MESSENGER SciBox is an automated closed-loop planning and commanding system used to optimize orbital science operations for the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. The system plans all science observations for the seven science instruments on the spacecraft and also automatically generates the command sequences that drive the instruments, the guidance and control system, the solid-state recorder, the solar panels, and the radio-frequency communication system. MESSENGER SciBox interacts with the instrument scientists, mission operations team, downlink processing system, and mission design engineers to form a closed-loop system. In orbital operation, the systems employ a feedback loop, with a one-week time step, to improve the system performance. Feedback inputs are used to predict observational performance, to track all science observations, to avoid planning redundant tasks, and to recover from operational anomalies. The software tool is automated because the entire process, from ingesting the feedback inputs to creating the spacecraft and instruments commands, can function without manual interaction. I. Introduction Science operation centers for most space missions generally consist of two components: the uplink system and the downlink system. The uplink system deals with planning and scheduling of science observations, whereas the downlink system deals with the processing of observations returned from the spacecraft. Traditionally, the planning and scheduling of science observations, and the creation of associated spacecraft and instrument commands for science operation, are so time-consuming and labor-intensive that little time is left for the planning team to have close interactions with the data processing team. Any such interactions tend to be ad hoc and informal. On some missions, the two subsystems are so decoupled that they are even housed in different institutions and on separate networks. The lack of tightly coupled interaction frequently results in inefficient use of resources and a less-thanoptimum operational schedule. In this paper we describe an automated planning and commanding system that uses a closed-loop iterative process to continuously refine the science operation schedule and to generate spacecraft and instrument commands for uploading to a spacecraft. The planning system iteratively interacts with the instrument scientists, mission operations center personnel, mission design team, and downlink processing system to produce a scienceobservation-packed operational schedule and to improve the precision of planned operations. The process of ingesting feedback information from the downlink system to the generation of spacecraft and instrument commands for uplink is completely automated. This closed-loop architecture has been implemented as part of science operations for the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft now in orbit about Mercury, and it has allowed the MESSENGER team to maximize scientific return for the community with a relatively small operational staff. The closed-loop architecture and its application to MESSENGER orbital operations are the focus of this paper.

The spectral radiances of Phobos and Deimos measured by the CRISM and OMEGA instruments are composed of both reflected solar and thermally emitted contributions. Thermal emission is controlled by surface temperature, and becomes increasingly important at longer wavelengths (> 2.5μm). Here we present a method to estimate surface temperatures using pairs of spectra from locations with the same emissivity but different temperatures. Knowing the surface temperature allows us to model the reflected and emitted contributions to the total radiance, retrieve spectral reflectance, and interpret important mineralogical information.

1 . Automated tools that simulate full orbital dynamics, instrument operation, and data acquisition as well as operational and resource constraints allow planners to develop schedules that are conflict free and fit within mission capabilities. Moreover, if the simulations have sufficient fidelity and are performed well enough in advance, they can also be used to identify and assess risks by analyzing the schedule for sensitivities to different contingencies. In this paper, we discuss a primary risk area for MESSENGER, available solid-state recorder (SSR) space, and describe how we used the tools in MESSENGER SciBox to model the instrument suite data generation, downlink telemetry volume, and the resulting SSR loading through the mission. We then discuss two examples to illustrate how this tool is used to design instrument operations and to analyze the impact of non- nominal downlink performance to specify required contingency responses using a combination of telemetry bandwidth increases and data decimation. Given this simulation and analysis, knowledge of the greatest risks and detailed plans for responses are already in place, providing greater assurance of mission success.

MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is the first spacecraft to visit Mercury since the Mariner 10 flybys in 1974 and 1975 and will be the first spacecraft to orbit the innermost planet, beginning in March 2011. The science payload is designed to study all aspects of Mercury and its environment and consists of seven instruments and a radio science experiment. During the primary orbital phase of the mission, the MESSENGER team faces the challenge of scheduling science observations to meet all measurement objectives while operating in a thermally harsh environment in geometrically challenging orbits. An efficient, automated science planning and commanding system called MESSENGER SciBox has been developed to support orbital analysis and strategic planning activities prior to orbital insertion, and to schedule and command the instrument and spacecraft operation during the orbital phase. In this paper we present the architecture of MESSENGER SciBox and its application to pre-orbital simulation and inorbit operational usage.

Introduction: Domingue and Vilas [1] examined the spectral variations that can be created by changes in viewing geometry (photometric variations) across a crater profile using lunar reflectance properties. The purpose of their study was to examine changes that can occur in such spectral properties as spectral slope, band center, and band depth if photometric corrections have not been applied. Using a shape model for the asteroid Itokawa [4], we conducted a similar examination of spectral variability due solely to photometric variations. This provides an initial evaluation of the percent of spectral variability across Itokawa’s surface that can be ascribed to photometric variability, and may impact interpretations of spectra of Itokawa’s surface.

The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is a hyperspectral imager on the Mars Reconnaissance Orbiter (MRO) spacecraft. CRISM consists of three subassemblies, a gimbaled Optical Sensor Unit (OSU), a Data Processing Unit (DPU), and the Gimbal Motor Electronics (GME). CRISM's objectives are (1) to map the entire surface using a subset of bands to characterize crustal mineralogy, (2) to map the mineralogy of key areas at high spectral and spatial resolution, and (3) to measure spatial and seasonal variations in the atmosphere. These objectives are addressed using three major types of observations. In multispectral mapping mode, with the OSU pointed at planet nadir, data are collected at a subset of 72 wavelengths covering key mineralogic absorptions and binned to pixel footprints of 100 or 200 m/pixel. Nearly the entire planet can be mapped in this fashion. In targeted mode the OSU is scanned to remove most along‐track motion, and a region of interest is mapped at full spatial and spectral resolution (15–19 m/pixel, 362–3920 nm at 6.55 nm/channel). Ten additional abbreviated, spatially binned images are taken before and after the main image, providing an emission phase function (EPF) of the site for atmospheric study and correction of surface spectra for atmospheric effects. In atmospheric mode, only the EPF is acquired. Global grids of the resulting lower data volume observations are taken repeatedly throughout the Martian year to measure seasonal variations in atmospheric properties. Raw, calibrated, and map‐projected data are delivered to the community with a spectral library to aid in interpretation.

The Magnetospheric Imaging Instrument (MIMI) onboard the Cassini spacecraft observed the saturnian magnetosphere from January 2004 until Saturn orbit insertion (SOI) on 1 July 2004. The MIMI sensors observed frequent energetic particle activity in interplanetary space for several months before SOI. When the imaging sensor was switched to its energetic neutral atom (ENA) operating mode on 20 February 2004, at ∼10 3 times Saturn's radius R S (0.43 astronomical units), a weak but persistent signal was observed from the magnetosphere. About 10 days before SOI, the magnetosphere exhibited a day-night asymmetry that varied with an ∼11-hour periodicity. Once Cassini entered the magnetosphere, in situ measurements showed high concentrations of H + , H 2 + , O + , OH + , and H 2 O + and low concentrations of N + . The radial dependence of ion intensity profiles implies neutral gas densities sufficient to produce high loss rates of trapped ions from the middle and inner magnetosphere. ENA imaging has revealed a radiation belt that resides inward of the D ring and is probably the result of double charge exchange between the main radiation belt and the upper layers of Saturn's exosphere.

CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) is a hyperspectral imager that will be launched on the MRO (Mars Reconnaissance Orbiter) spacecraft in August 2005. MRO’s objectives are to recover climate science originally to have been conducted on the Mars Climate Orbiter (MCO), to identify and characterize sites of possible aqueous activity to which future landed missions may be sent, and to characterize the composition, geology, and stratigraphy of Martian surface deposits. MRO will operate from a sun-synchronous, near-circular (255x320 km altitude), near-polar orbit with a mean local solar time of 3 PM. CRISM’s spectral range spans the ultraviolet (UV) to the mid-wave infrared (MWIR), 383 nm to 3960 nm. The instrument utilizes a Ritchey-Chretien telescope with a 2.12° field-of-view (FOV) to focus light on the entrance slit of a dual spectrometer. Within the spectrometer, light is split by a dichroic into VNIR (visible-near-infrared, 383-1071 nm) and IR (infrared, 988-3960 nm) beams. Each beam is directed into a separate modified Offner spectrometer that focuses a spectrally dispersed image of the slit onto a two dimensional focal plane (FP). The IR FP is a 640 x 480 HgCdTe area array; the VNIR FP is a 640 x 480 silicon photodiode area array. The spectral image is contiguously sampled with a 6.6 nm spectral spacing and an instantaneous field of view of 61.5 μradians. The Optical Sensor Unit (OSU) can be gimbaled to take out along-track smear, allowing long integration times that afford high signal-to-noise ratio (SNR) at high spectral and spatial resolution. The scan motor and encoder are controlled by a separately housed Gimbal Motor Electronics (GME) unit. A Data Processing Unit (DPU) provides power, command and control, and data editing and compression. CRISM acquires three major types of observations of the Martian surface and atmosphere. In Multispectral Mapping Mode, with the gimbal pointed at planet nadir, data are collected at frame rates of 15 or 30 Hz. A commandable subset of wavelengths is saved by the DPU and binned 5:1 or 10:1 cross-track. The combination of frame rates and binning yields pixel footprints of 100 or 200 m. In this mode, nearly the entire planet can be mapped at wavelengths of key mineralogic absorption bands to select regions of interest. In Targeted Mode, the gimbal is scanned over ±60° from nadir to remove most along-track motion, and a region of interest is mapped at full spatial and spectral resolution. Ten additional abbreviated, pixel-binned observations are taken before and after the main hyperspectral image at longer atmospheric path lengths, providing an emission phase function (EPF) of the site for atmospheric study and correction of surface spectra for atmospheric effects. In Atmospheric Mode, the central observation is eliminated and only the EPF is acquired. Global grids of the resulting lower data volume observation are taken repeatedly throughout the Martian year to measure seasonal variations in atmospheric properties.