Geoscience Reference
In-Depth Information
Fig. 2.
Geometry for the computation of the length of a trail as viewed from space.
Table 1. Meteor trail apparent length at the
FOV center versus orbit height.
Height
Apparent length
β
Angular velocity
(km)
(degrees)
(degrees/s)
400
2.00
2.70
1,000
0.70
0.90
10,000
0.07
0.09
36,000
0.02
0.02
of 15 km, and assuming a value of 20 km/s as geocentric velocity we obtain
the data listed in Table 1.
As can be seen, even from high orbits, the trail length is long enough
and the angular velocity are not prohibitive for modern CCD sensors.
2.4.
Lightning
Lightning play a key role in the dynamic interplay of forces occurring in the
Earth's atmosphere. Lightning distribution on Earth is not uniform. Most
recent data have been obtained by the NASA satellite optical transient
detector (OTD). The OTD has observed about 1.2 billion lightning per
year. On the oceans lightning are less frequent than on dry land and thicken
between equator and tropics. The electric activity is stronger in the north
hemisphere than in the southern one. The most “stormy” areas of our planet
