HIRDLS

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HIRDLS

• High Resolution Dynamic Limb Sounder

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Basics

• Set to fly on the Aura mission of NASAs Earth
  Observation System
• Joint US-UK (NASA-NERC) development
• Scheduled for launch in December 2002, then June
  2003, now June 17, 2004
• Will sound upper troposphere, stratosphere, and
  mesosphere (8km-80km) to determine
• Temperature/Pressure
• Concentrations of O3, H2O, CH4, N2O, NO2, HNO3,
  N2O5, CFC11, CFC12, ClONO2, and aerosols
• Locations of polar stratospheric clouds and cloud
  tops

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Operational Tidbits

• Operates in sun synchronous orbit at 705km
• Completes orbit in 105 minutes
• Takes 10,000 profiles per day with one complete
  profile in 12 hours
• Spatial Resolution
• Horizontal 5 x 5 (500km x 500km)
• Vertical 1-1.25km
• Measures infrared emission in 21 channels ranging
  from 570-1600 cm-1
• 4 sensors for CO2, 4 for O3, and 1 for each
  remaining constituent sampled
• Has an onboard gyroscope for accurate reporting
  of where the instrument was pointing for a given
  measurement

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Scan Cycle
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HIRDLS Limb Viewing Geometry
(Satellite moving clockwise)
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Data processing

1. CO2 mixing ratio is well known
2. Using this information and CO2 radiance
   measurements to determine temperature/pressure
   information
3. Using temperature/pressure data with blackbody
   formula to calculate mixing ratios of the
   constituent of interest

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Limb Radiance Spectra
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Weighting Functions Ch. 2-5
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