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MMO Thermal Analysis Status In Mercury Orbit (Jan-2006)

MMO Thermal Analysis Status In Mercury Orbit (Jan-2006). [Thermal Analyses] Maximum predicted temperatures of MMO internal components will exceed the allowable temperature at the worst hot case (perihelion EOL).

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MMO Thermal Analysis Status In Mercury Orbit (Jan-2006)

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  1. MMO Thermal Analysis Status In Mercury Orbit (Jan-2006) [Thermal Analyses] • Maximum predicted temperatures of MMO internal components will exceed the allowable temperature at the worst hot case (perihelion EOL). Studies of options to decrease the maximum temperature of MMO internal components are being performed. 1) to impose operational constraints on the Sun angle to the spin axis. • 92 +/-1 deg. normal • 90 +/-1 deg. around perihelion 2) to impose operational constraints on the MMO mode • Operating low heat dissipation modes around perihelion • Additional Option: Alternative reversed orbit around Mercury

  2. ν：Mercury True Anomaly +/-20° Orbit plane 0.4667AU Sun 0.3075AU Mercury N Spin axis HGA Solar Mercury MMO S Periherm latitude: South 15° Periherm latitude: North 5° MMO orbit at aphelion N Spin axis HGA Solar Mercury MMO S Periherm latitude: South15° Periherm latitude: North5° MMO orbit at perihelion MMO Mercury Orbit for Thermal Analysis

  3. MMO Predicted Temperature History on Mercury Orbit@Perihelion HOT-OBSCOM Mode (EOL)(Upper Deck Component:ACIM,TWT-1,Lower DeckComponent:MDP-2) NOT INCLULDE TEMPERATURE MARGIN NOT INCLULDE TEMPERATURE MARGIN Perihelion HOT-OBSCOM Mode Spin Axis VS Solar Axis =93°,Periherm Latitude= North5° Perihelion HOT-OBSCOM Mode Spin Axis VS Solar Axis =90°,Periherm Latitude= North5° -> Inner temperature of MMO will be decreased from 10 to 20 deg.C if the sun angle is changed 93 deg to 90deg. However, still exceeding the allowable temperature of the components.

  4. Solar Angle 91deg Solar Angle 93deg MMO Predicted Maximum Temperature on Mercury Orbit（HOT-OBSCOM @EOL）Upper Deck Component:ACIM,TWT-1, Lower Deck Component:MDP-2Maximum Predicted Temperature form Perihelion to Aphelion Upper Deck: ACIM, TWT-1 Lower Deck:MDP-2 ResolutionTo operate with the MMO attitude of 91 deg. Solar angle, during Mercury True Anomaly +/- 90 deg, (changing the MMO attitude from normal 93 deg. Solar angle) TEMPERATURE MARGINS NOT INCLUDED

  5. MMO Alternative Reversed Orbit Option • It will be possible that MMO maximum peak temperature of internal components can decrease by about 10 deg C in case of the alternative reversed orbit, compared to the current baseline orbit, because MMO temperature will decrease during eclipse. • From the thermal point of view, the MMO reversed attitude (up-side down) with the current baseline orbit is equivalent to the alternative reversed orbit option. However, the MMO reversed attitude option will have some impact on the attitude control subsystem, because visible stars from the star scanner attached to the lower surface will change from the south pole to the north pole. Therefore, the MMO reversed orbit option will be preferable than the MMO reversed attitude option. • The MMO reversed orbit option will not affect MMO payloads and science. ESA & JAXA are investigating this option.

  6. Eclipse Solar Heat Flux Mercury Eclipse Solar Heat Flux Mercury Alternative Reversed Orbit: South to North direction at Periherm MMO Alternative Orbit (reversed) Heat injection into the MMO Lower Deck (radiator) around periherm <Current Baseline Orbit> MMO takes Solar heat flux and Mercury infrared radiation before eclipse <Alternative Reversed Orbit> MMO takes Solar heat flux and Mercury infrared radiation after eclipse It will be possible that MMO maximum temperature of internal components can decrease in case of the alternative reversed orbit, compared to the current baseline orbit. Because MMO temperature will decrease during eclipse. Current Baseline Orbit: North to South direction at Periherm

  7. MMO On-orbit predicted temperature time historyPerihelion,HOT-EOLSolar Angle:91°MMO OBS Mode Temperature margins of 20 degC are not included. Temperature margins of 20 degC are not included.

  8. MMO On-orbit predicted temperature time historyPerihelion,HOT-EOLSolar Angle:91°MMO COM Mode (Communication) Temperature margins of 20 degC are not included. Temperature margins of 20 degC are not included.

  9. MMO On-orbit predicted temperature time historyPerihelion, HOT-EOLSolar Angle:91°MMO STBY Mode (StandBy) Temperature margins of 20 degC are not included. Temperature margins of 20 degC are not included.

  10. Ref: MMO Predicted Temperature on Mercury Orbit @Perihelion (EOL) NOT INCLULDING 20 degC TEMPERATURE MARGIN Sun:91deg OBS <reverse> Sun:91deg COM <reverse> Sun:91deg STBY <reverse> Sun:91deg OBS Sun:91deg COM Sun:91deg STBY

  11. Ref: MMO Predicted Temperature on Mercury Orbit@Perihelion (EOL) NOT INCLULDING 20 degC TEMPERATURE MARGIN Sun:91deg OBS <reverse> Sun:91deg COM <reverse> Sun:91deg STBY <reverse> Sun:91deg OBS Sun:91deg COM Sun:91deg STBY

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