THz sounding of Europas atmosphere

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THz sounding of Europas atmosphere

• Paul Hartogh, Nicolas Thomas, et al.
• MPS Lindau, University of Bern

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Galilean Satelites Europa

• HIFI (Herschel Space Observatory) RTE model
• Water density profiles according to Shematovic et
  al., 2005
• T-profile const. 103 K (mean surface
  temperature)
• Signal comes from limb
• Collisional line excitation (LTE)
• Europas disk diameter 0.75 arcsec
• Results Line amplitude gt 10 mK in band 6 (worst
  case estim.)
• 3-sigma detection requires about 250 h
• Higher atmospheric T emission could be much
  stronger, depending on model Tobs lt 50 h for HIFI

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• Problem Europas atmosphere at HIFI detection
  limit due to beam dilution. Detection possible,
  but expensive in terms of observation time.
• Solution orbiter with THz sounder

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Atmosphere of Europa water detection from an
orbiter

• Capabilities of the THz Sounder
• Beam filling factor 1
• Input of radiative transfer model from Shematovic
  et al.
• Water line amplitude gt 4K
• 5 sigma detection of water line lt 1 s
  integration time gt very high vertical and
  horizontal resolution of submm meas.
• Separation of water sources (sputtering,
  sublimation), identification ofsources on
  Europas surface
• Retrieval of vertical profile up to 1000 km
  above surface
• Analysis of escape processes

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Europas atmosphere O, O2, OH, H2O number
density and escape flux
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What else?

• Other Galilean Satellites
• Composition of Ios volcanic outgassing
• Jupiters stratosphere

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Instrument Characteristics

• HEB receiver with miniaturized low power sorption
  cooler or classical Schottky approach
• 10 30 cm telescope diameter
• Chirp Transform Spectrometer
• Heritage Rosetta MIRO, HIFI (Herschel)
• Mass 5-10 kg (potential for reduction)

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Summary

• THz sounder can globally characterize the
  atmosphere of Europa
• Identifies sources of water (processes,
  geography)
• Determination of escape flux
• Atmospheres of other Galilean Satellites
• Chemistry of Ios atmosphere