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4. Fall 97 AGU Special Session SM02 on Magnetospheric Constellation
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From: Vassilis Angelopoulos and Rod Heelis

Dear Colleagues,

An upcoming special session at AGU titled: "Science closure and enabling
technologies for magnetospheric constellation missions" is aimed at 
incorporating the science community's feedback on the design of the
"constellation" mission. The current implementations of the mission evolved
from the recent Science Definition Team meeting on geospace multiprobes. The
engineering studies from GSFC which characterized the mission "feasible within
the Solar Terrestrial Probe line" give the science community the "green light"
to engage in discussions on various aspects of the mission. 

The objective of Constellation is to synthesize an instantaneous "image"
of a part of the magnetospheric system, to resolve spatiotemporal ambiguities,
address cause and effect relationships, and study cross-scale coupling.
The aim is to resolve the major long-standing questions in the field of
magnetospheric physics, such as: what magnetospheric system drives the
quiet and the active aurorae, what causes/triggers magnetospheric substorms
and storms, and how does the solar energy flow manifest itself through the
various parts of the magnetospheric system. These aims can be addressed
in several complementary ways all limited in total weight by the requirement
of a single Delta 7920 launch vehicle: By a large number (>100) of "free
flying" probes equipped with a magnetometer, by a smaller number (50-60) of
~8kg autonomous probes that additionally have an ion and electron analyzer,
or by a smaller number (10-20) of spacecraft with either more comprehensive
instrumentation or with propulsion. In the latter category, a new type
of measurement is being considered, that entails sending a radio signal
from each spacecraft to all others, and measuring the total electron
density between spacecraft. This allows a reconstruction of the density
(and total B) on the common orbital plane in a tomographic fashion, with
a resolution of 1 Re. In addition, alternative strategies of telemetering
the data are being studied, that entail a laser beam sent from the ground
to the spacecraft and back. The beam is modulated at acoustical frequencies to
produce a carrier signal for data transmission.

The scientific community must respond to the challenge.  Given that 
the realization of a mission of that magnitude takes 5-7 years from 
the definition phase, we are at the right time to be thinking hard 
about these issues. The science community must clearly define the 
issues that will require resolution in the post-ISTP era and the 
measurement techniques that will allow closure from such a mission. 
At the same time improvements in instrumentation that can reduce the 
cost or enhance the science return from the mission (e.g., composition,
waves and energetic particles albeit on a subset of the probes) can be 
brought forth and discussed in the context of the mission.

The session description is included below. Science and engineering
talks that pertain to all mission implementations are strongly encouraged.
Invited talks discuss the various mission implementations, but also
address the questions: how many spacecraft are needed, how can one
reconstruct the magnetospheric current systems from the mission, how
science closure can be reached, what new and upcoming technologies can
enhance the mission or reduce its cost. 

Please note the deadline for abstract submission: August 27 for postal/
express mail and e-mail abstracts; September 3 for Interactive Web Form 
Abstracts

      Sincerely,

      Rod Heelis,
      Vassilis Angelopoulos 

SM02 Science closure and enabling technologies for magnetospheric
constellation missions.

The magnetospheric constellation mission entails a large number of
identical probes, performing in situ and coordinated remote sensing
measurements. Science and engineering studies summarized in the "Heelis
report" on Geospace Multiprobes conclude that in today's technological and
fiscal reality it is possible to discuss several implementations of this
mission concept. Contributions from theory, simulation, data assimilation,
and modeling on measurement strategies and science closure of the major
outstanding questions in the field are encouraged. Which pertinent emerging
technologies can further enhance science return and/or reduce mission cost?
Papers on instrument and satellite component miniaturization, novel
propulsion, tracking and data acquisition techniques are requested.

Conveners: Vassilis Angelopoulos, Space Sciences Laboratory, University
of California, Berkeley, CA, 94720, tel: 510-643-1871, fax: 510-643-8302,
e-mail: vassilis@ssl.berkeley.edu; Rod Heelis, University of Texas at Dallas,
Center for Space Sciences, PO Box 688083, Richardson, TX 75083,
tel: 972-883-2822, fax: 972-882-2761, e-mail: heelis@utdallas.edu