RSAA Colloquia / Seminars / Feast-of-Facts: Friday, 01 July 2016, 14:30-14:50; Duffield Lecture Theatre

Sven Flegel

"Analysis of the ASTRO-H breakup and its impact on the collision risk of intact objects"

In Earth orbit, over 250 objects to date have exploded, collided with other objects or have broken up due to malfunctions or for unknown reasons. Such ’breakups’ are especially critical whenever they occur in highly utilized regions such as near 800 km altitude, where most Earth observation satellites reside or in the GEO region near 36000 km altitude which is heavily utilized by telecommunications satellites. Collision velocities on the order of 10 km/s are typically encountered in low Earth orbits; at these velocities even small pieces of debris can cause a satellite’s mission to end instantly. Because atmospheric drag decreases roughly exponentially, debris at 800 km altitude may remain on orbit for decades or even centuries and so can collide with other objects many years in the future with potentially catastrophic consequences. Long-term simulations show that the collision cascading, also known as the ”Kessler Syndrome”, will become a dominant source for debris. Large, massive objects are the driver within this process as a complete breakup will create many more fragments which in turn can trigger catastrophic collisions. In February 2016, the X-ray Astronomy Satellite “Hitomi”, also known as ASTRO-H was launched with a multitude of scientific payloads to examine the universe. Not even two months into its mission, the spacecraft suffered an anomaly in which several large pieces including the solar panels and scientific boom separated from the main body - the cause: a mixture of machine and human error. Although Hitomi’s orbit was below the critical 800 km altitude, it was neighbour to some other significant satellites whose demise would be hard felt. The talk explores details of the breakup and investigates the potential risk which the fragments may pose to active spacecraft in their vicinity and to the Kessler Syndrome.