Possible scientific applications in the field of the neutral ionized atmosphere and of the solid Earth in terms of the TSS are summarized. Studies of the vertical, zonal, and meridional neutral winds and temperature, whose extensive variations suggest the importance of energy transfer mechanism in modifying the structural properties of the region are reviewed. Layers below the F region of high plasma density that propagate to lower altitudes with drift velocities will be studied for their electron and ion composition and motion. These are to be measured by the TSS in conjunction with ground based radar observations. Basic fluid dynamics problems will be studied onboard tethered satellites. Studies will be conducted on the structure of the equatorial electrojet, in particular its longitudinal and meridional extent. Magnetic measurements will also be used to probe the tether current distribution in the plasma sheath

Mariani, F.

English

NASA Technical Reports Server

N86-28412
SCIENCE APPLICATIONS.
Franco Marian!
Dipartimento Fislca II Universlta
117
https://ntrs.nasa.gov/search.jsp?R=19860018940 2020-03-20T14:14:40+00:00Z
1 GENERAL.
The possibility of doing science by tethers and/or tethered
vehicles is now in the process of becoming a reality in the next
few y ears .
Following early qualitative suggestions and studies, a serious
start of quantitative studies is due to G.Colombo and M.Grossi,
who in the early 1970's suggested .to tether satellites to the
Shuttle by means of long strings up to a length of 100 km.
A cooperative program was estabilished in the following years
between USA and Italy, until in 1983 a M.O.U. was signed by the
two countries; this was followed in 1984 by an A.O. stating that
NASA and PSN/CNR "joj.njt_li ___ a.Q.D.P.un^ e ___ an __ oggor tijnity_ __ for
_p..a.rjt_§._c_i.p._§.t_i.on __ _in __ th^ __ firs t __ thr.6..6. __ f .lights^ __ of __ the ___ Tethered
Sjrtj:_l_l_ijtj __ System __ l!SSl_on_the_Sp.ace_Shuttle^ __ These_f light s_a re
®2S£JCt_ed_to__qccur_between_1.987_and_i990J. __ The_TSS_is_cgmp_r^sed_of
two_major_jl.ements^_the_De2ioy_eri_to_be_sup_p_lied_by__NASAJ __ and_the
SajteJ.j._iteJL_to_be_provided_by__PSN/.CNRi __ I_n __ additign., ___ i.t __ i.s __ the
_injt_enjt_ion __ of __ NASA __ and __ PSN/CNR __ to __ sup.Eiy_ __ two __ li.erns_gf _cgre
^3uJ:£niJJ}^_f or_jthese_f l^igh ts^j^_a_thr ee_-axi§_ __ agceiergmete.!! j ___ E.L§.c.e_d
on-bo^rd_the_Sajte_ll. i. t6j __ and_an_e_iec trgn_gun_, __ tg_be_rngunted_gn_tlie.
^ __ Scj.ence_instrumentatign_can_be __ accgmmgdated. __ on __ b_Q_£.b.
Theoretical and experimental proposals for the definition and
development of investigations for the first three flights and for
analysis and interpretation of data were solicited. The answer
by the scientific community was very encpuranging : about 80
proposals were presented, approximately 1/5 from Europe and Italy
in particular, 4/5 from USA and non-european countries.
It is my intention in this presentation, to summarize possible
scientific applications in the field of the neutral or ionized
atmosphere and of the solid Earth. As concerns the field of
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electrodynamic interactions, it will be the subject of another
presentation so, here, I shall only list as an appendix a summary
of the satellite and deployer scientific instrumentation selected
for the first mission (the electrodynamic mission).
It is very important to remark that the TSS environment is a
sort of huge laboratory where many different physical parameters
influence each.other in a very complicate way, under the external
influences of the solar EUV radiation and the magnetospheric
particles and the internal influence of the terrestrial gravity
and magnetic field. It is worth to point out that while the
interpretation of data from some types of experiments does not
require a very precise determination of the geographic
coordinates of the TSS-satellite, in other cases there are very
stringent precision requirements, to the point that these may be
the absolutely essential feature before significant physical
interpretation can' be attempted; this is the case of all
parameters defined in a reference system anchored to the solid
earth (gravity and geomagnetic field).
In this respect the study of TSS dynamics is interesting and
useful "per se" because of the novelty of the system and the
related need of better understanding. But from the view point of
other experiments, the TSS dynamics is also inherently related to
the possibility of measuring fine quantities. For example doubts
have been expressed about the feasibility of gravity gradient
measurements because "the dynamic noise expected in a ' tethered
satellite is far higher than in a free flyer and may negate the
advantages of flying at this unusually low orbital height". This
same comment also applies to geomagnetic field measurements.
119
2 NEUTRAL ATMOSPHERIC MOTIONS AND COMPOSITION.
To study vertical, zonal and meridional neutral winds and
temperature, whose extensive variations suggest importance of
energy transfer mechanism in modifying the structural properties
of the region. Thermospheric circulation models suggest
existence of horizontal scale vortices generated by auroral
processes at high latitudes, between 120 and 200 km altitude.
In this region, minor neutral constituents generated by
auroral and solar particles are conveyed to other atmospheric
regions by the winds. Also, the distribution mechanism of the
EUV energy is an important goal. The EUV • energy flux is
relatively small (;yieV/cm /sec), but the gas density also is
small, so large effects are produced by this energy source.
Another energy flux reaches the upper atmosphere from the solar
wind and the ionization through the magnetosphere, in the form of
precipitating particles. This effect is dominant at high
latitudes, but global effects can also be observed during
geomagnetic disturbances. Electric currents and ion drifts
transfer energy and momentum to neutrals, producing winds at
velocity of I km/sec.
Energy of tidal motions can also propagate from lower
atmosphere to the thermosphere where it is finally.dissipated.
In this region also important ionospheric effects are generated
by the wind system (S dynamo currents, electrojects, etc.).
All above processes strongly affect the composition and the
thermal and dynamic regime of the neutral atmosphere, in-the
range from 100 to 200 km altitudes where only a few in-situ
observational data do exist. -
A major factor which may limit the accuracy or even the
feasibility of in-situ measurements by hypersonic vehicles at.TSS
low altitudes is represented by the collisions suffered by free
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stream neutrals and ions as they pass through the ram cloud ahead
of the satellite.
Also important is the ionization produced by neutrals
impacting the exposed surface of the s/c and the instrument
sensors.
3 IONOSPHERIC ELECTRON AND ION COMPOSITION. IRREGULARITIES AND
DISTURBANCES.
Below the F region, "intermediate layers" of high plasma
density are often observed. These layers propagate to lower
altitudes with drift velocities of the order of 20 m/sec.
Composition and motion of this layers are important parameters to
be measured by the TSS, in order to understand their
phenomenology, also in conjunction with ground-based radar
observations. A variety of plasma structures at different
spatial and temporal scales in the lower F region will be
studied.
Local measurements of electron densities and temperatures, as
well as of d.c. electric fields and ionospheric current will
contribute basic informations on the overall energy balance.
Large and medium scale travelling ionospheric disturbances
will -also be studied. These disturbances have typical
wavelengths of some thousands .km and can propagate from high to
equatorial latitudes. Also, acoustic-gravity waves generated in
the E region, which might be the source of the spread-F, will be
possibly, 'observed .
A number of metallic ions (Na , Mg , Si , Fe , etc) are mixed
to the most commom ions. Some of them are long-lived and can be
transported by both neutral winds and electric field. Ion
121
composition measurements will help to sort out the most important
ion sources and to determine the role played by meteoritic ions.
4 FLUIDODYNAMICS.
Basic fluidodynamics problems can be studied onboard tethered
satellites. In particular, aerodynamic and heat transfer
coefficients within a variety of conditions which cannot be
obtained by the current wind tunnel technology, due to the
impossibility of making thermo-fluid-dynamic measurements at
combined low Reynold number and large Mach number regime. An
additional advantage of using the TSS as "open wind tunnel" is
the long time range of operation, as compared with any existing
or proposed ground facility.
5 MAGNETIC FIELDS.
The magnetic field at TSS altitudes is the sum of fields from
different sources: the global geomagnetic field of internal
origin, the field due to anomalies of limited extent associated
with permanently magnetized subsurface structures, ionospheric
currents driven by large scale atmospheric motions or originating
in the magnetosphere and, finally, the induced electric current
flowing along the tether (in the case it is conducting).
Separation of the different contributions may become a
formidable task unless the dynamics of the tethered satellite
(location and attitude) is perfectly known and any possible
spurious field from the s/c is below the magnetic sensors
122
sensitivity.
Studies will be conducted on the structure of the equatorial
electrojet, in particular its longitudinal and meridional extent.
Also, the closure of the current loop as a whole will be studied.
Toroidal magnetic field structures, not observable from ground,
have been suggested, which can only be detected by in-situ
measurements.
The S diurnal field variation will also be observed and the
q .
induced effects on the Earth will be possibly determined in a
more direct way by comparison with ground observations.
Crustal field anomalies will be detectable, hopefully,
expecially for the lower altitudes flights.
Magnetic measurements will also be used to probe the tether
current distribution in the plasma sheath around the s/c, as a
necessary complement to the local plasma parameters
determinations.
6 GRAVITY ENVIRONMENT.
Exact knowledge of the Earth's gravitational field is
important in many technical and scientific areas (Earth
resources, oceanphysics, motions of tectonic plates, inertial
navigation, etc.). The low altitude TSS missions will be useful
to this end, if the dynamics of the tethered satellite will be
sufficiently well known to determine gravity gradients with the
required, high, accuracy. Studies presently in progress seem to
indicate good chances of flying gravimetric gradient instruments
in the following missions.
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7 REMOTE SENSING.
The TSS facility for remote sensing purposes may prove useful
to increase significantly the accuracy of future real time
cartographic systems from space. In • this framework, two
operational missions have been suggested: one using two linear
array systems for along-track stereoscopic observation; the other
using a synthetic aperture radar combined with an interferometric
tecnique. Feasibility studies are presently in progress.
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ORIGINAL PAGE IS
POOR QUALITY
APPENDIX
SCIENCE FOR THE FIRST TSS E L EC T H CH) Y N A Ml C MISSION
SCPntTC OBJECTVES
STUDY OF ELECTRODYNAMIC INTERACTION BETWEEN THE TSS AMI AMBIENT PLASMA
STUbY OF DYNAMICAL FORCES ACTING ON THE TETHERED SATELLITE
SAT*7* I HE XSTRUMENTATTON (and P i ' s )
RESEARCH ON ELECTROOYNAMIC TETHER EFFECTS (RETE) - M. OOUROWOLNY
CNR/TSI - FRASCAH - ROME
WAVE SENSORS ON TWO EXTENDABLE BOOMS (4 m EACH) TO EXPLORE SPACE
CHARGE REGION AROUND SATELLITE.
TETHER MAGNETIC FIELD MEASUREMENT (TEMAG) - F. MARIANI - 2ND
UNIVERSITY OF ROME - TOR VEROATA - ROME
TWO MAGNETOMETERS ON FIXED UOOM (05 cm) TO MEASURE MAGNETIC FIELD AND
DYNAMICS OF TETHERED SATELLITE.
RESEARCH ON ORBITAL PLASMA - ELECTRODYNAMICS (ROPE) N. STONE - NASA/MSFC
HUNTSVILLE - ALABAMA
PARTICLE SENSORS ON FIXED BOOM (115 cin) AND ON SATELLITE TO STUDY SATELLITE
PLASMA INTERACTION.
DEPt-OYER tCrmiMENTATinN
SHUTTLE ELECTROOYNAMIC TETHER SYSTEM (SETS) - P. BANKS - STANFORD
UNIVERSITY - STANFORD - CALFORNIA
VARIOUS NSTRIIMENTS TO STUDY TETHER CURRENT - VOLTAGE CHARACTERISTICS,
CHARGE CONTIU*. ANO EMISSION AT ORBITER. OTHER PLASMA AND IONOSPHERIC
PROCESSES.
THEORY AND OROUhP-BASED UISTRVAT1ON5
nCORY AND MODELING IN SUPPORT OF TETH'R - K. PAPADOPOII.OS - SCCNCE
APPLICATIONS, INC. - McLEAN - VHiniNIA
INVESTIGATION ON TSS DYNAMICS S. HERGAMASCHI - IJNIVERSITY OF PADOVA
PADOVA
fWESTIGATlON AND MEASl IHEMI^ IT Ol' DYNAMIC NOISE IN TSS - G. GIJLLAHORN - SAO
CAMBRnGE - MASSACIH F.!»:TS
DETECTION OF ELECTRO WNAMIC 11 C/EI.F EMISSIONS BY THE TETICR • O. T ACCOM
UNIVERSITY OF GENOVA - GENT1VA
MVESTIGAT1ON OF EI.ECTROOYNAMIC EMISSIONS BY TI-C TETHER R. ESTES - SAO
CAMBRIDGE MASSACHUSSETS.
ITALY IS RESPONSIBLE FOl THE INTEGRATION OT Tl F. SCIENTIFIC INSTRUMENTATION ON THE SATELLITE
125
ORIGINAL
OF POOR ;QUAIirr
TSS CORE E HI) 11'ME NT
TETHER C U R R E N T - V O L T A P E C O N T M O L (ICVC) S Y S T E M
P U R P O S E
FOR THE ELECTRODYNAM1C MISSIONS THE TCVC SYSTEM WILL SPECIFICALLY ALLOW INVESTIGATION
OF THE TSS-S ELECTRICAL POTENTIAL BY CONIKOLI.ING THE CURRENT THAT FLOWS BETWEEN THE
SATELLITE AND THE ORBITER THROUGH THE TETI-CR AS A RESULT OF THE EMF GENERATED (UP TO
5 KV) BY MOTION OF THE TSS ThflOUHH THE GEOMAGNETIC FIELO
THIS FUNCTION IS FUNDAMENTAL TO ThC OPERATION OF THE ELECTRODYNAMIC TETHER AND IS
ESSENTIAL FOR THE TSS SCIENTIFIC INVESTIGATIONS.
T H R E E - A X I S AC CE LE R OME T E R-G YR O S Y S T E M
P U R P O S E
THE THREE-AXIS ACCELEROMETER-GYRO SYSTEM WILL PROVIDE A HIGHLY ACCIIHAIE ASSESSMENT OF
DYNAMIC PERTURBATION TO THE MOTION OF THE TETHERED SATELLITE.
THIS INFORMATION IS REQUIRED TO DETERMINE THE SUITAIJILITY OF T>C TETHERED SATELLITE
AS A PLATFORM FOR A VARIETY OF INVESTIGATIONS OF CRUSTAL - INDUCED MAGNETIC AND
GRAVITATIONAL EFFECTS.
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