Airborne re-entry observation campaign of the Cluster-II salsa re-entry

After their end of operation, the four Cluster-II satellites are re-entering the Earth’s atmosphere. The first Cluster-II satellite, named Salsa , re-entered on the 8th of September at 18:46 UTC (2024-09-08T18:46 UTC) over the South Pacific, approximately 2000 km west of Easter Island. An airborne observation team was on station aiming to observe the satellite’s break-up. This paper reports the design and execution of the airborne observation under the challenging situation of an entry under plain daylight conditions. The mission planning and preparation in coordination with the observation prediction leads to the flight mission details. Due to the highly eccentric orbit, the entry predictions were particularly challenging and resulted in a wider spread of potential entry corridors. Therefore, based on the very last perigee, only 52 h before the actual entry, and spacecraft data after the manoeuver, the team received the last orbit information at 20:30 UTC on the 7th of September (2024-09-07T20:30UTC). Based on this data an appropriate flight path for the aircraft was designed. On board a Falcon 900 business jet, the team deployed six different stations with a total of 26 cameras. All cameras were time-synchronized to the GPS time using a centralized time server. The mission was successful. The infrared cameras detected the entry for approximately 23 s beginning at around 18:47:08 UTC.