PSR Section 7

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Section 7 Atmospheric Corrector
. . . Dennis Reuter EO-1 LEISA Atmospheric
Corrector
2
LEISA Atmospheric Corrector (LAC) Contribution to
EO-1

• Validation of Wedged Filter Approach for
  Spacecraft Instrumentation
• Atmospheric correction for ALI Multispectral
  images
• Atmospheric correction for Landsat-7 images
  (Formation Flying)
• Direct study of Spatial Resolution Degradation
  (cross-comparison with Hyperion)
• Retrieved atmospheric parameters
• Cross-comparison with MODIS

3
LAC BLOCK DIAGRAM
28 V
Lenses
power
Power Conversion
digital
RS 422
Digital Buffers and
Formatting
SPACECRAFT
bias
1773
1773 Interface, Array
Control and TEC Control
clock
TEC
ELECTRONICS
l
MODULE
3 Wedged Filter/ Array Assemblies
OPTICS MODULE
4
LAC Characteristics

• High Spectral - Moderate Spatial Resolution
  Hyperspectral Imager using Wedged Filter
  Technology (LVE).
• Spectral Coverage 0.9 - 1.6 mm 256 Bands
  Selected for optimal correction of High Spatial
  Resolution Images.
• Spectral Resolution 35 cm-1 (Dl 3 nm _at_ 0.9 mm,
  9 nm _at_ 1.6 mm)
• Swath Width 185 km Matches Landsat.
• Spatial Resolution (pixel) 356 mradian (250
  meter _at_ 705 Km).
• Three 256 x 256 Element InGaAs Arrays TEC
  Stabilized (lt285 K).
• Three 15 Degree FOV 3 Element Lenses.
• Two Modules Bolt-onOptics Module and
  Electronics Module.
• Mass 10.5 kg (EM, 4.4 kg OM 3.9 kg Cable 2.2
  kg).
• Power 48 W (Peak) lt15 W (Orbital Average).

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Performance Testing

• Box Level
• Cards Simulated on an Individual Basis
• TECs Tested with Engineering Backplane (Focal
  Plane)
• Focal Plane Timing Tested with Multiplexers
• Subsystem Level
• OM Limited Set of Images Obtained with EM
  Simulator
• Engineering Model Vibration Tested
• EM Operation Tested by Interface to OM Simulator
• Instrument Level
• Vibration and Thermal-Vacuum
• Radiometric, Spectral Calibration and Alignment
• EMI/EMC

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LAC Test Descriptions

• Vibration
• Individual modules tested to proto-flight level
  (1.25 x expected maximum flight loads)
• Instrument mounted on Spacecraft and tested to
  flight level
• Thermal Vacuum (Pre-Spacecraft Integration)
• Four cycles to survival levels (-10C to 50C
  Range expected on orbit 20C? 10C)
• Operation from 0C to 30C (Orbital Predict
  20C, 30C worst case)
• Images Obtained Using LAC GSE
• Thermal Vacuum (Integrated with Spacecraft)
• Four Cycles
• Operation from 0 C to 30 C (No Operation at 40
  C)
• Images Using Spacecraft System (WARP, XBPAA,
  etc.)

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LAC Test Descriptions

• EMI/EMC
• Instrument Level Tests Conducted and Radiated
  Emissions, and Radiated Susceptibility
• Alignment
• Orientation of Arrays with respect to Alignment
  Cube using Theodolites
• LAC Alignment to ALI on Spacecraft Using
  Theodolites
• Optical Calibration
• Wavelength and Instrumental Shape Grating
  Monochrometer 1 to 100 nm Steps
• Radiometric Calibrated Black-body (all 4 TEC
  Settings)
• Flat Field Diffuse Source Illuminating Lenses
  and Solar Calibrators

8
LAC Test Results / Actions

• Vibration (Proto-flight, Module Level)
• OM Arrays contacted by LVE some damage to
  arrays and LVEs wire bonds broken on one array
• Incorrect assembly of LVE mount
• Wire bonds repaired on array
• One LVE replaced with flight spare
• LVE mount re-assembled correctly
• Module re-vibrated with no damage
• EM 1773 Fiber Alignment Cylinder Cracked
• Failure mode observed in other 1773 interface
  applications
• Cylinder replaced
• Module re-tested with no damage
• Vibration (Satellite, Instrument Level) No
  damage

9
LAC Test Results /Actions

• EMI/EMC
• Excessive radiated / conducted Emissions (20 - 30
  dB in some places)
• Interpoint Power Supply filtering
• Additional Filter Assembly mounted on EM
• Filter reduces excess emissions to at most 5 dB -
  waiver granted
• Components destroyed during conducted
  Susceptibility Test
• Incorrect test conditions
• Components replaced
• Test was not repeated - waiver granted

10
LAC Test Results /Actions

• Thermal Vacuum (before Spacecraft integration)
• Instrument operated for approximately 10 hours
• Mount temperatures lt 25 C, continuous operation
  for 1 hour
• Mount temperature 30 C, Digital Board overheated
  in 40 minutes
• No modification Maximum operating time in-flight
  20 minutes
• Thermal Vacuum (Spacecraft)
• Instrument operated for approximately 20 hours
• Dark current consistent with previous results
• Mount 40 C Power Board reached Red-Limit temp
  in lt 5 minutes
• Power board Red-Limit set for mount temperature
  at lt 30 C Models indicate Red-Limit can be
  increased 20 C
• Excellent TEC control

11
LAC Test Results /Actions

• Optical Calibration
• Radiometric
• Initial results consistent with models
• Offset error limits dynamic range to 11 bits.
  Difficult to differentiate High Albedo from
  Specular Reflection
• Unexpected temperature dependence of Quantum
  Efficiency
• Spectral
• Filters have excellent spectral characteristics
• Alignment Within 2 arc-min of ALI Track --
  achieved 1
• Flat Field Solar Calibrators consistent with
  Diffuse Illumination

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Modifications

• Software
• Red-Limits on currents eliminated
• TEC set-points lowered to reflect improved
  thermal results on Spacecraft
• Hardware
• No additional hardware modifications required
• NO SIGNIFICANT OPEN ISSUES INSTRUMENT HAS RUN
  SEVERAL HUNDRED HOURS 50 TROUBLE-FREE
• REQUIRED ORBITAL OPERATION 50 HOURS

13
Waivers and NCRs

• 5 waivers
• 3 EMI / EMC
• Parts tracability
• Degraded performance of TEC 3 during instrument
  T/V
• Not apparent in Spacecraft T/V tests
• 9 NCRs
• Waivers and NCRs available in GSFC system