Chandrayaan-1 M3 Reflectance Image (REFIMG)

REFIMG – Reflectance Image

Instrument: M3

PDS Data Set ID: CH1-ORB-L-M3-2-L2-REFLECTANCE-V1.0DOI: 10.17189/1520414

The Moon Mineralogy Mapper (M3) Reflectance Image (REFIMG) data products consist of photometrically calibrated reflectance data (unitless, where a stored value of 1.0 represents 100% reflectance). Processing involves converting the at-sensor radiance data to reflectance (I/F, applying an Apollo 16 normalization factor and a photometric correction, the normalizing by a wavelength-independent scaling factor such that 100% reflectance is stored as the signed integer value 30,000.

In addition to the reflectance data file, the REFIMG products include a supplemental data file. Band 1 provides the 1489-nm channel photometrically-corrected to a sphere to preserve topography (i.e., photometrically-corrected albedo); a stored value of 1.0, unitless, represents 100% reflectance. Band 2 contains the temperature estimated and applied by the thermal correction step of the calibration process; units are Kelvin. Band 3 contains the longest wavelength band that is scientifically useful and has topography from the radiance image; none of the calibration steps has been applied.

All M3 REFIMG products are standardized to remove the different effects of the four possible orbit limb and flight yaw mode combinations:

  1. Descending/forward

  2. Descending/reverse

  3. Ascending/forward

  4. Ascending/reverse

In ascending limb data the lines/times are reversed, so all CALIV3 images 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 Raw Image (RAWIMG) data.

Description of M3 Operating Modes

M3 Mode

Description

# Channels

# Samples

Format

Target

Produces the maximum spectral resolution science data.

255

610

32-bit Floating Point

Global

Reduces spectral resolution by 3 times.

  • 4 block of 2x and 4x summing

  • 44 lines of summed by 4x and 42 lines of summed by 2x

The spatial data is summed in a 2 by 2 format.

85

304

32-bit Floating Point

Contents of an M3 REFIMG Image Cube File.

M3 REFIMG products have the following file names:

M3xyyyymmddThhmmss_V01_ttt.xxx (with one detached PDS label for all files)

where:

x = imaging mode

G = global mode

T = target mode

yyyy = year of the time stamp from the first image frame of the image cube

mm = month of the time stamp from the first image frame of the image cube

dd = day of the time stamp from the first image frame of the image cube

hh = hour in UTC of the time stamp from the first frame of the image cube

mm = minute within in the hour in UTC of the time stamp from the first frame of the image cube

ss = second within the minute in UTC of the time stamp from the first frame of the image cube

ttt = type of data product

L1B = Level 1B (.LBL)

RDN = Spectral Radiance data (.IMG or .HDR)

LOC = Pixel-located data (.IMG or .HDR)

OBS = Observation geometry data (.IMG or .HDR)

TIM = Observation timing data (.TAB)

xxx = file name extension

IMG = image object

HDR = detached header file

TAB = ASCII data table

In ODE, REFIMG products have the following product IDs:

M3XYYYYMMDDTHHMMSS_V01_RFL