In 2020 the United States Space Force (USSF) released an implementation of the SGP4-XP propagator, an advanced version of the existing SGP4 propagator stated to deliver accuracy roughly equivalent to that of the USSF’s Special Perturbations Ephemeris propagator (SPEPH) with runtimes only 50% to 100% longer than SGP4. This paper presents an analysis of the performance characteristics of the SGP4-XP propagation algorithm and considers new and existing practical applications where it can be used more effectively than SGP4.
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The James Webb Space Telescope (JWST) was launched from Kourou Spaceport on December 25, 2021, at 12:20 UTC on an Ariane 5 launch vehicle. The launch vehicle inserted JWST into a 30-day transfer trajectory to the Sun-Earth-Moon (SEM) Lagrange point L2 region. JWST executed three mid-course correction maneuvers (MCCs) to insert the spacecraft into a quasi-halo orbit about SEM L2; JWST will maintain its trajectory about L2 for at least 5.5 years, with a goal of at least 10.5 years. This paper summarizes the flight dynamics support for JWST, including the prelaunch nominal trajectory design, the launch window analysis, contingency planning for trajectory-related anomalies, mission operations support for the first 6 months, and a comparison of the planned and achieved actual JWST trajectory results. The orbit determination strategy, both planned and executed, will be summarized, and the method of addressing the anomalies as they occurred will be included.
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DSCOVR (Deep Space Climate Observatory) is a National Oceanic and Atmospheric Administration (NOAA) space weather, space climate, and Earth observation satellite operating in a Sun-Earth L1 Lissajous orbit. This report summarizes the two-burn maneuver campaign performed in Summer 2021 to transfer DSCOVR from the collapsing phase into the expansion phase of the Lissajous orbit to avoid the Solar Exclusion Zone (SEZ). The two-maneuver campaign per- formed in July and August 2021 was successful and resulted in saving the mission 31 kilograms of fuel and 100 m/s of delta-v reserved for SEZ maneuvers which are no longer required until 2026 or 2027.
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The NASA James Webb Space Telescope (JWST) mission successfully launched on Dec 25, 2021 , at 12:20 Coordinated Universal Time (UTC). During the 30-day transfer to the second Sun-Earth-Moon (SEM) libration point (L2), JWST executed three mid-course correction (MCC) maneuvers to insert into a quasi-halo orbit about L2. This paper covers the design and modeling for these three maneuvers with a focus on the timeline around the execution of each MCC maneuver. It will summarize the actual on-board events as well as the contingency preparation done for maneuver planning, monitoring, and final post-burn reconstruction of all three MCC maneuvers.
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The NASA James Webb Space Telescope (JWST) mission successfully launched on December 25, 2021, at 12:20 UTC. This paper details several novel challenges encountered in the orbit determination (OD) of JWST during the launch and early orbit. The first OD solution used only 6.5 hours of tracking data, much less than the 24 hours of data usually required for libration orbiters on an outbound trajectory. In addition, the observatory area exposed to solar radiation pressure changed through a series of sunshield deployments while concurrent momentum unloads and attitude telemetry outages occurred. This paper covers how the Flight Dynamics Team (FDT) prepared for these challenges, how these challenges were handled on-orbit, and the performance of the resulting OD solutions.
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The James Webb Space Telescope (JWST) was successfully launched on December 25, 2021 12:20 UTC on an Ariane 5 rocket out of Kourou, French Guiana on a direct, lower energy manifold transfer out to the Sun-Earth-Moon (SEM) L2 point. Three mid-course correction (MCC) maneuvers, designated MCC-1, MCC-1b, and MCC-2, were required to provide the energy necessary to reach L2 due to a purposeful biasing down of the launch vehicle. This paper will document the prelaunch preparation, nominal planning, contingency preparation, and successful execution of the three mid-course correction maneuvers.
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Recently, lunar Near Rectilinear Halo Orbits (NRHO) have been the focus of much study, and they have been selected as the target orbit for the Gateway mission, formerly the Deep Space Gateway. Also, the Deep Space Network (DSN) is increasingly congested and over-subscribed. In this work, the performance of relative-only navigation between a spacecraft in an NRHO and a relay in a Distant Retrograde Orbit is examined and compared to simulated DSN tracking using a Square Root Information Filter. Various tracking scenarios are examined using a closed-loop simulation where navigation errors inform maneuver planning and maneuver execution errors affect navigation performance. Results indicate that relative-only navigation can provide comparable levels of orbit determination error and orbit maintenance costs.
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NASA is currently working on the spacecraft and trajectory design for the Gateway mission that will reside in a Near Rectilinear Halo Orbit (NRHO). In the NRHO, Gateway will nominally require orbital maintenance maneuvers once per revolution. Separately, NASA is also working to develop technologies and techniques for relative navigation in cis-lunar space. Together, these concepts represent an opportunity for interesting research in cis-lunar navigation performance.
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This paper provides a thorough review of how ballistic lunar transfers (BLTs) can be used to transfer from Earth to near rectilinear halo orbits (NRHOs) in an efficient manner.
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Spacecraft departing from the Gateway in a Near Rectilinear Halo Orbit (NRHO) experience gravitational forces from the Moon, the Earth, and the Sun, all of which can be simultaneously significant. How do these celestial objects influence the trajectory of spacecraft? Find out more by reading this white paper.
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The NASA Conjunction Assessment Risk Analysis (CARA) program has been performing routine on-orbit satellite conjunction risk analysis for unmanned NASA spacecraft since 2005, and has developed a robust operations procedure and set of recommended best practices for operational conjunction assessment. Read this article to learn more about the CARA program's updated requirments.
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The L2 station keeping plan for the James Webb Space Telescope achieves zero velocity in the x-component at the fourth successive crossing of the XZ plane of the rotating libration point frame. The techniques developed to determine the minimum maneuver direction in a full ephemeris model, along with strategies to cope with the attitude constraints imposed by the sunshield that prevents the ability to maneuver along the stable eigenvector, are examined in this study.
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Trajectory analysis in the presence of multiple gravity fields is complex, and innovative computational tools are needed to simplify complicated design spaces, generate large quantities of data quickly, and visualize the output for user accessibility. Explore the tools required for success.
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In 2020 the United States Space Force (USSF) released an implementation of the SGP4-XP propagator, an advanced version of the existing SGP4 propagator stated to deliver accuracy roughly equivalent to that of the USSF’s Special Perturbations Ephemeris propagator (SPEPH) with runtimes only 50% to 100% longer than SGP4. This paper presents an analysis of the performance characteristics of the SGP4-XP propagation algorithm and considers new and existing practical applications where it can be used more effectively than SGP4.
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The FreeFlyer Team is proud to bring you FreeFlyer 7.8, optimized for your mission! FreeFlyer 7.8 is packed with new user-requested features to improve your mission’s success.
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