Swift acrobatics in response to GW170817

Below you will see a visualisation of the maneuvers that the Swift spacecraft performed in the course of its tiling observations in response to GW170817. This campaign was comprised of 744 individual pointings that covered 92% of the galaxy-convolved gravitational wave error region. Swift is the only spacecraft that can perform this type of fast-response tiling, and will remain so for the foreseeable future.

The video shows a skymap. The large and small red circles are the sun and moon constraints on the sky, respectively. Everything shaded green/blue is behind the Earth from the perspective of the spacecraft. The dancing red dot shows the position of the Swift X-ray Telescope field-of-view on the sky. The small black dot sweeping across the sky is the position of the spacecraft itself in Earth-centered coordinates. Everytime the Sun and Moon cross the map, Swift has completed one orbit of the Earth. This takes approximately 96 minutes in real-time, so the video is sped-up by 3000x in the beginning. However, you will see that this rate is not constant. This ‘video’ is actually a compilation of snapshots, one for each slew maneuver. When the spacecraft is performing a large number of successive slews, as during tiling, the video will appear to slow down. When the video begins Swift is engaged in normal operations, long complex and rapid slewing maneuvers across the sky (the red paths). However, after a little bit the red dot stops dancing across the sky and will appear to jiggle around in one place. This is the spacecraft performing the tiling. The Atitude Control System is keeping the telescopes focused on this one small region of the sky, even as the spacecraft itself swings around the earth at 17,000 mph. Enjoy, and keep in mind that for any other spacecraft such a video would be interminably boring!

Thanks to Jeff Gropp.