Geoscience Reference
In-Depth Information
detection from space of luminous transient events in the Earth atmosphere
and/or on the dark side of other planetary objects. One of such a detec-
tor as been designed and a prototype (smart panoramic optical sensor
head, SPOSH) has been constructed at Galileo Avionica S.p.A (Campi
Bisenzio,Italy).Effortshavetobedonenowtoplacethisinstrumenton
space platforms conceived for other missions in order to low the costs.
In what follows we review the possibility of space observations for the
most important luminous transient phenomena. For sake of clarity we clas-
sify the transient phenomena in “Earth phenomena” and “Planetary phe-
nomena”, even though some of them originate in a similar physical context.
2. Earth Phenomena
Transient luminous phenomena on Earth occur mainly in its atmosphere at
different heights. Their origin is due essentially to the interaction of cosmic
debris with the high layers of atmosphere and the electric activity that is
present in it at different levels.
Interest for meteors is due to the information they can provide about the
history of the solar system and the properties of the original planetesimals,
as well as to the large influence of meteors on the upper atmosphere. The
Hunten particles (suspended atmospheric particles at altitudes between 80
and 100 km of meteoroid origin) act as condensation nuclei for sporadic
phenomena, as noctilucent clouds and meteor trails provide valuable infor-
mation in turbolence and wind diagnostics.
Concern is rising also about the space debris issue, given the increasing
risk for aerospace vehicles. From the event identification standpoint, it can
be dicult in many cases to discriminate meteors from space debris events.
Lightning is a phenomenon of high interest in different scientific fields,
including studies of the water cycle, and also taking into account less known
events like jets, sprites, etc. Among the different electric phenomena in the
atmosphere, satellite observations of lightning and auroras are relatively
easy. More dicult are the observations of red sprites, blue jets, and elves,
due to their superposition to stormy cells where lightning are numerous.
2.1.
Meteors
Asteroids and comets are the sources of small interplanetary bodies. The
collisions between asteroids in the main belt, besides producing km-sized
asteroids, generate huge numbers of fragments having sizes spanning from
a hundredth of millimeter to some tens of meters, intermediate between
