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M3 Instrument Design and Expected Performance Robert O. Green 12 May 2005

M3 Instrument Design and Expected Performance Robert O. Green 12 May 2005. M3 Science Measurement Requirements. Spectral Range: 400 to 3000 nm at 10 nm sampling Spectral signatures of interest High spectral and spatial uniformity Enables scientific imaging spectroscopy

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M3 Instrument Design and Expected Performance Robert O. Green 12 May 2005

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  1. M3 Instrument Design and Expected PerformanceRobert O. Green12 May 2005

  2. M3 Science Measurement Requirements • Spectral Range: 400 to 3000 nm at 10 nm sampling • Spectral signatures of interest • High spectral and spatial uniformity • Enables scientific imaging spectroscopy • High Precision (Signal-to-noise ratio) • Low concentration components, low illumination areas of the Moon • Spatial swath 40 km with sampling ~70m • Global coverage from planned orbit and data downlink limits • Excellent calibration (spectral, radiometric, spatial) • Enables scientific imaging spectroscopy • High Instrument and Team heritage • Low risk and science success

  3. M3 Instrument Approach • A simple, high uniformity and high throughput “Zakos” Offner imaging spectrometer design • JPL convex three zone blazed e-beam lithographic grating • 640 by 480 element substrate removed HgCdTe detector array and 6604A readout (sensitive from 400 to 3000 nm) • K508 Ricor cryocooler with backup (Clementine, CRISM, etc.) • Deployable calibration panel for solar view radiometric calibration

  4. M3 Optical Configuration 25 degree FOV unobscured F/3.5 TMA Telescope Slit Single spherical mirror JPL e-beam curved grating OS Filter MCT Detector 400 to 3000 nm 20 mm 1) Telescope mirrors aligned to machine tolerance w/ shims 2) Spectrometer components held to machine tolerance w/ shims plus fine rotation only on grating and detector.

  5. M3 Optical Configuration 24 degree FOV unobscured F/3.5 TMA Telescope Single spherical mirror JPL e-beam curved grating Slit OS Filter 640 cross-track MCT Detector 400 to 3000 nm 1) Telescope mirrors aligned to machine tolerance w/ shims 2) Spectrometer components held to machine tolerance w/ shims plus fine rotation only on grating and detector.

  6. The M3 “Zakos” Design Provides a Uniform Imaging Spectrometer Cross Track Sample Depiction -Grids are the detectors -Spots are the IFOV centers -Colors are the wavelengths Spectral Cross-Track <5% Spectral-IFOV-Shift <5% The keys to M3 are: - Design - Manufacture - Alignment - Stability Cross Track Sample Wavelength

  7. Pushbroom Imaging Spectrometer are Not Inherently UniformExample: Cross-Track Spectral Non-Uniformity Cross Track Sample Depiction -Grids are the detectors -Spots are the IFOV centers -Colors are the wavelengths Hyperion 40% non-uniform Wavelength Cross Track Sample Failure by Twist Wavelength Failure by Frown

  8. Pushbroom Imaging Spectrometer are Not Inherently UniformExample: Spectral-IFOV-Shift Spectral-IFOV-Shift creates spectra where different wavelengths arrive from different locations on the ground. Example 80% SIS Depiction Below -Grids are the detectors -Spots are the IFOV centers -Colors are the wavelengths Wavelength Failure by Spectral-IFOV-shift

  9. The M3 “Zakos” Design Provides a Uniform Imaging Spectrometer Cross Track Sample Cross Track Sample M3 is designed with: Spectral Cross-Track <5% Spectral-IFOV-Shift <5% Wavelength

  10. M3 Instrument Selected Component Heritage

  11. M3 JPL Three Zone Convex e-Beam Grating The ability to control the area and blaze of multiple zones allows optimization of throughput and signal-to-noise ratio. These gratings also have very low scattered light.

  12. M3 Technology ReadinessJPL Detector Focal Plane and Drive Electronics* • RSC 6604A FPA @JPL • - Dimension 640 by 480 • - Detector pitch 27 microns • Full well ~650,000 e- JPL 6604A Drive electronics Test 6604A Image *These are currently not flight qualified, but exist and function

  13. Example JPL Offner Spectrometer Assembly Grating location Spectrometer Mirror 1 and 2 Entrance Slit SWIR Detector Array

  14. M3 Instrument CharacteristicsDiagram

  15. M3 Instrument Measurement Characteristics

  16. M3 Instrument CharacteristicsSpectral • Range: 400 to 3000 nm • Sampling: 10 nm across spectral range • Response: <=1.2 of sampling FWHM • Accuracy: Calibrated to 5% of sampling • Precision: Stable within 1% of sampling Note: There are three filter zone boundaries where performance will be degraded. (~750, 1400, 2500 nm)

  17. M3 Instrument CharacteristicsRadiometric • Range: 0 to twice equatorial reference radiance • Sampling: 14 bits measured, 12 reported • Response: Linear to 99.5% (after calibration) • Stability: 5% between calibrator views • Accuracy: 10% absolute radiometric calibration • Precision: SNR > 400 equatorial reference, > 100 polar reference

  18. M3 Proposal Benchmark Reflectance

  19. M3 Proposal Instrument SNR Problem: high signal at 1500 nm drives detector read rate to at least 4 reads per ground sample. This drives power, data handling, mass and risk saturation.

  20. M3 Current Instrument SNR Solution: Adjust the efficiency spectrum of the grating. This is possible with JPL ebeam lithographic grating technology. Less risk of saturation and better SNR margin at 3000 nm.

  21. M3 Instrument CharacteristicsSpatial • Range: 40 km swath (24 degree field-of-view) • Sampling: 70 meters average cross and along track (600 cross-track samples) • Response: FWHM of IFOV @ <1.2 of sampling • Accuracy: 0.1of IFOV

  22. M3 Instrument CharacteristicsSpatial • Surface Projected slit images has 0.313 degrees of curve over +- 12 FOV • Will be calibrated and included in georectification • Less than distortions imposed by topography • Less than distortions from framing camera approach • Basically, this degree of freedom is used to help gain the spectral cross-track and spectra-IFOV-Shift uniformity

  23. M3 Instrument CharacteristicsUniformity • Spectral-Uniformity: < 10% variation of spectral position and FWHM across the field of view • Spectral-IFOV-Shift: < 10% IFOVs variation over the spectral range • Vignetting: Radiometric response within 10% across the field-of-view Wavelength Cross Track Sample

  24. Calibration S/C REFERENCE FRAME Calibration Panel Normal +Y (Velocity) +Z (Anti Sun) Sun Vector (At Calibration) +X (Moon Nadir)

  25. M3 Data Modes and Limitations • Global Mode • Lossless compression sufficient to map the lunar globe in one optical imaging period within data rate constraints • Nominally 2 by 2 spatial and 3 spectral averaging • 335 Orbits • Target Mode (three optical imaging periods) • Full spectral and spatial resolution • Nominally 600 by 600 scene • As many scenes as permitted within available data rate • ~3800 per optical imaging period • The available data rate may be less than assumed in the proposal • A NASA Deep Space Network option is being explored. DSN would help greatly.

  26. M3 Additional Characteristics • Baseline dark signal data will be acquired from the un-illuminated portion of the moon on each imaging orbit. • Cross-track elements 1-10 and 631-640 are masked and used to monitor dark signal levels during the imaging orbit. • Cross-track elements 11-20 and 621-630 are not illuminated by the spectrometer slit and are used to monitor scattered light.

  27. M3 Instrument Science Commands • These are the envisioned basic instrument commands for science data measurement. • Global Mode • Maybe upload averaging table • Target mode • Start collect • Stop collect • Deploy calibration panel • Retract calibration panel • Integrations per ground sample (1,2 or possibly 3) • There will be many other derived commands to allow the instrument to function

  28. The team, approach and capability to achieve these M3 Science Measurement Requirements is in Place • Spectral Range: 400 to 3000 nm at 10 nm sampling • Spectral signatures of interest • High spectral and spatial uniformity • Enables scientific imaging spectroscopy • High Precision (Signal-to-noise ratio) • Low concentration components, low illumination areas of the Moon • Spatial swath 40 km with sampling ~70m • Global coverage from planned orbit and data downlink limits • Excellent calibration (spectral, radiometric, spatial) • Enables scientific imaging spectroscopy • High Instrument and Team heritage • Low risk and science success

  29. M3 Optical Configuration 25 degree FOV unobscured F/3.5 TMA Telescope Single spherical mirror JPL e-beam curved grating Slit OS Filter 640 cross-track MCT Detector 400 to 3000 nm 1) Telescope mirrors aligned to machine tolerance w/ shims 2) Spectrometer components held to machine tolerance w/ shims plus fine rotation only on grating and detector.

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