7. Outer margins of the fractures are diffuse, suggesting liquid water venting from the fractures 6, 8. Subsurface liquid is also suggested by non-synchronous rotation of Europa 9. The ice shell and possible water layer is estimated to be total 100-200 km thick 10. The lower part of the shell is presumed to be geothermally heated, which could result in melting the lower ice shell. Europa's volcanism is strongly suggested by the active volcanism of Io, the Jovian satellite J1 4, 11. Jupiter's tidal force influences the Io's magmatism, and the same is assumed for the case of Europa. As a result, Europa is presumed to have a liquid water layer between the outer ice shell and the rocky interior. The ice shell and water layer are estimated to be a total of 100-200 km thick (Table 1) 10. Even the lowest estimation of 100 km thick is 10 times larger than the maximum depth of the Earth's ocean. However, hydrostatic pressures will not be proportionally high, as Europa's gravity (1.3 m s-2) is 13% of the Earth's gravity (9.8 m s-2). Hydrostatic pressure at 100-200 km deep in Europa's ocean will be ca. 130-260 MPa, which is equivalent to 13-26 km deep in the Earth's ocean. Higher values are possible, assuming higher density of Europa's seawater, although the chemical composition is not yet known.
The H-II Transfer Vehicle (HTV) is a Japanese unmanned cargo transfer vehicle developed for the International Space Station (ISS) re-supply and waste disposal purposes. HTV1 through HTV3 completed the mission successfully, and HTV4 through HTV7 are planned to be launched once a year continuously. Under the circumstance that the achievement is evaluated highly and the expectation for the new usage of HTV is increased, we have prepared a new platform and report some experiments plan with using it in the paper.
The H-II Transfer Vehicle (HTV) is Japan's unmanned cargo transfer spacecraft that delivers cargo/supplies. It has on-orbit platform function to provide a demonstration to users from HTV4. ElectroDynamic Tether (EDT) technique, which is a promising candidate as a debris removal device, is planned to be demonstrated using HTV6. The demonstration concept is that the end-mass with 700 meter tether is deployed and currents on the tether are driven by emitting electrons from HTV after departure from ISS. This mission is called Kounotori Integrated Tether Experiments (KITE), and there are some demands for unique operations of the HTV in order to perform KITE. The objective of the paper is to evaluate KITE feasibility from the standpoint of HTV operation.
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