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DLR Earth Sensing Imaging Spectrometer (DESIS) Status and Calibration Update
DLR Earth Sensing Imaging Spectrometer (DESIS)
Status and Calibration Update
• 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
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)
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
MUSES is located on ExPRESS Logistics Carrier 4(ELC 4) aboard the International Space Station
MUSES Location on the ISS
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.
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
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
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
