dlr earth sensing imaging spectrometer (desis) · the desis optical on-ground calibration and...
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DLR Earth Sensing Imaging Spectrometer (DESIS)
Status and Calibration Update
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• Coverage of ~90% of populated Earth
• Coverage of ~100% of ocean shipping lanes and major navigational ports
• Coverage of 100% of tropics and equatorial region
• Sophisticated spacecraft bus with required resources
• Upgrade and exchange of instruments as technology and/or markets evolve
• Traditional barriers to entry minimized
Earth Observation From the ISS – Why It Works
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Remote Sensing Platform
Designed, built, owned & operated
by Teledyne
Facility Class Payload on ISS
• Up to 4 attached instruments
• Installed and removed robotically
Launched on June 3, 2017
• Full Operational Capability
Multi-User System for Earth Sensing (MUSES)
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MUSES Platform Capabilities
Characteristic MUSES Performance Target
Field of Regard
Outboard Cross-Track: 5°
Inboard Cross-Track: 45°
Along-Track: +/- 25°
Thermal Control Passive
Star Tracker Sodern SED26
Inertial Measurement
Unit
Honeywell Miniature Inertial Measurement Unit
(MIMU)
Precision TimeSourced from the ISS GPS,
≤ ± 250 μsec to MUSES instruments
Pointing Accuracy ≤ ± 60 arc seconds
Pointing Knowledge≤ ± 30 arc seconds
(~ 60 m on ground from 400 km altitude)
Location knowledge Sourced from the ISS GPS, ± 50 meters, RMS
Orbit 51.6° Inclination, 400 km altitude ± 5% (nominal)
Data ProcessingLinux Server on-board ISS with redundant 6 TB
storage
Daily Downlink Capacity 225 GB
Miniature Inertial
Measurement Unit
External Wireless
Adapter
Power Control Unit
Star Tracker
MUSES Client
Computer
Inner Gimbal /
Pointing Platform
Electronic Control
Unit
Outer Gimbal
Ethernet Wireless
Controller
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MUSES is located on ExPRESS Logistics Carrier 4(ELC 4) aboard the International Space Station
MUSES Location on the ISS
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Payload Options
Secondary Payload Accommodations (2)
Maximum Mass: 50 kg
Maximum Height: 35”(92 cm)
Maximum Width: ~10” (~25 cm) dia Core
Maximum Power: 112W @ 28 Vdc
Primary Payload Accommodations (2)
Maximum Mass: 100 kg
Maximum Height: 35“(92 cm)
Maximum Width: ~18” (~46 cm) dia Core
Maximum Power: 224W @ 28 Vdc
Ride-Share Accommodations
Size / Mass: 6U-27U
Multiple payloads in a single canister enable a cost-
effective alternative to Cube-Sat free flyers.
Imaging and space qualification options with payload
return.
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DESIS-30: MUSES First Payload
• Teledyne and DLR partnered to build and operate the DESIS-30 instrument from the MUSES Platform on the ISS.
• Teledyne has commercial rights to imagery while DLR retains rights for scientific use.
• Launched on June 29, 2018.
• Installed on August 27, 2018.
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Instrument Specification
Characteristic DESIS Features
F# / Focal Length 2.8 / 320 mm, telecentric
FOV / IFOV 4.1° / 0.004°
Ground Sampling Distance 30 m @ 400 km altitude
Ground Swath 30 km @ 400 km altitude
Spectral Range 400 nm – 1000 nm
Spectral SamplingMeasured: 235 @ 2.55 nm
Programmable binning factor (1 to 4)
Quantization 13 bits + 1 gain bit
Spatial Pixels 1024
Radiometric Linearity 95% (10% - 90% FWC)
MTF @ Nyquist (no smearing) > 20%
FWHM < 3 nm
On-board CalibrationDark Field for DSNU
LED Array for PRNU
Independent Pointing Pointing Unit, ±15° Along Track
Independent Time and Position On-board GPS Figures courtesy of DLR.
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First Images
Image courtesy of DLR.
• Processed successfully to level 1C (georeferenced and resampled to UTM grid
using bilinear interpolation).
• Accuracy (linear in each principal direction –
north east was below one pixel size w.r.t.
Landsat ETM+ panchromatic worldwide
reference).
• The image is composed by the bands at 463
nm, 553 nm und 639 nm wavelength
mapped to BGR.
• Full Width Half Maximum (FWHM) of ~ 3.5 nm
for all bands.
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DLR responsibility▪ Prelaunch calibration
▪ Initial instrument on-orbit checkout
▪ Calibration throughout system life
Onboard calibration
Vicarious calibration
TBE responsibility▪ Image quality validation
Automated tools and methods
▪ Support DLR calibration
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SpaceX CRS-15 Launch June 29, 2018
DESIS/MUSES Integration August 27, 2018
First Image w/in 48 hrs.
On-Orbit Checkout Aug-Sept 2018 Timeframe
On-Orbit Cal/Val Initiated Sept 2018
Early Data Available TBD as early as Oct 2018
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Summary of Activities:
▪ Integration of detector and optics (Alignment)
▪ Measurement of spatial and spectral mapping (interior geometry) MTF
FWHM
▪ Measurement of Smile/Keystone
▪ Absolute radiometric calibration
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Test equipment: gimbal with collimator, monochromator and integration sphere
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The DESIS optical on-ground Calibration and Verification was performed in DLR’s calibration lab for two DESIS configuration levels:
▪ Sub-system: optics + sensor assembly + EGSE stand-alone on gimbal
▪ Full system: full instrument at container level (with CAL and POI unit)
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DESIS optics + sensor assembly level mounted on gimbal facing the collimator illuminated by monochromatic light from monochromator
DESIS optics + sensor assembly level mounted on gimbal and facing the absolute calibrated integrating sphere
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Focusing and focus fixation Optics Wavefront Spectral mapping of center wavelengths and FWHM per pixel Spectral calibration using pen-ray lamps Flat-fielding and absolute calibration in spectral radiance Dark signal, linearity and saturation, hot pixels Photon Transfer Curve PTC Geometric calibration System /detector spatial MTF in spatial and in spectral direction Spectral calibration of the LED‘s of CAL unit Spectral calibration of CAL unit – in-flight spectral calibration procedure Radiometric calibration of CAL unit – in-flight radiometric calibration procedure POI unit performance, POI axis vs. Slit Polarization Focus, CAL unit vs. temperature @ TV test
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Covering full spectral range of DESIS (400 nm –1000 nm) with 9 different types of LEDs
IMOS lenses are used for collimating the light to a cone of ± 16°
Temperature stabilized
Calibration Unit used for PRNU cross-calibration and DSNU calibration
Total Dose Test (30 MeV) shows high stability of peak and dominant wavelength and spectralbandwidth
Most LEDs showed a 1% increase in intensity, but two LED types showed a decrease by 4%; this effect can be used to compensate LED degradation during in-flight
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Changes sight ±15° in the along-track direction
Earth Sensing Mode
▪ 11 measurement positions ±15° (every 3°)
▪ Repeatability / accuracy 0.004° (14 arc seconds)
▪ Target replacement time ≤ 0.5 seconds
BRDF Mode
▪ Collection of up 5 image tiles at different angles(30 km x 30 km tiles at nadir)
▪ Used for BRDF & altitude extraction
Forward Motion Compensation Mode (experimental)
▪ Used to increase SNR for specific targets
▪ Programmable speed between0.6 °/sec and 1.5 °/sec
▪ Accuracy better than 0.001° (1/4 pixel)
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A list of potential land acquisition targets for the DESIS sensor in support of:▪ Calibration (radiometric, spatial, geometric)
▪ Atmospheric Correction
▪ Validation
▪ Underflights and Coincident Satellites
Over 100 land target sites have been identified for inclusion
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Potential land targets selected for the collection deck are typically used by various groups, and may be instrumented▪ CEOS LandNet Sites
▪ CEOS Pseudoinvariant Calibration Site
▪ RadCalNet
▪ AERONET Sites
▪ NEON-Core Terrestrial Sites
▪ Ameriflux (DOE) and other flux networks
▪ LTER (Long Term Ecological Research)
▪ ARM (Atmospheric Radiation Measurement)
▪ NEON AOP (Airborne Observation Platform)
▪ DLR Calibration Sites
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A list of potential water acquisition targets for the DESIS sensor in support of:▪ Radiometric Calibration
▪ Validation
▪ Coincident Satellites
40 water target sites have been identified for inclusion
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Potential water targets selected for the collection deck are typically used by various groups, and may be instrumented
▪ MOBY (Marine Optical Buoy)
▪ BOUSSOLE (Buoy for the acquisition of long-term optical series)
▪ Pseudoinvariant Water Sites
▪ AERONET Ocean Color Sites
▪ NEON-Core Aquatic Sites
▪ LTER (Long Term Ecological Research)
▪ Research Cruises
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Information is being collected for each potential target site▪ Location and size
▪ Acquisition requirement (cloud fraction, solar angle)
▪ Time of operation or Season
▪ Instrumentation
▪ Additional Users
Users in the land and water calibration/ validation communities are being asked to review and refine the calibration sites▪ Providing additional information and prioritizing targets