Synthetic aperture radars (SARs) have a significant heritage in terrestrial applications and have demonstrated new scientific opportunities in planetary missions. Here, we present the technical details of the Mini-RF bistatic SAR architecture and experiment, which utilizes the DSS-13 (X /C-band) radio telescope as a transmitter and the Mini-RF instrument onboard the Lunar Reconnaissance Orbiter (LRO) as the receiver. We first analyze the X /C-band bistatic radar system performance and describe the polarimetric channel calibration process. Next, we outline the image-processing technique that leverages hybrid-polarimetry and time-domain backprojection processing (TDBP) to focus and normalize polarimetric bistatic SAR images. We also demonstrate the effectiveness of the bistatic radar technique by presenting primary and derived data products, including Stokes parameters and circular polarization ratios (CPRs). We further highlight the importance of precise lunar surface imaging in this bistatic radar configuration, as the Mini-RF experiment represents the first implementation of the X /C-band polarimetric bistatic SAR in planetary science to image the lunar surface. We conclude by discussing the advantages and challenges of future bistatic radar architectures, with the goal of inspiring cost-effective polarimetric SAR systems for planetary exploration.

The Lunar CRater Observations and Sensing Satellite (LCROSS) impacted a Centaur rocket stage into a permanently shadowed region (PSR) in Cabeus crater, excavating water ice and other volatiles. We used the Miniature Radio Frequency (Mini-RF) instrument on the Lunar Reconnaissance Orbiter and the ShadowCam instrument on the Korean Pathfinder Lunar Orbiter to detect the probable 22-m diameter crater that resulted from the LCROSS impact. The crater formed superposed upon a dense small crater population along a crater ray from a larger pre-existing crater. From its geologic context, the ice and regolith excavated by LCROSS were likely modified within the last 0.1-0.5 Gyr. An upper limit for the excavated volatiles is similar to 0.9 Gyr, as the location was not a PSR prior to that time. A young age for the LCROSS-detected volatiles supports the idea that they were mostly emplaced by an exogenic mechanism, such as from comets or the solar wind. Plain Language Summary The LCROSS experiment formed an impact crater in an area of permanent shadow on the Moon, striking the surface at 2.5 km/s with a 2,300 kg spent rocket body on 9 October 2009. The impact ejecta from this cratering event included detectable amounts of water and other volatiles, which is perhaps the most direct evidence for significant water deposits on the Moon. However, since the impact location is in permanent shadow (no direct solar illumination), it proved hard to observe definitively the crater that LCROSS formed. Here, we use data from Mini-RF, which illuminated the surface with S-band radar, combined with ShadowCam, which acquires images within permanent shadows, to find the probable LCROSS impact crater. The impact crater is 22-m in diameter, a bit smaller than was inferred indirectly after LCROSS. We also present new evidence that the volatiles in the ejecta likely got there in the last 20% of lunar history, which is important for understanding their origin and evolution.

Lunar Reconnaissance Orbiter (LRO) was launched in 2009 to study and map the Moon and is now completing its fifth extended science mission. The LRO (see Figure 1 ) hosts a payload of seven different scientific instruments. The Cosmic Ray Telescope for the Effects of Radiation instrument has characterized the lunar radiation environment and allowed scientists to determine potential impacts to astronauts and other life. The Diviner Lunar Radiometer Experiment (DLRE) has identified cold traps where ice could reside and mapped global thermophysical and mineralogical properties by measuring surface and subsurface temperatures. The Lyman Alpha Mapping Project has found evidence of exposed ice in south polar cold traps as well as global diurnal variations in hydration. The Lunar Exploration Neutron Detector has been used to create high-resolution maps of lunar hydrogen distribution and gather information about the neutron component of the lunar radiation environment. The Lunar Reconnaissance Orbiter Camera (LROC) is a system of three cameras [one wide-angle camera and two narrow-angle cameras (NACs)] mounted on the LRO that capture high-resolution black-and-white images and moderate resolution multispectral (seven-color band) images of the lunar surface. These images can be used, for example, to learn new details about the history of lunar volcanism or the present-day flux of impactors. The Miniature Radio Frequency (Mini-RF) instrument is an advanced synthetic aperture radar (SAR) that can probe surface and subsurface coherent rock contents to identify the polarization signature of ice in cold traps. The Lunar Orbiter Laser Altimeter (LOLA) has been used to generate a high-resolution, 3D map of the Moon that serves as the most accurate geodetic framework available for co-locating LRO (and other lunar) data. The data produced by the LRO continue to revolutionize our scientific understanding of the Moon, and are essential to planning NASA’s future human and robotic lunar missions.

We present an overview of the operations, calibration, geodetic control, photometric standardization, and processing of images from the Mercury Dual Imaging System (MDIS) acquired during the orbital phase of the MESSENGER spacecraft’s mission at Mercury (18 March 2011–30 April 2015). We also provide a summary of all of the MDIS products that are available in NASA’s Planetary Data System (PDS). Updates to the radiometric calibration included slight modification of the frame-transfer smear correction, updates to the flat fields of some wide-angle camera (WAC) filters, a new model for the temperature dependence of narrow-angle camera (NAC) and WAC sensitivity, and an empirical correction for temporal changes in WAC responsivity. Further, efforts to characterize scattered light in the WAC system are described, along with a mosaic-dependent correction for scattered light that was derived for two regional mosaics. Updates to the geometric calibration focused on the focal lengths and distortions of the NAC and all WAC filters, NAC–WAC alignment, and calibration of the MDIS pivot angle and base. Additionally, two control networks were derived so that the majority of MDIS images can be co-registered with sub-pixel accuracy; the larger of the two control networks was also used to create a global digital elevation model. Finally, we describe the image processing and photometric standardization parameters used in the creation of the MDIS advanced products in the PDS, which include seven large-scale mosaics, numerous targeted local mosaics, and a set of digital elevation models ranging in scale from local to global.

The Mini-RF radar instrument was initially included as a technology demonstration on NASA's Lunar Reconnaissance Orbit (LRO) spacecraft launched in 2009. During the nominal LRO mission, the data acquisition strategy transitioned from one centered on demonstrating the capability of the low-power, low-mass instrument design to one focused on addressing scientific questions central to the goals of the LRO mission. Mini-RF acquired individual radar images of the lunar surface, amounting to 98 TB of data, during a 14-month period of daily operation. As the LRO spacecraft was transitioning to its first extended mission, in December of 2010, a malfunction of the instrument transmitter prevented further data collection with the nominal instrument architecture. The Mini-RF receiver and other instrument subsystems were not affected by the malfunction so a campaign to observe the Moon in concert with a ground-based radar asset (Arecibo Observatory) using a bistatic architecture was devised. This architecture presents unique challenges to both planning for data acquisition and processing downlinked data to form a radar image of the lunar surface.

Introduction: The Mini-RF team is acquiring bistatic radar measurements of the lunar surface to understand the scattering properties of materials as a function of bistatic angle. These observations have produced the first lunar radar images ever collected with non-zero bistatic angles. The goal of these observations is to test the hypothesis that some permanently shadowed areas near the lunar poles contain water ice. Rationale: The bistatic angle is determined by the positions and orientations of the radar transmitter and receiver. For radar observations that use the same antenna to transmit and receive a signal, the bistatic angle is zero, and they are referred to as monostatic. NASA’s Mini-RF instrument on the Lunar Reconnaissance Orbiter is currently operating in a bistatic mode with the Arecibo Observatory acting as the transmitter and the Mini-RF antenna acting as the receiver. In this mode, Arecibo transmits a circular polarized S-band signal at a transmitted power of 200 kW. The portion of the signal reflected off the lunar surface and into the MiniRF antenna is received in orthogonal linear polarizations as well as their relative phase. This architecture is equivalent to the hybrid dual-polarimetric architecture of the monostatic mode for the Mini-RF instrument [1] and, therefore, allows for the calculation of the Stokes parameters (S1, S2, S3, S4) that characterize the backscattered signal (and the products derived from those parameters). The circular polarization ratio,

We present a method for safely handling the numerous time standards (UTC, TDB, TDT, Spacecraft Clocks, etc.) involved in space science data analysis. We define an instant of time as an opaque object (TSEpoch) that can only be represented by choosing a time system to represent it in. This removes the ambiguities and confusions of handling time as a primitive type in a large and complex code base. Timestamps, usually individual spacecraft clock times, are converted to TSEpoch objects when ingested into our analysis code, and only converted back to a time system when displayed to the end user. In some circumstances, of course, calculation speed is of the greatest importance; therefore we also discuss our framework for interfacing the TSEpoch class with a computationally efficient primitive representation of time.

SciBox is a new technology for planning and commanding science operations for Earth-orbital and planetary space missions. It has been incrementally developed since 2001 and demonstrated on several spaceflight projects. The technology has matured to the point that it is now being used to plan and command all orbital science operations for the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission to Mercury. SciBox encompasses the derivation of observing sequences from science objectives, the scheduling of those sequences, the generation of spacecraft and instrument commands, and the validation of those commands prior to uploading to the spacecraft. Although the process is automated, science and observing requirements are incorporated at each step by a series of rules and parameters to optimize observing opportunities, which are tested and validated through simulation and review. Except for limited special operations and tests, there is no manual scheduling of observations or construction of command sequences. SciBox reduces the lead time for operations planning by shortening the time-consuming coordination process, reduces cost by automating the labor-intensive processes of human-in-the-loop adjudication of observing priorities, reduces operations risk by systematically checking constraints, and maximizes science return by fully evaluating the trade space of observing opportunities to meet MESSENGER science priorities within spacecraft recorder, downlink, scheduling, and orbital-geometry constraints.

Radar provides a unique means to analyze the surface and subsurface physical properties of geologic deposits, including their wavelength-scale roughness, the relative depth of the deposits, and some limited compositional information. The NASA Lunar Reconnaissance Orbiter's (LRO) Miniature Radio Frequency (Mini-RF) instrument has enabled these analyses on the Moon at a global scale. Mini-RF has accumulated similar to 67% coverage of the lunar surface in S-band (12.6 cm) radar with a resolution of 30 m/pixel. Here we present new Mini-RF global orthorectified uncontrolled S-band maps of the Moon and use them for analysis of lunar surface physical properties. Reported here are readily apparent global- and regional-scale differences in lunar surface physical properties that suggest three distinct terranes, namely: a (1) Nearside Radar Dark Region; (2) Orientale basin and continuous ejecta; and the (3) Highlands Radar Bright Region. Integrating these observations with new data from LRO's Diviner Radiometer rock abundance maps, as well Clementine and Lunar Prospector derived compositional values show multiple distinct lunar surface terranes and sub-terranes based upon both physical and compositional surface properties. Previous geochemical investigations of the Moon suggested its crust is best divided into three to four basic crustal provinces or terranes (Feldspathic Highlands Terrane (-An and -Outer), Procellarum KREEP Terrane, and South Pole Aitken Terrane) that are distinct from one another. However, integration of these geochemical data sets with new geophysical data sets allows us to refine these terranes. The result shows a more complex view of these same crustal provinces and provides valuable scientific and hazard perspectives for future targeted human and robotic exploration. (C) 2014 Elsevier Inc. All rights reserved.