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SCIAMACHY: Instrument Operations and Performance Status

This article provides an overview of the operations and performance of the SCIAMACHY instrument in its first 4 years in orbit. It covers the instrument's optical assembly, thermal subsystems, operational details, and performance status. The article also discusses the availability, thermal configuration, and life limited items of the instrument, as well as the possibility of a mission extension.

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SCIAMACHY: Instrument Operations and Performance Status

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  1. SCIAMACHY 4 Years in Orbit – Instrument Operations and Performance StatusM. Gottwald, E. Krieg / DLR-IMFS. Noël, H. Bovensmann, M. Wuttke / IUP-IFE

  2. Agenda • instrument • optical assembly • thermal subsystems • operations • instrument status • availability • thermal configuration • performance • Life Limited Items • mission extension

  3. Instrument – Optical Assembly Level 2: • channels 3 & 4 (VIS) • channel 5 (NIR) • channels 6-8 (SWIR) Level 1: • channels 1 & 2 (UV) • entrance optics • calibration unit • pre-disperser prism

  4. Instrument – Thermal Subsystems • Optical Bench Module (OBM) • cooled via RAD A • T = -17.6°C to -18.2°C • active thermal control (ATC) • detectors • cooled via SCIAMACHY Radiant Cooler (SRC) • T  195 K – 230 K (channels 1-6) • T  140 K – 160 K (channels 7 & 8) • open loop heater control (TC) • detectors • decontamination • SRC cooling capacity may degrade because of contamination • decontamination heaters to raise T on reflecting surface (if needed) • decontamination brings T of OBM and detectors close to 0°C  contaminants are removed

  5. Operations • instrument operations are • continuous • highly autonomous • implemented in states and timelines • organised in mission scenarios • mission planning implements high duty cycle • limb/nadir on dayside • sun occultation each orbit • sub-solar each day • moon occultation whenever possible • dedicated eclipse measurements • calibration&monitoring measurements on daily, weekly and monthly timescales

  6. Instrument Status - Availability • instrument operation related information available via http://atmos.caf.dlr.de/projects/scops/ • instrument availability status • duty cycle > 95% • unavailabilities: • platform anomalies • instrument anomalies: CCA MCMD Check error, Single Event Upsets (SEU) • planned: orbit control manoeuvres (OCM), S/W updates

  7. Instrument Status – Thermal Configuration • Optical Bench Module • very stable average T/orbit = -17.9°C • seasonal variations in power consumption of ATC heaters  adjustment required in about 2007

  8. Instrument Status – Thermal Configuration • channels 1-6 • maintained in temperature limits via trim heater adjustments • seasonal variation • no obvious degradation

  9. Instrument Status – Thermal Configuration • channels 7 & 8 • thermal status mainly determined by ice layer • decontamination lowers T, then rising T during built-up of layer • decontamination 2004/2005 yielded stable thermal conditions

  10. Instrument Status - Performance • ice on channels 7 & 8 • reduces throughput • modified decontamination procedure to raise T to maximum values • 'second cold trap' hypothesis to explain 2004/2005 decontamination

  11. Instrument Status - Performance • optical throughput channels 1-6 • reduction of 3-4% per year in UV (trend is increasing) • very stable in VIS, NIR & SWIR • details see presentation by Noël et al. at this conference

  12. Instrument Status - Performance Limb tangent height offset • further – selected – performance issues • limb tangent height • spatial stray light • light leak in channel 7 • Bad and Dead pixels in channels 7 & 8 issues require further analysis to improve data analysis

  13. Instrument Status – Life Limited Items • mechanical items (aperture stop, neutral density filter, nadir calibration window), calibration lamps (SLS, WLS) and cryogenic heatpipes have life limitations  LLIs • operations must not exceed specified in-flight budgets • present mission scenarios ensure in-flight budgets for a 5 years lifetime

  14. Mission Extension • SCIAMACHY's performance fully supports a mission extension until 2010 and beyond • non-conformances are under investigation or corrective countermeasures have been implemented • adjustment of mission scenarios is required to handle LLI in-flight budgets

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