Data Set Information
DATA_SET_NAME HAYABUSA LIDAR V2.0
DATA_SET_ID HAY-A-LIDAR-3-HAYLIDAR-V2.0
NSSDC_DATA_SET_ID NULL
DATA_SET_TERSE_DESCRIPTION Hayabusa LIDAR raw and calibrated data for all mission phases.
DATA_SET_DESCRIPTION
Data Set Overview
  =================
 
    The HAYABUSA spacecraft included a LIght Detection and Ranging (LIDAR)
  altimeter.The primary objective of LIDAR was to establish the range between
  the HAYABUSA spacecraft and the asteroid Itokawa for navigation purposes
  during the surveying and collection phases of the mission. It provided
  excellent estimates of the location of the spacecraft relative to the
  asteroid.
 
    The secondary scientific objective of the LIDAR included determining the
  mass of the asteroid, and measuring its global surface elevation and
  roughness.
 
    The Calibrated Data Record (CDR) contains LIDAR science and telemetry data
  that have been converted to engineering and physical units. The Experiment
  Data Record (EDR) is the source for the science data, while the House
  Keeping Experiment Data Record (HKEDR) and telemetry provide the data needed
  to determine the position of the HAYABUSA spacecraft relative to the
  asteroid. Resulting orbit, geometric, and calibration data have been
  incorporated, to determine the location of the LIDAR boresight on the
  surface of the asteroid provided in the CDR. With an appropriate shape model
  and density estimates for Itokawa, these can be used to obtain topographic
  profiles of the surface, e.g. [CHENGETAL2002] of Itokawa.
 
    The confirmed time resolution of the HAYABUSA lidar equals aproximately
  1.67ns which is equivalent to 0.5m in range. This values was derived from
  the data obtained over the very flat and smooth Muses-C Regio.  See
  [BARNOUIN-JHAETAL2008]. For further information about the Hayabusa LIDAR and
  its data set may be found in [MUKAIETAL2006] and [BARNOUIN-JHAETAL2008].
 
 
      Data
      ====
 
    All the HAYABUSA LIDAR data records are ascii tables. Each EDR contains
  three columns of data. The first column is the the Mission Elapsed Time in
  units of spacecraft ticks when the LIDAR range was measured. One spacecraft
  tick equals 1/32 of a second. The second column is equal to this same time
  but translated into units of Universal Coordinated Time UTC. The third
  column equals the range measured by the LIDAR at the time indicated. The
  LIDAR collected data at 1 Hz (1 return per second) for the entire duration
  of the encounter with Itokawa (~3 months).
 
    The EDR is composed of three files: EDR20050911_20050929.TAB which
  corresponds to data acquired during the GATE Position Phase when the
  HAYABUSA spacecraft was at ~20km distance from the surface of the asteroid;
  EDR20050930_20051028.TAB which corresponds to data acquired during the HOME
  Position Phase when the HAYABUSA spacecraft was at 3-7km distance from the
  surface of the asteroid; EDR20051029_20051125.TAB which corresponds to the
  TOUCH DOWN phase when the HAYABUSA spacecraft attempted to sample the
  surface of Itokawa.
 
    The housekeeping (HKEDR) file has not been included in the archive because
  the mission has not yet given permission for it to be archived in PDS.  When
  permission is given to archive it, it will be added.  The first three
  columns of this HKEDR are identical to those in the EDR file. The next two
  columns provide the illuminated centroid of Itokawa within the reference
  frame of the wide angle camera, ONC-W1. This camera is part of the AMICA
  instrument package and more information is given in the description for that
  instrument. In brief, it is a 512 by 512 pixel imager with a field of view
  of 60 degrees.
 
    The software aboard the HAYABUSA spacecraft imager found the centroid of
  the largest illuminated object in the field of view of this ONC-W1, with DN
  values greater than a threshold of 5DN. This happened at 2 min intervals,
  and was accompanied by a LIDAR range and time listed in the first three
  columns of the HKEDR file already discussed. The first of the two pixel
  values gives the x or sample location of the centroid. The second one gives
  the y or line location of the centroid. The one HKEDR file includes data for
  the entire mission.  A pixel value for x and y of zero implies the asteroid
  filled the entire field of view of the ONC-W1.
 
 
    The CDR data files are of three kinds. The first is an unfiltered (UF)
  version of the data after the processing described in the next section was
  undertaken. The second is composed of the same set but was filtered (F) to
  remove any estimated surface point which was located more that 10m from the
  predicted intersection of the vector defining the pointing of the LIDAR
  boresight and the shape model of the asteroid. The third is an optimized
  (OPT) version that is built on the filtered data. The filenames include F,
  UF and OPT respectively.  The CDR files include information on both the
  HAYABUSA LIDAR and the boresight of the Near Infra-Red Spectrometer aboard
  HAYABUSA. The NIRS data is provided as a courtesy to others HAYABUSA related
  efforts because it is exactly aligned with the LIDAR.
 
    All three filtered, unfiltered and optimized CDR files list the following
  data in their column order:
      1. The spacecraft mission elapsed time (MET)
      2. The equivalent spacecraft time in UTC
      3. The X,Y and Z estimate of the spacecraft location derived during the
  LIDAR data processing (see processing section below)
      4. The estimated X,Y,Z position of the LIDAR and Near Infra-Red
  Spectrometer (NIRS; Co-aligned with the LIDAR) footprint using the LIDAR
  processed spacecraft position, the LIDAR boresight vector, and the measured
  range.
      5. The predicted X,Y,Z position of the LIDAR footprint at the
  intersection of the LIDAR boresight vector with the a high resolution
  asteroid shape model [GASKELLETAL2008B] using the LIDAR processed spacecraft
  position.
      6. Incidence, emission and phase angle of the center of the LIDAR/NIRS
  field of view (FOV) using the interection of the LIDAR boresight vector with
  a high resolution asteroid shape model [GASKELLETAL2008B], using the LIDAR
  processed spacecraft position.
      7. Size in m of the LIDAR and NIRS FOV obtained from the LIDAR FOV and
  measured LIDAR range to surface of the asteroid.
      8. Longitude and latitude of the center of the LIDAR/NIRS (FOV) using
  the measured LIDAR range, and the spacecraft positions given by the LIDAR
  processing.
      9. Predicted longitude and latitude of the LIDAR/NIRS (FOV) at the
  intersection of the LIDAR boresight vector with the asteroid shape model
  [GASKELLETAL2008B], using the spacecraft positions given by the LIDAR
  processing.
     10. Mean incidence, emission and phase angle from nine locations across
  the FOV of NIRS that were derived from nine vectors across the NIRS FOV
  (split into a 3x3 grid) whose intersection with the shape model
  [GASKELLETAL2008B] were determined using the spacecraft positions given by
  the LIDAR processing.
     11. Mean longitude and latitude of the NIRS FOV for the up to nine
  vectors within the NIRS FOV that intersect the asteroid shape model using
  the spacecraft positions given by the LIDAR processing.
     12. Predicted minimum and maximum longitude and latitude of the up to
  nine vectors within the NIRS FOV that intersect the asteroid shape model
  using the spacecraft positions given by the LIDAR processing.
     13. Number of vectors within the NIRS FOV (split into a 3x3 grid) that
  intersects the asteroid shape model using the spacecraft positions given by
  the LIDAR processing. This number of vectors was used in the calculation to
  estimate the previous mean incidence, emission and phase of NIRS, and the
  mean, minimum and maximum longitude and latitude values of NIRS.
 
      Processing
      ==========
 
    The CDR incorporates the best orbital solutions and LIDAR boresight
  locations derived by the HAYABUSA LIDAR team. As a first step, a new
  algorithm was developed to better locate the Hayabusa spacecraft relative to
  the asteroid. The most important data initially used was the housekeeping
  (HKEDR) data of the x-y pixel of the illuminated centroid obtained by the
  ONC-W1 (WAC) camera of AMICA. Additional data included the project supplied
  information on the pointing of the WAC (SPICE C-kernels), as well as a good
  shape model of Itokawa (generated by R. Gaskell and part of the HAYABUSA PDS
  delivery [GASKELLETAL2008B]).  Our algorithm assumes that the spacecraft
  attitude (i.e., its pointing) provided by the SPICE C-kernels as determined
  by the on board star cameras remained correct throughout the mission.
 
    The algorithm consists of first using a preliminary spacecraft location,
  the spacecraft attitude data and the shape model to create simulated images
  of Itokawa as seen by the WAC at the time the actual HKEDR was acquired. A
  predicted x-y pixel location for the illuminated centroid was computed from
  these simulated images simultaneously with a predicted range to where the
  LIDAR was pointing at the surface of the Itokawa. These predicted HK-data
  were then compared to the actual HKEDR in order to correct the spacecraft
  position. This comparison was repeated iteratively until the predicted and
  actual x-y pixel locations were within 0.1 pixel, and the predicted and
  measured ranges were within 0.5 to 3 m of each other, depending on the range
  of the spacecraft relative to the surface of the asteroid.
 
 
    The algorithm used to reproduce the HK data provides at 2 min intervals
  excellent estimates of the spacecraft position relative to Itokawa for most
  of the time that Hayabusa observed Itokawa. The data acquired by the LIDAR,
  however, was taken at 1 s intervals. Therefore, good estimates of the
  spacecraft position were still required for those periods between when HK
  data was acquired. After some trial and error, good estimates were obtained
  by initially using linear interpolation to first guess the locations of the
  spacecraft between those estimates provided by the HK data. We then fit all
  the positions using least squares to a second order polynomial or parabolic
  function between spacecraft maneuvers. Such a function should have a form
  that compares favorably with solutions to the semi-orbital equation of
  motion for the Hayabusa spacecraft that include the solar pressure acting on
  the spacecraft, because major maneuvers occurred fairly frequently (between
  a few hour to a few day intervals). Analysis of the resulting data indicate
  significant improvements on how well the new trajectory estimate for
  Hayabusa relative to what was initially provided by the project in the form
  of SPICE SP-Kernels.
 
    Further processing was then performed, where the following algorithm was
  used to improve the unfiltered lidar data. First, the lidar points were
  divided into subsets of no more than 1000 points each. The actual number or
  points per set was chosen so that the size of a bounding box containing the
  points did not completely wrap around the asteroid. Then for each lidar
  point in the set, a point on the asteroid near it was computed by
  intersecting with the asteroid (using the highest resolution shape model of
  Itokawa produced by Bob Gaskell) a ray originating from the spacecraft
  position in the direction of the lidar point. These intersection points were
  grouped together to form a second set of points in addition to the original
  (uncorrected) lidar points. A point matching scheme was then employed to
  find the optimal translation of the first set of points so that the distance
  between the lidar footprints and shapemodel were minimized. This optimal
  translation was then applied to the original lidar points and spacecraft
  positions to produce the improved data. This procedure was repeated for each
  subset of the lidar data.
 
    In this delivery, we provide three CDR files for each time range. The
  first includes boresight locations that have not been further filtered after
  the first set of above processing prior to optimization was undertaken. The
  second set filters the unfiltered version of the data to remove bad data in
  the filtered set: any estimated surface point which was located more that
  10m from the predicted intersection of the vector defining the pointing of
  the LIDAR boresight and the shape model of the asteroid were removed. This
  difference of 10m was chosen because most small scale variations in surface
  topography on Itokawa are less than this amount. This second set results in
  ~65% of the  LIDAR points being useful. This is equal to ~1.0 million LIDAR
  shots. The third optimized data set was able to use most of the unfiltered
  data to further increases the number of usable LIDAR points to ~1.3 million
  LIDAR shots. The EDR contains a total ~1.6 million LIDAR data originally
  collected by Hayabusa. The optimized data also provided some of the best
  estimates of the location of the Hayabusa spacecraft relative to the
  asteroid.
 
 
      Ancillary Data
      ==============
 
    As part of analysis, we found that the AMICA SPICE image kernel  needed
  further modification. A new version (amica_v202.ti) was prepared by Olivier
  Barnouin-Jha. In order to generate the CDR dataset, we used several project
  provided SPICE kernels including the planetary ephemeris kernel
  pck00008.tpc, the Itokawa Ephmeris and rotation kernel sb_25143_140.bsp and
  the HAYABUSA clock kernel hayabusa.tsc (the version of 2005-09-06).  These
  and the other SPICE kernels used to prepare the data files have been
  archived in the PDS SPICE archives.
 
 
      Coordinate System
      =================
 
    A planetocentric coordinate system is employed, which is body-centered,
  using the center-of-figure as the origin. The actual vector from the center
  of Itokawa to the surface should be primarily employed for scientific
  purposes because of the important curvature of Itokawa where some locations
  can possess more than one latitude and longitude. However, latitude and
  longitude data are also provided, but should be used with caution. The
  latitude is defined by the angle between the equatorial plane and a vector
  extending from the origin of the coordinate system to the relevant point on
  the surface.  Latitude is measured from -90 degrees at the south pole to +90
  degrees at the north pole.  Longitude extends from 0 to 360 degrees, with
  values increasing eastward (i.e., it is a right-handed coordinate system)
  from the prime meridian. This coordinate system is preferred for use in
  navigation and geophysical studies in which, for example, estimates of
  elevation or gravitational potential are generated mathematically.
 
      Modification History
      ====================
 
    The Hayabusa LIDAR CDR files were changed slightly in going from version 1
  to version 2 of the Hayabusa LIDAR data. The dates in the unfiltered and
  filtered data filename's were changed to match the dates used in the EDR
  filenames, with the exception of the data collected during the last TOUCH
  DOWN phase. The LIDAR data collected after November 18, 2005 could not be
  corrected. Furthermore, some duplicate data were present in the original
  version 1 of the LIDAR data, and these have been removed. Finally, the new
  optimized version of the CDR were generated in going from version 1 to
  version 2 of the LIDAR CDR. There were also some typos in the version 1
  'dataset.cat' document that have now been remedied.
 
 
     References
     ==========
 
      Mukai, T., Araki, H., Mizuno, T., Hatanaka, N., Nakamura, A.M., Kamei,
  A., Nakayama, H., Cheng, A., 2002. Detection of mass, shape and surface
  roughness of target asteroid of MUSES-C by LIDAR. Adv. Space Res. 29,
  1231-1235.
 
      Barnouin-Jha, O., A. Cheng, T. Mukai, S. Abe, H. Naru, R. Nakamura, R.W.
  Gaskell, J. Saito, and B.E. Clark 2008.  Small-scale topography of 25143
  Itokawa from the Hayabusa laser altimeter.  Icarus 198, 108-124.
 
      Cheng, A.F., O. Barnouin-Jha, L. Prockter, M. T. Zuber, G. Neumann, D.
  E. Smith, J. Garvin, M. Robinson, J. Veverka, and P. Thomas, Small-scale
  topography of 433 Eros from laser altimetry and imaging. Icarus 155, 51-74
  2002.
 
       Gaskell, R., Saito, J., Ishiguro, M., Kubota, T., Hashimoto, T.,
  Hirata, N., Abe, S., Barnouin-Jha, O., and Scheeres, D., Gaskell Itokawa
  Shape Model V1.0. HAY-A-AMICA-5-ITOKAWASHAPE-V1.0. NASA Planetary Data
  System, 2008.
DATA_SET_RELEASE_DATE 2012-01-23T00:00:00.000Z
START_TIME 2005-09-11T04:56:26.198Z
STOP_TIME 2005-11-25T10:04:00.844Z
MISSION_NAME HAYABUSA
MISSION_START_DATE 2003-05-09T12:00:00.000Z
MISSION_STOP_DATE 2010-06-13T12:00:00.000Z
TARGET_NAME 25143 ITOKAWA
TARGET_TYPE ASTEROID
INSTRUMENT_HOST_ID HAY
INSTRUMENT_NAME LIGHT DETECTION AND RANGING INSTRUMENT
INSTRUMENT_ID LIDAR
INSTRUMENT_TYPE ALTIMETER
NODE_NAME Small Bodies
ARCHIVE_STATUS LOCALLY_ARCHIVED
CONFIDENCE_LEVEL_NOTE
Confidence Level Overview
  =========================
 
    The resolution of the data is about 50 cm vertically. Along track spacing
  is variable. Small errors in the HAYABUSA emphemeris solutions and pointing
  knowledge yield uncertainties in absolute ground spot location to within 10
  m, but is often better in the case of the filtered and unfiltered data. The
  optimized (OPT) CDR data set has errors relative to the Itokawa shape model
  that are on the order of 3.5 m.
 
 
   Timing Uncertainty
   ==================
 
    The clock aboard Hayabusa possesses an estimated uncertainty of +/- 12
  seconds due to a periodicity in the control and operation of the analog
  signal processing unit.  This effect was somewhat remedied by the analysis
  used by the LIDAR science team. The relative pointing between the ONC-W2
  camera and AMICA were statically adjusted so that a simulated image using
  the Hayabusa shape model would match the location of Itokawa observed by
  AMICA. Both data sets suffer from the same timing problem and our approach
  would thus have minimized their effect over the lifetime of the mission.
  Additional errors due to this timing uncertainty are captured by the 10m
  uncertainty clearly established to be the accuracy of the LIDAR CDR filtered
  data.  Examples of the excellent match between the topography observed, the
  estimated location of the boresight using the LIDAR CDR dataset and
  observations of where this boresight should be in AMICA all indicate that
  this problem has a minor impact on the quality of the Hayabusa LIDAR data
  set (see Barnouin-Jha et al. [2008] for additional details.)
 
   Data Coverage/Quality
   =====================
 
    After processing using the optimal approach, 82% of the mission's data was
  found useful.
 
    Limitations
    ===========
 
    The HAYABUSA LIDAR data has met many of its design expectations. It has
  demonstrated a measurement precision of ~50 centimeters over flat terrain.
  After processing, more than 82 % of the data was found useful for
  topographic analyses, with average errors of 3.5 m or less.
CITATION_DESCRIPTION Mukai, T., Abe, S., Barnouin, O., Cheng, A., and Kahn, E., Hayabusa LIDAR V2.0. HAY-A-LIDAR-3-HAYLIDAR-V2.0. NASA Planetary Data System, 2012.
ABSTRACT_TEXT The HAYABUSA spacecraft included a LIght Detection and Ranging (LIDAR) altimeter. The primary objective of LIDAR was to establish the range between the HAYABUSA spacecraft and the asteroid Itokawa for navigation purposes during the surveying and collection phases of the mission. It provided excellent estimates of the location of the spacecraft relative to the asteroid. The Experiment Data Record (EDR) and Calibrated Data Record (CDR) from the Hayabusa LIDAR experiment are included in this data set. This updated version of the HAYABUSA LIDAR data includes a new CDR where the offsets between a high resolution shape model and the LIDAR data were minimized by optmizing the spacecraft trajectory.
PRODUCER_FULL_NAME CAROL NEESE
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