Compact High Resolution Imaging Spectrometer (CHRIS) siraelectro-optics

Transcription

1 Compact High Resolution Imaging Spectrometer (CHRIS) Mike Cutter

2 Summary CHRIS Instrument Design Instrument Specification & Performance Operating Modes Calibration Plan Data Processing

3 Instrument Design

4 System Level Architecture Optical Input PROBA PLATFORM Telescope Spectrometer Electronics AOCS Payload Processing Unit Data Handling System Telemetry & Command TM & TC Users Ground Station (Redu) Spectral Sira

5 Functional Block Diagram Telescope Spectrometer IMAGER CCD CCD Drive Electronics Digitisation ELECTRONICS Command Handling Data Formatting Power Conditioning Command Interface Data Interface

6 Optical Design # Patented design, low cost, capable of extension to SWIR

7 FOCAL PLANE ASSEMBLY

8 CHRIS

9 Specification & Performance

10 Specification Image area Spatial sampling interval Spectral range (nominal) Spectral resolution 18.6km x 18.6km (748 x 748 pixels) 25 or 50m 415nm to 1050nm 1.25 to 11nm Spectral registration ± 0.06 pixels Spatial registration ± 0.05 pixels Straylight Gain stage Digitisation 1% total for an extended source 4 levels (albedo 0.5,1,2,4 levels) 12 bits Signal-to-noise ratio 200 (@ target reflectance 0.2, 25m, 10nm)

11 Specification continued Data per (19x19 km 2 ) image 131 Mbits (16.4Mbytes) Number of images per orbit nominally 5 (81.9Mbytes) Power consumption < 10 W primary power Mass < 14 kg Volume 790 x 260 x 200 mm 3

12 MTF (ACROSS-TRACK) nm Across-track MTF - 546nm & columns 60, 380 & MTF Col 60 Col 380 Col Spatial frequency c/mm

13 Responsivity CHRIS Radiometric Calibration (G=3) Digital signal (ADU) for radiance of 1W/m^2/str/nm Wavelength nm

14 Wavelength Calibration WAVELENGTH CALIBRATION WAVELENGTH nm COLUMN NUMBER

15 Spectral Resolution SPECTRAL RESOLUTION AT 446 nm SPECTRAL RESOLUTION AT 546 nm SPECTRAL RESOLUTION AT 910 nm NORMALISED RESPONSE NORMALISED RESPONSE NORMALISED RESPONSE WAVELENGTH nm WAVELENGTH nm WAVELENGTH nm Wavelength FWHM 446 nm nm nm 10.6

16 Operating Modes

17 Multi-view CHRIS Data CHRIS will be able to acquire 5+ near-simultaneous views of any site

18 Platform Constraints Platform Pointing Along-track 0, ± 25º, ±44º pitch ground) Across-track <= +/-30º ground) Pointing Specification Absolute pitch/roll/yaw < +/- 0.1º Control of pitch/roll/yaw < +/ º/s (11% of imaging pitch rate) Maximum pitch rate 0.5º/s Observations baseline Motion compensation (approx. x3) Five images per observation orbit per day

19 Imaging Modes Earth Imaging Full 25m or 50m (nadir equivalent) Image 18.6 x 18.8 km Half 25 or 50m (nadir equivalent) Image 9.3 x 18.8 km Dark Imaging Eclipse observations Flat Fielding In-orbit solar calibration (yaw steer - limited aperture) Observation of ground calibration sites Internal LED source Wavelength calibration Selected ocean scene

20 Maximum number of spectral bands Name Across-track sampling nadir (number of image pixels) Along-track sampling nadir Maximum number of spectral bands per image line Full swath 25x25m 25m (748) 25m Full swath 50x25m 50m (374) 25m Full swath 50x50m 50m (374) 50m Half swath 25x25m 25m (374) 25m Half swath 50x25m 50m (190) 25m Half swath 50x50m 50m (190) 50m NB. One spectral band will be used for smear correction.

21 Calibration Plan

22 In-flight Calibration Flat field (monthly TBD) In-orbit solar calibration (yaw steer - limited aperture) Internal LED source Ground calibration sites DC Offsets (per observation orbit TBD) Dark reference pixels (located at side of CCD image area) Smear pixels (located at ends of CCD image area) Over-scanned pixels Eclipse observations (plus temperature monitoring) Wavelength (monthly TBD) Oxygen absorption 760nm

23 Routine Health Checks Offset & average dark signal levels Dark field non-uniformities Response non-uniformities Temporal noise Absolute spectral response Linearity

24 Data Processing Plans

25 Observational & Data Aspects Ground Station Receive data packets Transmit image & ancillary data Monitor satellite health Archive data PROBA Platform Recieve requests Schedule platform manoeuvres Command CHRIS Store image data Transmit to ground Ground Station Uplink requests Sira Format data Radiometric correction Wavelength correction Data validation Transmit data to users Arcive data sets Sira Collate & check requests Prepare configuration files Review scheduling options Transmit files to Redu User Processing Geo-correction Atmospheric correction Algorithm implementation Validation with ground site data Publication of results User Requests Longitude/Lattitude/Altitude Pointing requirements & limits Number of imaging lines Observation time (day/night) Spectral & spatial configuration Motion compensation level (tbd)

26 Processing Related Sira Validation & preparation of observing requests first level sanity checks of user requests generation of instrument configuration files etc. Level 1a data processing acquire data sets (1-4 weeks after observations) radiometric correction wavelength calibration (tbd) routine instrument health checks Production of data sets for users Supply data sets to users (1 week turn around) Format (tbd)