To
50-th Anniversary of Yu.A.Gagarin flight and
in Memory of Prof. Luigi Broglio, Founder of University satellites Program Luigi Broglio and the San Marco satellites Filippo Graziani, Ugo Ponzi This article has
two chapters. First chapter is prepared by Prof.F.Graziani. In this one it is
highlighted the role and place of Engineering Aerospace School of Sapienza
University of I. Introducing Chapter on Universities satellites The Engineering Aerospace School of Sapienza
University of Rome is honoured to host the 1st IAA Conference on
University Satellites Missions and the 1stCubesat Winter Workshop,
dedicated to the new generation of university satellites: micro, pico,
femtosatellites, from cubesats to pocketsats. In particular the 1st Cubesat
Winter Workshop will provide the opportunity to students to have an overview of
the current status of the university microsatellites, as well as to exchange
different points of view through a variety of sessions, laboratories and
forums. We are also very proud to recall that the In fact, the year 2011 marks the 50th Anniversary
of the beginning of the Piloted Astronautics
Era: on During the COSPAR session, held in Florence
that year, where the Russian space representatives announced the breaking
news:"The first human in outer space", our very own Professor Luigi Broglio,
Dean of the Engineering Aerospace School for over thirty five years, invited
some of his dear American colleagues and friends to dinner. And while having
dinner that night, he proposed a joint program to investigate upper-air density
and associated ionosphere phenomena related to the solar activity in the
equatorial region, using small satellites. "You are brave" said the Americans, and then
readily continued "we will support you". The idea of the San Marco Project was
hence born! The activity on small
satellite design, manufacture and integration involving Professors and
Researchers of the Engineering
Aerospace School of Sapienza University of Small satellites at that time meant 150 kg of
weight, but compared to today's miniaturized components can be easily scaled at
least to one order of magnitude less! The Conference and the Workshop are directed
also to both past and present students already skilled and experienced in
satellite design and manufacture, as well as to beginner students for which special
laboratories will be organized during the workshop, and last but not least to
future students (high school students) for which a full half-day meeting is
specially dedicated. Professors and Industry Representatives are
warmly invited to offer their experience and valuable support to the young
people attending this workshop. Moreover, since Conference
and the Workshop are inserted in the memorial week dedicated to the memory of
Professor Luigi Broglio (1911-2001), all participants are invited to see the
films on the San Marco Project (San Marco satellites and San Marco Equatorial
Range in Also, off the beaten track tourist walks in the
streets of Ancient Roma will be organized, as we wish that the glorious past history of Roma and the prestigious
future projects of the Astronautical
Era can mix together in the present
Conference on University Satellites Missions and Cubesat Workshop! The low cost of developing
and launching a CubeSat has opened the possibility of bringing CubeSats as
educational tools into the classrooms of many universities and even some high
schools. Unlike larger projects, the short development time for CubeSats of
typically two years from initial design to launch is very compatible with the
duration of Master and PhD theses. As educational hands-on projects CubeSats
are ideal and it is, therefore, no surprise that the CubeSat community is
rapidly growing. The CubeSat standard was defined in 1999 by Industry is also getting involved by launching
CubeSats for technological applications, by developing and selling CubeSat
subsystems and deployers and offering launch services. Space agencies and other
institutions are using CubeSats for biological, microgravity and re-entry
research. More and more large rocket companies are beginning to cater for the
needs of this emerging new market segment. A number of CubeSats can be equipped
with common instruments and launched, deployed and operated together as a
distributed sensor network for atmospheric or space weather research, for Earth
environment monitoring or ship identification and tracking at very low cost. Each year, numerous conferences in different
parts of the world are organized which include CubeSat sessions. However, there
are currently only two workshops which are dedicated to CubeSats and are held
every year on a regular basis. These are the CubeSat Developers' Workshop
in April in The Education Office of the European Space
Agency (ESA) organized a Vega Maiden
Flight CubeSat Workshop on 22-24 January 2008 at ESTEC in the Nowadays, there are an estimated 100
universities in 30 European countries interested in developing CubeSats and
there is, therefore, clearly a need for continuing this series of European
CubeSat conferences. The 1st
CubeSat Winter Workshop in II. Main Chapter The San Marco Project First and foremost let me express a warm note
of thanks to the organizers who, while planning the topics of the Conference on
university satellite missions, elected to reserve time for L.Broglio and the
San Marco satellites notwithstanding their "space age antiquity". But it is just this remoteness that is one of
the many merits accompanying their achievements: that is, the merit of being
ahead, with the activities of the San Marco Project, of any other Italian
initiative of this type and of trail-blazing a path to the first effective
operation of Italian universities in this field. In addition to this primogeniture, one must
underscore the fact that it was not an operation of scientific or technological
content limited to just one sector but rather a comprehensive achievement that
dealt with the fundamental requirements of space activity, tackling and solving
the knotty problems associated with design, construction, ground testing and
launch of satellites as well as the related satellite data acquisition. In fact, the effort deployed at that time was
directed at establishing also a base in Kenya (the San Marco Range equipped
with launch structures, and satellite control and telemetry instrumentation), a
Center in Rome with installations and laboratories for satellite development
and environmental tests - namely, Centro Ricerche Aerospaziali (CRA) located on
Via Salaria, destined to become in time the current Centro di Ricerca Progetto
San Marco (CRPSM ) - and training and organizing the personnel of various
specializations assigned to the operations in the above named sites. What was achieved back then and the results we
are still gleaning - partly thanks to the introduction of fresh resources -
allows us to state that, on the whole, the activities carried out by the San
Marco Project reached a magnitude as yet unsurpassed by any other
space-dedicated Italian university structure. What were the results obtained? Let me list a few significant ones: - the first Italian scientific
satellite (San Marco 1) injected into orbit in December 1964. So, - the subsequent satellites SM 2, 3, 4
and 5 were also built by CRA. They were launched from - hospitality offered by said SM
satellites to NASA and German experiments to the end of establishing a broad
investigative capability into the statics and dynamics of neuter and ionized
atmosphere; - the achievement claimed by the
so-called "Balance" (of which more details later on) as an original instrument
for in situ measuring of aerodynamic drag; - the success of - the orbital launches from - the use of the Range ground
structures for scientific activity in support to other Italian, European, US
and Chinese missions that could avail themselves of San Marco Stations control,
command and telemetry capabilities; - development of studies on
fundamental remote sensing methodologies and the resultant applications of data thus acquired for land
management activities and natural resources monitoring; - last but not least, the great
impulse imparted to the renovation of didactics within the The importance acquired by the use of the above
mentioned structures even recently results from
the wide spectrum of cooperative
relationships instituted by San Marco Project with many of the world's main
players in the field of space activities. L.Broglio's figure and
professional life Whenever I pause to ponder over such numerous
and compelling achievements - both in terms of contents and precocity with
respect to other space operators, be it Italy or Europe - I cannot help
remembering and renovating my admiration for the figure of Luigi Broglio who,
of all this, was the promoter and whose birth centenary falls this year while
his demise occurred in this month, a decade ago. L.Broglio's life and the history of the San
Marco Project are so interrelated that it will be easy in this venue to proceed
to a commemoration of his accomplishments by just retracing the main steps of
the Project itself. Bearing in mind, however, that although the constraints of
time will force me to illustrate him as the protagonist of this glorious
undertaking, I certainly do not mean to detract from him the great number of
his other accomplishments that rightly made him a distinguished scientist and
Teacher. By now, everybody is in agreement that L.Broglio
was indeed the Father of the Italian space activity. And if we consider Space
as a summation of all the elements that constitute and manifest it (that is to
say, the disciplines that nourish it, the technological means that support it
down to the applications that realize it), please allow me to say in no
uncertain terms that L.Broglio deserves this recognition because of the way he
successfully operated ahead of his contemporaries in each of these areas. L.Broglio's academic and military careers were
with no doubt decisive for his entering the field of space activities with such
far-reaching actions. As a teacher and Principal of the School of
Aerospace Engineering that he restructured
in 1963, L.Broglio had the opportunity to concern himself with a number
of fundamental topics of space culture: aeronautics and rocketry, with in-depth
studies of structure mechanics and heat transmission problems, aero-elastic and
aero-thermodynamic similarities, astrodynamics and re-entry problems, as well
as theoretical and experimental research on high atmosphere motions. And so he
arrived at original scientific results of great importance that were the fruit
of his intellectual vivacity, of an unusual culture coupled with the acuteness
of his analyses and the immediate perception of the essential aspects of the
problems at issue. L.Broglio used to aim at results of a concrete
nature and useful for applications, as it happened for example in the 50's with
his "Method of Balanced Forces" whereby, at a time when computers were unknown,
the mathematical model of aeronautical structures not sufficiently restrained
(wings) was conformed to the convergence requirements characteristic of successive
approximation methods. Or, among many other instances, his elegant treatment of
boundary conditions and of non-linearity in Space/Time problems of thermal
conduction in bodies subjected to convective and radiative heating. Concurrently, L.Broglio was a brilliant officer
of the Air Force Engineer Corps whose pinnacle he reached at the end of his
career, gaining the esteem of the High Command and the priceless support that
the Italian Air Force would contribute to the successive operational phases of
the San Marco Project. It is safe to assume that the symbiosis between
University and Armed Forces - that enabled the San Marco Project to reach such
relevant objectives - was a comparison of collaboration that, I presume, was
never again attained with such amplitude. All this was possible because of L.Broglio's
numerous insights: he was indeed able to put to good use the positions reached
in the execution of his military and academic duties, after perceiving ahead of
time the realities of space and identifying the practicable paths that could get
round the obstacles. Nowadays, cooperation in space activities under
bilateral or international agreements is a recurring fact among major space
players. Fifty years ago was this indeed the formula arrived at intuitively by L.Broglio
to govern his relationship with NASA. Birth of the San Marco
Project At that time L.Broglio had developed at the
School of Aerospace Engineering remarkable operational capabilities in the
sectors of advanced aeronautical research and rocketry, and was about to bridge
a few gaps so as to enable his group to play in the immediate future an
effective role in space activities. It was necessary to absorb and study in
depth the elements of the new culture, to be able to design and develop satellites,
have a vehicle for injection into orbit, own a launch base and staff it with
specialized personnel. - a satellite with a scientific
objective of great relevance at the time (in situ measurement of atmospheric
density at orbital altitudes by means of an innovative instrumentation); - a launch Base, likewise conceptually
original, capable of launching satellites into direct equatorial orbits; - personnel experienced in launch
techniques and readily available for further training on the vehicle. His proposal, approved by NASA whose decision
fell for LTV's Scout vehicle, had the backing of the Italian Air Force,
National Research Council (CNR), and national Government that allocated the
necessary funds. In essence this was the content of a
"Memorandum of Understanding" signed in 1962 by Vice-President Johnson for the The Agreement opened a phase of close
cooperation in the scientific and technological fields between NASA and CRA.
This cooperation lasted for more than thirty years and had a considerable
political weight since it was for long the major space cooperation program
between the two countries. Originality of the
satellite mission Entering into that Agreement L.Broglio
contributed with original ideas that enabled The first mission included an Italian
experiment - promptly accepted by NASA - that was indeed a piece of further
evidence of the way L.Broglio managed to conceive solutions conceptually appropriate
when the objective was difficult to achieve because of absence or insufficiency
of technological supports. At that time measurements
of high-altitude atmospheric density were carried out by in-situ ionization
sensors sadly characterized by poor accuracy. Otherwise, an indirect method was
used that was based on the aerodynamic force
F= CDrV2/2 arrived at by the variation of orbital parameters astride
a long series of satellite passes, but the end result was only averaged out
data. L.Broglio's intuition was instead that of
obtaining direct measurements of aerodynamic force by means of the so-called
"Balance" placed on board the satellite. To do this, it became necessary to configure
the satellite in two parts that were capable of sliding with respect to each
other. - an internal heavy body containing
all on board instrumentation; - an external shell secured to the
central body with an elastic joint. The aerodynamic force acting upon the shell was
measured by detecting the deformation of the elastic joint. It is therefore worth
noting that it was not an accelerometer, in which the sensor is subjected to
its own inertial force, but rather an oscillating two-mass system where the
force to be measured acts directly on the lesser mass (shell) as would be the
case in a dynamometer. The concept was straightforward but its
practical application presented a few arduous engineering problems that needed
solving. Because the satellite was spin-stabilized, it
became obviously necessary to have the CG of the internal body coincide with
the CG of the shell, and house the elastic element in this point. Moreover, to obtain favorable measuring
conditions it was necessary for the shape of the shell to be at least
axial-symmetric with respect to the spin axis or, still better, spherical so as
to reduce the aerodynamic force down to a simple resistance regardless of the
satellite attitude. The balance instrument At first, in order for the elastic joint to be
sensitive to forces and insensitive to momentum, we made use of three linear
elements with one degree of freedom, placed in series at 90° to each other in
the direction of the satellite body axes. As a result, joint deformation was
decomposed automatically in the three components along the axes and measured as
the relative displacement between the two rigid bases of each of the three
linear elements. The joint thus conceived and designed was called "Balance" by
analogy with the balances/scales
used in aerodynamic tunnels. The number of linear elements could be reduced to
two if the spin axis remained constantly perpendicular to velocity. In the
history of San Marco satellites, the transition to a two-component system only
took place when the control system was able to maintain said required attitude
with great accuracy. The utilization of a pair of linear elements on each axis
made it possible to attain a complete symmetry of mass also with regard to the
mechanical parts of the Balance. The measurement of deformations, that is, the
displacement δ between the two bases of each
linear element was obtained using differential transformer-type sensors.
Mounted in pairs to each element, they could also compensate automatically for
the effect produced by ever possible
thermal deformations. The study of the Balance response to forces
variable over time was conducted using a three-body mathematical model (central
body, shell, rigid coupling between the two measuring groups x and y). For example, in the case of San
Marco 5 satellite the minimum natural frequency ω0 was equal to 15.88 rad/s. In view
of the actual value of spin velocity equal to Ωsp = 0.628 rad/s, the ratio Ωsp/ω0 = 0.04 demonstrates that the Balance
responded in a static way to the modulation induced by the satellite rotation.
In addition, because the response may
be considered still flat for an excitation with frequency ω¢ such that the value ω¢/ω0 is not greater than about 0.2, it followed that the Balance was able to
investigate phenomena with frequency ω¢= 0.2ω0 = 3.2 rad/s still responding statically. Which corresponds to a resolution power
relative to a path along the orbit given by S=2πV/ω¢= 15.7 km (that is to say, 2750 samplings for
an orbit with Perigee at 200 km and Apogee at 600 km). The satellite Project The shell was required to be very light with
respect to the internal body, which also points out the advantage of the model
used (San Marco model) over the accelerometer. The satellite design, that put into practice L.Broglio's
original concept, satisfied its particular requirements of function and
configuration thanks to a series of solutions, the principal instances of which
are only briefly mentioned here: - the spherical shape of the shell was
obtained by using truncated cones pieced together so as to facilitate the
insertion of mica "windows" for illumination of the solar cells mounted to the
internal body and more openings around the shell to allow installation of
mechanical elements (satellite side supports, antennas, inertia booms mounted
to the internal body) or access to attitude sensors and other on board
instruments; - installation of the Balance to the
satellite internal body and shell in the two poles of the latter using
cylindrical axial arms designed such as to cross the shell in a contact-free
way; the same "no contact" positioning applied to the support of the internal
body attachment flange too; - device to block the motion of the
internal body relative to the shell, active from completion of assembly to
injection for protection of the Balance; - addition of four articulated arms on
plane x y to recover a ratio of
inertia Iz /Ix= Iz /Iy compatible with the
stability of the spin motion. The same figure shows the satellite SM 5 with
some of its characteristics. Worthy of note is the high value of mass density
due to the requirement to accommodate into internal body of the satellite NASA
and DLVR instruments that went along with the Balance. They were an Airglow
Solar Spectrometer for solar and interplanetary radiation; a Wind and
Temperature Spectrometer for neutral particles components and kinetic
temperature; six Electric Field Sensors (EFI) for the electric field
components. Because of the presence of EFI (provided with four retractable
wires with terminal masses with functions of electrode at a distance of 20 m
from the axis) it became necessary
to evaluate also the interrelation
of the motion of these with the motion of the satellite rigid body. Conclusion Here it is not analyzed all board systems, such
as power supply, data handling, telemetry, attitude determination and control,
which also sometimes required original solutions. Likewise, it would be difficult to dedicate a
detailed chapter to the scientific results obtained by the Balance and other
experiments. Therefore, to complete this outline of L.Broglio's
achievements in the framework of the scientific objective of the satellite
mission, which we have only begun to describe, let me just say that in the
whole series of San Marco satellites his intuition, that is, the Italian
experiment of the Balance, turned
out to be completely functional to the objective, supplying very interesting
results for the study of quasi-static and dynamic conditions of the high
atmosphere in the belt from 140 to 600 km of altitude. Exhaustive evidence of this may be drawn for
example by the comparison results, that show the correspondence between
thermospheric phenomena/orbital events and the Balance response. With this last brief mention of L.Broglio's
scientific merits, I hope to have completed - however summarily - the portrait
of a personage who was undoubtedly exceptional, and well-deserving, for the
Italian academic world and the Country. A personage who did not confine himself to
transmit to others his far-seeing ideas but who, rather, led from the front and
saw them through till the successful achievement of difficult objectives that
aroused the world's scientific interest. It was a long,
hard journey but L.Broglio could set out on it because he was also endowed with
great human qualities that I have not had the possibility to mention so far,
that is, the courage to take upon himself the onus of heavy responsibilities
vis-à-vis the Government and the Country's public opinion, the tenacity
and faith in his work. And I think I would do him wrong if, next to
him, I were not to mention the large group of San Marco Project collaborators,
each of whom deserves our deep gratitude. It is impossible to
remember all of them. I will therefore confine myself to mentioning my departed
colleagues: Professor Giorgio Ravelli and Professor Carlo Arduini, with whom I
shared the responsibility of satellites design and development, and Professor
Michele Sirinian who led the organization and execution of the orbital
launches. |
© 1995-2008 Kazan State University