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Lunar DEM generated from Chandrayaan-1 TMC stereo imagery and Lunar Map sheets are now available.
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Chandrayaan-1 Long Term Archive Release

Chandrayaan-1, the maiden Indian mission to Moon was launched during October-2008. The main objective of the mission is the photo-selenological and chemical mapping of the Moon. It carried 11 instruments onboard including SAC developed Terrain Mapping Camera (TMC) & Hyper Spectral Imager (HySI). TMC is the prime imaging payload to collect stereoscopic data of lunar surface. It has 5m spatial resolution and 20 km swath operating in panchromatic band (500-880 nm), is an optical imaging payload comprising three cameras with different view angles viz., fore, aft and nadir, accomplished through the use of suitably displaced linear arrays in the focal plane of a single lens. The Hyper Spectral Imager (HySI), operating in the visible and near Infrared spectral region, is one of the three imaging instruments onboard Chandrayaan-1 spacecraft for mineralogical study of the Moon. HySI is designed to map entire lunar surface in 64 contiguous bands in the visible and near infrared (VNIR: 421-964 nm) with a spatial sampling of 80m. A wedge filter is employed for the spectral separation and the image is mapped on an area detector.

1.    Chandrayaan-1 Long Term Archive (LTA)

(http://www.issdc.gov.in/)

The data acquired at various phases of the Chandrayaan-1 mission from TMC, HySI, M3, SARA and MiniSAR are processed as per the processing level definitions and provided with Planetary Data System (PDS) standards for archival. The instrument data in PDS has gone through a peer review process (as per the standard guidelines of PDS) by the expert reviewers from various global archive agencies and a Long Term Archive (LTA) is prepared for TMC, HySI and SARA. The peer review for M3 and MiniSAR has been carried out by their respective agencies and the data has been submitted to Indian Science Data Archive (ISDA) at ISSDC. ISDA holds the science data for all the Indian science missions, and is responsible for data archival and dissemination.

The LTA can be accessed from the current site http://www.issdc.gov.in/. This site has the facility to browse through the available datasets of TMC, HYSI, MIniSAR, M3 and SARA and download the required data. TMC, HySI and SARA datasets can be downloaded on the request basis currently. Users can view M3 and MiniSAR and download the full data archives from the http://ode.rsl.wustl.edu/moon/indexDataSets.aspx. The PDS data once downloaded can be viewed by the PDS viewers available from ISSDC or by any other standard viewers. User needs to register once to browse and to get access to the data. The procedure is self explanatory for browse and data access, when the user goes to the site and logins in. A sample screen shot of TMC browse is shown in Figure-1. Table-1 gives the instrument wise data archive information of LTA in the current version.

Browse application provides a user interface to the user which allows the user to search for the available TMC, HySI, HySI Band to Band Registered (BBR) and Digital Elevation Model (DEM) on the basis of date of pass, orbit_number and latitude/ longitude. The user can view the Thumbnails (JPEG) of all the datasets along with metadata. It also showcases the peer-reviewed SARA, M3 and MiniSAR datasets. The PDS data contains relevant documentation in the Document directory. More information about the data can be found out in these documents.

Figure-1: Chandrayan-1 TMC Browse snapshot

The user can also visualize the mosaics of the TMC, DEM and HySI North Pole and South Pole datasets as shown in the Figure-2 as well as the Globe View as in Figure-3.

Screenshot-2.png

Figure-2: Chandrayan-1 TMC North Pole Mosaic

The TMC and HySI data sets are based on the latest version of SPICE generated for entire mission (except for the period from 14th Nov. 2008 to 02nd Dec. 2008) of imaging. SARA browse datasets are available for the full season.

Table-1: Instruments wise Data Archive Information of LTA in the current version

 

S.No.

Instrument ID

Data Set Id

Total No. of Products Archived

Date Range

  1.  

TMC

CH1ORB-L-TMC-2-NPO-EDR-RAW-DATA-V1.1

1003

 

2008-12-03 to 2009-08-17

 

 

CH1ORB-L-TMC-3-NPO-RDR-FULL-RES-V1.1

1003

  1.  

HYSI

CH1ORB-L-HYSI-2-NPO-EDR-RAW-DATA-V1.1

772

 

2008-12-09 to 2009-08-17

 

 

CH1ORB-L-HYSI-3-NPO-RDR-FULL-RES-V1.1

772

 

 

CH1ORB-L-HYSI-4-NPO-REFDR-FULL-RES-V1.1

552

  1.  

SARA

CH1ORB-L-SARA-2-NPO-EDR-CENA-V1.0

753

2008-12-08 to 2009-08-13

 

 

 

CH1ORB-L-SARA-2-NPO-EDR-SWIM-V1.0

699

  1.  

MMM

 

http://ode.rsl.wustl.edu/moon/indexDataSets.aspx

  1.  

MiniSAR

 

Figure-3: Chandrayaan-1 TMC Globe View (as seen in the Web Site)

 

1.1                     Chandrayaan-1 LTA Sample Images from TMC & HySI

1105_sinousrille_07_02_2009.jpeg

Figure-4: TMC - Sinousrille

1130_crater_10Feb2009.jpeg

Figure-5: TMC - Small Floor Crater

farside_crater_2324.jpeg

Figure-6: TMC - Far Side Crater

Hale_2792_complex_crater.jpeg

Figure-7: TMC - Hale Complex Crater

Overlapping_Craters_523.jpeg

Figure-8: TMC - Overlapping Crater

three.jpg

Figure-9: TMC - Interesting Moon Feature

 

795_rille_features_13Jan2009.jpeg

 

 

 

 
Figure-10: TMC Moon Feature - Rille

876_rimaegassendi_overview_20Jan2009.jpeg

Figure-11: TMC Moon Feature Crater Rimaegassendi

 

 

HYS_795_13Jan2009_rille_b16.jpegHYS_795_13Jan2009_rille_b32.jpegHYS_795_13Jan2009_rille_b48.jpegHYS_795_13Jan2009_rille_b64.jpeg

Band 16 ---------- Band 32 ---------- Band 48 ---------- Band 64

Figure-12: HySI - Rille

 

HYS_872_20Jan2009_Rimaegassendi_b16.jpegHYS_872_20Jan2009_Rimaegassendi_b32.jpegHYS_872_20Jan2009_Rimaegassendi_b48.jpegHYS_872_20Jan2009_Rimaegassendi_b64.jpeg

Band No. 16 ---------- Band No. 32 ----------- Band 48 ---------- Band 64

Figure-13: HySI Crater Rimaegassendi

 

FMAITRE_CRATER_B18_32_56_18062009.bmp

Figure-14: HySI - Fmaitre Crater (Color assignment -Bands 18 (B), 32 (G), 56 (R))

 

Figure-16: HySI Small Floor Crater (Color assignment -Bands 18 (B), 32 (G), 56 (R))

RING_CRATER_05062009_B18_32_56.bmp

 

Figure-15: HySI - Ring Crater (Color assignment -Bands 18 (B), 32 (G), 56 (R))

SMALLFLOOR_CRATER_B18_32_56_16062009.bmp

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1.2                     Tools for Viewing Data Products in LTA

The data products archived in LTA are as per PDS archive standard. All the data sets are in PDS. Tools used for viewing data products are defined below.

     Ch1 PDS Viewer

The Ch1 PDS Viewer was java based software designed & developed in house. This software is provided in LTA under software directory of TMC and HySI instruments. The users can download and install at their end. The information on installation steps and user manual are provided along with the software. The software takes TMC & HySI PDS data sets as an input which mainly include data label file and geometry label file and displays the image product along with geometry information. Figure-17 below shows the display of TMC instrument data from the software. The data is CODMAC Level-3 i.e. Reduced Data Record (RDR).

 

CH1-PDS_Viewer_TMC.JPG

Figure-17: TMC Instrument data by Ch1PDSViewer

 

Figure- 18 given below shows the display of HySI instrument data from the software. The data is CODMAC Level-3/4 data. The HySI image data is composed of 64 bands stored in PDS as a spectral qube.

CH1-PDS_Viewer_HYSI.JPG

Figure-18: HySI Instrument data by Ch1PDSViewer

2.    TMC Digital Elevation Model & Ortho Images

 

The prime objective of TMC is to provide the triplet imagery of the lunar surface towards lunar mapping. For lunar mapping the basic inputs are Digital Elevation Models (DEM) to provide elevation of the surface at a predefined intervals and orthoimages to represent the surface features. The Digital Elevation Model (DEM) in this case is generated using Nadir and Aft images of Terrain Mapping Camera (TMC). Ortho images are generated using Nadir images and the DEM generated from Nadir and Aft images.

Lunar Digital Elevation Models (DEM) are generated from possible passes of Chandrayaan-1 TMC stereo imagery, having around 646 full pass DEMs using indigenous software called LDEM version 3.0. Qualitative check (subjective) only has been carried out on all the DEMs. With respect to some of the available Lunar DEMs in the public domain, the planimetric accuracy may vary up to 200 m and DEM height ranges may have some bias.

2.1 Characteristics of the DEM

PROJECTION

1. Selenographic for equatorial region (in decimal degrees) with Latitude range between +75 and -75 degrees having pixel scale at 0.000833degree

2. Polar Stereographic for south and north pole regions (in meters) with Latitude range beyond +75 to +90 degree North Pole and Latitude range beyond -75 to -90 degree South Pole having pixel scale at 25meter

DATA VALUES USED

1. Latitude values would be from -90 to 90 degree

2. Longitude values would be from 0 to 360 degree

3. SemiMajorAxis = 1738000 m

4. SemiMinorAxis = 1735000 m

5. No Height Value = -20000

 

FILE FORMAT

1.      The final DEM product is in TIFF file format, conforming to TIFF 6.0 standard with 16 Bits/Sample

2.      Sample Format: signed integer (2bytes)

3.      Compression Scheme: None

 

GENERAL INSTRUCTIONS

The No height value/undefined height value in the DEM is -20000 and this has to be ignored for display and processing purposes.

2.2 Characteristics of the Orthoimage

PROJECTION

 

1. Selenographic for equatorial region (in decimal degrees) with Latitude range between +75 and -75 degrees having Pixel Scale at 0.0001666degree

 

2. Polar Stereographic for south and North Pole region (in meters) with Latitude range beyond +75 to +90 degrees North Pole and Latitude range beyond -75 to -90 degrees South Pole having Pixel Scale at 5meter

 

DATA VALUES USED

 

1. Latitude values would be from -90 to 90deg

2. Longitude values would be from 0 to 360deg

3. SemiMajorAxis = 1738000 m

4. SemiMinorAxis = 1735000 m

 

FILE FORMAT

 

1.      The final ortho product is in TIFF file format, conforming to TIFF 6.0 standard with 16 Bits/Sample

2.      Sample Format: unsigned integer (2bytes)

3.      Compression Scheme: PackBits

4.      If the ortho image size exceeds 4GB limit (before compression) then it is generated in BigTIFF file format.

5.      All orthoimages are packBits compressed.

 

GENERAL INSTRUCTIONS

 

Wherever DEM is having undefined height value of -20000, orthoimage will have zero(0) pixel value.

 

A few sample gray scale images of DEM are given in Figure-19.

ch1_tmc_20081124_I00178_D00181_024359_seg1_NA_dem.jpg

ch1_tmc_20081207_I00342_D00342_142640_seg1_NA_dem.jpg

ch1_tmc_20090206_I01086_D01091_151726_seg1_NA_dem.jpg

ch1_tmc_20090801_I03157_D03162_023801_seg1_NA_dem.jpg

ch1_tmc_20090622_I02710_D02715_102048_seg1_NA_dem.png

ch1_tmc_20090622_I02708_D02713_060540_seg1_NA_dem.png

ch1_tmc_20090512_I02240_D02243_063025_seg1_NA_dem.png

ch1_tmc_20090607_I02545_D02551_202802_seg1_NA_dem.png

Figure-19: Sample Digital Elevation Model of a TMC Image (dark to bright gray tone represent the minimum to maximum height value of the respective DEM)

3.    Lunar Atlas

The third data set is the release of some map sheets of Lunar Atlas generated from Chandrayaan-1 TMC data.

Lunar Atlas comprises of lunar topographical maps which is a collection of ortho-image, contours, annotation, grids and other mapping features. Lunar Topographical maps have been generated at 1:50,000 mapping scale with a contour interval of 100 m. The contours overlaid on the map are extracted from the Digital Elevation Model (DEM) generated by Photogrammetric restitution of Chandrayaan-1 TMC triplet. The maps show the names of prominent features (mostly craters) present on the moon surface taken from IAU list. These maps followed the mapping scheme and standards prepared by ISRO to prepare global topographical maps of the moon at 1:50,000. The details of Mapping Standards followed are:

1.      Projection System: Selenographic projection for equatorial region (70 N to 70 S) and Polar stereographic projection for North and South Pole regions (60N90N and 60S-90S). The Center latitude for Polar stereographic projections is 90 N and 90 S for north and south poles respectively. Moon mean radius datum has been used for the mapping.

2.      Scale: The maps published are of 1:50,000 scale. Exact map scale varies slightly according to the latitude extent. The true scale is based on the centre of each 1:250,000 grid of map.

3.      Indexing Scheme: The Indexing scheme used for this atlas is unique and derived first time for entire moon at 1:250,000, 1:50,000 and 1:25,000 scales. The different index maps are provided to user to locate the maps from 1:1 M to 1:25,000. This Indexing scheme is the extension of Lunar Topographic Orthophoto Map Series (LTO) of NASA. The indexing scheme and the naming convention of maps are shown in Figure-20(a) & 20(b) respectively.

4.      Features: Each page of this atlas consists of an overview of 1:50,000 / 1:25,000 annotated topographic image map that depicts a particular region of the lunar surface. It is not feasible to give a name of every crater on the moon. Each map consists of at least one name of a crater and also identifies the satellite craters associated with the main crater.

5.      File Format: The Composed maps are provided in jpeg file format and can be opened in any jpeg viewer.

. A few sample maps of the Lunar Atlas are given in Figure-21.

 

Figure-20 (a): Map Index of the Chandrayaan-1 mapping (1:1 million Red & 250 K Yellow)

Figure-20 (b): Naming Convention for Chandrayaan-1 Maps at different scales

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