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Highlights of AATSR Commissioning. David Llewellyn-Jones AATSR Principal Investigator Space Research Centre University of Leicester including contributions provided by Dave Smith, Jack Abolins (RAL) Lisa Horrocks (Met Office), and Marianne Edwards (Leicester). AATSR on ENVISAT.

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highlights of aatsr commissioning

Highlights of AATSR Commissioning

David Llewellyn-Jones

AATSR Principal Investigator

Space Research Centre

University of Leicester

including contributions provided by Dave Smith, Jack Abolins (RAL) Lisa Horrocks (Met Office), and Marianne Edwards (Leicester)

aatsr on envisat
AATSR on ENVISAT
  • Imaging radiometer
  • Thermal Infrared, near infrared and visible wavelength channels
  • Third in a series, designed to measure Global Sea-surface temperature (SST) for climate applications
  • accuracies better than 0.5C
  • High radiometric performance required (better than 0.1C accuracy) and achieved
why is aatsr such a good thermal radiometer
Why is AATSR such a good thermal radiometer?
  • High signal-to-noise ratio detectors

- active cooling system (Stirling cycle coolers)

  • Stable calibration system

- two black-bodies, spanning essential dynamic range

- viewing black bodies with same optical path as scene

- viewing each-body each scan

- stable thermal environment for each black-body

some highlights of commissioning results
Some highlights of Commissioning results. .
  • Radiometric Noise
  • Black-body temperatures
  • Compare & contrast with AVHRR
  • Overall thermal performance of instrument
  • Geophysical Validation
  • Comparisons with MERIS and ATSR2
radiometric noise
Radiometric Noise

Note: For thermal channels, NET specification is 0.05K

slide8
AATSR Black-body Temperature recordsshowing variations over one daywith near-sinusoidal orbital variations superimposed
a single orbit record of avhrr black body temperature passing the terminator
A single orbit record of AVHRR Black-body temperaturepassing the terminator
black body crossover test
Black-Body Crossover test
  • Exchange roles of AATSR black-bodies

- ie heat the cooler BB and allow heated BB to cool, monitoring BB temperatures as function of time

  • At ‘crossover’ point, both black bodies are nominally at same temperature and should give same detector signal
  • This test would reveal problems with prt sensors or in emissive surfaces of the black-bodies
  • Results show discrepancies of less than 30mK
aatsr black body crossover test
AATSR Black-body ‘crossover’ test

This plot identifies the time at which

both sets of black-body temp sensors

indicate the same temperature.

At this time both BB’s

give same signal to within <30mkK

overall thermal performance
Overall thermal performance
  • Blackbodies
    • Orbital variation ~ ±0.1°C
    • Rate of change <0.015°C per two minutes (reqt. <0.02°C)
  • Fore-Optics
    • Orbital variation ~ ±0.5°C
    • Rate of change <0.04°C per two minutes (reqt. <0. 2°C)
  • FPA Baffle Tube
    • Orbital variation ~ ±0.5°C
    • Rate of change <0.04°C per two minutes (reqt. <0. 2°C)
geophysical validation
Geophysical Validation
  • Over 15 validation projects in progress worldwide. 7 have already collected in situ data
  • Comparisons at UK Met Office between AATSR METEO SST and in situ buoy data show promising results
  • For Vis/NIR channels, good comparison with MERIS (better than 5%)
first aatsr buoy sst comparisons a o carroll l horrocks uk met office
First AATSR-Buoy SST comparisons(A O’Carroll & L. Horrocks, UK Met Office)
  • For the period 19-21st August 2002: mean ESA skin - buoy SST difference = 0.039 (=0.348)
  • For the period 22-27th August 2002: mean ESA skin - buoy SST difference = -0.096 (=0.583)
  • Some minor anomalies in polar regions
  • Bearing in mind skin-bulk temperature differences and known uncertainties in buoy data, this is a very satisfactory starting-point for the AATSR validation programme, indicating that AATSR is already very close to meeting its geophysical performance specifications.
summary and conclusions
Summary and Conclusions
  • Next presentation (Dave Smith) will show detailed results
  • In the essential areas of radiometric noise and BB performance AATSR is comfortably within specification
  • In all other respects AATSR is within specification
  • Excellent comparisons with ATSR2 and MERIS
  • First Validation results (Lisa Horrocks and Anne O’Carroll) extremely promising, details in later presentation from Marianne Edwards
  • Stable operation – only one unavailability notice so far
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