Data Set Overview  :   This volume contains the Level 1B (L1B) Archive, a collection of  radiometrically-calibrated and pixel-located data products acquired  during from November 2008 through August 2009 by the  Moon Mineralogy Mapper (M3) instrument during the Chandrayaan-1 mission to the Moon.The data were acquired while the instrument was operated  in global or targeted mode. The documentation in the DOCUMENT  directory provides detailed information about the data files and their  format and content.  A M3 Level 1B Data Product consists of pixel-located, resampled,  calibrated data in units of spectral radiance that make up one  observation tagged by a unique file name. The data in one Level 1B  Product represent a consistent instrument configuration (frame rate,  pixel binning). There is a single multiple-band image  (BIN; suffix *_RDN.IMG) stored in one file with a detached PDS label  (ASCII; suffix *_L1B.LBL), and a detatched header file (ASCII;  suffix *_RDN.HDR), plus several files containing data related to  pixel location (BIN; suffix *_LOC.IMG), observation geometry (BIN;  suffix *_OBS.IMG), and UTC timing for each image line (ASCII;  suffix *_TIM.TAB).   As of Septemer 2011, we have developed a detector-temperature-driven  empirical gain adjustment to the M3 Level 1B data. We refer to this  correction as the SSC_ADJ correction and it is based on a family of  spectral gain curves that are applied to each Level 1B radiance cube  after its nominal radiometric calibration. Based on the detector  temperature for each scene, a single curve is chosen from the family  of temperature-based curves and each spectrum in the radiance cube is  multiplied by this correction factor. This update should replace  versions 1.0 and 2.0 of the M3 Level 1B data products.  Processing  :   Level 1B processing involves the following operations:   - converts the decompressed, uncalibrated image cube data into  resampled, scaled, calibrated spectral radiance image cubes  - calculates the surface location of all pixel centers  - calculates the observation geometry and illumination on a  pixel-by-pixel basis  - calculates the UTC time for the middle of the integration period  for each frame of the image data   Data  :   Under the Data directory there is a separate subdirectory based on  the start and end times of a 13-week imaging period. Each imaging  period subdirectory is further divided into subdirectories for each  month of an Optical Period (OP). Each OP month subdirectory is further  divided based on the type of data product (e.g. Level 0 or Level 1B).   YYYYMMDD_YYYYMMDD/YYYYMM/L1B directory:  ----------------------------------  This directory contains the following files:   *RDN.IMG  --------  The L1B multiple-band spectral radiance image cube has  dimensions of sample, line, and wavelength. The size and format of the  M3 spectral radiance image cube depend on the observation mode  (global/target).   M3 calibration data such as wavelength centers,  full-width half-max values and radiometric gain factors can be found in  the CALIB directory of the archive volume.   In target mode, the spectral radiance image cube has the following  characteristics:   32-bit floating point  Little endian  256 spectral channels  608 spatial samples  N image lines  Band interleaved by line   In global mode, the spectral radiance image cube has the following  characteristics:   32-bit floating point  Little endian  85 spectral channels  304 spatial samples  N image lines  Band interleaved by line   During the transmission and encoding/decoding of the  data, some data elements may be lost. Data lost to poor compression or  complete packet loss are noted in the *.LOG files located in the EXTRAS  directory.   All M3 L1B spectral radiance image cubes are standardized to remove  the different effects of the four possible orbit limb and flight yaw  mode combinations: descending/forward; descending/reverse;  ascending/forward and ascending/reverse. In ascending limb data the  lines/times are reversed, so all L1B spectral radiance image cubes  have the northernmost image line first. In descending/reverse and  ascending/forward modes the samples are reversed, so the first sample  is on the west side of the image and do not appear left-right mirrored.  In descending/forward no changes in lines or samples are performed;  this is the only case that matches the Level 0 data. Refer to the  ORBIT_LIMB_DIRECTION and SPACECRAFT_YAW_DIRECTION keywords in the PDS  label (*_L1B_LBL) to reconcile a specific Level 1B spectral radiance  image cube with the associated Level 0 data.   Due to the successive loss of the two star trackers the data become  progressively more difficult to model. Hence our models increase in  complexity and parameterization. For M3 we have been forced into development of three different  spacecraft attitude models that describe the orientation of the  Chandrayaan-1 spacecraft during an orbit. These models were developed  sequentially as we processed data collected during the mission.   A detailed description of each model and the keywords associated with each model are provided in the M3 Data Product SIS.  *RDN.IMG.HDR  ------------  Each L1B spectral radiance image cube file will be accompanied by a  detached ASCII header file. A detached header provides compatibility  with ENVI software.   *L1B.LBL  --------  A spectral radiance image cube label (*_L1B.LBL) is detached and points  to the following L1B data products:   - the single multi-band image (*_RDN.IMG) and its respective detached  header file (*_RDN.HDR),  - the pixel location data (*_LOC.IMG) and its respective detached header file (*_LOC.HDR),  - the observation geometry data (*_obs.img) and its respective detached  header file (*_OBS.HDR),  - the UTC timing data (*_TIM.TAB)   *LOC.IMG  --------  The pixel location data for each image are stored in a three-band, band- interleaved-by-line, binary file of double precision 8-byte values, in  little-endian byte order. The three bands of the file, in order, are as follows:   1) longitude (reported in decimal degrees)  2) planetocentric latitude (reported in decimal degrees)  3) radius (reported in meters from the Moon center)   There are no embedded headers or other data in the file. Each  location file will be accompanied by a detached header file.  A detached header provides compatibility with ENVI software. The  location file is, in essence, a three-band set of 'detached  backplanes' that match the sample and line spatial extent of the  spectral radiance image cube data. No map correction or resampling is  applied to the radiance image cube; the file only reports the  surface locations of the unadjusted pixel centers.   *LOC.HDR  --------  Each location data file will be accompanied by a detached ASCII  header file. A detached header provides compatibility with ENVI  software.   *OBS.IMG  --------  The observation geometry data for each image are provided in a ten-band, band-interleaved-by-line, binary file of single precision 4-byte values, in little-endian byte order. The ten bands of the file, in order, are as follows:   1) to-sun azimuth angle (decimal degrees, clockwise from local north)  2) to-sun zenith angle (decimal degrees, zero at zenith)  3) to-sensor azimuth angle (decimal degrees, clockwise from local north) 4) to-sensor zenith angle (decimal degrees, zero at zenith)  5) observation phase angle (decimal degrees, in plane of to-sun and  to-sensor rays)  6) to-sun path length (decimal au with scene mean subtracted and noted  in PDS label)  7) to-sensor path length (decimal meters)  8) surface slope from DEM (decimal degrees, zero at horizontal)  9) surface aspect from DEM (decimal degrees, clockwise from local north) 10) local cosine i (unitless, cosine of angle between to-sun and local  DEM facet normal vectors)   Similar to the location data, these files are, in essence,  ten-band set of 'detached backplanes' that match the sample and line  spatial extent of the spectral radiance image cube data. No map  correction or resampling is applied to the radiance image cube; the  file only reports the observation parameters of the unadjusted pixel  centers.   *OBS.HDR  --------  Each observation geometry data file will be accompanied by a detached  header file. A detached header provides compatibility with ENVI software.  *TIM.TAB  --------   The timing file (*TIM.TAB) is an ASCII file with four columns of data.  The first column lists the line number of the multiple-band spectral  radiance image cube (*RDN.IMG). The second column lists the corresponding UTC time for the middle of the integration period for each spectral  radiance image cube line or major frame of the data and is expressed as:  YYYY-MM-DDTHH:MM:SS.SSSSSS.  The third column lists Year reference of Decimal Day of Year (DDOY) as  extracted from the earliest time of each spectral radiance image cube  line expressed as: YYYY.  The fourth column lists DDOY which represents the number of days elapsed  since 00:00 UTC of January 1 of the year associated with the time stamp  of the first image line. The DDOY format is as follows: DDD.dddddddddddd  where DDD represents the integer number of days and dddddddddddd  represent the fractional part of the day of year value.   Note that the M3 Level 0 data products have two representations of image  frame times captured in the 1280-byte image frame header:  1) a copy of the raw bytes of CH-1 and M3 binary clock tick data  and 2) a nominal conversion of those raw clock ticks to a UTC time in an  ASCII format. This nominal conversion is built on the assumed  operation of the clocks in a wholly stable manner with fixed tick  rates and no drift or unexpected rate issues. To achieve optimized  timing for subsequent processing, the Level 1B code develops  individual clock conversion models for each image of sufficient  length. This per-image modeling accommodates any clock drift or rate  changes and provides the best possible frame times for the Level 1B  data products. As such, the ASCII UTC times in the Level 0 data products may differ from those in the Level 1B data products. The Level 0 data  product times should be considered deprecated and are only approximate  UTC frame times. The per-image optimized conversion used in the Level 1B processing yields the most accurate image frame times and these are the  times reported in the timing file.   File Naming Convention  :   The file naming convention for L1B data products is as follows.   M3GYYYYMMDDTHHMMSS_VNN_PT.EXT   Or   M3TYYYYMMDDTHHMMSS_VNN_PT.EXT   M3: The instrument.  G or T: The imaging mode; G for global mode and T for target mode.  YYYY: The year of the time stamp from the first image frame of the  image cube.  MM: The month of the time stamp from the first image frame of the  image cube.  DD: The day of the time stamp from the first frame of the image  cube.  T: A single character string that precedes the UTC time of the  time stamp from the first frame of the image cube.  HH: The hour in UTC of the time stamp from the first frame of the  image cube.  MM: The minute within the hour in UTC of the time stamp from the  first frame of the image cube.  SS: The second within the minute in UTC of the time stamp from the first frame of the image cube.  VNN: The version number of the product.  PT: The type of data product:  L0 : Level 0  L1B : Level 1B  RDN : Spectral Radiance data  LOC : Pixel Location data  OBS : Observation geometry data  TIM : Observation timing data  EXT: The file name extension:  IMG : Image object  HDR : Detached header file  LBL : Detached label file  TAB : ASCII text file   All fields must occupy the allotted number of characters. Thus, if fewer digits are required to express a number than are allotted, the  convention fills the unneeded spaces with leading zeroes.   Coordinate Systems  :   The coordinate system used is the new 'Standardized Lunar Coordinate  System for the Lunar Reconnaissance Orbiter' (LRO Working Group, 2007).  This new lunar coordinate system is being adopted as an international  standard and will greatly facilitate the direct integration of data  from multiple missions and among international partners. The  coordinate system is based on planetocentric coordinates in the Mean  Earth/Polar Axis (ME) reference frame. The z-axis is the mean axis  of rotation with the positive direction pointing north. The x-axis is  the intersection of the Equator and Prime Meridian, as defined by the  mean Earth direction. The y-axis completes the frame in a right-handed  sense and points in the direction of +90 degrees longitude. Latitude  ranges from +90 to -90 form the North Pole to the South Pole.  Longitude will be reported as 0 to 360 degrees increasing to the East.   Software  :   The M3 team uses the commercial software packages ENVI and IDL to display  and analyze M3 data products. ENVI and IDL are distributed by ITT Visual  Information Solutions and are available at http://www.ittvis.com/.  In addition, PDS' NASAView Image Display Software can also be used for  basic image viewing of M3 L1B data products:  http://pds.nasa.gov/tools/nasa-view.shtml.  Nevertheless, the data are in no way in any proprietary format. Instead  they are arranged as simply and as openly as possible. The provision of  both ENVI and PDS labels will guarantee the data will be readily  accessible to the widest possible audience.   Media/Format  :   The M3 archive will be made available online via Web and FTP  servers. This will be the primary means of distribution.  Therefore the archive will be organized as a set of virtual  volumes, with each data set stored online as a single volume. As  new data products are released they will be added to the volume's  data directory, and the volume's index table will be updated  accordingly. The size of the volume will not be limited by the  capacity of the physical media on which it is stored; hence the  term virtual volume. When it is necessary to transfer all or part  of a data set to other media such as DVD for distribution or for  offline storage, the virtual volume's contents will be written to  the other media according to PDS policy, possibly dividing the  contents among several physical volumes.

Confidence Level Overview  :   Confidence level information will be provided after more thorough  analysis of the data.   Review  :   Prior to creation of the final version of this archival data set,  its keys elements including samples of data products, PDS labels  and catalog files, and the Software Interface Specifications, were  examined during a peer review held by PDS Imaging Node in January 2010.   Data Coverage and Quality  :   The M3 image acquisition time will be divided into peak periods or  Optical Periods (OP) when lighting is optimal for observation. The  Optical Periods occur twice a year and are understood to have two  central months of optimal illumination (solar beta angles -30 deg to  +30 deg) with two optional two-week wing periods (solar beta angles  +/-30 deg to +/-45 deg) on either side of the optimal 2 months (thus,  one Optical Period equals 13 weeks). Each 13 week optical period is  followed by a 13-week hiatus. The original instrument operations plan  included the acquisition of the entire surface of the Moon in  low-resolution Global Mode during the first Optical Period (OP1)  while OP2, OP3, OP4 were reserved for high resolution Target Mode  data acquisition.   However, the mission was cut short, just before the halfway point, in  August, 2009 when the spacecraft ceased operations. Despite the  abbreviated mission and numerous technical and scientific challenges  during the flight, M3 was able to cover more than 95% of the Moon in  Global Mode. Only minimal high-resolution Target Mode images were  acquired, as these were to be the focus of the second half of the  mission. The technical challenges encountered during the mission  have complicated the data processing and calibration. These challenges  include thermal issues, loss of the spacecraft star trackers and a  raising of the orbit from 100 km to 200 km on May 19, 2009. Details  of these challenges are currently being documented and will be  referenced and/or included in the delivery of the M3 PDS Archive  Volume. Nonetheless, the data products released in the M3 PDS Archive  Volume will contain optimal calibration and characterization.  (NOTE: If these docs are included in the archive, put them in  DOCUMENT directory, not EXTRAS.)   M3 operations were sustained for two Optical Periods. (For more  detailed information regarding the spacecraft operation schedule,  please see the MISSION.CAT.) Please see the M3 Data Product SIS for  more detail/information.    Limitations  :  None.