| DATA_SET_DESCRIPTION |
Data Set Overview
=================
This data set contains version 1.0 of the Level 2 Archive for
the Moon Mineralogy Mapper instrument (M3). It is a collection of
reflectance-calibrated and pixel-located data products acquired
during from November 2008 through May 2009 by M3 during the
Chandrayaan-1 mission to the Moon. The data were collected 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 2 Data Product consists of pixel-located, resampled,
calibrated data as reflectance (unitless) that make up one observation
tagged by a unique file name. The data in one Level 2 product represent
a consistent instrument configuration (frame rate, pixel binning). There
is a single multiple-band reflectance image stored in one file (BINARY;
*_RFL.IMG) with a detached PDS label (ASCII; suffix *_L2.LBL), and a
detached header file (ASCII; suffix *_RFL.HDR). A Level 2 product also
includes a supplemental file (BINARY; *_SUP.IMG) that contains three
images to assist analysis:
1) The 1489-nm reflectance image photometrically corrected to a sphere
(retaining topographic illumination),
2) A map of the derived temperatures used for thermal correction, and
3) The longest wavelength band (number 84 for global or 253 for
target) of the Level 1B radiance image (*RDN.IMG) that is
scientifically useful; this band contains both reflected solar and
thermal emitted components and is highly sensitive to local
topography.
For scientific results from M3 see Pieters, et al. (2009b)
[PIETERSETAL2009B], Pieters, et al. (2009c) [PIETERSETAL2009C], Besse,
et al. (2011) [BESSEETAL2011], Besse, et al. (2012) [BESSEETAL2012],
Boardman, et al. (2011) [BOARDMANETAL2011], Buratti, et al. (2011)
[BURATTIETAL2011], Cheek, et al. (2011) [CHEEKETAL2011], Clark, et al.
(2011) [CLARKETAL2011], Clark, et al. (2012) [CLARKETAL2012], Hicks, et
al. (2011) [HICKSETAL2011], Green, et al. (2011) [GREENETAL2011],
Isaacson, et al. (2011) [ISAACSONETAL2011], Klima, et al. (2011)
[KLIMAETAL2011], Kramer, et al. (2011a) [KRAMERETAL2011A], Kramer, et
al. (2011b) [KRAMERETAL2011B] McCord, et al. (2011) [MCCORDETAL2011],
Mustard, et al. (2011) [MUSTARDETAL2011], Nettles, et al. (2011)
[NETTLESETAL2011], Pieters, et al. (2011) [PIETERSETAL2011], Staid, et
al. (2011) [STAIDETAL2011], Thaisen, et al. (2011) [THAISENETAL2011],
and Whitten, et al. (2011) [WHITTENETAL2011].
Processing
==========
M3 Level 2 processing involves converting the at-sensor radiance data
from Level 1 to 'reflectance' at an incidence angle (i) of 30 degrees
and an emission angle (e) of 0 degrees. Here we define 'reflectance' as
radiance factor (RADF; Hapke, (1993), p. 262, Eq. 10.5 [HAPKE1993])
consistent with Level 2 data from SELENE Spectral Profiler (Yokota, et
al. (2011) [YOKOTAETAL2011]). The process includes a limb-darkening
based photometric function to correct all M3 data to the reference i=30
degrees, e=0 degrees geometry using normalization factors derived from
highland units. M3 reflectances are thus 'normalized' as if they were
all measured at i=30 degrees, e=0 degrees.
Level 2 processing consists the following sequential operations:
1) Solar Irradiance Correction,
2) Statistical Polishing,
3) Thermal Removal,
4) Photometric Correction,
5) Ground Truth Correction** (optional), and
6) Flag degraded channels.
** The Ground Truth Correction step was intentially turned off
in the Level 2 pipeline and thus the data in this archive
have NOT been corrected to ground truth.
For a detailed description of each operation, including how to
independently apply the Ground Truth Correction, please see the M3
Data Product Software Interface Specification, DPSIS.PDF, located in
the DOCUMENT directory. Please note that version 3.0 of the Level 1B
radiance data products archived in the PDS data set
CH1-ORB-L-M3-4-L1B-RADIANCE-V3.0 were used as input to this Level 2
process.
Calibration files used by the Level 2 process are located in the CALIB
directory. It includes tables of multiplicative factors for the ground
truth correction for researchers to apply to the Level 2 data as needed.
See the M3 Data Product Software Interface Specification, DPSIS.PDF,
located in the DOCUMENT directory.
References used to develop the Level 2 process include Anderson, et al.
(2000) [ANDERSONETAL2000], Hapke, (1993) [HAPKE1993], Kurucz, et al.
(1995) [KURUCZ1995], Nobel, et al. (2006) [NOBLEETAL2006], and Yokota,
et al. (2011) [YOKOTAETAL2011].
Data
====
The DATA directory contains 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 2 for this archive).
For a detailed description of reflectance products located in the DATA
directory, please see the M3 Data Product Software Interface
Specification, DPSIS.PDF, located in the DOCUMENT directory.
Coordinate System
=================
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. For a detailed
description, see the M3 Data Product Software Interface Specification,
DPSIS.PDF, located in the DOCUMENT directory.
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/. M3 data products can also be read by the
commercial package ACT-REACT which from Applied Coherent Technology
Corporation at http://www.actgate.com/home/act-react.htm. In addition,
the free PDS NASAView software package can also be used for basic image
displaying of M3 L2 data products. It is available at:
http://pds.nasa.gov/tools/nasa-view.shtml.
Nevertheless, the data are not in a proprietary format and are arranged
as simply and as openly as possible. The provision of both PDS labels
and ENVI headers 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. The M3 Level 2 archive
is organized as one data set and stored electronically as a single
volume for online access via the World Wide Web and FTP.
|
| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview
=========================
The data files in this data set were reviewed internally by the M3
project.
Review
======
Prior to the creation of this archival data set, a sample that included
several data products, PDS labels, catalog and indexfiles, and
documentation such as the M3 Data Product Software Interface
Specification passed a peer review held by PDS Imaging Node in May 2011.
Liens placed by the peer reviewers have been resolved in this archival
data set.
Data Coverage and Quality
=========================
The M3 image acquisition time is 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 discussed in the M3 Data Product Software Interface
Specification, DPSIS.PDF, located in the DOCUMENT directory.
Nonetheless, the data products in this data set contain optimal
calibration and characterization.
M3 operations were sustained for two Optical Periods which are described
in the M3 Data Product Software Interface Specification in the DOCUMENT
directory. For more detailed information regarding the spacecraft
operation schedule, please see the MISSION.CAT.
Limitations
===========
None.
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