The Lunar Reconnaissance Orbiter Miniature Radio Frequency (Mini-RF) Technology Demonstration

Abstract

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 spaceborne 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

Direct observations of asteroid interior and regolith structure: Science measurement requirements

“…Such images allow detection of embedded structures masked by surface deposits, which make optical identification impossible. The polarization ratio is then the quantity of interest as currently used for planetary surfaces (see for example Nozette et al, 2010;Thompson et al, 2011 for Mini-RF on LRO and MiniSAR on Chandrayan-1). These images allow identification of not only large blocks or lakes, but also variation of the regolith texture and composition in order to understand stratigraphic relations of the different units, layers or lenses.…”

Planetary Geology with Imaging Radar: Insights from Earth-based Lunar Studies, 2001–2015

“…A radar sounder surveyed the Moon as part of the Kaguya mission, and orbital imaging sensors at X-band (4.2 cm) and S-band (12.6 cm) have flown with the Chandrayaan-1 and LRO missions (Nozette et al 2010). The success of so many deep-probing studies with the Earth-based 70 cm system (Section 7) suggests that longer-wavelength orbital imaging radar could make significant new lunar discoveries.…”

Impact Ejecta Characterization for Small-Sized Fresh and Degraded Lunar Craters Using Radar Data

“…Thus effectively a 12.6 cm Mini-RF total backscatter image measures the surface and nearsubsurface roughness at scales of centimetres to decimetres, allowing prominent detection of the ejecta blankets deposited around the craters. In addition, since these images have a constant incidence angle of 48, the sensitivity to ejecta blankets does not vary from image to image making Mini-RF an ideal tool for similar studies 8,[20][21][22] .…”

“…Mini-RF on-board LRO utilizes new wideband hybrid polarization architecture to measure Stokes parameters of the reflected signal 22 . In the present study, in order to obtain the estimates on the spatial ejecta extent, we make use of Stokes parameter 1 (S1), which is the sum of the horizontal and vertical linear polarization channels providing the intensity information.…”