IGS 1B Re-Entry [SPACEFLIGHT101]

どうやら情報収集衛星レーダー1号が大気圏に再突入したようです。

According to USSTRATCOM Data, the Spacecraft re-entered on Thursday, July 26, 2012 at 9:52 GMT +/-2 Minutes. This places the decay and entry location over the Pacific Ocean, about 1,300 Kilometers north-east of New Zealand. The Spacecraft was making an ascending pass, traveling from south to north with its orbital trajectory taking it east of New Zealand traveling north to pass between Fiji and Tonga. Taking the 2-minute uncertainty into account, the vehicle could have decayed along a 1,800-kilometer trek. At the opening of the Entry Window, IGS 1B was about 650 Kilometers east of East Cape, North Island, New Zealand. For a decay at the +2-Minute-Mark, the vehicle would have been 500 Kilometers south east of Fiji and 250 Kilometers north-west of Tonga. These numbers represent the point of Orbital Decay referring to a point at an altitude of 80 Kilometers. At that point, the satellite should start breaking up as thermal and aerodynamic loads increase. The components of the vehicle are still possessing a major portion of the kinetic energy going forward in the direction of travel, along their ground track. For typical spacecraft, 20-40% of the vehicle’s mass make it to the surface in the form of larger fragments. Dense components of satellites usually come down 800 to 1,300 Kilometers downrange from the Orbital Decay Point. Their journey back to Earth is strongly influenced by atmospheric properties like crosswinds that play a major role during atmospheric descent. In conclusion, it is highly probable that surviving components of IGS 1B have impacted the Ocean since there were no major land masses in the +/-50-Klimeter swatch along the possible entry ground track.

IGSレーダー1号は2003年に光学1号と共にデュアルロンチされたもので、情報収集衛星としては初モノ。このレーダー1号は2007年3月に電源系トラブルで運用停止になってましたが、上層大気の影響でそのまま徐々に高度を落として日本時間7月26日18時52±2分頃に再突入。場所は運良く毎度お馴染みNZ沖だったようです。お疲れさまでした。