First Community-wide Sun-Earth Connection Roadmap Workshop
George Siscoe
Boston University Center for Space Physics
725 Commonwealth Av, Boston, MA 02215
April 1996
The first SEC roadmap workshop was held April 10-12 at the Applied Physics
Laboratory. Approximately one hundred members of the space physics community
attended. The first day of the workshop was devoted to the presentation of
concepts for future missions, which ranged from a Mercury orbiter or flyby
mission to a small satellite mission for the study of red sprites. On the
second day, the participants divided into four subgroups. Each subgroup was
assigned one of four broad science themes and tasked with articulating a
coherent set of science objectives within its assigned theme. Particular
emphasis was to be placed on multidisciplinary objectives that could lead to
collaborative undertakings with the astrophysics and planetary science
communities. If possible, science objectives were to be formulated in
language that would convey to the public and Congress the importance and
excitement of the enterprise of space physics and underscore its relevance
to humankind's efforts to address fundamental questions about the origins of
the solar system, the universe, and life itself. Subgroups were also charged
with identifying the technologies needed to achieve the science objectives.
The four science themes, which had been worked out by the core group at its
planning meeting on February 29-March 1, were:
- How does the Sun work as a variable, magnetic star? (solar physics)
- How does the Sun interact with other planets and the interstellar
medium? (heliospheric physics)
- How does solar variability affect the geospace environment?
(magnetospheric physics)
- How does solar variability affect our home in space? (ionospheric-
thermospheric-mesospheric physics)
Following the subgroup meetings, the workshop participants re-assembled in
plenary session to receive reports from the subgroup chairs on the
recommendations developed by each subgroup.
On the final day of the workshop, the participants divided into two teams.
Team A was made up of representatives of the ITM and heliospheric physics
communities; Team B, of members of the magnetospheric and solar physics
communities. Each team was charged with synthesizing the results of the
subgroup discussions and developing a first outline of an SEC strategic plan
for the period 2000-2020. The recommendations of the two teams were
presented to the SEC roadmap core group at the conclusion of the workshop.
Together with strategic planning recommendations that will come out of the
SECAS meeting scheduled for May 1- 3, these recommendations will serve as
the basis for the first draft of the SEC roadmap. A preliminary attempt to
integrate the results of the subgroup discussions and the recommendations of
Teams A and B is presented in the following section.
The core group met briefly following the end of the workshop to develop a
list of possible future Solar Terrestrial Probes. The following were
identified as strong candidates for STP missions:
- Mercury Orbiter
- Grand Tour Cluster
- Solar Stereo Mission
- Magnetospheric Stereography Mission
- Global Electrodynamics Mission
- Mesospheric Coupler
- Microsatellite Constellation
The core group also included Solar B in its list of candidate missions for
the near term. Solar B is a mission of opportunity rather than an STP
mission.
Magnetospheric physics has reached a threshold from which a new leap
can be launched that will solve major, long-standing problems and open
up major new areas of research. The leap will be achieved with a new
tool for magnetospheric research that will give the ability to obtain
continuous sequences of magnetospheric images simultaneously in 3-D
with spatial coverage broad enough to encompass the main
magnetospheric process and with resolution great enough to see the
associated movements and transformations of the relevant
magnetospheric structures. The new tool comprises a constellation of
autonomous micro-satellites with advanced detectors that provide
pixels out of which magnetospheric images are rendered with tailored
software. A key strategic element in the implementation of this global
in-situ imaging concept is deployment over time of groups of microsats
in planned stages, each self-justified, each building on its
predecessors, and each moving the accumulating constellation directly
toward a global imaging capability.
- The Next Leap in Magnetospheric Physics
- Science Objectives: Examples
- "To explore, use, and enable..."
- Strategic Principles
- Implementation Issues
The magnetosphere is the fourth geosphere, the other three being the
lithosphere, the hydrosphere, and the atmosphere. Distinct ages mark the way
humankind has thought about this fourth geosphere. First came the Classical
Age, dating to Aristotle, which saw the fourth geosphere as a sphere of fire
whose occasional visible flames produce the northern lights. Then came the
Age of Reason, during which William Gilbert declared Earth to be a "great
magnet," and the fourth geosphere became a magnetic field reaching into
space. Three hundred years later, after the discovery of subatomic
particles, a modern-age fourth geosphere appeared. Chapman and Ferraro
envisioned sporadic ionized streams from the Sun that squeeze Gilbert's
magnetic geosphere into a bubble. In the present age, which might be called
the Age of Space Realization, the picture of the fourth geosphere unites
Aristotle's plasma-fire, Gilbert's magnetic field, and Chapman-Ferraro's
solar streams and adds internal structure: a continuous solar wind confines
the geomagnetic field to a cavity with a long tail supported internally from
collapse under magnetic tension by hot plasma that makes, as a by-product,
the polar lights.
Viewed as a project to determine what the fourth geosphere is as a physical
object, the progression of ages has essentially arrived at the answer with
the present age of space realization. It seems unlikely that another
conceptual leap will add a new category of substance, field, or structure
requiring the space age picture of the magnetosphere to be substantially
revised. Nonetheless, a future, fifth age is in the offing that will redraw
the way we depict the magnetosphere and create images against which the
present picture will seem as out of date as Chapman and Ferraro's empty
bubble seems now. This next age, which might be called the Age of Space
Utilization and Habitability, will replace the present static picture of the
magnetosphere with a dynamic, moving picture of the global magnetosphere
responding to real solar wind conditions and performing its own internal
modes of behavior. The present age populated the Chapman-Ferraro bubble with
plasma to reveal internal structures. The next age will animate these
structures to reveal global behavior.
The following examples illustrate the nature of the next leap in
magnetospheric physics. The leap will be from a picture showing the nominal
outline of the boundary and plasma sheet--a still life--to a video tape of
measurements showing the progression of macro-scale deformations of the
boundary and plasma sheet following a sudden change in solar wind conditions
as it propagates from nose to tail; we will actually see how the
magnetosphere manages to reconfigure its plasma sheet to follow the IMF as
it rotates through, say, 180 degrees. The leap will be from a sketch of the
magnetosphere's major current systems, which now have uncertain or unknown
connections, to a 3-D, rotatable computer graphic showing streamlines of the
curl of the simultaneously measured global magnetic field; the global
electrical wiring diagram in its multiplicity will simply reveal itself. The
leap will be from a line plot showing the magnetic field at point as that
point partakes in a global magnetospheric oscillation--a wiggle plot--to
images showing global magnetic field lines oscillating; magnetospheric
seismology will have come of age. And the leap will be from a dozen cartoons
showing a dozen ideas of what a substorm is to a spectator's view of actual
substorms igniting, exploding, and fading; think of Yohkoh-like images of
the magnetosphere erupting in a series of substorms. In summary, with the
next leap in magnetospheric physics, magnetospheric depictions will go from
static pictures of structures based on data averages and cartoons of
dynamical processes under- determined by the data to continuous image
sequences based on simultaneous global measurements that spatially resolve
3-D structures and temporally resolve dynamical processes.
To develop a particular but important example, consider substorms. No one
need tell members of the substorm community how thoroughly the envisioned
leap will revolutionize their discipline. Still, our sister field,
meteorology, has an analogy that helps illustrate its importance. The
extratropical cyclone is the dominant weather system of the midlatitudes,
and in that sense it is analogous to the substorm, the dominant weather
system of the magnetosphere. Its characteristic pattern of warm and cold
fronts radiating out from a migrating low pressure center which forms,
deepens, then dissipates as the fronts fold and collapse on each other
epitomizes the complex, basic fluid dynamics that operates on the large
scale in the Earth's geospheres. This is not to say that the substorm shares
the same dynamics as the extratropical cyclone. Rather, the point of the
analogy is that both are large scale, both are significantly structured,
both go through a life cycle of onset, growth, and decay, and both are
incomprehensible from the perspective of a point measurement or even from
the perspective of a number of point measurements up to a network of
sufficient size and density.
Before proceeding with the analogy, however, we should take advantage of the
meteorological setting to emphasize a point that has been well established
in the disciplines that treat the three lower geospheres. The point is this:
large scale dynamical processes in geophysical fluid dynamics--the branch of
physics that applies here--are every bit as fundamental as the microphysical
processes that ultimately convert ordered energy into disordered energy.
Moreover, they are the processes whose effects give a geosphere its
characteristic dynamical modes of behavior, for example, mantle convection
and plate tectonics for the lithosphere, surface and abyssal ocean currents
for the hydrosphere, tropical and extratropical cyclones for the atmosphere,
and geomagnetic storms and substorms for the magnetosphere, to name just a
few. Accordingly, determining the modes of large scale dynamics is an
important priority in a research program that has as its goal the
understanding of any geosphere. The leap we are discussing aims at
determining the modes of large scale dynamics for the magnetosphere.
In 1743 Benjamin Franklin showed that the storms we now call extratropical
cyclones do not form, grow, and die in place but instead move from place to
place. The local start-to-finish experience of a storm results not from its
building up and then dying away but from its passing through. More than a
century elapsed before a network of in-situ observing stations grew large
enough to simultaneously encompass a 3-D low-pressure center, spot its
onset, follow its growth, track its motion, and record its decay. The
pattern of the temperature field that accompanies the storm is the essential
piece of information that led to understanding the physical mechanism that
drives the storm, the mechanism meteorologists now call the baroclinic
instability.
By analogy, substorm research is at the Benjamin Franklin stage. We know
that the substorm evolves from a center having a more-or-less fixed location
in the magnetosphere, but we have yet to establish a magnetospheric
observing network large enough and dense enough to actually encompass a
substorm, resolve its onset within a 3-D measuring matrix, follow its
growth, and record its decay. There is no reason to think that the substorm
is less complex than the extratropical cyclone and, hence, no reason to
think that it will yield the secret of its mechanism more readily than did
the extratropical cyclone, for example, even before we can describe with
empirical, model-independent knowledge what the substorm is as a
spatio-temporal physical event.
There is a second and crucial aspect of the analogy--a lesson from
meteorology that applies with full force to magnetospheric physics. The only
known way to obtain simultaneous, spatially comprehensive information on
data fields of invisible parameters, such as pressure and temperature in
meteorology and magnetic fields and currents in magnetospheric physics, is
through simultaneous multi-point in-situ observations. One cannot remotely
sense pressure fields, and one cannot remotely sense magnetic fields and
currents. Yet these are the physical quantities that provide the force that
drives the dynamics in the two geospheres. The distributed force fields are
defined in these quantities. They are the quantities that must be imaged to
understand the dynamics. To obtain such images requires taking simultaneous,
multi-point in-situ observations with sufficient spatial coverage to
encompass the phenomena and high enough station density to resolve their
features.
The leap from static pictures of averaged structures and cartoon sequences
of processes to continuous sequences of global, 3-D, synoptic images of the
magnetosphere is widely recognized to be the logical next move in
magnetospheric science. For example, the 1995 publication of the Space
Studies Board of the National Research Council, A Science Strategy for Space
Physics, states under its section on magnetospheric physics that, after
completing ISTP, "Global imaging of the magnetosphere [is the] highest
priority for magnetospheric investigation. Its importance has long been
recognized and it should be the next observational thrust in the field." But
we need not belabor this point farther. It is obvious by analogy with the
experience of meteorology, and it is obvious in its own right.
Magnetospheric physics, the discipline, has reached the point where it knows
that the domain for which it has assumed responsibility has numerous
globally coherent dynamical modes, both driven and inherent, but it does not
know what many of them are, including some that are the most salient. The
need to find out what they are is critical to its central mission of finding
out how the magnetosphere works as a global geosphere. For this, continuous
sequences of global, 3-D, synoptic images of the magnetosphere are
essential.
In talking about executing a "leap" in magnetospheric science, we mean
bringing about a major increase in the power of the tools that
magnetospheric physicists use to advance their science, an increase in power
great enough to solve major, long-standing problems and great enough to open
up major new areas of research. For the leap to be successful, it must
transform the field, rid it of stagnating conflicts that hold back any field
whose central paradigms are grossly under-determined by the data, and lift
it to a level where it can describe with authority the physical nature of
the processes that characterize its domain and that make it a special branch
of science. If, therefore, this section were to list a delimited set of
science objectives, even a long one, it would reveal a failure to understand
the concept of a leap. A leap should take us to where we cannot know from
here the questions that will be asked. This is the criterion that defines
the leap's success.
For instance, questions about the magnetospheric site of the onset of
magnetospheric substorms, which now consume the field, would be
incomprehensible in the context of the Chapman-Ferraro featureless magnetic
bubble. For an example from another field, consider geophysics. At the time
of the advent of plate tectonics, who imagined that nearly all textbooks
then existing on geophysics would be antiquarian novelties within two
decades? The power of paleomagnetism to make global maps of magnetic
anomalies made possible the transformation of a field. The present day
questions in geophysics simply could not have been formulated before the
advent of plate tectonics. The power of continuous sequences of global, 3-D,
synoptic images of the magnetosphere has the potential to similarly
transform magnetospheric physics. Still, it is useful to name some
long-standing problems that the envisioned leap will likely make obsolete
and to imagine examples of new types of problems that might occupy the
post-leap magnetospheric community. Continuous sequences of global, 3-D,
synoptic images of the magnetosphere have the potential to answer most if
not all questions unanswered during the last three decades on mesoscale and
macroscale structures and dynamics of the magnetosphere in terms of
explicit, complete spatio-temporal physical descriptions. These include such
major long-standing questions (MLSQs) as the following.
The following are major unresolved questions in the field of space physics
that can be answered through continuous sequences of global, 3-D, synoptic
images of the magnetosphere:
What is the origin of the plasma sheet? The images will show how it recovers
after substorms: from the front, from the sides, or from behind.
What is the geometry of the plasma sheet for all IMFs? The classical
butterfly cross-sectional shape based on averages for all IMF directions is
grossly inconsistent with data binned on unidirectional IMF. This holds
especially for the usual Parker spiral orientation and for northward IMF.
Thus, we do not know what the plasma sheet looks like at any instant most of
the time.
Where do the field-aligned currents that are known from maps at the
ionospheric level go in the magnetosphere? These currents, named region 0,
region 1, region 2, NDC, cusp, and mantle, are mostly at high latitudes
where field lines mapping from the ionosphere to the magnetosphere is highly
uncertain. Some carry as much current as flows in the major structural
currents of the magnetosphere: the Chapman-Ferraro current, the storm-time
ring current, and the tail current. They obviously carry major amounts of
energy and information between the magnetosphere and the ionosphere, in both
directions. Though some models exist that connect some of the field-aligned
currents at the ionospheric level to magnetospheric sources and loads, none
is verified and most are controversial.
What is the spatio-temporal evolution of a substorm seen in its entirety? As
indicated in the previous section, the importance of answering this question
cannot be overstated.
What is the spatio-temporal evolution of a magnetic storm seen in its
entirety? The standard picture of a geomagnetic storm features a symmetrical
ring current. Yet during the growth of this ring current, the asymmetry in
the disturbance field exceeds or equals the symmetrical disturbance, up to
and including the maximum disturbance. Evidently the process of creating the
symmetrical ring current entails the action of an asymmetric current system
as powerful as the ultimate symmetrical ring current. There is virtually
everything to be learned in an empirical sense about the global, 3-D
asymmetrical development of the magnetic storm. Without empirically knowing
how a storm develops, we cannot understand the operation of the physical
mechanisms that cause it.
What is the relation between the magnetic storm and the substorm? Though
this is part of the previous question, it has a history and an interest of
its own. Here the emphasis is on the role of substorms in storm
phenomenology and on determining whether they are central to storm
development rather than on the cause of magnetic storms, substorms being one
possibility. Thus, the answer that substorms play a minor role in storm
development would be a celebrated finding here, but it would not answer the
previous question.
What are the modes of coherent magnetospheric behavior? All previous
questions are subsumed under this one. They epitomize global modes of
coherent behavior but do not exhaust them. Other known modes include
traveling convection vortices, continuous magnetospheric convection, global
resonances, and quasi-simultaneous activations of day-side and night-side
processes as seen in various auroral and ionospheric-electrodynamic data.
Consider next possible major new question types (MNQTs) that might be asked
in the post-leap era of magnetospheric physics, questions such as the
following.
The following questions exemplify the new types of questions that space
physicists might ask in the new "post-leap" era made possible by the
availability of continuous sequences of global, 3-D, synoptic images of the
magnetosphere.
What are the time-dependent, global magnetospheric responses to changes in
solar wind conditions of all kinds, including IMF changes? This question
type is rich in examples, but we will pick three and discuss them here and
in the next two MNQTs. Recall the example given earlier of a sudden change
in solar wind conditions washing over the magnetosphere. Take a case where
the IMF rotates from an away sector northward into a toward sector faster
than open field line reconnection can transfer much flux. According to one
model, generally endorsed and supported by available data, the point where
the plasma sheet meets the magnetopause will try to follow the IMF in its
excursion. But it cannot negotiate the transition across straight north
without flipping over, which is not an option. What happens then? Is there a
snapping back? A sudden flip of the attachment geometry by 180 degrees?
Probably not, but that our ignorance could suggest such an option shows how
open to discovery and new knowledge this question type is.
What are the global responses to IMF changes that trigger substorms? It is
known that a high percentage, perhaps over 50\%, of substorms are triggered
by sudden changes in solar wind conditions, often by northward turnings of
the IMF. What are the corresponding changes in magnetospheric conditions
that trigger the substorms?
What are the global magnetospheric responses to interplanetary shock waves
and vice versa? We know that strong shocks can create new radiation belts in
a matter of minutes. Obviously they also make sudden, dramatic changes in
other magnetospheric properties. In turn, they are strongly refracted within
the magnetosphere and reflected off the ionosphere. These processes of
magnetospheric transformation and reconfiguration and of shock refraction
and reflection can be documented with continuous sequences of global, 3-D,
synoptic images of the magnetosphere. Such data will open up a rich field
for magnetospheric model testing.
How well does a given quantitative model of substorm dynamics simulate
substorms, in general and in particular? In the postleap era, when the
substorm will be comprehended as an empirically described spatio-temporal
physical event, cartoon descriptions of the substorm will be obsolete. It
will be an era of quantitative physical models in which the data will be
capable of testing and guiding model development through detailed
spatio-temporal comparisons, both in generic studies and in case studies.
How well does a given quantitative model of magnetic storm dynamics simulate
storms, in general and in particular? All comments from the previous MNQT
also apply here.
How well does a given quantitative model of any of the other modes of
coherent magnetospheric behavior simulate that behavior, in general and in
particular? This question adds to the last two MNQTs all the known modes of
coherent magnetospheric behavior, including traveling convection vortices,
continuous magnetospheric convection, global resonances, and quasi-
simultaneous activations of day-side and night-side processes.
How well does a given quantitative model of the new super mode of coherent
magnetospheric behavior, discovered in the post-leap era, simulate its
behavior, in general and in particular?
Strategic principles (SPs) by which NASA can move under its Sun-Earth
Connections theme to reach a capability of obtaining continuous sequences of
global, 3-D, synoptic images of the magnetosphere include the following:
Build on existing and future program elements. The SunEarth Connections
theme and its partners in other agencies already have missions that can be
integrated into the service of developing a global magnetospheric imaging
capability. These missions include ISTP, FAST, ACE, TIMED, IMAGE, DMSP, GPS
and other DOD, DOE, and NOAA satellites.
Make clear and sharp distinctions between the goals of these missions and
the goals of the global magnetospheric imaging mission. The discussions in
the earlier sections, with their descriptions and illustrations of the "next
leap" concept and scientific objectives, do this.
Build over time in planned phases. This principle is aimed at reducing and
controlling the cost per unit time and at allowing the project to integrate
the experience gained from earlier phases into implementing later phases.
Evolve in steps from the existing constellation of satellites up to a
constellation with full imaging capability. Each step should have a
self-justifying scientific objective. Each step can use the full satellite
constellation that has evolved up to its time to set its mission goals.
Compose steps out of groups of "autonomous, micro-spacecraft with advanced
detector capabilities." Such satellites might be dubbed "pixies" since they
provide the pixels for the global magnetospheric images. As a top priority,
constantly evolve pixie configuration to increase imaging capability.
Design pixies for minimum instrument complement, duty cycle, and data rate
consistent with global imaging objective. Let no other objective compromise
this principle. Its enforcement is critical to keeping the cost per
satellite low enough to build a constellation numerous enough to achieve the
ultimate global imaging objective.
Build L1 solar wind station into constellation concept. Continuous solar
wind data are essential to the success of the project.
To the extent possible, build remote sensing imagers into the constellation
concept--for example, a high-altitude polar imager of auroras and an
IMAGE-type imager of magnetospheric plasma populations.
Develop software graphics routines, based, for example, on analytic, 3-D,
least-squares fitting algorithms, to turn pixilated images into continuous
3-D graphics with full rotating and slicing power. Provide the capability
for users to mix, match, and create images of many types using combinations
of parameters and features for multi-purpose applications, for example, to
generate animated images of boundaries, plasma populations, electrical
current stream lines, magnetic field lines, pressure contours, and so on.
Operate imaging constellation as a facility. There should be no instrument
PI with associated MO\&DA. The facility should belong to the community which
can apply for funds to use its data resources for research and applications.
Aggressively develop outreach programs. For example, the project could
exploit the existence of many pixies to extend some meaningful form of
nominal ownership of individual pixies to educational institutions and other
high-profile outreach targets.
Besides its strategic importance in propelling the advance of magnetospheric
science into a new era, achieving the capability to obtain continuous
sequences of global, 3-D, synoptic images of the magnetosphere is responsive
to the goals listed in the current NASA Strategic Plan. The mission
statement in the NASA Strategic Plan contains three themes, the second of
which is the heading to this section. The goals under this theme that relate
to the "Space Science Enterprise," the code name for the Office of Space
Science, include demonstrating "a system for reliable space weather
forecasting" in the 1996-2002 time frame, and, in the 2003-2009 time frame,
achieving a capability to "monitor and predict space weather." While not
their direct, primary objective, it is nonetheless true that continuous
sequences of global, 3-D, synoptic images of the magnetosphere would,
probably more than any other achievable capability, provide the
understanding needed to carry out the first goal. If the images were
obtained in near real time, they could also facilitate achieving the second
goal. Another major aspect of the project described here is responsive to
the NASA Strategic Plan. The third theme under the mission statement is "To
research, develop, verify, and transfer advanced aeronautics, space and
related technologies." The goals under this theme that relate to the "Space
Science Enterprise" include developing autonomous, microspacecraft with
advanced detector capabilities. Precisely such development will be needed to
carry out the project of obtaining continuous sequences of global, 3-D,
synoptic images of the magnetosphere. We discuss this topic in the following
sections.
There are many implementation issues that must be resolved during a mission
concept study phase. Some of these are the following:
Designing the optimum mission. This is a most critical task. Under- design
will frustrate science objectives because of limited science capability, and
over-design will compromise mission objectives because of excessive cost. To
the end of finding the optimum mission, it is useful to adopt a
functionalist perspective. Think of the global magnetospheric imaging
mission as a new tool for magnetospheric research whose function is to
achieve the next leap in magnetospheric science. Then the question is, What
is the minimum power the tool needs to solve major, long-standing problems
in magnetospheric science and to open up major new areas of research? The
problem has two parts: defining the minimum pixie and defining the minimum
satellite constellation.
Defining the minimum "pixie"*. A zero-base approach. The following is an
example of how one might proceed to define the minimum pixie. Start with an
instrument complement consisting of nothing but a vector magnetometer and
build from there. Specifying the global magnetic field gives the global
electrical currents by taking the curl. In regions of subsonic
plasmas--which includes most of the magnetosphere most of the time--one then
gets the pressure from the static force balance equation. The information
thus acquired already goes a long way in the direction of obtaining
continuous sequences of global, 3-D, synoptic images of the magnetosphere.
Then ask, How much new information is added for what price with each
additional instrument? Select instruments on the basis of most information
added for least cost until a cost ceiling is reached or until an obvious
point of diminishing return is reached, which ever comes first. In this
exercise, it is essential to weigh the value of information added by how
well it provides a pixel for global images. After instrument definition,
determine the minimum duty cycle and data rate. There is no point in a duty
cycle faster than needed to resolve the propagation time of information in
the global system, for example.
*Pixie = a microsatellite that provides the "pixels" for global
magnetospheric images
Defining the minimum satellite constellation. The constellation must
ultimately be able to resolve the spatial structures of interest and their
movements and transformations. The zero-base approach applies here as well.
In this case, it works by building up to the minimum constellation in
stages, each stage justified in part by information obtain in the previous
stages. Still, there are optimal ways of designing stages which must be
considered.
Position and attitude requirements. Not only is there a minimum
constellation size, there is an optimal constellation distribution which
gets the most useful global images out of the minimum constellation. In this
case, optimization must consider the delivery costs associated with
achieving the distribution. Moreover, the satellite density must be great
enough and the attitude determination accurate enough to give reliable
determinations of derived quantities, such as the vector electric current
density. Design specification need to be calculated.
Telemetering requirements. The problem of retrieving information from a
large constellation of micro-satellites must be addressed in the concept
definition phase. There are opportunities for groundbreaking innovations in
this area. Low data rates will help reduce the receiver requirements. The
degree of success here will set the horizon for exploiting multi-point
micro-satellite projects in general.
Data handling. How centralized and how distributed should be the data
acquisition, processing, distribution, and storage tasks? There is an
obvious role for strong centralization of primary functions. But there might
be advantages in performing some tasks in a distributed mode. There is also
an opportunity here to extend nominal ownership to outreach targets. These
issues need to be systematically explored.
Imaging software. This project opens up a new arena for graphics software
development. The software must solve the problem of creating continuous
images out of multiple point measurements as the points move. It must also
create images of all parameters, directly measured and derived, for example,
images of magnetic field lines and electric current stream lines. It must
also create images of many user specified types, for example, images out of
contours of scalar quantities, images out of stream lines of vector
quantities, combinations of images, 3-D images from arbitrary viewing
positions, and 2-D images in arbitrary planes.
TOC Comments?
siscoe@buasta.bu.edu