NineYearsofAtmosphericRemoteSensingwithSCIAMACHY-InstrumentPerformance.ppt

Nine Years of Atmospheric Remote Sensing with SCIAMACHY – Instrument PerformanceGottwald, Krieg, Lichtenberg, Slijkhuis – DLR-IMFNoël, Bramstedt, Bovensmann, von Savigny – IUP, Univ. of BremenSnel, Krijger – SRON

IGARSS2011 > G. Lichtenberg > 28 July 2011

Slide 2

Topics

instrument

operations

instrument status and performance

mission extension


Slide 3

SCIAMACHY on ENVISAT

26 m × 10 m × 5 mSatellite dimensions

8.2 tSatellite mass

10No. of instruments

100.6 minOrbit period

10 a.m. (sun-synchronous)Descending node crossing

800 kmMean altitude

98.5°Inclination

ENVISAT nominal mission profile


Slide 4

Instrument – Optical Assembly

Level 1:

channels 1 & 2 (UV)

entrance optics

calibration unit

pre-disperser prism

Level 2:

channels 3 & 4 (VIS)

channel 5 (NIR)

channels 6-8 (SWIR)


Slide 5

Viewing Geometries

scientific

nadir

limb

sun occultation

moon occultation

calibration & monitoring

sun occultation

moon occultation

subsolar

internal calibration lamps (WLS, SLS)


Slide 6

Instrument – Thermal SubsystemsOptical Bench Module (OBM)

cooled via RAD AT = -17.6°C to -18.2°Cactive thermal control (ATC)

detectorscooled 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

decontaminationSRC cooling capacity may degrade because of contaminationdecontamination heaters to raise T on reflecting surface (if needed) decontamination brings T of OBM and detectors close to 0°C

→ contaminants are removed


Slide 7

Operationsinstrument operations are

continuous

highly autonomous

implemented in states and timelines

organised in mission scenarios

limb/nadir on dayside

sun occultation each orbit

sub-solar every 3rd day

moon occultation whenever possible

dedicated eclipse measurements

calibration&monitoring measurements on daily, weekly and monthly timescales


Slide 8

instrument operation related information available via

http://atmos.caf.dlr.de/projects/scops/

launch March 1, 2002

end

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ase

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Instrument Status - Availability


Slide 9

Thermal Systems: ATC and OBM Temperature

only small orbital variation of TOBM

very stable orbital mean TOBM

ATC degradation compensated by heater power adjustment


Slide 10

Thermal Systems: TC and Detector Temperaturestemperature control via TC heaters

TC system degrades

detectors 1-6: 0.1-0.3 K / year

detectors 7 & 8: approx. 1 K

ice layer effect


Slide 11

Life Limited Items

mechanical items (neutral density filter, aperture stop, nadir calibration window) and thermal item (cryogenic heatpipe) have assigned in-flight activation budgets

electrical items (WLS, SLS) have assigned in-flight switching budgets

operations concept goal is not to exceed LLI limits


Slide 12

Optics - Throughput optical throughput channels 1-6

reduction of 3-4% per year in UV

very stable in VIS, NIR & SWIR

solar eclipse


Slide 13

channels 6+, 7, 8:

6% pixel loss / year about 10-15% ‘good’ pixels by end 2013

in 7 & 8: throughput loss 1-2% / year due to ice layer (decontaminations are still an option to remove ice)

Detectors - Degradation

channel 2: detector material degradation (2% sensitivity loss / year) 25% loss by end 2013


Slide 14

Limb Tangent Height

pointing knowledge essential for geolocation retrieval, particularly limb tangent heights

continuos improvement over the mission lifetime: current limb tangent height accuracy about 0.002-0.003° = 120-150 m


Slide 15

mission in nominal ENVISAT orbit ended 22 October 2010

Mission Extension 2010-2013

since then modified drifting orbit

no inclination manoeuvres

altitude lowered by 17 km

instrument configuration successfully adapted to new orbit

SCIAMACHY continues to deliver high quality data


Slide 16

SCIAMACHY – Exploring the Changing Earth’s Atmosphere

SCIAMACHY – The Need for Atmospheric Research from Space

ENVISAT – SCIAMACHY’s Host

The Instrument

Instrument Operations

Calibration and Monitoring

SCIAMACHY In-Orbit Operations and Performance

From Radiation Fields to Atmospheric Concentrations – Retrieval of Geophysical Parameters

Data Processing and Products

Validation

SCIAMACHY’s View of the Changing Earth’s Environment

NineYearsofAtmosphericRemoteSensingwithSCIAMACHY-InstrumentPerformance.ppt

Technology