this proposal is a follow-up of the lws graing spectrum obtained of saturn as part of the guranteed time giants proposal. three, weak, rotational methane absorption features are observed but with a greater strength than anticipated. the original guaranteed time proposal included a full fabry-perot scan of saturn, but in light of the reduced sensitivity of iso, this has been replaced by several miniscans targeting specific lines; methane was not included. it is proposed to observe these methane lines at high spectral resolution to determine the tropospheric concentration of methane. methane is an important source of opacity, so that further to obtaining the c/h ratio, its abundance tells us of its contribution to the overall thermal balance of the planet. the determination of the methane vertical concentration profile using iso lws at far-infrared wavelengths does not suffer from the drawbacks of previous near-infrared studies (saturation, scattering etc.) and should be an important new measurement of the currently uncertain value for the satrunian c/h ratio. methane is important also as the starting point for a network of photochemical reactions occurring in the the stratosphere. determination of the tropospheric vertical mixing ratio profile (which is expected to be uniform) and comparison with the profiles of ethane (c2h6), etylene (c2h2) and acetylene (c2h4) from the guaranteed time proposal will provide a picture of the balance of both the carbon photochemistry and vertical mixing as a function of altitude.
Instrument
LWS03
Temporal Coverage
1997-07-19T08:24:29Z/1997-07-19T11:35:05Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, 1998, Saturn: Determination Of The Tropospheric Methane Abundance Profile, 1.0, European Space Agency, https://doi.org/10.5270/esa-djklr3g
