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SUMMARY:A novel satellite mission concept for upper air water vapour\, aer
 osol and cloud observations using Integrated Path Differential Absorption 
 LiDAR Limb Sounding - Alex Hoffman\, University of Cambridge
DTSTART:20111128T141500Z
DTEND:20111128T151500Z
UID:TALK33081@talks.cam.ac.uk
CONTACT:Dr Alex Archibald
DESCRIPTION:In this talk\, I am going to present a collaborative new Earth
  Observation space-mission concept conceived during the Alpbach Summer Sch
 ool 2010 and further developed during the Obergurgl 2010 follow-up worksho
 p. Our team proposed a new satellite constellation to deliver high quality
  measurements of upper air water vapour. The concept centres around a LiDA
 R in limb sounding by occultation geometry\, designed to operate as a mono
 static very long path system for differential absorption measurements. A s
 econdary payload of a fairly conventional medium resolution multispectral 
 radiometer allows wide-swath cloud and aerosol imaging. I will make a case
  for the scientific objectives of the proposed mission\, but predominantly
  focus on some of its high-level engineering aspects.\n\nIn this regard\, 
 I will present some of the numerous challenges encountered in and characte
 ristic for such an integrated design project\, along with some of the succ
 essive trade-offs and intermediate design solutions proposed. Some of thes
 e challenges include orbit and constellation considerations\, performance 
 of laser systems in space\, retroreflector and telescope concerns as well 
 as pointing\, acquisition and tracking issues and spacecraft attitude cont
 rol.\n\nI will conclude on a preliminary performance analysis with a syste
 m sized to send 75mJ pulses at 25Hz at four wavelengths close to 950nm\, t
 o up to 5 microsatellites in a counter-rotating orbit\, carrying retrorefl
 ectors characterized by a reflected beam divergence\nof roughly twice the 
 emitted laser beam divergence of 15 microrad. This provides water vapour p
 rofiles with a vertical sampling of 110m\; preliminary calculations sugges
 t that the system could detect concentrations of less than 5ppm up to roug
 hly 40-50 km of altitude.
LOCATION:Unilever Lecture Theatre\, Department of Chemistry
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