SHARAD-SPECIFIC PDS KEYWORD PARAMETERS

SYNTHETIC_APERTURE_DURATION
The coherent integration time (seconds) for SHARAD signals processed using 
the synthetic aperture technique. Multiplication of this value by the MRO 
tangential velocity tabulated in the *GEOM.TAB files yields an approximate 
physical length of the aperture.

MULTILOOK_DOPPLER_BANDWIDTH
The frequency span (Hz) over which radar echoes are averaged, following 
synthetic aperture processing for each spatial footprint along the ground 
track. This frequency span is measured to either side of the zero-frequency 
component of the Doppler spectrum.

NUMBER_OF_LOOKS
The number of frequency-resolved cells included in the multi-look averaging. 
This varies with the chosen frequency span and the Doppler resolution set by 
the inverse of the coherent integration time.

CHIRP_FREQUENCY_ENVELOPE
The frequency-dependent amplitude variation used in range compression of the 
raw echo data. All radargrams in this archive use a uniform-amplitude model.

RANGE_COMPRESSION_WINDOW
The windowing function used to reduce sidelobes resulting from range 
compression of the raw echo records. All radargrams in this archive use a 
Hann function.

AZIMUTH_PROCESSING_WINDOW 
The windowing function used to reduce sidelobes resulting from azimuth 
(along-track) synthetic aperture processing of the raw echo records. All 
radargrams in this archive use a Hann function.

PHASE/1.0E16
The scalar coefficient of an empirically derived phase distortion function 
used in suppression of ionospheric image blurring and delay offsets for 
solar zenith angles less than 100 degrees. A value for this coefficient is 
derived at intervals of about 23 seconds along the orbit track by optimizing 
a radargram image quality metric. The value used in the processing is 
reported here scaled by a factor of 1.0x1016.