LRO DIVINER Gridded Data Record Level 2 (GDR_L2)
GDR_L2 – Gridded Data Record Level 2
Instrument:Diviner Lunar Radar Experiment
PDS Data Set ID: LRO-L-DLRE-5-GDR-V1.0
For more information about Diviner GDR_L2 products, see the RDR and Derived Product SIS.
For more information about all Diviner products, see the Diviner Archive SIS.
The Diviner Lunar Radar Experiment Gridded Data Record (GDR) Level 2 data products are derived directly from the Reduced Data Record (RDR) data product. They directly mimic the format and intent of the Lunar Orbiter Laser Altimeter (LOLA) GDR data product for maximum compatibility with LOLA and other products.
Level 2 GDR products include solar reflectances, brightness temperatures, and time-related values such as local time and Julian Date that are binned and averaged according to 27-day LRO mapping cycles. Each averaged product is further split into daytime (local time 06:00 to 18:00) and nighttime (local time 18:00 to 06:00) data products.
For each averaged gridded product, an analogous pair of count and error estimate products is created.
The Level 2 GDR products are gridded in cylindrical longitude and latitudinal space and in polar stereographic space (to +/- 75 degrees latitude) at varying resolutions.
Cylindrical maps are provided at resolutions of 128, 64, 16, 4, and 1 pixels per degree (ppd). This last resolution value produces global lon-lat maps during the LRO primary mission with minimal low-latitude gores.
Polar stereographic maps are provided at a single resolution of 126.347 ppd, which corresponds to a map scale of 240 meters per pixel (m/pix).
Only nadir-pointing data are used in these datasets (RDR activity flag 110 – on moon, standard nadir). The thermal channel data is further constrained to brightness temperature values of 10 to 450 K as anything outside this range contains bad data. Observations with excessive noise is also culled. The finite field of view of the Diviner footprints is taken into account to produce the master maps, which avoid resolution aliasing problems at higher latitudes. All footprints are projected by locating the fields of view in three dimensions onto a LOLA digital elevation model of the Moon.
All GDRs consist of images employing scaled binary 16-byte integers with the extension .IMG, and associated geotagged JPEG2000 format files with the extension .JP2, as well as a sample low-resolution JPEG image with the extension .JPG, for easy viewing. Each format has a detached PDS label that describes their contents and includes useful metadata. The label has the extension .LBL.
The following table lists the values in each gridded data product:
|
Value |
Description |
|
VB1 |
Channel 1 Visual Brightness |
|
VB2 |
Channel 2 Visual Brightness |
|
TB3 |
Channel 3 Brightness Temperature |
|
TB4 |
Channel 4 Brightness Temperature |
|
TB5 |
Channel 5 Brightness Temperature |
|
TB6 |
Channel 6 Brightness Temperature |
|
TB7 |
Channel 7 Brightness Temperature |
|
TB8 |
Channel 8 Brightness Temperature |
|
TB9 |
Channel 9 Brightness Temperature |
|
LTIM |
Local Time (binned using “circular” averaging) |
|
JD |
Julian Date |
Diviner GDR_L2 products have the following file names:
DGDR_vvv_bbb_ppp_yyyymmddt_rrr_xxx (with detached PDS labels for each product)
where:
vvv = value binned, e.g. VB1
bbb = bin type
AVG = average
ERR = error
CNT = count
ppp = projection
CYL = cylindrical
POLN = north polar
POLS = south polar
yyyymmdd = date beginning the mapping cycle
t = time of day
D = daytime
N = nighttime
rrr = resolution; for cylindrical maps, in pixels/degree; for polar maps, in meters/pixel
xxx = file type/extension
IMG.IMG = 16-bit LSB binary integers
JP2.JP2 = JPEG2000
In ODE, GDR_L2 products have the following product IDs:
DGDR_VVV_BBB_PPP_YYYYMMDDT_RRR_XXX