However, major challenges this "old" mission faces are the aging on-board systems, the ongoing evolution of ground-segment technology, manpower turnover and a tightening budget. This paper summarises the effects of aging of the INTEGRAL spacecraft components and its ground segment in times of austerity as well as their impact on operations, team structure, costs and scientific programme execution. Furthermore, it discusses how to retain expertise and interest and illustrates the potential of extending INTEGRAL's mission well into the next decade.

In early 2015, ESA's high energy astronomical observatory INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory) performed a series of manoeuvres to enable the disposal of INTEGRAL via an uncontrolled re-entry into the Earth's atmosphere in 2029. These manoeuvres used approximately half of INTEGRAL's remaining fuel. At the current rate of consumption, fuel would be exhausted by early 2020 already and thus probably be the satellite's lifetime limiting element. Following these manoeuvres, different ways to reduce propellant usage were investigated.This paper summarises the general concepts of various fuel saving options. Indications suggest that it is possible to achieve major propellant savings in the coming years at very low implementation costs. This could allow ESA to extend INTEGRAL's science operations phase considerably and thus provide the high energy astronomical community with a solid observatory well into the next decade. Furthermore, it could possibly even allow for a controlled re-entry in 2029 with some residual propellant available for a trim manoeuvre in the mid to late 2020ies. Such a manoeuvre would enable ESA to fine-tune the re-entry longitude, position and profile.

Space debris in orbit poses a serious threat: Even a tiny screw or a piece of paint travelling at very high velocity can cause major damage if it hits a satellite. Any single impact can cause a cascade of collisions and eventually lead to a domino effect: Each collision generating space debris increases the likelihood of further collisions creating even more space debris. Up to now the growth of the debris population has been dominated by object break-ups (intentional or unintentional). However, the IridiumCosmos collision illustrates the risks associated with debris population growth driven by the collisional domino effect. The numerous close approaches, near-misses and the increasing risk of collisions have prompted space agencies across the world to selfcommit to guidelines aiming to limit space debris population growth and the resulting collision threats.The Gamma-Ray observatory INTEGRAL with its 3.5 tons is ESA's heaviest science mission ever flown. Analyses have shown that once out of fuel, INTEGRAL would not re-enter during the next at least 200 years without intervention from ground. In this long period, it would initially pose a modest debris hazard in the protected sub 2000 km and the geostationary zone but could eventually become a major debris contributor in case of a collision. Therefore, despite the fact that INTEGRAL was launched before the ESA space debris guidelines were formulated, an investigation of potential disposal options has been performed several years after launch including graveyard orbit, disposal manoeuvre, break up and re-entry analyses. This paper summarises the different disposal options as well as the disposal concept and strategy ultimately chosen via parametric numerical propagations and break-up analyses. Furthermore, the in-depth planning of the disposal manoeuvres and their successful execution in 2015 are presented. Finally, the detailed assessment of the resulting consequences for the scientific mission and the routine mission operations are discussed including the re-entry characteristics and possible fine-tuning of the re-entry longitude, position and profile in the next decade.