CURRENT ABSTRACT FILE ON CD-ROM --------------------------------------------------------------------------- General Information: This Compact Disc was produced by the Information Processing Division's (IPD) Data Distribution Facility (DDF) at NASA Goddard Space Flight (GSFC) in Greenbelt, Maryland. This Disc conforms to the ISO 9660 format and as such are constrained to the 8.3 file naming convention. The Disc is platform independent, and will not contain any specific platform information (e.g. RMS data specifics). The data was collected for the International Solar Terrestrial Physics (ISTP) Program. See the ISTP Data Format Control Document for details. The directory hierarchy on this CD-ROM is composed of three major sub- directories with minor subdirectories as required. The major subdirectories and root files are given below: VOLDESC.SFD Volume description in ASCII and shall serve as the starting point for CCSDS SFDU access to the data on the disc. 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The file names will appear in upper case under those operating systems which are case-sensitive. --------------------------------------------------------------------------- THE GLOBAL GEOSPACE SCIENCE PROGRAM AND ITS INVESTIGATIONS ---------------------------------------------------------- M. H. Acuna, K. W. Ogilvie, D. N. Baker*, S. A. Curtis, D. H. Fairfield, W. H. Mish NASA/ Goddard Space Flight Center, Laboratory for Extraterrestrial Physics, Greenbelt, MD 20771 * Now at the Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder CO Introduction The Global Geospace Science Program (GGS) is designed to improve greatly the understanding of the flow of energy, mass and momentum in the solar-terrestrial environment with particular emphasis on "geospace". GGS has as its primary scientific objectives: a) Measure the mass, momentum and energy flow and their time variability throughout the solar wind-magnetosphere- ionosphere system that comprises the geospace environment; b) Improve the understanding of plasma processes that control the collective behavior of various components of geospace and trace their cause and effect relationships through the system; c) Assess the importance to the terrestrial environment of variations in energy input to the atmosphere caused by geospace plasma processes. Early space probes like the Explorer and IMP series of satellites and more recently ISEE (International Sun Earth Explorers), Dynamics Explorer and AMPTE (Active Magnetospheric Particle Tracer Explorer) carried out localized studies of these regions but without the global emphasis of GGS. Geospace is defined as the near-Earth space environment and it encompasses the regions toward the Sun where the heliosphere is disturbed by the Earth's magnetic field, as illustrated in Figure 1. Single spacecraft missions have suffered in the past from the disadvantage that it is extremely difficult to separate time dependent phenomena (i.e., transient disturbances), from the spatial structures encountered along the spacecraft trajectory (e.g., magnetospheric boundaries). The spatial boundaries define several characteristic regions in geospace which play different roles in the transport, storage and evolution of mass, momentum and energy in the system. Moreover, the integrated magnetospheric system responds with poorly known cause-effect relationships to perturbations induced by solar activity [see for example, Akasofu and Chapman, 1972; Yamide and Slavin, 1986; Hargreaves, 1992]. Mass, momentum and energy are carried by the charged particles that comprise the solar wind and some of these particles can enter the Earth's magnetosphere. This coupling between the Sun and the Earth has been known for many years as it is best evidenced by the spectacular auroral phenomena which are visible at high latitudes in the southern and northern hemispheres [see Frank and Craven, 1988; Meng, Rycroft and Frank, 1989]. This complex energy chain, from the Sun's interior through the corona, the interplanetary medium and the magnetosphere, and its ultimate deposition in the Earth's atmosphere is illustrated in Figure 2. Several spacecraft names are associated with the blocks in the figure to indicate the missions that principally address the particular region of solar-terrestrial space. The overall study of this energy chain is a daunting task which cannot be undertaken by a single nation alone. The recognition of this fact led to the concept and development of the International Solar Terrestrial Physics Program (ISTP), an international effort designed to coordinate solar-terrestrial research in a synergistic manner, taking advantages of the unique resources and already planned space missions by the United States, Europe, and Japan. The Global Geospace Science Program is the US contribution to the ISTP Science Initiative. It was designed to address the goal of detailed understanding of the global features of the geospace system by integrating a number of key elements in its planning. First, the acquisition of coordinated and concurrent data from spacecraft placed in key orbits that allow the synergistically selected onboard instruments to sample simultaneously the principal regions of geospace where energy and momentum are transported and stored. These key regions are the upstream interplanetary medium (WIND), the geomagnetic tail (GEOTAIL, provided by Japan), the polar regions (POLAR) and the equatorial magnetosphere (equatorial science, originally covered by the EQUATOR spacecraft). Second, the incorporation for the first time of theory and global models as an integral part of the program, to allow the prompt and ready interpretation of the spacecraft measurements. The third and final component of the GGS Program is the development of a Central Data Handling Facility (CDHF) for the purpose of processing, storing and distributing the GGS data sets to the investigators in a rapid and cost effective manner. This concept makes use of advanced data processing, management and visualization tools which address the problems experienced with previous mission data sets in this area. The fundamental objective of obtaining a detailed understanding of the global geospace system is therefore facilitated as never before. The US GGS Program is thus made up of the WIND and POLAR spacecraft and instruments, theory and ground based investigations and data sets obtained from equatorial spacecraft operated by the National Oceanics and Atmospheric Administration (NOAA) and the Los Alamos National Laboratory (LNAL). The NASA GGS Program, the Solar Terrestrial Science Program (STSP) of the European Space Agency (CLUSTER and SOHO spacecraft) and the Japanese Institute of Space and Astronautical Science (ISAS), (GEOTAIL spacecraft), are all part of the ISTP effort. Additional contributions are planned from the former InterCosmos organization (IKI) of Russia, and other international efforts coordinated through the Inter-Agency Coordination Group (IACG). The IACG was formed by NASA, ESA, ISAS and IKI to coordinate the space missions to comet Halley in 1986. After successfully accomplishing this task, the IACG selected the coordination of solar-terrestrial research as its next objective (see article by E. Whipple, this issue). The Max Planck Institute for Extraterrestrial Physics in Germany is also planning to build and launch a small spacecraft (EQUATOR-S) designed to support in-situ equatorial measurements and recover some of the objectives originally assigned to the EQUATOR spacecraft. Finally, and although not a formal part of ISTP, significant data sets and scientific contributions are also expected from the Solar Terrestrial Energy Program (STEP), a program of the Scientific Committee on Solar Terrestrial Physics endorsed by the International Council of Scientific Unions (ICSU). This issue describes the WIND and POLAR spacecraft, the scientific experiments carried onboard, the Theoretical and Ground Based investigations which constitute the US Global Geospace Science Program and the ISTP Data Systems which support the data acquisition and analysis effort. The scientific instruments carried aboard the GEOTAIL spacecraft, an integral part of the ISTP/GGS program supported by Japan and which was launched on 24 July 1992, are described in the "Geotail Prelaunch Report" [1992], while complete descriptions of the experiments and investigator teams for the CLUSTER and SOHO spacecraft are given in "CLUSTER: Mission Payload and Supporting Activities" [1993] and "The SOHO Mission: Scientific and Technical Aspects of the Instruments" [1988]. Tables I-V summarize the investigations, Principal Investigators and Institutions associated with the GGS Science Teams. The WIND and POLAR spacecraft and their orbits WIND and POLAR are cylindrical, spinning spacecraft of traditional design which will be launched by DELTA II vehicles from the Cape Canaveral Air Force Station, Florida, and the Western Space and Missile Center in Vandenberg, California, respectively. WIND spins at 20 RPM to allow the instruments to sample the ambient charged particle distribution function with good time resolution while POLAR spins at 10 RPM to accommodate the requirements of a despun platform where visual, ultraviolet and X-ray wavelength imagers and specialized charged particle instruments are mounted [see papers by Frank et.al.; Torr et. al.; Imhof et. al., this issue]. Both spacecraft have been implemented with stringent electrostatic, magnetic and electromagnetic constraints to minimize potential interference with the sensitive measurements carried out by the scientific instruments. The spacecraft record the science and engineering data on magnetic tape recorders which are then played back to the ground during tracking passes. There is no requirement for either spacecraft to provide real time science data; however, they can be operated in this mode for limited periods of time when ground tracking facilities are available. This capability is important if the WIND spacecraft is to be used as an early detection and warning system for disturbances induced by solar activity, a desired objective of the Forecast Center of NOAA's Space Environmental Laboratory. Detailed engineering design features of the WIND and POLAR spacecraft and their subsystems are given in the article by Harten and Clark, this issue. The initial orbit selected for WIND is based on a general class of orbits commonly called "double lunar swing-by" [Farquhar, 1991] due to the fact that the gravitational attraction of the Moon is used through periodic encounters with the spacecraft to maintain the semimajor axis of the orbit roughly aligned with the Earth-Sun direction during the entire mission. The WIND orbit is illustrated in Figure 3 and was selected by the Science Team for the purpose of providing a radial mapping of the interplanetary medium and the Earth's foreshock region by the onboard instruments at the beginning of the WIND mission. After a preselected time has elapsed (6-12 months), the WIND spacecraft will be placed in a "halo" orbit around the Lagrangian point (L1) between the Earth and the Sun [Farquhar, 1970] utilizing the onboard propulsion system which has a total delta-V capability in excess of 500 meters/sec. The halo orbit was used in the recent past to maintain the ISEE-3 spacecraft at the Lagrangian point to act as an upstream monitor of solar wind conditions, [Ogilvie et. al., 1978] and is intended as well for ESA's SOHO spacecraft since it allows continuous remote sensing of the Sun's corona and photosphere without periodic perturbations induced by the rotation of the Earth as in ground based observatories. The double lunar swingby technique has also been used by the GEOTAIL spacecraft to maintain its orbit apogee continuously in the geomagnetic tail, as shown in Figure 4 . For scientific reasons which are related to the ability to predict conditions at the Earth's orbit based on observations carried out at the L1 point, it is desired that the semiaxes of the final halo orbit achieved be as small as possible. However, the minimum distance is bounded by a limit dictated by communications requirements such that ground-based antennas tracking the spacecraft do not have to point close to the Sun which is a very powerful noise radio source and would interfere with command and data acquisition functions. An additional constraint that must be satisfied by the double lunar swingby orbit is that eclipse-induced shadows must not last for more than 90 minutes at any time during the prime mission in order to maintain thermal and power design constraints on the GGS instruments and spacecraft. To maximize the performance of the onboard scientific instruments and the communication system, the WIND spin axis will be maintained perpendicular to the ecliptic plane to within ñ 1 degree. Particular attention was placed on building a magnetic, electrostatic and electromagnetically clean spacecraft. The accurate measurement of very low energy plasmas and weak electric and magnetic fields imposes significant system level requirements on the spacecraft due to the sensitivity of the science instruments. All exterior surfaces including thermal blankets, solar cells and control paints are conductive to ensure the equipotential behavior of the spacecraft as well as an excellent Faraday shield for electric field radiation shielding. Long booms place the magnetometers and search coil sensors away from the main spacecraft body to reduce interference to a minimum. The POLAR spacecraft is similar in design to WIND except for the addition of a despun platform and a real time data rate capability that is an order of magnitude greater (56 KB/sec.), as required to support the imaging investigations. POLAR will be placed in a 90 degree inclination, elliptical orbit with a 9 Re apogee and a 1.8 Re perigee, as shown in Figure 5. Initially and during the prime mission, the orbit apogee will be located over the north polar regions but with a small (10 degrees or less) southward tilt towards the Earth-Sun line. This is required by the visible, ultraviolet and X-ray imaging experiments carried onboard [Torr et. al.; Frank et. al.; Imhof et. al., this issue] whose prime objectives are to acquire images and carry out a quantitative assessment of the energy deposited in the auroral region. Over the life of the POLAR mission, orbital mechanics will cause the orbital line of apsides to precess slowly to higher latitudes, swing over the north pole and continue southward. However, the perigee altitude is sufficiently high such that the maximum precession rate is less than 10 degrees/year. Like WIND, POLAR carries a propulsion system with 500 meters/sec delta-V maximum capability. This system will be used to perform attitude re-orientation maneuvers every six months and to raise the initial injection perigee from a few hundred kilometers to the 1.8 Re desired by the Science Team to sample the auroral particle acceleration region. The attitude maneuvers are required because the POLAR spin axis will be placed normal to the orbit plane to allow the imagers to view the high latitude regions almost continuously, and to enable the particle instruments to map the complete charged particles distribution function, including the loss cone [Roederer, 1970]. As the Sun angle changes during the year, the amount of power generated by the solar array will vary. To maintain adequate power margins and to satisfy the thermal requirement that the despun platform not be exposed to the sun for extended periods of time, the POLAR spacecraft spin axis orientation will be "flipped" 180 degrees every six months using the onboard propulsion system. The Science Instruments The complement of instruments and investigations associated with the GGS Program and summarized in Tables I-V are representative of the state-of-the-art in the field of experimental and theoretical space and magnetospheric physics research. These investigations were competitively selected by NASA in 1980 in response to an Announcement of Opportunity for the then planned Origin of Plasmas in the Earth's Neighborhood (OPEN) program which would have involved four spacecraft strategically placed in the four key geospace regions discussed earlier . The evolution of the OPEN program into an international collaboration caused the reorganization of several selected science teams and also led to the decision to replace some of the spacecraft and instruments with contributions from international partners like the Institute of Space and Astronautical Science in Japan who provided the GEOTAIL spacecraft . In addition, budget and schedule limitations led NASA to delete the EQUATOR spacecraft and its investigations originally proposed for the OPEN program, and the decision to utilize data from existing, orbiting spacecraft and ground-based measurements in its place. Other significant changes for the science experiments involved the POLAR despun platform. Initially it was conceived as a two-axis despun system to allow imaging as well as the positioning of narrow field of view particle detectors along the ambient magnetic field line thus making possible the mapping of the corresponding charged particle loss cone. However, power, mass and other design considerations led to the simplified single-axis despun platform currently implemented in this spacecraft. The evolution of the technology of imaging charged particle detectors during the long period between investigation selection and the start of the implementation phase introduced new elements in the development of the GGS instruments. To recover the science capability lost with the single axis despun platform design and to bring the instrumentation to "world class science" levels, major design updates and science enhancements were allowed by the GGS Project Officein almost all GGS experiments immediately following the selection of the prime contractor in 1988. Not only additional new technology detectors were incorporated in the instruments, but advanced data processing techniques were added to their data processing units made possible by technological developments and devices which were non-existent or high risk at the time of investigation selection. Similar "enhancements" were implemented in the ground based and theoretical investigations as well. The GGS instruments cover a very large dynamic range of measurement capability in the areas of electromagnetic fields, plasma and energetic particles, global auroral imaging and cosmic and gamma ray bursts. The applicable spectral coverage and dynamic ranges are summarized in Figure 6. The requirement to acquire simultaneous data from several spacecraft as a requisite for scientific success led to a strategy of overlap coverage in particle instruments and partial and full redundancy in imaging and electric and magnetic field detectors to prevent catastrophic single point failure modes. In addition, several technological factors drove the conceptual design of the instruments. First and foremost was the ready availability for spaceflight use of microprocessors and memory devices. In contrast, while ISEE3 contained a single microprocessor based instrument with a total of 512 bytes of storage, the average GGS instrument incorporates at least two microprocessors and several tens of kilobytes of memory. Thus the concepts of "microprocessor control" and "flight software" took a whole new dimension, allowing an unprecedented versatility in the achievement of desired performance characteristics and in the operational philosophy for the GGS science instruments. Second and distinct from previous spacecraft, WIND, POLAR and GEOTAIL are operated in the "store and dump mode". This implies that there exist long periods of time (e.g., 24 hours for WIND) when the spacecraft are not in contact with the ground controllers and the instruments must be designed to "safe" themselves if any anomaly occurs. This requirement for autonomous response to faults was not present in previous missions of this type. The following papers describe the instruments in detail as well as their outstanding performance characteristics which are expected to yield data of unprecedented scope and quality essential to accomplish the GGS science objectives. The global GGS data sets and the specialized ISTP contributions, interpreted in the framework provided by the models and theoretical investigations, are expected to lead to the detailed understanding of the global geospace system behavior as well as that of many incomplete and poorly known phenomena such as magnetic field line merging and reconnection, the triggering mechanisms for magnetospheric substorms and the production of the aurora that results from energization and flow of charged particles throughout the magnetosphere [Dyer, 1972; McCormac, 1976]. Significant contributions will also be made to the study of the bow shock and solar wind flow past the Earth, and how all of the above phenomena are controlled by the interplanetary medium and ultimately by the Sun [Yamide and Slavin, 1986; Hargreaves, 1992]. The heritage of the GGS instruments and science team is extensive, beginning with the earliest spaceflight instruments developed for upper atmosphere, ionosphere and magnetosphere research. Each instrument represents the latest contribution of small, dedicated research groups associated with universities, industry and government laboratories. In contrast to the large orbiting laboratory class spacecraft, the majority of the GGS instruments are built "in-house" and with the direct participation of the investigators and team members involved. This implementation mode, prevalent during the early years of the space program evolved significantly with the advent of very large, observatory class spacecraft, with the attending increase in complexity in terms of documentation and management requirements. The long duration of the implementation phase of the GGS instruments (14+ years) introduced many new elements which affected significantly the cost and risk associated with each investigation. However, the instruments described in this issue illustrate the extraordinary efforts carried out by the GGS investigators in overcoming these very difficult challenges. The outstanding contributions of the large number of engineers, scientists, mathematicians, data analysts, instrument managers, software specialists and innumerable other personnel that make a complex program like GGS a success, are evidenced throughout the papers in the papers in this issue. The Central Data Handling Facility and Science Planing and Operations Facility As mentioned in the introduction and in parallel with the integration and test of the spacecraft and flight instruments, imaginative science planning and instrument operations tools, data analysis and visualization concepts are being developed to complement the measurements and promote the efficient interpretation and analysis of the data. These concepts involve ideas and products derived from a strong interaction among modellers, theoreticians, experimentalist and data processing specialists. These are described in detail in this issue in the papers by Ashour-Abdalla et. al., Papadopoulos et.al., Hudson et. al. Mish et.al. where new concepts and data products such as "mission oriented theory", "theory projects", "key parameters", "science planning tools", and others are described. The successful achievement of the science objectives of GGS depends critically on the ultimate ability to acquire, process and analyze vast amounts of data from very sophisticated and complex instruments which may interact strongly with the carrier spacecraft. This difficult problem has been recognized for many years and addressed in a variety of ways with increasing success. One of the elements that has proven to be of high value is the prompt generation of medium time resolution, summary data sets which can be used as general indexes to the more general, high time resolution data. Typical examples of these data sets are the Dynamics Explorer "data pool tapes", Voyager "summary tapes", AMPTE's "summary data tapes", etc. These data products allow the rapid assessment and selection of intervals of high scientific interest for further detailed study. This approach is driven by the fact that the typical ratio of data volume analyzed in detail to the total data volume generated is usually small. For the design of the GGS system, this ratio was estimated at a ten percent average over the total investigation complement. This fraction has been organized in terms of "Key Parameters" selected for each investigation from recommendations of the Science Working Group and Principal Investigators. These data have a typical time resolution of 1 to 3 minutes and reflect fundamental geophysical parameters and time series associated with each investigation. A summary of the GGS Key Parameters for each GGS investigation is given elsewhere in this issue in the paper by Mish et. al.,. It is extremely important to note that these Key Parameters are uncalibrated, utilize "predict" orbit and attitude data rather than actual, processed values and hence cannot be used for formal scientific work. Their fundamental utility lies in the fact that they are processed immediately following data reception at NASA's Goddard Space Flight Center and made available for scientific assessment within 48 hours of acquisition. Thus, a prompt analysis of the Key Parameters can be used to respond to changing geophysical conditions or solar events, reconfigure the operating modes of the science instruments and evaluate potential high interest periods for further study. A secondary, engineering function of the Key Parameters is to provide a quick assessment of the performance of the instruments and to observe their operating modes for consistency with the primary science goals of the mission. The organization that has the responsibility of processing the data acquired by the GSFC Data Capture Facility (DCF) into Key Parameters and other data products for distribution to the GGS Investigators, is the Stanley Shawhan Central Data Handling Facility, named after the late, first Director of NASA's Space Physics Division. A block diagram of this facility and its functional interfaces is shown in Figure 7. It operates fundamentally as a "black box" where raw data are processed routinely under central direction and configuration control into key parameters and level zero data products that are distributed to the ISTP/GGS investigators for processing at their Remote Data Analysis Facilities (RDAF's). Detailed descriptions of the functional blocks and data products are given in the paper by Mish et. al., this issue.in almost all GGS experiments The responsibility for coordinating the science operations of the GGS instruments is handled by the Science Planning and Operations Facility (SPOF) under the direction of the GGS Project Scientists and the Science Working Group. This facility receives, analyzes and coordinates the commands requested to be sent to the instruments by the investigators with the purpose of identifying and resolving science conflicts. Engineering evaluation, instrument health monitoring and conflict resolution are carried out at the Project Operations and Control Center (POCC). The proposed instrument configuration and operational modes are formatted into short and long range "Science Operation Plans" which are evaluated for consistency with the GGS science objectives to insure conflict-free operation of the instruments. After this process is completed, the results are passed to the Project Operations Control Center where the final "command loads" are assembled for transmission to the spacecraft at the appropriate times and subsequent execution. To perform the functions of science coordination, conflict resolution and key parameter quality monitoring the SPOF has its disposal a number of specially developed tools in the form of geophysical data bases and models, orbit visualization and analysis software, and interactive key parameter display software. The tools, data products and software utilized by the SPOF have been designed to follow the general guidelines recommended by the Inter-Agency Consultative Group (IACG), mentioned earlier in this paper, to promote standardization and common format throughout ISTP missions. Further descriptions of these systems and facilities are also given in the Whipple and Mish et. al. papers in this issue. Acknowledgements On behalf of the GGS investigators, we would like to express our appreciation to NASA, ESA and ISAS which have made the GGS, STSP and GEOTAIL programs possible, to the GGS Project Manager J.Hrastar for his unrelenting efforts to make the project a success, to W. Worrall and the staff of the CDHF and SPOF organizations for their outstanding efforts on the ground data system, and to the countless other personnel that have contributed over the last 14 years to this program. The outstanding coordination efforts of the National Space Science Data Center and the IACG through its Working Groups in the areas of science campaigns, the promotion of common methods, formats, data products and standards, electronic data communication, etc. is hereby recognized and appreciated. Figure Captions Figure 1 - The Earth's geospace environment. The interaction of the solar wind with the Earth's magnetic field creates a supersonic shock wave and a magnetospheric cavity bounded by the indicated surfaces. The orbits of the GGS spacecraft are designed to provide coverage of key regions of geospace. Figure 2 - The solar-terrestrial energy chain. The Sun's energy flows from the interior through the photosphere, corona and interplanetary medium to the vicinity of the Earth where it interacts with the geomagnetic field and atmosphere. Figure 3 - The selected orbit for the WIND spacecraft. Periodic encounters with the Moon are used to maintain the apogee near the Earth-Sun line ("double lunar swing-by's"). The final orbit is a "halo" orbit around the L1 libration point. Figure 4 - The GEOTAIL orbit is similar to the WIND orbit except that lunar swingby maneuvers are used to maintain the apogee inside the geomagnetic tail. The initial orbit reached distances in excess of 200 Re. In the fall of 1994 the apogee of the GEOTAIL orbit will be reduced to approximately 30 Re. Figure 5 - The POLAR spacecraft orbit. This orbit was selected as a compromise among conflicting requirements by imaging and charged particle investigations. Figure 6 - The measurements, spectral coverage and dynamic range of the GGS flight instruments. Significant overlap redundancy exists among similar classes of experiments. Figure 7 - Overview of the ISTP/GGS ground data system showing the serial flow of data from the spacecraft, receipt by the Deep Space Network on to the Data Capture Facility, the Central Data Handling Facility, the Data Distribution Facility and finally to the individual PI Teams for processing at the Remote Data Analysis Facilities and the NSSDC. Also shown is the Science Planning and Operations Facility, an off-line facility where the science planning is coordinated. Tables I - WIND Investigations and Institutions Table II - POLAR Investigations and Institutions Table III - GEOTAIL Investigations and Institutions Table IV - Ground Based Investigations and Institutions Table V - Theory and Modeling Investigations and Institutions References: Akasofu, S.I. and S. Chapman, "Solar Terrestrial Physics", Oxford University Press, 1972. "CLUSTER: Mission, Payload and Supporting Activities", ESA SP-1159, March 1993. Dyer, 1972 - "Critical Problems of Magnetospheric Physics", Proceedings of the Joint COSPAR/IAGA/URSI Symposium, Madrid, Spain, E. R. Dyer, editor, 1972. Farquhar, R. W., " A new Trajectory Concept for Exploring the Earth's geomagnetic Tail", Journal of Guidance and Control, April, 1991 Farquhar, R. W., "The Control and Use of Libration Point Satellites", NASA Technical Report TR-R346, September 1970 Frank, L.A. and J. D. Craven, "Imaging results from Dynamics Explorer I", Rev. Geophys. 26, 249, 1988. "GEOTAIL Pre-Launch Report", Institute of Space and Astronautical Science, SES-TD-92-007SY, April 1992. J.K. Hargreaves, "The Solar Terrestrial Environment", Cambridge University Press, 1992 B. M. McCormac, "Magnetospheric Particles and Fields", D. Reidel Publishing Co., Dordrecht-Holland, 1976 Meng, C.I., M. J. Rycroft and L. A. Frank, "Auroral Physics", Cambridge University Press, 1989. Ogilvie, K. W., A. Durney and T. von Rosenvinge, "Description of the Experimental Investigations and Instruments for the ISEE Spacecraft", IEEE Trans. Geoscience Electronics, GE-16, No. 3, 1978. "The SOHO Mission: Scientific and Technical Aspects of the Instruments", ESA SP-1104, November 1988. Roederer, J. G., "Dynamics of Geomagnetically Trapped Radiation", Springer-Verlag, New York, 1970 Yamide, Y and J. A. Slavin, "Solar Wind-Magnetosphere Coupling", D. Reidel Publishing Co., Dordrecht-Holland, 1986 --------------------------------------------------------------------------- Spacecraft: Geotail Brief Description The Geotail mission will measure global energy flow and transformation in the magnetotail to increase understanding of fundamental magnetospheric processes. This will include the physics of the magnetopause, the plasma sheet, and reconnection and neutral line formation, i.e., the mechanisms of input, transport, storage, release and conversion of energy in the magnetotail. Geotail, together with Wind, Polar, SOHO, and Cluster projects, constitute a cooperative scientific satellite project designated the International Solar Terrestrial Physics (ISTP) program which aims at gaining improved understanding of the physics of solar terrestrial relations. Geotail is a spin-stabilized spacecraft utilizing mechanically despun antennas with a design lifetime of about four years. The nominal spin rate of the spacecraft is about 20 rpm around a spin axis maintained between 85 and 89 deg to the ecliptic plane. Geotail is cylindrical, approximately 2.2 m in diameter and 1.6 m high with body-mounted solar cells. Geotail also has a back-up battery subsystem which operates when the spacecraft is in the Earth's shadow (limited to 2 hrs). Real-time telemetry data transmitted in X-band are received at the Usuda Deep Space Center (UDSC) in Japan. There are two tape recorders on board, each with a capacity of 450 Mbit which allows daily 24-hour data coverage and are collected in playback mode by the NASA Deep Space Network (DSN). The Geotail mission is divided into two phases. During the 2-year initial phase, the orbit apogee is kept on the nightside of the Earth by using the Moon's gravity in a series of double-lunar-swing-by maneuvers that result in the spacecraft spending most of its time in the distant magnetotail (maximum apogee about 200 Earth radii) with a period varying from one to four months. During the second phase the apogee will be reduced to 30 Earth radii to study the near-Earth neutral line formation. Geotail CPI Brief Description ------------------------------ The objective of this investigation is to make comprehensive observations of the three-dimensional velocity distribution functions of electrons and positive ions, with identification of ion species. The instrument contains three sets of quadrispherical analyzers with channel electron multipliers. These three obtain three-dimensional measurements for hot plasma and solar wind electrons, for solar wind ions, and for positive-ion composition measurements. The positive-ion composition measurement includes five miniature imaging mass spectrometers at the exit aperture of the analyzer, and covers masses from 1 to 550 u/Q at 100 eV, and 1 to 55 u/Q at 10 keV. The hot plasma analyzer measures electrons and ions in the range 1-50,000 eV/Q. The solar wind analyzer measures ions from 150 to 7,000 eV/Q. Sequencing of the energy analyzers and mass spectrometers, and other control functions, are provided by two microprocessors. caveat supplied by Bill Patterson on 25 August 1994: There are problems with some Hot Plasma parameters, particularly the HP average energy and the densities. These parameters will be recomputed and there will be better definitions of the HP parameters in the skeleton table in a new version. The Solar Wind parameters appear to be generally ok. Geotail EFD Brief Description ------------------------------ The objectives of this investigation are studies of (1) the large scale configuration of the electric field in the magnetotail, (2) tail electric field variations during substorms, (3) the electric field in the plasma sheet, (4) the electric field near the magnetopause and in the plasma mantle at locations tailward of those covered by similar measurements on ISEE 1, (5) micropulsation and low frequency wave measurements at frequencies covering the local gyrofrequency (<1Hz) and lower hybrid frequency (<10Hz) in the tail, (6) plasma density as deduced from measurement of the floating potential of the spacecraft, and (7) electric field comparisons (with the aid of the other spacecraft in the ISTP program) at different points along the same magnetic field line, at different points along a common boundary, or in different regions of the magnetosphere. The instrument consists of two orthogonal double probes, each of which is a pair of separated spheres on wire booms that are located in the satellite spin plane and whose difference of potential is measured. The separation distances between the pair of sensors are variable and as great as 160 m tip-to-tip. One operating mode involves length ratios of the two antennas of about 2:1 in order to verify instrument operation through showing that the electric field signature is proportional to the boom length. A second reason for two pairs of wire booms in the satellite spin plane is the requirement for measurements having a time resolution far better than the satellite spin period. Geotail EPIC Brief Description ------------------------------ The principal objective of the EPIC (energetic particle and ion composition) investigation is to explore the distant magnetotail region and obtain information on the origin, transport, storage, acceleration and dynamics of suprathermal and non-thermal particle populations. The instrument performs three-dimensional distribution measurements by using both total energy (LEMS -- low energy composition system) and velocity/composition detectors (ICS - ion composition system), measuring ions and electrons with energies >20 keV, and ions with energy >8 keV/nucleon, respectively. Composition measurements are made by using a thin foil time-of-flight technique which resolves the H and He isotopes, and provides elemental resolution up to approximately argon. The instrument also measures the non-thermal components to 6 MeV for protons, 480 keV for electrons, and 400 keV/nucleon for ions with Z>2. Directional measurements with a time resolution <1 s are possible. GEOTAIL EPIC KP Data Caveat -------------------------- 1. Prior to March 8, 1993, the >34keV electron anisotropy parameters a1, a2, phi1, and phi2 are not useable. After this date, all electron intensity and anisotropy data are not useable due to EPIC key parameter software calibration problems. 2. A small subset of the ICS key parameters are not correct because the EPIC KP software failed to recognize when the instrument was in a reduced aperture or calibration mode. Please contact Dr. Richard McEntire at richard_mcentire@jhuapl.edu or (301)953-5410 or Dr. Tony Lui at anthony_lui@jhuapl.edu or (301)953-6000, ext. 8407 to verify whether your periods of interest are affected. 3. In periods of low flux, the 96-second averaging interval is insufficient for calculating meaningful anisotropy measurements. Large values of a1 and a2 and random values of phi1 and phi2 result. 4. Not all aspects of the STICS key parameters have been fully validated. 5. Several miscellaneous corrections are needed to the EPIC KP CDF file meta information: a) The range of all phi1 and phi2 anisotropy parameters should be -pi to +pi, not 0.0 to 2pi. b) The range of all a1 and a2 anisotropy parameters should be 0.0 to 2.1, not 0.0 to 2.0. c) The lower bounds of the two STICS proton differential intensity energy bands are not correct. For the given center values of 9.38 and 22.86 keV, the minus values to specify the lower limits of the bands should be 0.11 keV and 0.27 keV, respectively, not 0.3 keV and 0.0 keV, respectively. Stewart Nylund (ISTP::NYLUND) Geotail HEP Brief Description ------------------------------ There are three scientific objectives to be studied by this investigation: (1) plasma dynamics in the geomagnetic tail, (2) solar flare particle acceleration and propagation, and (3) the origin, lifetime and propagation of cosmic ray particles. There are five instruments that make up this investigation: Low-energy particle Detector (LD), Burst Detector (BD), Medium-energy Isotope detectors (MI-1 and MI-2), and High energy Isotope detector (HI). LD and BD are mainly dedicated to magnetospheric studies. MI and HI concentrate on solar flare and cosmic ray studies. The LD sensor system consists of three identical Imaging Ion Mass spectrometers which use time-of-flight/energy measurement, and covers 180 degrees in polar angle over the energy range 20--300 keV for electrons, 2 keV--1.5 MeV for protons, and 2 keV--1.5 MeV per charge for ions. LD provides distribution of electrons and ions with complete coverage of the unit sphere in phase space, and electron and proton flux in 4 azimuth sectors, helium and oxygen flux at an azimuth of 0 degrees. The BD sensor consists of three delta-E x E telescopes which identify particles by their energy loss and residual energy over the energy range 0.12--2.5 MeV for electrons, 0.7--35 MeV for protons, and 0.7--140 MeV for helium. The three telescopes each have an opening angle of 30 degrees by 45 degrees with look directions of 30, 90, and 150 degrees to the spin axis. BD provides count rates for high energy electrons, protons and helium, as well as electron and proton fluxes in four 90 degree azimuth bins. The MI and HI instruments are all silicon semiconductor detector telescopes utilizing the well-known dE/dx x E algorithm for isotope identification: mass and nuclear charge. The MI instrument measures elemental and isotopic compositions of solar energetic particles and energetic particles in the heliosphere with 240 KeV/q. For use at this orbit, the instrument was designed for high sensitivity with moderate energy and angular resolutions. The ESA is composed of a set of spherical plates such that the bending angle from the center of the entrance aperture is a constant 60 degrees, independent of the polar angle of entry. Electrons and ions are analyzed alternately with this single ESA. After leaving the ESA, the particles are accelerated into an array of six spiral-configuration channel electron multipliers (CEMs). Each CEM covers a separate polar angle field of view (FOV). The FOVs are fan-shaped and centered at +/- 11.5, 34.5, and 57.5 degrees polar angle, where 90 degrees is the spin axis direction (actively controlled to point to the center of the earth). Three-dimensional measurements are obtained by using spacecraft rotation, at a nominal 6 rpm, to sweep the FOV through the full 360 degree range of spacecraft azimuth angle while recording counts in the six polar angle FOVs. Measurements are made in standard cycles at each of 24 angles (15 degree spacing) in azimuth during each 10 s spacecraft revolution. Approximately 92% of the unit sphere is observed by the MPA. Normal instrument operation is composed of five types of cycles arranged in an eight-cycle sequence that repeats every 86 s. This provides both two-dimensional and three-dimensional distributions, with varying resolutions. For more details of the instrument, see the paper by S. J. Bame et al., Rev. Sci. Instrum., 64, (4), pp. 1026-1033, 1993. LANL SOPA Brief Description ------------------------------ The Synchronous Orbit Particle Analyzer (SOPA) consists of three nearly identical silicon solid state detector telescopes, pointed at 30, 90, and 120 degrees to the satellite's earth-centered spin axis. Similar instruments are on board all three of the constellation of geosynchronous spacecraft 89-046A, 90-095A, and 91-080B. The working end of the telescope consists of a very thin front silicon detector, D1, followed by a thick back detector, D2. The D1 sensors are mounted with the thin aluminum contact out. The thinner than usual Al contact was chosen to minimize the entrance deadlayer to allow as low a proton threshold as possible. Measurements show that the deadlayer is approximately 30 micrograms/cm**2. The detector stack is surrounded, except for the aperture, by passive low-Z (aluminum) and high-A (copper) shielding, which excludes side-penetrating protons up to about 65 MeV and electrons up to 6 MeV. The front collimator baffle is designed to require at least two-fold scattering of particles not in the acceptance angle of the detector to encounter the D1 detector. This provides an extremely sharp angular cutoff of incident particles. The full acceptance angle of the telescopes is about 11 degrees. Each telescope has a geometrical factor of 8.49 E-4 cm**2 sr for ions, and 1.09 E-3 cm**2 sr for low-energy electrons. A single rotation requires about 10 s, and in that time, 64 cuts of the unit sphere are taken by the three telescopes in a certain pattern. Passive cooling keeps the telescope temperatures within the range -15 to +5 C. In this range, essentially all of the noise associated with leakage current in the surface barrier detectors is eliminated. Even so, the high capacitance of the D1 sensors (~500 pF) requires setting the first energy threshold relatively high. The numerous thresholds and logic channels (including anti-coincidence) result in identification of differential fluxes of protons from 50 KeV to 50 MeV. Differential fluxes of electrons are determined from 50 KeV to 1.5 MeV, with integral flux above 1.5 MeV. The differential flux range for alpha particles is 0.5--1.3 MeV; for CNO, 1.5--3.55 MeV; for carbon, 5.0--13 MeV; for nitrogen, 6.0--14 MeV; and for oxygen, 7.2--15 MeV. Integral ion fluxes are determined for sulphur above 8 MeV, and for bromine above 15 MeV. A sun sensor with three collimators that overlap the fields-of-view of the three telescopes provides input to tag the pulse pairs that are potentially contaminated by sun-generated pulses from D1. For more details of the instrument, see the paper by R. D. Belian et al., J. Geophys. Res., 97, A11, pp. 16897-16906, 1992, from which this information was obtained. LANL/MPA KP Data Caveat ---------------------- The MPA KP data values are preliminary and have a number of problems which will be corrected when we revise our algorithms and re-process the data. However, that could be a while in coming. It is to be understood that the MPA data set contains very preliminary values (not publishable!) and any investigators interested in using them should contact us before embarking on any extensive study using them. Michelle Thomsen (S:ESSDP1::thomsen) --------------------------------------------------------------------------- Spacecraft: GOES 6 (7) Brief Description: GOES 6 was the eighth in a series of NASA-developed, NOAA-operated, geosynchronous, and operational spacecraft. The spin-stabilized spacecraft carried (1) a visible infrared spin-scan radiometer (VISSR) atmospheric sounder (VAS) to provide high-quality day/night cloudcover data, to take radiance-derived temperatures of the earth/atmosphere system, and to determine atmospheric temperature and water vapor content at various levels, (2) a meteorological data collection system to relay processed data from central weather facilities to regional stations equipped with APT and to collect and retransmit data from remotely located earth-based platforms, and (3) a space environment monitor (SEM) system to measure proton, electron, and solar X-ray fluxes and magnetic fields. The cylindrically shaped spacecraft measured 190.5 cm in diameter and 230 cm in length, exclusive of a magnetometer that extended an additional 83 cm beyond the cylindrical shell. The primary structural members were a honeycombed equipment shelf and a thrust tube. The VISSR telescope, which was mounted on the equipment shelf, viewed the earth through a special aperture in the side of the spacecraft. A support structure extended radially from the thrust tube and was affixed to the solar panels, which formed the outer wall of the spacecraft to provide the primary source of electrical power. Located in the annulus-shaped space between the thrust tube and the solar panels were stationkeeping and dynamics control equipment, batteries, and most of the SEM equipment. Proper spacecraft attitude and spin rate (approximately 100 rpm) were maintained by two separate sets of jet thrusters mounted around the spacecraft equator and activated by ground command. The spacecraft used both UHF-band and S-band frequencies in its telemetry and command subsystem. A low-power VHF transponder provided telemetry and command during launch and then served as a backup for the primary subsystem once the spacecraft attained synchronous orbit. GOES 6 was moved from its 135 deg W position to a more central 98 deg W position when GOES 5 failed on July 29, 1984. GOES-6 (7) EPS Brief Description ------------------------------ The energetic particle monitor consisted of three detector assemblies, each covering limited regions of the overall energy spectrum. The first two detector assemblies monitored protons in seven energy ranges between 0.8 and 500 MeV, and alpha particles in six ranges from 4 to >400 MeV. There was also one channel for the measurement of electrons in the >=500 keV range. The third detector, the high energy proton and alpha detector (HEPAD), monitored protons in four energy ranges above 370 MeV and alpha particles in two energy ranges above 640 MeV/nucleon. GOES-6 (7) MAG Brief Description ------------------------------ not available at this time. GOES 6 and 7 KP Data Caveat --------------------------- 1. There are several difficulties with some of the present GOES KP data; however, even with these limitations, the data can be useful for such activities as event detection and understanding the level of disturbance of the geomagnetic field. It is to be understood that this data cannot be published or presented without the PI's authorization. 2. In addition to comments imbedded in the CDF's regarding data quality, some additional comments regarding the data are provided below. (the following quality information was provided by Dr. Howard J. Singer, Acting Chief Geospace Branch, NOAA R/E/SE 303-497-6959) : GOES 6 - Magnetometer A variety of malfunctions of the spin plane components (He and Hn) of this instrument have occurred since at least September 1992. These data are useful for detecting a variety of disturbances in the space environment, but the actual field values are not to be trusted. The parallel, or spin axis, component (Hp) of the field appears to be unaffected by the spacecraft or instrument difficulties; however, the offset of this component is difficult to calibrate and questionable. Interpretation of the data is also complicated by the fact that the GOES 6 spacecraft orbit has become more inclined to the equatorial plane than is typical of the GOES satellites. GOES 7 - Magnetometer The GOES 7 magnetometer transverse components (He and Hn) failed on May 2, 1993. At this time an offset also appeared in the spin axis component. This offset was removed on May 18, 1993; however as with GOES 6, the absolute value of the spin axis component also has uncertainties. (the following quality information was provided by Dr. Herb Sauer NOAA R/E/SE 303-497-3681) : Energetic Particle Detectors The GOES E1 and P1 channels were designed to measure the geostationary flux of electrons of energy E>2 MeV and protons of energy E such that .6 < E < 4.2 MeV. Because of radiation damage to the GOES-6 E1 detector, these data are not included in the data-set. The GOES -7 electron detector also responds to protons of energy E > 80 MeV. Therefore, during solar energetic particle events, the electron data are often compromised to the extent that they may primarily represent the detector response to energetic protons. GOES-7 particle detector data is missing during an eclipse and for approximately the following 4 hours. Finally, the geomagnetic cutoff at geostationary orbit is of the order of 1 MeV, which is within the energy range of the P1 channel. Therefore, the flux observed during a solar energetic particle event by channel P1 is a composite of trapped protons at the lower channel energies and event protons which reach the satellite from sources outside the magnetosphere. --------------------------------------------------------------------------- Ground Based Experiment: Dual Auroral Radar Network (DARN) The Dual Auroral Radar Network (DARN) is one of the Ground-Based Instruments (GBI) of the ISTP/GGS project. As it is currently configured, DARN consists of 6 independent radar systems. Each radar is briefly described below (moving from East to West): 1. STARE The Scandinavian Twin Auroral Radar Experiment. This is a VHF radar system which uses two radars observing a common volume to determine plasma drift velocities in the ionospheric E-region. The two radars are located in Finland and Norway. The institutions involved are the Finnish Meteorological Institute and the Max Planck Institut f$r Aeronomie. 2. SABRE The SABRE radar is a single VHF radar located at Wick, Scotland. It is similar to the STARE radars, but uses only a single radar rather than a pair. The radar is operated by the Univ. of Leicester, UK. 3. Goose Bay HF radar The Goose Bay radar is an HF radar located in Goose Bay, Labrador. It observes the ionospheric plasma drift velocities in both the E and F-Regions. It is operated by the Applied Physics Laboratory. 4. SHERPA The SHERPA radar is an HF radar similar to the Goose Bay radar. It is located in Schefferville, Quebec. Its field of view partially overlaps that of the Goose Bay radar, and it is possible to determine 2-D plasma velocity vectors in some cases, by using the data from the 2 radars. However, unlike STARE, the 2 radars operate independently. SHERPA is operated by CNRS in France. 5. BARS The Bistatic Auroral Radars System is one component of the Canadian CANOPUS system. It is a dual VHF radar system similar to STARE and observes plasma drift velocities in the E-region. 6. Halley Station radar The Halley radar is located at Halley station Antarctica. It is an HF radar virtually identical to the Goose Bay radar, and its field of view is magnetically conjugate to that of the Goose Bay radar. The Halley radar is operated by the British Antarctic Survey. The combined observations from Halley and Goose Bay form the Polar Anglo-American Conjugate Experiment (PACE). ----------------------------------------------------------------------