Although no known asteroid poses a threat to Earth for at least the next century, the catalogue of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation 1 , 2 . Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid 1 – 3 . A test of kinetic impact technology was identified as the highest-priority space mission related to asteroid mitigation 1 . NASA’s Double Asteroid Redirection Test (DART) mission is a full-scale test of kinetic impact technology. The mission’s target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by the impact of the DART spacecraft 4 . Although past missions have utilized impactors to investigate the properties of small bodies 5 , 6 , those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft’s autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in the orbit of Dimorphos 7 demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

The Origins, Spectral Interpretation, Resource Identification, Security–Regolith Explorer mission will return a sample to Earth from asteroid (101955) Bennu. Digital terrain models (DTMs) of the asteroid, and products enabled by them, are key to understanding the origin and evolution of the asteroid, providing geological and geophysical context for the sample, maximizing the amount of sample returned, navigating the spacecraft, and ensuring the safety of the spacecraft during sampling.The mission has two approaches for producing these DTMs: a camera-based approach and a lidar-based approach. We provide an overview of the methods used for these two approaches and how they fit into the originally planned mission. We also discuss a summary of tests using these plans to evaluate the expected performance of the DTMs and describe the data products derived from them.

Planning and commanding a space operation is inherently a very complex task. It requires highly skilled operators from various disciplines to coordinate in a timely manner to ensure smooth and successful operation. The process involves translating user requests into a series of satellite operations, searching for observation and data collection opportunities, scheduling required resources and contact with ground stations, generating command sequences to drive payloads and spacecraft, and validating the generated command sequences against operational health and safety constraints. Resolving conflicts manually is an intensive iterative process that underuses a space system's resources and renders it less responsive to sudden schedule changes. As space missions become ever more ambitious, this manual approach is challenged to cope with the increasing complexities of space systems. Responding to this challenge is SciBox, an autonomous planning and commanding system and a technology enabler for space operations. The Johns Hopkins University Applied Physics Laboratory (APL) has been investing in SciBox since 2001. Continual improvement to SciBox and to the SciBox development process enabled the creation of more efficient space operational systems packed with more capabilities. This article describes the architecture of SciBox, the approach to its development, how its capabilities were incrementally developed, and how its use has grown over several space missions.

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.

Launched in 2004, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft continues on its journey to become, in 2011, the first spacecraft to orbit the planet Mercury. The goal of MESSENGER's one-year orbital mission is to answer several key questions about the structure and history of Mercury and its environment. The science and mission operations teams are testing a concept of operations to use the instrument payload most efficiently and to achieve full mission success. To ensure that all essential observations are obtained and to allow for contingencies, an advance science planning (ASP) effort will develop the full yearlong mission baseline plan prior to orbit insertion. To ensure that the plan can be adapted in response to unexpected events over time, an adjusted baseline plan will be regenerated in the ASP process every five weeks during the actual orbital mission. The near-term science planning (NTSP) activity converts weeklong portions of the baseline plan into executable commands to conduct the orchestrated observations. A feedback process from NTSP to ASP will be used to ensure that the baseline observing plan accounts for and reschedules any unsuccessful observations. A testing and validation plan has been developed for the processes and software that underlie both advance and near-term science planning.

Performing scientific observations of a planet from orbit is a complicated endeavor for a spectrograph with a small field of view. Adding in a second spectrometer with a different field of view, and attempting to observe three different aspects of the planet with a total of five detectors, constrained by severe orbital, pointing, and downlink limitations, increase the challenge. On board the MESSENGER spacecraft, the Mercury Atmospheric and Surface Composition Spectrometer (MASCS), which consists of two separate instruments (the Visible and Infrared Spectrograph – VIRS – and the Ultraviolet and Visible Spectrometer – UVVS), will be facing precisely that challenge during the orbital operation phase of the mission to Mercury. As the cruise operations and three successive flybys of Mercury have demonstrated, manually sequencing observations for these two instruments is a labor-intensive task. In order to help schedule MASCS observations of both the surface and the planetary exosphere more efficiently, a planning tool called SciBox will be employed to generate the initial observation suite for each orbital period and coordinate MASCS observations with the other science instruments aboard the spacecraft.

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.

The MESSENGER Science Operations Center (SOC) is an integrated set of subsystems and personnel whose purpose is to obtain, provide, and preserve the scientific measurements and analysis that fulfill the objectives of the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. The SOC has two main functional areas. The first is to facilitate science instrument planning and operational activities, including related spacecraft guidance and control operations, and to work closely with the Mission Operations Center to implement those plans. The second functional area, data management and analysis, involves the receipt of science-related telemetry, reformatting and cataloging this telemetry and related ancillary information, retaining the science data for use by the MESSENGER Science Team, and preparing data archives for delivery to the Planetary Data System; and the provision of operational assistance to the instrument and science teams in executing their algorithms and generating higher-level data products.

Launched in August 2004, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft continues on its journey to become, in 2011, the first spacecraft to orbit the planet Mercury. The goal of MESSENGER's prime one-year orbital mission is to answer several key questions about the structure and history of Mercury and its surrounding environment. The science and mission operations teams have developed (and are testing) a concept of operations to use the instrument payload (seven instruments plus radio science) most efficiently and to ensure full mission success. The extreme temperatures and solar radiation at Mercury require that the spacecraft and its payload be protected by a sunshade, which must face the Sun at all times. Spacecraft pointing is therefore narrowly constrained. Furthermore, the science investigations have competing pointing requirements. To ensure that all essential observations are obtained and to allow for contingencies, an advance science planning (ASP) effort is used to develop a full yearlong mission baseline plan far in advance. The ASP maps out the entire orbital observing plan for all instruments including calibration activities. To ensure that the plan can be adapted in response to unexpected events and spacecraft and instrument performance over time, an adjusted baseline plan will be regenerated in the ASP process every five weeks during the actual orbital mission. The near-term science planning (NTSP) activity converts weeklong portions of the baseline plan into executable commands to conduct the orchestrated observations. A feedback process from NTSP to ASP will be used to ensure that the baseline observing plan accounts for and reschedules any observations that were not successful. In addition, targets of opportunity can be inserted into the baseline plan when appropriate. In this paper we describe the MESSENGER payload orbital concept of operations, the approach used to develop it, and how it will be executed by the science and mission operations teams. We describe the software and processes to be used for both advance science planning and near-term science planning. We also describe the testing and validation plans for both the processes and tools.