The CCD photometric observation of comet 103P/Hartley 2 with broadband optical filters was carried out at Xuyi Station of Purple Mountain Observatory, Chinese Academy of Sciences by use of Near Earth Object Telescope （NEOT）. We monitored the comet from September 30 to November 4, 2010 and investigated the variation of activities. The Afp parameter derived from our r broadband data varies from 46.0 to 126.0 cm and increases with time. The dust production rate in terms of Afp was measured and a tentative calculation of the dust （or gas） loss-rate of nucleus was executed under the assumption that the nucleus of comet 103P/l-lartley 2 is spherical. The r-band image and the surface brightness profile taken on September 30, 2010 was measured and the gradient of surface brightness profile of 103P/Hartley 2 showed m 〈 -1.5,
The interplanetary radiation environment is detrimental to space missions,giving rise to cumulative damage to both astronauts and payloads and enhanced background levels in detectors.Therefore,there is a pressing need for a reliable simulation of these harmful effects for risk assessment and shielding optimization in manned space missions.We have modeled the interaction processes of the two most abundant galactic cosmic ray particle fluxes(protons and helium nuclei) using the Geant4 toolkit for a given space vehicle model.The total energy deposited due to protons and helium nuclei is calculated in this work,and the energy deposited due to the secondary particles generated by this radiation is also estimated.
BAO Gang Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China
Maintaining the geodesic motion of the test mass is vital to ASTROD I space mission. However,the electrostatic charging of the test mass due to cosmic rays and solar energetic particles will result in Coulomb and Lorentz forces and consequently influence the test mass motions. To estimate the size of these effects,a credible simulation of test mass charging processes is critically required. Using the GEANT4 software toolkit,we have modeled the charging processes and predict how the ASTROD I test mass will charge positively at a rate of 217370 e + /s,due to solar energetic particles(SEPs) at～0.5 AU caused by the largest SEPs event on 29,September,1989. In addition to Monte Carlo uncertainty,an error of ±30% in the net charging rates was added to account for uncertainties in the spectra,physics and geometry models.
BAO Gang & LIU Lei Purple Mountain Observatory,Chinese Academy of Sciences,Nanjing 210008,China
