LRO Mini-RF Map-Projected Calibrated Data Record (MAPCDR)

MAPCDR – Map-Projected Calibrated Data Record

PDS Data Set ID: LRO-L-MRFLRO-5-CDR-MAP-V1.0

For more information about MAPCDR products, see the Mini-RF Data Product SIS.

For more information about Mini-RF products, see the Mini-RF Archive Volume SIS.

The Mini-RF (MRFLRO) Map-Projected Calibrated Data Record (MAPCDR) products are map-projected calibrated single swatch CDR image data. The science products are in an oblique cylindrical projection. Each pixel is represented by two 4-byte floating point values and an 8-byte complex value (one 4-byte floating point real and one 4-byte floating point imaginary value) for a total of 16 bytes per pixel. The first two numbers are the intensity images for H & V receive, respectively. The complex value is the cross power intensity image between the H & V receive.

All MAPCDR image products are each accompanied by four stokes parameters files, a circular polarization ratio image, a same-sense polarization image and an opposite-sense polarization image. The Mini-RF transmits a right circular polarized signal, and receives horizontal and vertical polarized signals, and the phase between the polarizations. The MAPCDR file consists of four pieces of information per pixel: the received power on the horizontal polarization (E_RH), the received power in the vertical polarization (E_RV), and the real and imaginary portions of the cross product between the two polarization signals (Re E_RHE_RV* & Im E_RHE_RV*).

The four Stokes parameters (S1, S2, S3, and S4) are related to the data in the CDR files by the following equations:

S₁ = <|ERH|² + |ERV|²>

S₂ = <|ERH|² - |ERV|²>

S₃ = 2Re<ERHERV*>

S₄ = -2Im<ERHERV*>

Mini-RF transmits two orthogonal, linearly polarized waves with a phase shift of (nominally) one quarter of the wavelength, and the resulting superposition of these forms a (nominally) circularly polarized beam.

The same-sense circular polarization product (SC) describes the polarization state of the received field that has an identical polarization to the transmitted beam. This product is calculated as one half of the difference between the Stokes S₁ and S₄ parameters (SC = 0.5*S₁ – 0.5*S₄).

The opposite-sense circular polarization product (OC) describes the polarization state of the received field that has the opposite circular polarization to the transmitted beam. This product is calculated as one half of the sum of the Stokes S₁ and S₄ parameters (OC = 0.5*S₁ + 0.5*S₄).

The final product, the circular polarization ratio (CPR) is the ratio of the same-sense circular polarization to the opposite-sense circular polarization (CPR = SC/OC). The average CPR value of the entire lunar surface is on the order of 0.3. CPR values for certain types of surface deposits may be either anomalously low (near zero for very smooth terrain) or anomalously high (>1.0 for blocky large-scale rough features). High CPR also is due to volumetric backscattering from thick deposits of frozen volatiles, such as water-ice.

Degree of polarization (m): The fraction of radar backscatter that is polarized is given by the ratio m = (S₂² + S₃² + S₄²)^1/2/S₁. The average value of m at the moon is about 0.6.

Note: since December 26 2010, the Mini-RF instrument has not transmitted the RF energy required to create radar images of the lunar surface. The Mini-RF team looked at the initial 13 collects attempted from that date forward and noted that in all but one collect the data appeared bad, looking like noise. The team continued to attempt data collections at a reduced rate (about 1 collect per day) through January 23, 2011. Products included in this data set made from data collected after December 26, 2010, do not contain scientifically useful data.

MRFLRO MAPCDR products have the following file names:

Lfm_nnnnn_2tt_prU_aahddd_Vz.xxx (with one detached PDS label for both files)

where:

L = LRO

f = frequency band

S = S-band

X = X-band

m = radar mode

B = Baseline SAR

Z = Zoom

ooooo = orbit number

2 = MAPCDR

tt = product type

CD = calibrated data records

S1, S2, S3, S4 = Stokes parameters S₁-S₄

SC = same-sense polarization image file

OC = opposite-sense polarization image file

CP = circular polarization ratio image file

p = projection

E = equirectangular

O = oblique cylindrical

r = pixel resolution bin scale in pixels per degree (ppd)

G = 64

H = 128

I = 256

J = 512

K = 1024

U = un-normalized floating point data type

aa = lunar latitude of the center of the bistatic image, range 0 to 90 degrees

h = hemisphere of the latitude, N for northern latitude or S for southern latitude

ddd = lunar longitude of the center of the bistatic image, range 0 to 359 degrees

z = product version number

xxx = file extension

IMG = processed image file

TXT = unstructured text data (e.g., parameter files)

In ODE, MAPCDR products have the following product IDs:

LFM_NNNNN_2TT_PRU_AAHDDD_VZ