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AATSR Function & Performance. Thermal Cooler Performance Scan mirror performance. In-Orbit Temperatures Vs. Flight Predictions. Thermal Stability. 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

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Aatsr function performance
AATSR Function & Performance

  • Thermal

  • Cooler Performance

  • Scan mirror performance



Thermal stability
Thermal Stability

  • 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)



Thermal summary
Thermal - Summary

  • In-orbit temperatures for all units show positive margins compared to the EOL predictions

  • Fore-optics temperatures meet and exceed requirements for actual temperature and orbital stability



Cooler performance trends
Cooler Performance – Trends

Max commanded compressor A amplitude = 2.679

Software increases amplitude to maintain a commanded FPA baseplate temperature

Thermal load increasing with time as water condenses, with the rate of condensation slowly reducing as the mission progresses and ENVISAT-1 loses its atmosphere.


Cooler performance summary
Cooler Performance - Summary

  • Cooldown to 80K achieved in ~5 hours

  • Cooler software is controlling the compressor amplitude to maintain the FPA temperature at 80K as required

  • Thermal load on the FPA increases with time as water condenses on surfaces

    • Recovers to nominal conditions after outgassing

    • Rate of condensation slowly reduces as the mission progresses and ENVISAT loses its atmosphere.


Scan mirror performance
Scan mirror performance

  • Average rotation rate = 150.0032ms 0.42ms

    • Determined from average time difference between source packets (OBT resolution 4ms)

  • Current when running ~ 0.35A and is stable

  • Scan mechanism running in as expected, jitter levels have become almost negligible

    (Some scan mirror jitter can be expected during early stages of mission while the lead-bronze lubricant tracks are being established which will improve with time)



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