The Miniature Radio Frequency (Mini-RF) system
is manifested on the Lunar Reconnaissance Orbiter (LRO) as a technology
demonstration and an extended mission science instrument. Mini-RF represents a
significant step forward in space borne RF technology and architecture. It
combines synthetic aperture radar (SAR) at two wavelengths (S-band and X-band)
and two resolutions (150 m and 30 m) with interferometric and communications
functionality in one lightweight (16 kg) package. Previous radar observations
(Earth-based, and one bistatic data set from Clementine) of the permanently
shadowed regions of the lunar poles seem to indicate areas of high circular
polarization ratio (CPR) consistent with volume scattering from volatile
deposits (e.g. water ice) buried at shallow (0.1-1 m) depth, but only at
unfavorable viewing geometries, and with inconclusive results.
The LRO Mini-RF
utilizes new wideband hybrid polarization architecture to measure the Stokes parameters
of the reflected signal. These data will help to differentiate “true”
volumetric ice reflections from “false” returns due to angular surface
regolith. Additional lunar science investigations (e.g. pyroclastic deposit
characterization) will also be attempted during the LRO extended mission. LRO’s
lunar operations will be contemporaneous with India’s Chandrayaan-1, which
carries the Forerunner Mini-SAR (S-band wavelength and 150-m resolution), and
bistatic radar (S-Band) measurements may be possible. On orbit calibration,
procedures for LRO Mini-RF have been validated using Chandrayaan 1 and
ground-based facilities (Arecibo and Greenbank Radio Observatories).
The Miniature Radio
Frequency (Mini-RF) system is manifested on the Lunar Reconnaissance Orbiter
(LRO) as a technology demonstration and an extended mission science instrument.
Mini-RF represents a significant step forward in space borne RF technology and
architecture. It combines synthetic aperture radar (SAR) at two wavelengths
(S-band and X-band) and two resolutions (150 m and 30 m) with interferometric
and communications functionality in one lightweight (16 kg) package. Previous
radar observations (Earth-based, and one bistatic data set from Clementine) of
the permanently shadowed regions of the lunar poles seem to indicate areas of
high circular polarization ratio (CPR) consistent with volume scattering from
volatile deposits (e.g. water ice) buried at shallow (0.1–1 m) depth, but only
at unfavorable viewing geometries, and with inconclusive results. The LRO
Mini-RF utilizes new wideband hybrid polarization architecture to measure the
Stokes parameters of the reflected signal. These data will help to
differentiate “true” volumetric ice reflections from “false” returns due to
angular surface regolith.
Additional lunar science investigations (e.g.
pyroclastic deposit characterization) will also be attempted during the LRO
extended mission. LRO’s lunar operations will be contemporaneous with India’s
Chandrayaan-1, which carries the Forerunner Mini-SAR (S-band wavelength and
150-m resolution), and bistatic radar (S-Band) measurements may be possible.
Data quality and instrument characteristics suggest that hybrid polarity is
highly desirable for future exploratory radar missions in the Solar system. The
new technologies being qualified on LRO Mini- RF include: Microwave Power
Module (MPM) based multi-frequency transmitter, wideband dual-frequency panel
antenna, all digital receiver and waveform synthesizer incorporating field
programmable gate array (FPGA) and analog-to-digital conversion at 1 GHz
sampling. The Mini-RF parts qualification program, which included commercial
technology, allowed innovative components to gain space qualification.
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