How do you steer a space telescope with no thrusters?

In 2020, a European space telescope lost its thrusters. Sunlight was slowly twisting it, and nothing was left to push back. So its engineers turned the sunlight against itself. This is the story of ESA's Integral gamma-ray observatory: how half a turn about the line to the Sun let the same light that was filling its reaction wheels empty them again, and how, the next year, one wheel switching off led to a tumble, with about three hours of battery to work with. Told from ESA's own reports, with Integral's real flight data redrawn so you can watch it happen. Where this comes from ESA, Rescuing Integral: No thrust? No problem: https://www.esa.int/Enabling_Support/... ESA, Three hours to save Integral: https://www.esa.int/Enabling_Support/... ESA, Safe at last: https://www.esa.int/Enabling_Support/... De Marco et al., New Safe Mode for INTEGRAL Mission (SpaceOps 2023): https://publications.spaceops.org/202... Kuulkers et al., INTEGRAL reloaded (New Astronomy Reviews, 2021), the wheel data: https://arxiv.org/abs/2106.12446 Richard Southworth on Space Rocks, How to save a spacecraft (2021):    • Uplink 59: How to save a spacecraft: INTEG...   Pictures: ESA, NASA, NASA/JPL-Caltech and The Planetary Society (LightSail 2, CC BY 3.0). The spacecraft model and drawings are simplified, not to scale; the charts are traced from the published figures. Spot something wrong? editor@thecontrolroom.tv #space #engineering #ESA