone: Sun-Synchronous Orbit congestion is driven by global constellations; unilateral restraint cannot secure the commons.

Thus PSLV's mitigation architecture is significant less for the debris it removes than for the operating norm it institutionalises. Sustaining it requires converging DFSM with binding international rules and progressing from mitigation to active debris removal — building on rendezvous-and-docking capability demonstrated by SpaDeX [3] — so that space remains, in treaty terms, a province of all humankind.

(~325 words)

Sources: 1. ISRO — PSLV-C62 / EOS-N1 Mission — KID Capsule re-entry demonstrator, NSIL commercial mission profile 2. ISRO — Indian Space Situational Assessment Report (ISSAR) 2024 — PS4 de-orbit to 350 km, IS4OM role, close-approach alerts, PSLV-C3 debris 3. PIB — Parliament Question: Space Debris Management — Debris Free Space Missions 2030 target, Indian debris inventory, POEM, SpaDeX 4. UNOOSA — Long-term Sustainability of Outer Space Activities — 21 voluntary LTS guidelines adopted by COPUOS, 2019