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z Colombo – his early years and training experience - founding
member Eng. Giampiero Barbieri
- Pighin Since the
beginning the studies of Giuseppe Colombo were devoted to “celestial mechanics” … a field where the
dynamics of an artificial satellite or of a celestial body find a logic both
at orbital level and at a level of local stability. A
knowledge of both Kepler and Newton’s theories is necessary to start
the study of these phenomena ….. of Newton’s: the numerical integration addressed to
bodies having a “peculiar physical shape” and the whole array
of studies and simplifications for the analysis of the energy exchanges between
major and minor bodies …of course, a deep familiarity with differential equations is also requested … Colombo is
a dreamer, but he is not unprepared. The launching of the first Sputnik into orbit, made him feel sure
his thoughts and theories were feasible and within reach of the present-day technology. Colombo – his early years and training experience I wish to
recall the
fascinating contrast between Galileo and Colombo … Galileo, closed-barred into
his Copernican and heliocentric vision, never managed to free himself from “terrestrial
mechanics” … the way he conceived inertia was emblematic: “ … could I lay down
on the Earth’s greatest circle a frictionless band, a ball pushed on it would
rotate about the globe forever …” Colombo, instead, had «a mentality capable to
cast aside the traditional terrestrial mode used to face problems» (1)… proof of this is given by all
the vast amount of studies devoted to the “Tethered system” or “satellites
connected by a tether (cable)”, where actions or energies, effective only in
the outer space, can be carried out or exploited … Moreover, satellites launched
into space are subject to a number of local disturbances and instabilities, such as nutations, directional changes … but Colombo was well organized
for answers … his knowledge and experience allowed him to be appointed to the
chair of “vibration mechanics” at the University of Padua … knowledge pertaining
to terrestrial matters was immediately transposed onto spatial problems. Colombo, also,
was a man of faith. He was life devoted and participant to his parish
church activities … some of his friends were in touch with him for lifetime,
like Luigi Gui, a prominent politician of the Democrazia Cristiana (Christian Democrats) The American adventure – the stability of satellites Colombo’s skills
improved very much. Meanwhile the race towards space got started … Colombo
was trying to find a way to meet the top management of the NASA (National
Aeronautics and Space Agency - U.S.A.), but wisely, he took the matter easy …
his friendship with Giuseppe Jacchia, a fellow of his at
the University of Genoa, will become of great help … Jacchia
observes the sky with love and passion, combining space and geophysics
together … a subject, among others, of particular concern to Jacchia … Jacchia, at the time, was working at the HCO (Harvard College Observatory) in
Cambridge … the meeting in Genoa, between Jacchia and Colombo, at the end of the
fifties, allowed Colombo to be presented to the SAO (Smithsonian
Astrophysical Observatory) and to start a collaboration with the SAO … what convinced
the management of the SAO was the experience Colombo showed for the
understanding and the solution of the stability problems artificial
satellites had in space … during the time of his collaboration, Colombo was
able to prove: «that the satellite’s temperature fluctuations and other
electromagnetic anomalies, measured by the instruments aboard, were the
origin of the variations of the angular velocities » (1) Another
issue to which Colombo gave an answer was the supposed existence of disturbing
elements, such as dusts, accumulated around the Lagrangian
stability points L4 and L5 of the Earth’s orbit: … Colombo studied the problem
making use of all his experience. He was a “mechanic of the space” and proved, calculations
at hand, that the stability, in these points, was that much negligible, that
the presence of perturbing clouds of dust could be excluded… Mercury’s 3:2 spin-orbit resonance Irwin
Shapiro will become another great friend of Colombo. He was an astrophysicist,
with whom Colombo endlessly discussed of several problems … Shapiro was observing Venus and
Mercury using radar-ranging techniques, trying to test a correspondence with
Einstein’s general relativity theory (GR) … others, like Gordon Pettingil and Rolf Dyce made use of the measurements
given by the Arecibo radio-telescope to further analyze
in detail Mercury’s motion
of rotation … What is deduced
from the measurements is: the period of rotation is about 59 days, instead of the 88
considered reasonable till that time (it was assumed, in fact, that its
resonance structure should be similar to the Moon’s … that always shows the
same face to the Earth, so Mercury should have shown always the same face to
the Sun) … but the Arecibo measurements gave a different feedback … Of course, Colombo came to know about
the 59 days measurement, and immediately considered the possibility of an exact
resonance
only a
slight axial asymmetry of the planet must be conceived … together with Shapiro he published an
important, unforgettable, scientific paper work ……
z The concept
of “resonance” becomes the key that
is needed to read the mind of Colombo, and that allows to understand his
theories, among which, those concerning the Saturn’s rings … Work takes
into consideration the advanced results achieved with modern telescopes … «the great division in
the C ring, once again, corresponds to a resonance effect generated by the
motions of the large moon Titan, constantly hidden behind a thick mass of
clouds». (1) «Already in 1976, a
photometric asymmetry was found in the A ring. It was suggested it depended
from large particles, locked into the rings, in a synchronous way. Colombo understood
it was not so, and assumed instead, it rather was due to a gravitational
clustering of small particles in the rings. This hypothesis is now generally accepted
as the most reliable explanation and, also, is the first evidence derived
from the observation of the density waves in the rings. (1)
z Mariner 10 ... the robotic space-probe … During a
symposium on Mariner 10 and on the targets of such mission, Colombo suggested to carefully
consider the possibility to fly by Mercury three times, using “gravity assist” techniques. Colleagues of his objected:
«Only a stroke of good
luck may grant success to such an operation» (1) … Colombo had
different ideas and expressed them quite strongly. An accurate computerized
simulation took place, and showed his claims were sound and correct. Fuel on
board, at the time, took up much space and weighed too much. Colombo’s innovation
overcame this limit: “in place of terrestrial mechanics, he used spatial mechanics”. Some
mysteries could have become legible: i.e. the extraordinary density of Mercury
with respect to satellites alike, such as the Moon, Ganymede and Callisto. The account of the collisions regarding this planet would
have become known, allowing a better understanding of the dynamics of the proto-planetary
disk that gave origin to all. Technically,
after launch from Earth, Mariner 10 will make
use of a gravitational slingshot manoeuvre with Venus; immediately after will fly by Mercury and again encounter
Mercury twice. Its orbital period
was almost exactly twice Mercury’s. As a result of the 3:2 spin-orbit resonance, it would be again brought
back in the same spatial configuration. At first, Mariner
10 will encounter Mercury at a range of just 705 km.; the third time at
only 327 km … this will allow
to measure a weak magnetic field, shape and consistency of which will be
carefully analysed by the MESSENGER mission.
z The Halley comet’s adventure ... In the late
Seventies many discussions took place on the possibility to approach a comet, in order to capture
its shape and other measurable features of its nucleus. Only Colombo’s great
knowledge of celestial mechanics will allow this to become: «A mission that is the
result of his imagination». (1) The
spacecraft will head towards the comet, releasing a smaller probe towards it… Colombo will call the mission
“Giotto”, remembering that,
the transit of the comet Halley in 1301, had been represented by this famous
painter in his masterpiece: “L’adorazione dei
Magi”
(The adoration of the Magi). In Europe, one
of Colombo’s greatest achievements allows the Giotto mission to anticipate
the Hipparchus mission … The mission
is not at all easy … the spacecraft will have to face the mechanical
impact with all the particles released by the comet. Its integrity is
at great risk … a double shield will be set up, one of plastic and one of
aluminium to dampen the effects of the impacts. «For the Giotto mission,
in addition to the aspects of the long sidereal cruise, in accordance with
the appropriate cosmic trajectories, Colombo studies the complex nutation
motions to which the probe could become subject, trying to prevent and to
eliminate them, before they become a source of problems». (1) Giotto, after
a journey of about an astronomic unit (approx. 150 million km.) will near the nucleus
of the comet at a range of 596 km. Later on, definitive
break-downs will prevent further measurements. The shape
of the nucleus is “potato-like”, which today is, also, common
knowledge for many other smaller bodies. Additionally, matter is emitted into
space from many points and becomes shiny under the Sun light.
z Conclusions ... Bepi Colombo was very much close to his
family. It was his family that supported his many wanderings throughout
Europe and across America at the cost of great sacrifices … his faith, in which he always
believed, was also of great help and support to him … Faith, indirectly,
forged him
into a man of great reserve. In my opinion, this aspect, by analogy, taught him
how to become sturdy in pursuing his targets. Evidence of
this is given by the lack of photographs related to him … for sure, his character
was not similar to Einstein’s … but whoever was in touch and knew him said he was
quite friendly and kindly natured … this is how Riccardo Mazzella, a student of his,
remembers him: «I must say, after 30
years, my reminiscence is quite faint. I was a student of Astronomy, perhaps
in my second or third year. Just now I do not exactly remember. What fascinated me was
the way Bepi could explain complicated matters in a
very simple and easy way. He made us understand how to solve problems of
celestial mechanics, putting forward ideas that even the NASA thought
excellent. At the time, he was collaborating to a space project. His ideas
allowed the same spacecraft to fly by Mercury many times. Really, this meant making
the best of the mission. » It is in
silence that the best and most important targets are achieved … thanks Bepi …… z
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