The Concept and preparation of MSCMultiSpectral Camera System Calibration Operation

1
The Concept and preparation of MSC(Multi-Spectral
Camera) System Calibration Operation

• Sang-Soon Yong, Seung-Hoon Lee, Sang-Ryool Lee,
• Sung-Woong Ra, Asaf Guberman, Michael Berger
• Korea Aerospace Research
  Institute, Korea
• Chungnam National Univ., Korea
• ELOP, Israel

2
THE DESCRIPTION OF KOMPSAT-2

• The mission objective of KOMPSAT-2
• Continuing the satellite earth observation after
  KOMPSAT-1 with improved capability
• Providing information for surveillance of large
  scale disasters and its countermeasure,
• Acquisition of high resolution images for GIS
  (Geographic Information Systems)
• Composition of printed maps and digitized maps
  for the territories
• Balanced development of Korean territories, and
  survey of natural resources.

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THE DESCRIPTION OF MSC

• The description of main Payload(MSC) on KOMPSAT-2
• Imaging channel PAN Chromatic (1m) and four(4)
  Multi-Spectral channels (4m)
• Swath width Data downlink rate 15km(_at_685Km)
  320Mbps through X band
• Duty Cycle Lifetime 20 of orbit period 3
  years
• Performance

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MSC CONFIGURATION AND ELECTRICAL INTERFACE

• MSC Configuration

• Electrical Interface
• - External Interface with S/C
• Power interface
• Analog and digital command/telemetry, such as
  1553B discrete commands
• - Internal Interface
• Digital command/telemetry, high level pulse
  command, and analog telemetry interface
• Image data interface.

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THE OPERATION CONCEPT PARAMETER
? Push bloom imaging by TDI detector ?
Automatic normal operation ? Compatibility of
spacecraft tilting (Roll axis 56 deg.,
Pitch axis30 deg.) ? Operation parameter -
Line rate and gain offset - Number of sector
for recording - Compression ratio, Huffman
quantization table - Encryption key and so on.
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MSC MISSION AND OPERATION PREPARATION NORMAL
OPERATION

• Defined MSC Mission
• DCSU Initialization
  Antenna deployment
• Direct Imaging
  Recorded Imaging
• Record Playback Imaging
  Playback
• OBC Data Recording
  Calibration
• Service
• Each mission will be automatically operated by
  the mission script ordered by planed and stored,
  or real-time mission commands.
• Each mission will be initiated by the commanded
  start-time.
• The sequence of immediate commands in each
  mission scripts will be executed in defined
  delta-time.
• Time of mission start shall be an absolute time
  based upon On Board Time (OBT) and no
  simultaneous mission execution is allowed.

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MSC CALIBRATION MISSIONS

• The objectives of calibration
• a) Produce a data set of value
• - to long-term monitoring programs
• - to allow intercomparison of data on
  time scales exceeding that of an individual
  satellite
• b) Provide data synergism
• c) Allow data exchange between spacecraft
  instruments
• MSC three(3) calibration missions
• - Radiometric calibration
• - NUC(Non Uniformity Correction) calibration
• - Focus calibration
• General condition and preparation of the
  calibration operation
• - No compression, no encryption and specific
  site or location and so on
• - Adequate spacecraft control according to
  MSC calibration

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MSC CALIBRATION MISSIONSRADIOMETRIC
CALIBRATION(1/2)

• The purpose
• - To gather response of the Electro-Optical
  detectors illuminated by OBRC(On-Board Radiometic
  Calibration) source
• The condition of operation
• - During total darkness, over an unpopulated
  area with no illumination source on the ground,
  like Ocean area.
• - no compression, nominal line-rate, no
  encryption and recording mission
• Summarized timeline

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MSC CALIBRATION MISSIONSRADIOMETRIC
CALIBRATION(2/2)

• Prepared sequence and results interpretation
• v On Ground (For all PAN channels (PRM and
  RED) and all MS bands)
• 1) Recorded images under OBRC Source ON
• 2) Subtracted to recorded images under OBRC
  source off
• 3) Compute average value of the gray level
  for each pixel in each Image channel
• 4) If the global averages have changed, the
  individual pixel values should be corrected by a
  factor equal to the change for each specific
  detector output.
• ? No change of lamp intensity if the
  difference between the global averages for
  pre-launch and the current mission are less
  than 3,
• v In orbit
• - Repeat above sequence 1) to 3)
• - Correct the individual pixel values If
  the global averages have changed
• v If a significant global average change has
  been detected, the best course is to perform
  vicarious calibration
• ? Taking imagery of known and controlled
  areas, or areas where on-ground measurements can
  be made simultaneously with the satellite
  imaging)
• ? If these results do not indicate a
  significant change in detector sensitivities,
• MSC optics parameters unchanged
• while the lamp output changed
  (degraded).

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MSC CALIBRATION MISSIONSNUC(Non-Uniformity
Correction) CALIBRATION(1/2)

• The purpose
• - To gather data regarding the correction of
  Non-Uniformity as done in the NUC module
• The condition of operation
• - Linear correction by two(2) uniform
  appearance points, like polar ice field as
  bright region and night sky or ocean at night for
  five(5) TDI level
• - No NUC, no compression, lower line-rate, no
  encryption and recording mission
• Summarized timeline

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MSC CALIBRATION MISSIONSNUC(Non-Uniformity
Correction) CALIBRATION(2/2)

• Regular NUC Table generation method and
  procedure
• 1) Illuminate all pixels by uniform illumination
  .
• 2) Collect pixel data Li for 25 of
  saturation illumination.
• 3) Collect pixel data Hi for 75 of
  saturation illumination.
• 4) Generate NUC table for all PAN and MS channel
  with each TDI level using NUC Table Generation
  Algorithm
• 5) Update on board NUC table
• Passive NUC updating method and procedure
• - The method is based on collecting data from
  a large number of uncorrelated images in order to
  use the same statistical distribution of large
  number of lines
• (At least 20 images of different locations
  are necessary for desired accuracy)
• - For such a set, two data vectors have to be
  collected.
• The first is the sum (for each pixel) of
  the pixel values over all lines of all images.
• The second is the sum (for each pixel) of
  the pixel values squared over all lines of all
  images
• The collected (sum) vectors are first
  normalized.
• The averages, the variances and the goal
  variance are calculated and the corrections to
  the gains and to the offsets are derived.

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MSC CALIBRATION MISSIONSFOCUS CALIBRATION(1/4)

• The purpose
• - To correct effects of stress relief,
  gravitational relief, moisture release, thermal
  expansion by the best focus position
• The condition of operation
• - Three times imaging on known target with
  different PAN focus or MS focus setting
• - No compression, no encryption and recording
  mission
• ? The characteristics of focus mechanism
• Motor step velocity is 100 steps/sec
  where 1mm 7000 steps.
• The recommended motion shall be 50? (350
  steps) in each direction. It requires about
  3.5 seconds

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MSC CALIBRATION MISSIONSPAN CHANNEL FOCUS
CALIBRATION(2/4)

• Summarized timeline

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MSC CALIBRATION MISSIONSMS CHANNEL FOCUS
CALIBRATION(3/4)

• Summarized timeline

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MSC CALIBRATION MISSIONSPAN MS FOCUS
CALIBRATION(4/4)

• The Focusing Calibration Procedure
• - Based on obtaining 3 images of the same
  scene (or equivalent scenes) with different
  focus positions
• - The recommended focus step size was
  determined during EOS AIT to be 50 micron
  (350 steps) in each direction (execution time
  approximately 3.5 sec)
• ? The images may be taken either on
  consecutive passes over the same scene while
  taking angular viewing effects into account, or
  on successive same-viewing- angle passes over
  the same scene.
• - The images shall be processed by a function,
  which determines their HSF(High Spatial
  Frequency) content and the resultant values are
  stored. If angular effects need to be corrected,
  the correction should be done at this point.
• - The HSF content values for the different
  focus positions are next fitted to a parabolic
  function and its maximum is found.
• ? The position of the maximum is the optimal
  focus position.

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THE PREPARATION OF MSC CALIBRATION OPERATION

• MSC calibration activities are planned as parts
  of K2 LEOP (Launch and Early Operation Period).
• - 1st phase IAC (Initial Activation
  Checkout)
• - 2nd phase Calibration Validation I
• - 3rd phase Calibration Validation II
• The procedure and method for calibration are
  checked and evaluated by demonstrated data which
  have similar characteristics with KOMPSAT-2.
• - The procedure for radiometric calibration
  and NUC calibration
• The measurement of linearity and
  uniformity with OBRC source and several
  radiance levels.
• - The procedure for focus calibration
• The MTF measured and analyzed by edge
  method will be used for the comparison of
  different focuses
• ? See The results of advance
  preparation with demonstrated data

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THE EXAMPLE OF ADVANCE PREPARATION FOR
CALIBRATION PROCEDURE

• The results of advance preparation with
  demonstrated data

Analyzed results
Captured Image data
Processing Analysis
Focus B
Focus C
Focus A
To be conducted with MSC data
Comparison
Final Decision for Focus Calibration
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Conclusion

• The MSC is designed to comply with the mission
  objectives of KOMPSAT-2 as a main payload.
• The configuration and function of MSC hardware
  including electrical interface and the operation
  concept are designed to satisfy the requirements.
• The MSC three calibration operation, radiometric,
  NUC and focus calibration are considered for good
  quality data and each calibration operation are
  designed based on proper parameter condition
  time sequence and so on.
• The method and procedure of calibration
  operations and expected results are checked and
  evaluated with demonstrated data as parts of
  advance preparation.
• The procedure and detailed method of MSC
  calibrations will be updated and completed with
  more practices, such as rehearsal and field
  campaign with demonstrated data as advance
  preparation.

Finally, good quality Image data will be assured
through MSC Calibration Operation