A fireball of magnitude -6 appeared above the Belgian Ardennes on 18 March 2020 at 02h03m52.9s UT and was registered by cameras of the BeNeLux CAMS network, the Global Meteor Network and FRIPON. A trajectory and orbit could be computed. The orbit does not fit with any known meteor stream and therefore the fireball is a sporadic. The aphelion is situated just outside the orbit of planet Mars.
A very slow –6 magnitude fireball appeared 18 March 2020 at 02h03m52.9s UT and was about 6 seconds visible at the sky. The event has been recorded by four stations of the CAMS BeNeLux network (Figures 1, 2, 5 and 6) and by two all-sky cameras of the FRIPON network at Brussels and at Liège (Figures 3 and 4). The night was clear for most parts of Belgium. The fireball passed almost unnoticed for casual watchers because of the time of the night, with most Belgian residents being at home due to the Covid-19 lock-down measures and almost nobody on the road.
2 Trajectory and orbit
The fireball was registered at Nancy, France by CAMS 3901 (Tioga Gulon), at Cosmodrome, Genk, Belgium on RMS BE0003 (CAMS 003815), at Observatoire Centre Ardenne, Grapfontaine, Belgium on RMS BE0001 (CAMS 003814) and at Mechelen, Belgium on CAMS 809 and RMS BE0004 (CAMS 003831). Figure 7 has a different color for each camera that contributed to establish the trajectory in the atmosphere and all fit well. The event started very deep in the atmosphere at less than 85 km elevation. For this reason, some cameras missed the event because it happened too low out of reach for some cameras.
The FRIPON all-sky cameras are less sensitive than the small FoV cameras used for CAMS, therefore FRIPON detected the fireball a bit later when it was deeper in the atmosphere and bright enough to be detected (Figure 8). The meteoroid encountered Earth at a very low pre atmospheric velocity of about 12.1 km/s and suffered a very strong deceleration into the deeper layers of the atmosphere (Figure 9).
The trajectory as derived from the CAMS BeNeLux data has been plotted in Google Earth, combined with the trajectory obtained independently by FRIPON (Figure 10).
Although a –6 bright fireball in general is too bright for the cameras of the BeNeLux network because of the inaccuracy of the positions measured in the overexposed parts of the meteor, the resulting trajectory is very close to that obtained by FRIPON. If we zoom in on the projected ground track there is a small tilt that makes a difference of less than 200 meter with the begin and end point of FRIPON (Figure 11). CAMS detected the meteor when it was about magnitude +5 at 84 km altitude, it brightened to about –1 at 75 km where FRIPON detected it and reached maximum brightness at 60 km, where the overexposure generated pure scatter on the images of the CAMS network (Figure 12). The more suitable FRIPON camera for such bright events has a more reliable luminosity profile for the brightest part of the fireball path (Figure 13).
Table 1 summarizes the orbit data for this event. Initially, the preliminary CAMS results differed quite a lot from those of FRIPON. According to Carl Johannink this happens when partial data is used in a hurry. When all data was available the final result compares excellent to FRIPON. The Global Meteor Network rejected the event from automatic orbit calculations because of the too bright luminosity and there too poor accuracy of the positional measurement. The fireball is a sporadic as the orbit does not fit with any known shower.
Table 1 – Orbit of the fireball of 18 March 2020 at 02h03m52.9s UT CAMS BeNeLux orbit (Carl Johannink) compared to FRIPON (François Colas).
|αg||144.99 ± 0.09°||–|
|δg||+57.15 ± 0.04°||–|
|Hb||84.4 km||74.5 km|
|He||31.8 km||34.5 km|
|vꝏ||12.11 km/s||12.02 km/s|
|vg||4.8 ± 0.01 km/s||–|
|a||1.28 A.U.||1.28 ± 0.01 A.U.|
|q||0.9877 A.U.||0.9877 ± 0.0002°|
|e||0.2282||0.2281 ± 0.0041|
|ω||196.56 ± 0.06°||196.58 ± 0.29°|
|Ω||357.69°||357.89 ± 0.007°|
|i||5.41 ± 0.01°||5.40 ± 0.06°|