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Exective summary

The Science of SCOPE

The SCOPE mission strategy

SCOPE in the Roadmap

SCOPE and the simulation studies

Link to Cross-Scale (ESA)

Scenario overview

A formation flight satellite mission "SCOPE" is now under study aiming at launching in 2017. "SCOPE" stands for 'cross Scale COupling in Plasma universE'. The main purpose of this mission is to investigate the dynamic behaviors of plasma in the terrestrial magnetosphere that range over magnitudes of both temporal and spatial scales. The basic idea of the SCOPE mission is to distinguish temporal and spatial variations of physical processes by putting five formation flight spacecraft into the key regions of the Earth's magnetosphere. The formation consists of one large mother satellite and four small daughter satellites. Three of the four daughter satellites surround the mother satellite 3-dimensionally maintaining the mutual distances of variable ranges between 5 km and 5000 km. The fourth daughter satellite stays near the mother satellite with the distance between 5 km and 100 km. By this configuration, we can obtain both the macro-scale (1000 km - 5000 km) and micro-scale (< ~100 km) information about the plasma disturbances at the same time. SCOPE's predecessor "GEOTAIL", launched in 1992, played a big role for understanding the ion behavior in the Earth's magnetotail and triggered interests toward further microscopic scale (electrons scale) phenomena.

image largeimage small Conceptual diagram of SCOPE (cross Scale COupling in Plasma universE) mission.
Following this successful work of GEOTAIL, SCOPE aims at observing the Earth's magnetotail where the ions and electrons interact with each other, with 5 satellites flying in formation. To fully resolve the time domain behavior from spatial distribution of the magnetospheric phenomena, simultaneous observations by spatially distributed spacecraft are essential. The launcher for SCOPE has been assumed to be M-V rocket (or its succession rocket) of JAXA. However, due to the termination of M-V rocket, we are now considering to use H2A. The orbits of SCOPE satellites are all highly elliptical with its apogee 30Re from the Earth center. The inter-satellite link is used for telemetry/command operation as well as ranging to determine the relative orbits of the 5 satellites in small distances, which cannot be resolved by the ground-based orbit determination 3). The technical challenges of SCOPE mission are as follows: (1) The 4 daughters are small satellites including propellant for formation control maneuver; (2) The 5 satellites fly very close to each other in formation. The typical formation is a 5 km tetrahedron at apogee; (3) The spacecraft’s onboard clocks are synchronized within 5msec by the inter-satellite link; (4) The relative distance is measured among all the satellites by onboard ranging equipments; (5) The relay operation of the 4 daughter satellites via the mother satellite should enable the ground station to conduct the concentrated management and operation.

Orbit

The primary region of interest for observation is a tailbox that is defined as a simple 25Re x 10Re x 4Re rectangular prism, whose position and orientation is defined in the neutral sheet coordinates. The neutral sheet coordinates is a non-inertial, right-handed Cartesian coordinate system, with its X-axis anti-sunward from the Earth's centre, Y-axis perpendicular to the X-axis along the equatorial plane, and Z-axis perpendicular to X- and Y-axis.

H2A rocket is assumed as the launch vehicle. The launch window is open throughout a year for this orbital sequence. The launch day determines when SCOPE encounters the tailbox. Because the tailbox is placed always in the anti-sunward direction, while the apogee direction is fixed in the inertial space, SCOPE can get into the tailbox roughly 1 month a year. The eclipse analysis indicates that spring and fall tailbox encounters are difficult, because of the long ecliptic duration by the Earth. Spring and fall tailbox are located on the ecliptic plane, the area largely covered by the Earth's shadow. The current equipment plan cannot allow the battery operation of 5 SCOPE satellites for more than 180 minutes. On the contrary, the perturbation analysis indicates that the summer and fall tailbox encounters are not preferable, because the orbital plane is perturbed much in these orbits due mainly to the lunar gravity. The sensitivity of the inclination on the tailbox staying time becomes maximum in the mid-summer and mid-winter, because the semi-major axis aligns the inclination angle direction. In these orbits, the staying time in tailbox decreases drastically year by year. The trade off between these two conditions suggests four seasonal possibilities for tailbox encounter, which are February, April, July and October.

The current baseline mission adopts a highly elliptic orbit of 25Re apogee, 10Re perigee. The orbit encounters the tailbox for about 1 month a year, when the apogee aligns anti-Sunward direction.

Structure

SCOPE will be launched by H2A launch vehicle at once. In the launch configuration, mother satellite and daughter satellites are attached to a "dispenser" (propulsion module) as shown in the Figure. After inserted into the initial orbit of 250 km x 24Re, the propulsion module takes them all together to the final orbit of 10Re x 25 Re apogee. Afterward, daughter satellites and mother satellite are undocked, and moves to the objective relative position to form the formation by its own RCS equipment. The mother and 3 daughters are spin-stabilized satellites with their spin axes perpendicular to the orbital plane. The rest one daughter is also spin-stabilized, but its spin axis is oriented toward the Sun. This special daughter satellite is called "near-daughter", as it is to fly within 100km even during the Phase-2 operation. The combination of the mother and the near-daughter enables us to measure all the three components of the electric field.

image largeimage small SCOPE satellites in the launch configuration.