Volume 31 Issue 8 - April 27, 2018 PDF
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Ionospheric plasma hole and gigantic shock waves induced by the launch of FORMOSAT-5 using the Space-X rocket
Charles C. H. Lin1,*, Min-Yang Chou1, and Ming-Hsueh Shen2
1 Department of Earth Sciences, National Cheng Kung University
2 Department of Aeronautics and Astronautics, National Cheng Kung University
 
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【106 MOST Outstanding Research Award】Special Issue

The launch of Taiwan’s first self-made satellite mission, FORMOSAT-5, had induced the greatest observed circular shock acoustic waves on record in the upper atmosphere followed by the ionospheric plasma hole. FORMOSAT-5 was the only passenger of the Space-X Falcon-9 rocket that delivered it to the mission orbit of 725 km altitude, thanks to the excellent launch contract management by National Space Organization (NSPO). NSPO signed the contract with SpaceX for launch service using Falcon-1 but had been upgraded to Falcon-9 due to decommission of Falcon-1, and the explosion accident of Falcon-9 on September 2016 had delayed the flight and cancellation of FORMOSAT-5’s shared flight satellites. The Falcon-9 has much greater carrying weight than that of FORMOSAT-5, thus it took a direct flight insertion to the satellite mission orbit. Usually, rockets travel in a curved trajectory after launch and deliver the satellites at ~200 km altitude followed by the orbit maneuvers to gradually elevate the satellites to their mission altitudes. Figure 1 shows the velocity and altitude profiles of the Falcon-9 rockets that carried JASON-3 (blue) and FORMOSAT-5 (red). The launch of JASON-3 mission went for the traditional curved trajectory while FORMOSAT-5 went nearly vertical to 725 km altitude instead (Figure 1).
Figure 1. Comparisons between the time profiles of rocket flights in velocities and altitudes for FORMOSAT-5 (red lines) and JASON-3 (blue lines) launches. JASON-3 was deployed at 200 km altitude while FORMOSAT-5 was deployed at 725 km mission altitude.

Nearly vertical rocket attitude of FORMOSAT-5 launch created an gigantic circular ripples in the ionosphere showing compressional increase (red) and decrease (blue) of plasma density in the altitude of ~300 km (Figure 2) with diameter of 1500 km, which is 4 times bigger than the area of California and 50 times bigger than Taiwan. It is the largest shock wave ever recorded induced by the rockets. A few minutes later, a plasma hole was created by the chemical recombination between the ionospheric plasma and water vapor of rocket exhausts. Figure 3 shows the ionospheric plasma hole spanned with an area of 900 km in diameter and lasted for ~2 hours. The plasma hole created has the effects of an “ionospheric front/cyclone” that were normally only created during the intense solar storm hitting Earth. Engineers using differential GPS technique to determine the more precise positioning and navigation would be impacted if the reference GPS stations were inside the plasma hole area.
Figure 2. The gigantic circular shock acoustic wave revealed in ionospheric plasma density showing compressional increase (red) and decrease (blue) induced by the Falcon-9 rocket that carried FORMOSAT-5 to its mission altitude of 725 km.

Figure 3. The launch also created an ionospheric plasma hole in the west coast of U. S. due to chemical reactions between charged particles in the ionosphere and water vapor of rocket exhausts. The rocket trail shown in the right side of figure is taken from the other launch for demonstration of rocket trajectory.

The upper atmosphere and ionosphere is the interface between Earth and Space, and the upper atmosphere has influence to the entire atmosphere. The artificial effect to the atmosphere induced by the rocket launches will impact the Earth’s atmosphere if it occurs more frequently. As the rocket launches are becoming usual and frequent due to reduced cost by reusable rockets, their impact to Earth’s environment will be important.
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